Form DEF 14A Trinseo PLC For: Sep 23

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934

Filed by the Registrant  ☒

Filed by a Party other than the Registrant  ☐

Check the appropriate box:

Trinseo PLC

(Name of Registrant as Specified In Its Charter)

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(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

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Trinseo PLC

REGISTERED OFFICE:

Riverside One

Sir John Rogerson’s Quay

Dublin 2

Dublin, Ireland

D02 X576

PRINCIPAL PLACE OF BUSINESS:

440 E. Swedesford Rd., Suite 301

Wayne, Pennsylvania 19087 USA

August 7, 2026

Dear Shareholder:

We cordially invite you to attend our 2026 annual general meeting of shareholders (the “Annual Meeting”) to be held on Wednesday, September 23, 2026 at 8:30 a.m. EST, in person at 440 E. Swedesford Road, Suite 301, Wayne, Pennsylvania 19380, United States. Shareholders in Ireland may participate in the Annual Meeting by audio and video link at McCann FitzGerald LLP, Riverside One, Sir John Rogerson’s Quay, Grand Canal Dock, Dublin 2, D02 X576, Ireland at 1:30 p.m. IST on September 23, 2026. Further details regarding admission to the Annual Meeting as well as the business to be conducted at the meeting are more fully described in the accompanying materials.

We describe in detail the actions we expect to take in the attached Notice of the 2026 Annual General Meeting of Shareholders and proxy statement. We have also made available a copy of our Annual Report on Form 10-K for our fiscal year ended December 31, 2025. We encourage you to read the Form 10-K, which includes information on our operations and products, as well as our audited financial statements.

As in previous years, we will be using the “Notice and Access” method of providing proxy materials to shareholders via the Internet. We believe that this process provides shareholders with a convenient and quick way to access the proxy materials and vote, while allowing us to conserve natural resources and reduce the costs of printing and distributing the proxy materials. We will mail to most of our shareholders a Notice of Internet Availability of Proxy Materials for the Annual Meeting containing instructions on how to access our proxy statement and Annual Report and vote electronically via the Internet. Each notice will also contain instructions on how to receive a paper copy of the proxy materials. All shareholders who do not receive a notice will receive a paper copy of the proxy materials by mail or an electronic copy of the proxy materials by email.

Your vote is important regardless of the number of shares you own. Whether or not you plan to attend the Annual Meeting, we encourage you to consider the matters presented in the proxy statement and vote as soon as possible. Instructions for Internet and telephone voting, as well as instructions to request to receive proxy materials by mail, are included with the Notice of Internet Availability of Trinseo’s Proxy Materials for the Annual Meeting. If you are a registered shareholder, you can also request to receive a proxy card and vote by mail.

Sincerely yours,

Frank A. Bozich
President and Chief Executive Officer

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Trinseo PLC

Annual General Meeting of Shareholders

440 E. Swedesford Rd., Suite 301

Wayne, Pennsylvania 19380

United States

September 23, 2026

8:30 a.m. EST

Trinseo PLC

REGISTERED OFFICE:

Riverside One

Sir John Rogerson’s Quay

Dublin 2

Dublin, Ireland

D02 X576

Principal executive offices of Trinseo PLC

440 E. Swedesford Rd., Suite 301

Wayne, Pennsylvania 19087 USA

+1 610-240-3200

NOTICE OF ANNUAL GENERAL MEETING OF SHAREHOLDERS

To the Shareholders of Trinseo PLC:

Notice is hereby given that an annual general meeting of shareholders (the “Annual Meeting”) of Trinseo PLC (“we,” “Trinseo” or the “Company”) will be held on Wednesday, September 23, 2026, at 8:30 a.m. EST, in person at 440 E. Swedesford Rd., Suite 301, Wayne, Pennsylvania 19380, United States. Shareholders in Ireland may participate in the Annual Meeting by audio and video link at McCann FitzGerald LLP, Riverside One, Sir John Rogerson’s Quay, Grand Canal Dock, Dublin 2, D02 X576, Ireland at 1:30 p.m. IST on September 23, 2026, for the purposes described below and in further detail in the proxy statement accompanying this notice:

All shareholders of record at the close of business on July 30, 2026 (the record date for the Annual Meeting) may attend.

Shareholders who wish to attend the Annual Meeting must register by going to the Company’s voting website, www.envisionreports.com/TSE and clicking on the box labeled “Meeting Attendance.” Shareholders of record who register to attend may vote their shares during the Annual Meeting. Shareholders who wish to vote their shares by proxy during the Annual Meeting must obtain a legal proxy, executed in their favor, from their broker, bank or other nominee.

Proposals 1, 2 and 3 are ordinary resolutions requiring either approval of a majority of the votes cast in person or by proxy at the Annual Meeting, or requiring advisory approval by shareholders which advisory approval will be taken into consideration by the Board.

Our Irish statutory financial statements for the fiscal year ended December 31, 2025, including the reports of the directors and statutory auditors thereon, will be presented at the annual general meeting. There is no requirement under Irish law that such statements be approved by the shareholders and no such approval will be sought at the annual general meeting. Our Irish statutory financial statements will be available on our website at investor.trinseo.com/home/financials, under “2025 Financial Statements,” after the date of this proxy statement but no later than September 1, 2026.

It is expected that the Notice of Annual Meeting and this proxy statement will first be available to shareholders on or about August 12, 2026. On or about August 12, 2026, the Company will also begin mailing a Notice of Internet Availability of Trinseo’s Proxy Materials to shareholders informing them that this proxy statement and voting instructions are available online. As more fully described in that Notice, all shareholders may choose to access proxy materials on the Internet or may request to receive paper copies of the proxy materials.

Shareholders of record at the close of business on July 30, 2026 are entitled to notice of, and entitled to vote at, the Annual Meeting and any adjournments or postponements thereof. Whether or not you expect to attend the Annual Meeting, please complete, sign, date, and promptly return the enclosed proxy card in the envelope that we have provided. Your prompt response will ensure that your ordinary

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shares of Trinseo PLC are represented at the Annual Meeting. You can change your vote and revoke your proxy by following the procedures described in this proxy statement.

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Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting To Be Held on September 23, 2026: our proxy statement is attached. Financial and other information concerning Trinseo is contained in our Annual Report to shareholders for the fiscal year ended December 31, 2025. The proxy statement and our fiscal 2025 Annual Report to shareholders are available on the Investor Relations section of our website at investor.trinseo.com. Additionally, you may access our proxy materials at www.envisionreports.com/TSE, a site that does not have “cookies” that identify visitors to the site.

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PROXY STATEMENT

Proxy Statement

The Board of Trinseo PLC solicits your proxy for the Annual Meeting to be held on September 23, 2026, and at any adjournments or postponements of the Annual Meeting, for the purposes set forth in the Notice of the Annual Meeting of Shareholders included in this proxy statement. As used in this proxy statement, the terms “we,” “us,” “our” “Company” or “Trinseo” refer to Trinseo PLC. Proxy materials, including this proxy statement and the Annual Report for our fiscal year ended December 31, 2025 (“fiscal 2025”) are being first provided to shareholders on or about August 12, 2026. Our registered address is Riverside One, Sir John Rogerson’s Quay, Dublin 2, Dublin, Ireland, D02 X576.

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QUESTIONS AND ANSWERS ABOUT THE ANNUAL MEETING AND THE PROXY MATERIALS

Questions and Answers about the Annual Meeting and the Proxy Materials

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QUESTIONS AND ANSWERS ABOUT THE ANNUAL MEETING AND THE PROXY MATERIALS

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QUESTIONS AND ANSWERS ABOUT THE ANNUAL MEETING AND THE PROXY MATERIALS

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PROPOSAL 1

Proposal 1—Election of Directors

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The election of each director requires the approval of a majority of the shares represented in person or by proxy at the Annual Meeting. Broker non-votes, if any, will have no effect on the outcome of this proposal.

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PROPOSAL 1

2026 Director Nominees

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Professional Experience:

Ms. Johnson served as President and Chief Executive Officer of Elevance Renewable Sciences Inc., a specialty chemicals company, from 2007 to 2015, and as Chairwoman from 2015 to 2016. Ms. Johnson joined Elevance after over 20 years’ experience working within the oil and petrochemicals industry for Amoco Corporation and BP p.l.c. (joining BP after its merger with Amoco in 1998). During this time she held both operational and functional roles, culminating in her role as Senior Vice President of Global Derivatives within BP’s global Innovene business, which included P&L accountability for multiple global commodity and specialty chemicals businesses. Ms. Johnson also served as director of TPC Group, a manufacturer of products derived from petrochemical raw materials, from 2011 to 2012 before the company was taken private. Ms. Johnson currently serves on the board of several private or non-U.S. public companies, including JM Huber and BlueScope Steel.

Education:

Ms. Johnson graduated from Brigham Young University with a degree in Management and Organizational Behavior (M.O.B.) and a B.S. in Psychology.

Other Public Company Directorships:

Current Directorships—

FMC Corporation (NYSE: FMC) since 2013

Director Qualifications:

Ms. Johnson brings to our Board valuable experience in operational leadership and chemical industry and technological expertise.

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Professional Experience:

Mr. Alvarado served as Chief Executive Officer of Commercial Metals Company (NYSE: CMC), a global manufacturer, recycler and marketer of steel and other metals, from September 2011 until September 2017, and as chairman of CMC’s Board of Directors from January 2013 until January 2018. He joined CMC in April 2010 as Executive Vice President and Chief Operating Officer, was named President and Chief Operating Officer in April 2011, and became President and Chief Executive Officer in September 2011 until his retirement. Prior to joining CMC, he was President and Chief Operating Officer of Lone Star Technologies, Inc. from 2004 to 2007. In June 2007, following the acquisition of Lone Star Technologies, Inc. by United States Steel Corporation, Mr. Alvarado was named President of U.S. Steel Tubular Products, Inc., a division of United States Steel Corporation, a position he held until March 2009. Mr. Alvarado began his career at Inland Steel Company in 1976 and spent 21 years with the company in roles of increasing responsibility. He then served in executive roles with Birmingham Steel Corporation and Ispat North America Inc. until joining Lone Star Technologies.

Education:

Mr. Alvarado has an MBA from Cornell University and a B.A. degree in Economics from University of Notre Dame.

Other Public Company Directorships:

Current Directorships—

Kennametal Inc. (NYSE: KMT) since January 2018
Arcosa, Inc. (NYSE: ACA) since November 2018
PNC Financial Services Group Inc. (NYSE: PNC) since January 2019

Director Qualifications:

Mr. Alvarado brings to our Board years of experience in a cyclical commodities-driven industry and significant perspective on global manufacturing operations and strategic planning.

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Professional Experience:

Mr. Bozich became the Company’s President and Chief Executive Officer in March 2019. From May 2013 until February 2019, Mr. Bozich had been the President and Chief Executive Officer at the SI Group, Inc., a leading global developer and manufacturer of phenolic resins and chemicals used in the production of antioxidants, engineering plastics, fuels and lubes, rubber and pharmaceutical ingredients. Prior to SI Group Inc., Mr. Bozich held several executive management positions at BASF Corporation, a multi-national chemicals and manufacturing corporation, including President of BASF’s Catalysts Division from 2010 to 2013, Group Vice President of Precious and Base Metal Service, and Group Vice President of the Integration Management Office. Prior to BASF, Mr. Bozich was Group Vice President, Enterprise Technologies and Ventures at Engelhard Corporation, which was acquired by BASF in 2006. He has also held leadership positions at Rohm and Haas, Croda Adhesives, Inc. and Apex Adhesives, which he founded in 1986.

Education:

Mr. Bozich holds a bachelor’s degree in Chemistry and a master’s degree in Business Administration from the University of Chicago, as well as a master’s degree in Chemistry from the University of Illinois.

Other Public Company Directorships:

Current Directorships—

OGE Energy Corp (NYSE: OGE) since February 2016

Director Qualifications:

Mr. Bozich is an accomplished CEO known for his strong personal leadership and track record of driving business growth and corporate transformation. His breadth of experience in leading chemical businesses in diverse and dynamic global markets is well-suited for the Company’s strategic priorities.

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Professional Experience:

Victoria Brifo is Senior Vice President and Chief Human Resources Officer at Air Products and Chemicals, Inc. (NYSE: APD). She is responsible for leading all aspects of the company’s Human Resources (HR) organization, including HR Operations, Diversity and Inclusion, Talent Management, and Compensation and Benefits, as well as Global Health and Wellness, and Corporate Aviation and Corporate Transportation. Ms. Brifo has been with Air Products since 2001, starting as a production site leader and progressing through several plant leadership positions before becoming Global Diversity Director in 2005. In 2008 she was named Global Manager of Electronics Operations and moved to the Merchant Gases group in 2011 to lead the Global Generated Gases business. In 2014 Ms. Brifo assumed the role of Global Transformation Leader for Industrial Gases. She was subsequently appointed Vice President, Global Gases, followed by Vice President, Equipment Sales, Plant Support and Central Procurement. Prior to joining Air Products, Ms. Brifo worked at LyondellBasell and Amoco Production Company.

Education:

Ms. Brifo holds degrees in chemical engineering and political science from the Massachusetts Institute of Technology.

Other Public Company Directorships:

None.

Director Qualifications:

Ms. Brifo brings to our Board significant experience in the chemicals and manufacturing industry, as well as leadership, management and human resources expertise.

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Professional Experience:

Mr. Cote is the President and Chief Operating Officer of Ecore International (“Ecore”), where he oversees the company’s day-to-day operations and execution of strategic initiatives. Mr. Cote joined Ecore in August 2025. Mr. Cote previously served as the Chief Executive Officer and President of Sensata Technologies Holding plc (NYSE: ST) from March 2020 until April 2024. Prior to his appointment as CEO, Mr. Cote served as President and as Chief Operating Officer of Sensata since July 2012 and as Executive Vice President of its Global Sensing Solutions business since November 2015. He joined Sensata as Senior Vice President and Chief Financial Officer in January 2007 and was appointed Executive Vice President in July 2007. From March 2005 to December 2006, Mr. Cote was Chief Operating Officer of the law firm Ropes & Gray. From January 2000 to March 2005, Mr. Cote was Chief Operating, Financial and Administrative Officer of Digitas. Previously he worked for Ernst & Young LLP from 1989 until 1997. Mr. Cote is a certified public accountant.

Education:

Mr. Cote received a B.A. degree in Business Administration and a Master of Accounting from Florida Atlantic University.

Other Public Company Directorships:

Current Directorships—

None.

Past Directorships—

Sensata Technologies Holding plc (NYSE: ST) from March 2020 to June 2024

Director Qualifications:

Mr. Cote brings to our Board significant executive management, financial and accounting experience.

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Professional Experience:

Ms. Desmond is the former Executive Vice President and Chief Financial Officer of DuPont de Nemours, Inc. and has previously served as Vice President and Co-Controller for DowDuPont and as finance leader for the Specialty Products division following the merger of DuPont with Dow Chemical. Ms. Desmond served in various leadership roles within DuPont in her 30-year career with the company including Vice President-Controller, General Auditor and Chief Ethics & Compliance Leader and Director-Investor Relations.

Education:

Ms. Desmond received a B.S. in Accounting from Mt. St. Mary’s University and is a certified public accountant (inactive).

Other Public Company Directorships:

Current Directorships—

IPG Photogenics Corporation (Nasdaq: IPGP) since 2021
Sylvamo (NYSE: SLVM) since 2021

Director Qualifications:

Ms. Desmond brings to our Board substantial finance and accounting experience, and extensive experience in the chemicals industry.

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Professional Experience:

Mr. Farrell is former Chairman, President and Chief Executive Officer of Church & Dwight Co. Inc. (“Church & Dwight”), serving from 2016 through 2025. Mr. Farrell previously served as Executive Vice President, Chief Financial Officer and Chief Operating Officer at Church & Dwight starting in 2014, starting as Chief Financial Officer in 2006. Prior to that, Mr. Farrell served as Chief Financial Officer of Alpharma Inc., as Vice President, Investor Relations & Communications at Ingersoll-Rand Ltd., and in various senior financial positions at AlliedSignal Inc. Mr. Farrell began his career with KPMG Peat Marwick LLP, where he was an audit partner.

Education:

Mr. Farrell received a B.S. degree from Manhattan College and is a certified public accountant (inactive).

Other Public Company Directorships:

Current Directorships—

Novanta, Inc. (NASDAQ: NOVT) since 2025

e.l.f. Beauty, Inc. (NYSE: ELF) since 2026

Past Directorships—

Lydall Co., Inc. (NYSE: LDL) from 2003 to 2021

Church & Dwight Co. Inc. (NYSE: CHD) from 2019 to 2025

Director Qualifications:

Mr. Farrell brings to our Board his experience as a chief executive officer, substantial financial and audit expertise and experience in the chemicals, industrial goods and consumer products industries.

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Professional Experience:

Prior to her retirement in 2019, Ms. Flaton worked in banking and finance, primarily assisting companies and clients with strategic transformation and financial turnaround. Ms. Flaton served as a Managing Director at Alix Partners from 2014 2019 and as a Managing Director at Lazard Freres from 2008 2014. Prior to that Ms. Flaton spent 13 years at Citigroup and Credit Suisse First Boston supporting clients in refinancings, capital raises and restructuring transactions

Education:

Ms. Flaton has an MBA from IMD (Lausanne, Switzerland) and a BS from the University of Delaware.

Other Public Company Directorships:

Current Directorships—

QVC Group, Inc. (Nasdaq: QVCGA) since 2025

Past Directorships—

Cano Health, Inc. (NYSE: CANO) from 2022 to 2023

Bed, Bath & Beyond (Nasdaq: BBBY) from Jan 2023 to Sep 2023

National CineMedia, LLC (Nasdaq: NCMI) from 2021 to 2023

Director Qualifications:

Ms. Flaton brings to our board over 30 years of experience in banking & finance, transformation & restructuring, and governance & risk management in her history serving as an independent director for both public & private companies.

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Professional Experience:

Ms. Frizzley currently serves as the president of Wildrose Partners LLC, an independent consulting company providing governance and related advisory services to multiple corporations, which position she has held since 2019. From 2016 through 2019, Ms. Frizzley served as Counsel at the law firm of Weil, Gotshal & Manges LLP.

Education:

Ms. Frizzley holds a BS degree from the University of Alberta and an LLB degree from the University of Toronto Faculty of Law.

Other Public Company Directorships:

Past Directorships—

Avaya Holdings Corporation (NYSE: AVYA) from 2022 to 2023

Virgin Orbit Holdings, Inc. (Nasdaq: VORB) from 2023 to 2023

iMedia Brands, Inc. (Nasdaq: IMNI) from 2023 to 2024

Surgalign Holdings, Inc. (Nasdaq: SRGA) from 2023 to 2023

Proterra Inc. (Nasdaq: PTRA) from 2023 to 2024

Invitae Corporation (NYSE: NVTA) from 2023 to 2024

KLD Discovery, Inc. (Nasdaq: KLDI) from 2024 to 2024

CalAmp Corp. (Nasdaq: CAMP) from 2024 to 2024

iHeart Media, Inc. (Nasdaq: IHRT) from 2024 to 2024

Akoustis Technologies Inc. (Nasdaq: AKTS) from 2024 to 2025

LanzaTechGlobal, Inc. (Nasdaq: LNZA) from 2025 to 2026

Director Qualifications:

Ms. Frizzley brings to our Board extensive corporate experience with complex corporate governance, strategic transactions, and business transformations.

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Professional Experience:

From 2010 to 2011, Ms. Beach Lin served as President and Chief Executive Officer of Calisolar, Inc., a manufacturer of solar silicon and multicrystalline solar cells. Prior to joining Calisolar, she was Executive Vice President, then Corporate Executive Vice President, at Celanese Corporation, a global technology and specialty materials company, from 2007 to 2010. Ms. Beach Lin joined Avery Dennison Corporation, a global leader in pressure-sensitive adhesives technology as Group Vice President from 2005 to 2007. Prior to joining Avery Dennison, from 2002 to 2005 she was President, Alcoa Closure Systems International, a division of Alcoa Incorporated, a global aluminum leader. From 1994 to 2001, Ms. Beach Lin held various executive positions at Honeywell International.

Education:

Ms. Beach Lin graduated with a BBA in General Management from the University of Toledo and has an MBA in Marketing and Policy and Control from the University of Michigan.

Other Public Company Directorships:

Current Directorships—

American Electric Power (NYSE: AEP) since 2012
Avient Corp. (NYSE: AVNT) since 2013

Past Directorships—

None.

Director Qualifications:

Ms. Beach Lin brings to our Board her experience as a chief executive officer and extensive experience in the global specialty chemicals industry.

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Professional Experience:

From 2016 to 2018, Mr. Steinmetz served as Chief Executive Officer of the Ceramtec Group, a global supplier of advanced ceramics. From 2009 to 2016, Mr. Steinmetz was Executive Director and Chief Executive Officer of Ruetgers N.V., Europe’s leading manufacturer of chemical raw materials made from coal tar. Prior to joining Ruetgers, Mr. Steinmetz was President of Sulzer Metco, a worldwide technology leader in coating materials, from 2004 to 2008, and was an Executive Vice President at Great Lakes Chemical Corporation from 2000 to 2004. Mr. Steinmetz currently serves as the Chairman of Benteler International AG and as Chairman of Fertiberia Sarl.

Education:

Mr. Steinmetz graduated with a M.S. in metallurgy from the Technical University Clausthal, Germany and has an MBA from INSEAD Fontainebleau, France.

Other Public Company Directorships:

None.

Director Qualifications:

Mr. Steinmetz brings to our Board significant global chief executive officer experience and decades of chemical industry experience.

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COPORATE GOVERNANCE

Corporate Governance

Board Nominees. Under its charter, our nominating and corporate governance committee is responsible for recommending to the Board candidates to stand for election to the Board at the Company’s annual general meeting of shareholders and for recommending candidates to fill vacancies on the Board that may occur between annual general meetings. It is the policy of the Board that directors should possess the highest personal and professional ethics, integrity and values. Board members are expected to become and remain informed about the Company, its business and its industry and rigorously prepare for, attend and participate in all Board and applicable committee meetings. The committee evaluates each individual in the context of the Board as a whole, with the objective of recommending a group that can best perpetuate the success of our business and represent shareholders’ interests through the exercise of sound judgment using its diversity of experience. In addition, the Board considers, in light of our business and Board composition, each director nominee’s experience, qualifications, attributes and skills that are identified in the biographical information described in Proposal 1.

Recommendation of Board Candidates. The nominating and corporate governance committee considers properly submitted recommendations for candidates to the Board from shareholders. Any shareholder recommendations for consideration by the Board should include the candidate’s name, biographical information, information regarding any relationships between the candidate and the shareholder within the last three years, a statement of recommendation of the candidate from the shareholder, a description of our shares beneficially owned by the shareholder, a description of all arrangements between the candidate and the recommending shareholder and any other person pursuant to which the candidate is being recommended, a written indication of the candidate’s willingness to serve on the Board, any other information required to be provided under securities laws and regulations, and a written indication to provide such other information as the Board may reasonably request. Recommendations should be sent to Angelo Chaclas, Corporate Secretary, Trinseo PLC, 440 East Swedesford Road, Suite 301, Wayne, PA 19087. The Board evaluates candidates for the position of director recommended by shareholders or others in the same manner as candidates from other sources. The Board will determine whether to interview any candidates and may seek additional information about candidates from third-party sources. As part of its ongoing succession planning, the Company seeks to identify potential Board nominees on behalf of the Board that meet the Board’s requirements with respect to diversity, experience, skill, and qualifications.

Shareholder Board Nominees. Shareholders who wish to nominate one or more persons for election as a director of the Company at an annual general meeting of shareholders, and who wish the nomination to be included in the proxy materials for that meeting pursuant to Rule 14a-8 under the Securities Exchange Act of 1934, must follow the requirements set forth in this proxy statement under “Shareholder Proposals & Director Nominations.” Shareholder director nominations must comply with the deadlines and other requirements in Article 101 of our Constitution, including the applicable notice, information and consent provisions.

Board Independence. Our Corporate Governance Guidelines provide that our Board shall consist of such number of directors who are independent as is required and determined in accordance with applicable laws and regulations and requirements of the NYSE. The Board evaluates any relationships of each director and nominee with Trinseo and makes an affirmative determination whether or not such director or nominee is independent. Under our Corporate Governance Guidelines, an “independent” director is one who meets the qualification requirements for being an independent director under applicable laws and the corporate governance listing standards of the NYSE. Our Board reviews any transactions and relationships between each director or any member of his or her immediate family and Trinseo. The purpose of this review is to determine whether there were any such relationships or transactions and, if so, whether they were inconsistent with a determination that the director was independent. The Company maintains a related party transactions policy and conflict of interest policy, as discussed below under “Related Party Transactions.” As a result of its review, our Board has affirmatively determined that all of our current directors and nominees, except for our CEO and President, Frank Bozich, are independent under the governance and listing standards of the NYSE.

Board Nominee Experience and Expertise. We believe that our director nominees should have a background in the chemicals, manufacturing or similar industry experience, or possess the appropriate management or governance experience and financial acumen to provide our Board with a broad range of talents, skills, character, expertise, professional experiences and backgrounds.

Risk Oversight. Risk is inherent in every material business activity that we undertake. Our business exposes us to strategic, credit, market, compliance, operational and reputational risks. To support our corporate goals and objectives, risk appetite, and business and risk strategies, we maintain a governance structure that delineates the responsibilities for risk management activities, and the governance and oversight of those activities, between management and our Board. The Board is committed to strong, independent oversight of management and risk through a governance structure that includes other Board committees. Under our structure, it is management’s responsibility to manage risk and bring to the Board’s attention risks that are material to Trinseo. The Board has oversight responsibility for the systems established to report and monitor the most significant risks applicable to Trinseo. The Board administers its risk oversight role directly and through its committee structure and the committees’ regular reports to the Board at Board meetings. The Board divides

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its risk oversight responsibilities between itself and its committees by having each review or assess key issues or areas of responsibility as follows:

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Board Leadership Structure. Under our Corporate Governance Guidelines, our Board may select a Board Chair at any time, who may also be an executive officer of the Company. The Board has chosen to separate the roles of Board Chair and Chief Executive Officer, which the Board believes is currently in the best interest of Trinseo and its shareholders. This structure permits our Chief Executive Officer to devote his attention to leading Trinseo and to executing on our business strategy.

Ms. Johnson is our current non-executive Board Chair and has served as a director since 2017. Ms. Johnson brings significant experience as Chair, including, but not limited to: (i) entrepreneurial and senior public company experience; (ii) expertise in environmental and corporate governance issues; and (iii) strategic transformation experience. Ms. Johnson has significant experience in the specialty chemical industry and as a public company director. As described above, the Board has determined that Ms. Johnson meets the definition of an independent director under NYSE listing standards.

Board Attendance. We expect our Board members to prepare for, attend, and participate in all Board and applicable committee meetings. Our Board held five meetings in 2025. The audit, compensation and talent development, and nominating and corporate governance committees held eight, six and six meetings in 2025, respectively. Our Board members attended 100% of our board and committee meetings in 2025.

We do not have a policy for the attendance of our directors at our annual general meeting of shareholders. In 2025, nine directors and no shareholders attended our annual general meeting. Eligible shareholders were permitted to attend in person by registering on our voting website. Notwithstanding any extenuating circumstances which would impact the safety of attendees, this year’s Annual Meeting will be held in person, using the same registration method for shareholders who wish to attend. There will not be a teleconference or video conference option.

Executive Sessions. Our Corporate Governance Guidelines provide that the non-management directors of the Board meet in executive session at least once during each regularly scheduled Board meeting to review matters concerning the relationship of the Board with executive directors and other members of senior management, and such other matters as it deems appropriate. Additionally, the Board is required to have least one executive session annually of its independent directors. Ms. Johnson acts as the chair of these executive sessions.

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COPORATE GOVERNANCE

Board Annual Performance Reviews. Pursuant to our Corporate Governance Guidelines the Board annually conducts a self-evaluation of the Board as a whole. In accordance with the written charters of our audit, compensation and talent development, and nominating and corporate governance committees, each committee also evaluates its performance on an annual basis and reports its findings to the Board.

Code of Business Conduct. We have adopted a written Code of Business Conduct applicable to all directors, officers and employees and a written Code of Ethics for Senior Financial Employees, applicable to our Chief Executive Officer, Chief Financial Officer, Treasurer, Principal Accounting Officer, Controller, and all employees performing similar functions. These policies are designed to maintain the integrity of our business and financial reporting. These codes cover, among other things, professional conduct, conflicts of interest, accurate recordkeeping and reporting, public communications and the protection of confidential information, as well as adherence to laws and regulations applicable to the conduct of our business. Copies of these codes can be found under the “Governance” tab on the Investor Relations section of our website, investor.trinseo.com by selecting the “Ethics and Compliance” link and then “supporting policies.”

Corporate Governance Guidelines. We have adopted Corporate Governance Guidelines that outline the Board’s governance policies and practices. The current version of our Corporate Governance Guidelines can be found under the “Governance” tab on the Investor Relations section of our website, investor.trinseo.com by selecting the “Ethics and Compliance” link and then “supporting policies.”

Communications with Directors. Shareholders and other interested parties may communicate directly with the Board, the non-management directors or the independent directors as a group, or specified individual directors, by writing to such individual or group c/o Corporate Secretary, Trinseo PLC, 440 East Swedesford Road, Suite 301, Wayne, PA 19087. The Corporate Secretary will forward such communications to the relevant group or individual at or prior to the next meeting of the Board. The Board has instructed our Corporate Secretary to review the correspondence prior to forwarding it and use discretion to not forward certain items deemed to be of a commercial or frivolous nature or otherwise inappropriate for the Board’s consideration. In these cases, the Corporate Secretary may forward some of the correspondence elsewhere in the Company for review and possible response.

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BOARD STRUCTURE AND COMMITTEE COMPOSITION

Board Structure and Committee Composition

We have a standing audit committee, compensation and talent development committee, nominating and corporate governance committee, and an environmental, health, safety, sustainability and public policy committee with the composition and responsibilities described below. Each committee operates under a charter that has been approved by our Board. A copy of each charter can be found on the Investor Relations section of our website, investor.trinseo.com, under “Governance,” “Committee Composition.” Chairs and members of each committee are appointed by the Board, and each member serves until his or her successor is elected and qualified, unless he or she is earlier removed or resigns. The nominating and corporate governance committee will recommend adjustments to committee assignments to the Board as it deems necessary during the year. In addition, from time to time, special committees may be established under the direction of the Board when necessary to address specific issues.

The table below provides information about the membership of our standing audit, compensation and talent development, nominating and corporate governance, and environmental, health, safety, sustainability and public policy committees during fiscal 2025:

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Audit Committee

The purpose of the audit committee is set forth in the audit committee charter. The audit committee’s primary duties and responsibilities are to:

A copy of the charter, which satisfies the applicable standards of the SEC and the NYSE is available on our website. The audit committee currently consists of Jeffrey J. Cote, Jeanmarie Desmond, Matthew Farrell and Henri Steinmetz. Our Board has determined that Ms. Desmond and each of Messrs. Cote, Farrell and Steinmetz are independent directors pursuant to Rule 10A-3(b)(1) under the

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BOARD STRUCTURE AND COMMITTEE COMPOSITION

Securities Exchange Act of 1934, as amended (the “Exchange Act”), and Section 303A.02 of the New York Stock Exchange Listed Company Manual. Ms. Desmond and each of Messrs. Cote and Farrell is also an “audit committee financial expert” within the meaning of Item 407(d)(5) of Regulation S-K. Ms. Desmond serves as chair of the audit committee.

Compensation and Talent Development Committee

The purpose of the compensation and talent development committee (the “compensation committee”) is to assist the Board in fulfilling its responsibilities relating to oversight of the compensation of our directors, executive officers and other employees and the administration of our benefits programs and equity-based compensation programs, including grants of equity and long term incentive awards. The compensation committee reviews and recommends to our Board compensation plans, policies and programs and approves specific compensation levels for all executive officers, and is responsible for oversight of executive leadership team succession planning. The compensation committee currently consists of Joseph Alvarado, Victoria Brifo, Matthew Farrell and K’Lynne Johnson. Mr. Alvarado serves as chair of the compensation committee. A copy of the compensation committee’s charter, which satisfies the applicable standards of the SEC and the NYSE, is available on our website. The compensation committee may delegate any of its responsibilities to subcommittees.

Nominating and Corporate Governance Committee

The purpose of the nominating and corporate governance committee is to (i) identify, screen and review individuals qualified to serve as directors (consistent with criteria approved by our Board) and recommend to our Board candidates for nomination for election at our annual meeting of shareholders or to fill Board vacancies or newly created directorships; (ii) develop and recommend to our Board and oversee the implementation of our corporate governance guidelines; (iii) oversee evaluations of our Board and (iv) recommend to our Board appointment of candidates for service as Board committee chair or member. The committee also reviews the outcome of shareholder engagement. The nominating and corporate governance committee currently consists of Joseph Alvarado, Jeffrey Cote, Jeanmarie Desmond, K’Lynne Johnson and Sandra Beach Lin. Mr. Cote serves as chair of the nominating and corporate governance committee. Our Board has adopted a written charter under which the nominating and corporate governance committee operates, which is available on our website. The nominating and governance committee may delegate any of its responsibilities to subcommittees.

Environmental, Health, Safety, Sustainability and Public Policy Committee

The Environmental, Health, Safety, Sustainability and Public Policy Committee (the “EHSS&PP committee”) was established for the purpose of assisting the Board in fulfilling its oversight responsibilities by assessing the effectiveness of programs and initiatives that support the environment, health and safety, sustainability, corporate social responsibility and climate change (“Sustainability”) policies and programs of the Company. Its duties and responsibilities are to:

The EHSS&PP committee currently consists of Frank A. Bozich, Victoria Brifo, Sandra Beach Lin and Henri Steinmetz. Ms. Beach Lin serves as chair of the EHSS&PP committee. A copy of its charter is available on the Company’s website. The EHSS&PP committee may delegate any of its responsibilities to subcommittees.

Compensation Committee Interlocks and Insider Participation

None of our executive officers serves as a member of the Board or the compensation committee of any other company that has any executive officers serving as a member of our Board or compensation committee.

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EXECUTIVE OFFICERS

Our Company’s Executive Officers

Biographical information concerning our President and Chief Executive Officer, Frank A. Bozich, who is a nominee to our Board, is set forth above under Proposal 1.

David Stasse, Executive Vice President and Chief Financial Officer. Mr. Stasse, age 56, has served as the Company’s Executive Vice President and Chief Financial Officer since July 2019. Mr. Stasse joined the Company in July 2013 as Vice President and Treasurer with responsibility for all treasury matters, including cash management, risk management, relationships with rating agencies and commercial banks, and financing matters. During his tenure he added responsibility for Investor Relations and Corporate Finance for the Company. Prior to joining Trinseo, Mr. Stasse was employed by Freescale Semiconductor, Inc., a global semiconductor manufacturer that served the automotive, networking, consumer and industrial markets, where he served as Vice President and Treasurer from 2008 to 2013. Mr. Stasse holds an MBA in Finance from the University of Maryland and a Bachelor of Science degree in Business Logistics from Penn State University.

Angelo N. Chaclas, Senior Vice President, Chief Legal Officer, Chief Compliance Officer and Corporate Secretary. Mr. Chaclas, age 63, has been the Company’s Chief Legal Officer, Senior Vice President, and Corporate Secretary since January 2015. Mr. Chaclas also became the Chief Compliance Officer in June 2018. In his role, he provides legal support for all capital markets, transactional, compliance, commercial, litigation, regulatory, governance, intellectual property and other operational activities of the Company worldwide. Mr. Chaclas joined the Company in 2010 as Associate General Counsel and Chief Intellectual Property Counsel, where he managed the Company’s global intellectual property portfolio and managed the legal activities of several of the Company’s commercial businesses and corporate functions. Mr. Chaclas holds a bachelor’s degree in Mechanical Engineering from Tufts University and a Juris Doctorate from Pace University.

Paula Cooney, Senior Vice President and Chief Human Resources Officer. Ms. Cooney, age 58, joined the Company as Senior Vice President, Human Resources in November 2021. Prior to joining Trinseo, Ms. Cooney was Senior Vice President and CHRO for FLIR Systems, Inc. where she provided strategic direction as the company’s human resources leader. Before FLIR Systems, Inc., Ms. Cooney served as Vice President, Human Resources and Communications for H.B. Fuller Company, where she worked for 10 years and held multiple roles in HR leadership. Prior to joining H.B. Fuller in 2010, Ms. Cooney enjoyed a nearly 15-year career at Intel Corporation, holding HR roles of increasing responsibility. Ms. Cooney holds an NCEA diploma in personnel management from the National College of Ireland, and a Master pf Business Studies in human resources and industrial relations from University College Dublin (Smurfit School of Business).

Roger Greene, Vice President, Controller and Principal Accounting Officer. Mr. Greene, age 50, joined the Company in September 2023. Mr. Greene served as Vice President, Chief Audit Executive of Corteva Agriscience leading the internal audit function. Mr. Greene also served as Global Business Controller for the Agriculture Division of DuPont from 2016 to 2019, and held leadership roles in DuPont’s corporate accounting and controllership groups. Before joining DuPont, Mr. Greene worked at PricewaterhouseCoopers in its Assurance practice. Mr. Greene holds a bachelor’s degree in accounting from Pennsylvania State University and is a Certified Public Accountant.

Han Hendriks, Senior Vice President, Chief Technology and Sustainability Officer. Mr. Hendriks, age 60, joined Trinseo in October 2022 as SVP and Chief Technology Officer. In October 2024, Mr. Hendriks was also named Chief Sustainability Officer. Prior to joining Trinseo, Mr. Hendriks was Chief Technology Officer at Yanfeng, one of the world’s leading automotive suppliers, headquartered in Shanghai. Mr. Hendriks was responsible for the company’s technology and “smart cabin” vision and strategy, as well as portfolio management, and led the design and development of new products from research to market launch. Prior to Yanfeng, Mr. Hendriks worked for Johnson Controls, holding multiple roles of increasing responsibility. Mr. Hendriks holds a Bachelor of Fine Arts in Architectural Design from the Academy of Fine Arts in Maastricht and an MBA from the University of Westminster, London, and he successfully completed a post-graduate Industrial Design program at the Università Internazionale Dell ‘Arte in Florence.

Francesca Reverberi, Senior Vice President, Engineered Materials and Polymer Solutions. Ms. Reverberi, age 54, was named Senior Vice President, Engineered Materials and Polymer Solutions in October 2024. Ms. Reverberi has led the Company’s Engineered Materials segment since August 2023 and previously served as Chief Sustainability Officer from September 2021 to October 2024. Ms. Reverberi also previously served as Senior Vice President, Engineered Materials & Synthetic Rubber, and as Global Business Director of Performance Plastics, Business Director of Basic Plastics. Prior to that, Ms. Reverberi served as Global Business Director for Synthetic Rubber. Ms. Reverberi joined Trinseo in June 2011 following the Company’s carve-out from The Dow Chemical Company. During her time at Dow, Ms. Reverberi served as Product Director for Emulsion Polymers, Europe and the Americas, as well as Commercial Manager in Dow Hydrocarbons Aromatics and Derivatives in Europe, including responsibilities for the C4’s business and held several positions in other specialty businesses such as Water Solutions and Chelants. Ms. Reverberi also serves a member of the board of directors of Avery-Dennison Corporation. Ms. Reverberi holds a Bachelor and Master of Science in Chemical Engineering from Politecnico di Milano and a Master of Business Administration from SDA Bocconi.

Rainer Schewe, Senior Vice President—Supply Chain & Manufacturing Services. Mr. Schewe, age 63, joined the Company in April 2020 as Vice President—Supply Chain Services, and assumed responsibility for Manufacturing Services in March 2024. Prior to joining Trinseo, Mr. Schewe served as Executive Vice President and Chief Supply Chain Officer for A. Schulman, Inc. (now LyondellBasell Industries). Prior to this role, he served as Vice President and Business Unit Director for Schulman’s Custom Performance Colors business in EMEA. Mr. Schewe holds a degree as a State-Certified Engineer in Chemical Engineering from Fresenius Akademie Wiesbaden in Germany, and an Apprenticeship as a Chemical Laboratory Technician from RWTH Aachen in Germany.

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EXECUTIVE OFFICERS

Bregje Roseboom-Van Kessel, Senior Vice President, Corporate Finance & Investor Relations. Ms. van Kessel, age 50, was appointed Senior Vice President, Corporate Finance and Investor Relations in October 2024. Ms. van Kessel previously served as Senior Vice President, Base Plastics from November 2022 to October 2024 and also led Trinseo’s Polystyrene & Feedstocks business from August 2023 to October 2024. Ms. van Kessel joined Trinseo in 2018 and previously served as Senior Director, Global Business Finance, where she led the business finance organization for all of Trinseo’s external reporting segments. Ms. van Kessel brings over 20 years of experience in business finance and change management and has held key financial leadership roles supporting global sales and marketing, supply chain, R&D and brand development for global markets. Ms. van Kessel holds a master’s degree in medicine and an executive MBA in finance and control from Maastricht University. She is a registered controller and a member of the Chartered Institute of Management Accountants.

Arthas Yang, Senior Vice President, Latex Binders. Mr. Yang, age 44, was appointed as Senior Vice President, Latex Binders in March 2024, after having served as the Global Business Director for the CASE business of Latex Binders. Mr. Yang joined Trinseo in June 2010 following the Company’s carve-out from The Dow Chemical Company. During his tenure, Mr. Yang has held multiple key positions within the Company, including Technical Service & Development Leader, Product Manager, Marketing Manager, and Regional Commercial Director, for businesses including Latex Binders, Engineered Materials, and the former synthetic rubber division. Mr. Yang holds a Masters in Materials Science and Bachelor of Physics from Tsinghua University, and a Master of Business Administration from Shanghai Jiao Tong Hong Kong University of Science and Technology.

Executive Officers Skills and Experience

Similar to our Board, the Company believes a broad range of backgrounds and personal experience help the Company operate, strategize and solve problems more effectively. Based on their backgrounds and prior experience, we believe our executive officers bring an array of viewpoints and skills to our leadership team.

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TRANSACTIONS WITH RELATED PERSONS

Transactions with Related Persons

Certain Relationships and Related Transactions

Our audit committee charter requires that the audit committee review and approve all related party transactions. The Company also has a written Related Party Transactions Policy and requires its officers and directors to submit a related party questionnaire annually, and provide updates as needed. When related party transactions between us and our officers, directors and principal shareholders and their affiliates are approved by the audit committee, it does so with the understanding that the terms of such transaction are no less favorable to us than those that we could obtain from unaffiliated third parties.

Our Conflict of Interest Policy is designed to help our directors, executive officers, and employees address situations that may involve a conflict of interest, which may include related party transactions. These include situations in which an individual’s personal interests are in conflict with the interests of the Company; situations in which an individual or family member receives personal benefits as a result of his or her position with the Company; and situations that may otherwise cast doubt on his or her ability to act objectively with or on behalf of the Company. The Company annually surveys our executive officers and directors regarding potential conflicts of interest. If such conflicts are reported or found, the Legal Department and/or our Chief Compliance Officer will seek to mitigate or eliminate such potential or actual conflicts of interest.

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STOCK OWNERSHIP INFORMATION

STOCK OWNERSHIP INFORMATION

The following table sets forth information regarding the beneficial ownership of our ordinary shares, nominal value $0.01, as of June 30, 2026 by:

As of June 30, 2026, we had 36,559,868 ordinary shares outstanding (excluding treasury shares), all of which were held by public investors (including certain of our directors and executive officers), the details of which are reflected in the table below.

Information with respect to beneficial ownership has been furnished by each director, director nominee, executive officer or beneficial owner of more than 5% of our ordinary shares. We have determined beneficial ownership in accordance with SEC rules. These rules generally attribute beneficial ownership of shares to persons who possess sole or shared voting or investment power with respect to such shares. The information does not necessarily indicate beneficial ownership for any other purpose. Under these rules, the number of ordinary shares deemed outstanding includes shares issuable upon exercise of options held by the respective person or group which may be exercised within 60 days after June 30, 2026. These shares are deemed to be outstanding and beneficially owned by the person holding those options for the purpose of computing the percentage ownership of that person or entity, but they are not treated as outstanding for the purpose of computing the percentage ownership of any other person or entity.

The inclusion in the following table does not constitute an admission that the named shareholder is a direct or indirect beneficial owner. Unless otherwise indicated and subject to applicable community property laws, to our knowledge, each shareholder named in the following table possesses sole voting and investment power over the shares listed, except for those jointly owned with that person’s spouse.

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SECURITIES AUTHORIZED FOR ISSUANCE UNDER EQUITY COMPENSATION PLANS / DELINQUENT SECTION 16(A) REPORTS

Securities Authorized for Issuance under Equity Compensation Plans

The following table sets forth certain information as of December 31, 2025 with respect to compensation plans under which ordinary shares of the Company may be issued.

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Delinquent Section 16(a) Reports

Section 16(a) of the Securities Exchange Act of 1934, as amended, requires our directors and executive officers, among others, to file with the SEC an initial report of ownership of our shares on a Form 3 and reports of changes in ownership on a Form 4 or a Form 5. Persons subject to Section 16 are required by SEC regulations to furnish us with copies of all Section 16(a) forms that they file. Under SEC rules, certain forms of indirect ownership and ownership of company stock by certain family members are covered by these reporting requirements. When requested, we assist our executive officers and directors in preparing initial ownership reports and reporting ownership changes and will file these reports on their behalf. Based solely on a review of the copies of such forms in our possession, and on written representations from our current directors and executive officers, we believe that all of our executive officers and directors filed the required reports on a timely basis under Section 16(a) during 2025, with the exception of a Form 4 amendment filed on June 27, 2025 by Jeffrey J. Cote to correct the number of shares indirectly held previously reported on June 24, 2025.

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PROPOSAL 2

Proposal 2—Advisory Vote on Named Executive Officer Compensation

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COMPENSATION DISCUSSION AND ANALYSIS

Compensation Discussion and Analysis

This compensation discussion and analysis (CD&A) section is intended to provide information about our 2025 compensation objectives and programs for our named executive officers, listed below (together, our “NEOs”).

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Compensation Philosophy and Design

Overview

Our executive compensation policies and programs are designed to attract, retain and motivate key executives through competitive and cost-effective programs that reinforce executive accountability and reward the achievement of business and individual results. Executive compensation consists of four main elements: (1) base salary, (2) annual cash incentive awards, (3) long-term incentive compensation, and (4) retirement savings and benefit programs. The relative weighting of each element is aligned with our philosophy of linking pay to performance. A substantial percentage of our executives’ compensation is provided in the form of performance-based variable compensation with a greater emphasis on variable components for our senior executives. Annual cash awards are directly linked to corporate results and short-term performance measures, including financial and non-financial goals. Our long-term equity incentive and cash incentive awards align our executives’ interests with those of our shareholders and our long-term business objectives. Executive retirement and benefits programs are generally consistent with the broader employee programs offered in the country where an executive primarily provides services to the Company. We provide limited perquisites to our executives, and such perquisites are only provided to the extent that they reflect particular business needs and objectives.

We strive to provide our NEOs with a compensation package that is market competitive within our industry, recognizes and rewards superior individual and Company performance, and seeks to achieve greater talent retention.

Compensation Mix

The target mix of compensation in 2025 was a mix of salary and short- and long-term incentive compensation, with long-term incentive compensation remaining the largest component of our NEOs’ overall compensation package. We believe this incentivizes long-term value creation and provides continued alignment between the interests of our NEOs and shareholders.

Maintaining Best Practices Regarding Executive Compensation

Our compensation committee intends to compensate our NEOs in a manner that is consistent with the objectives and design principles outlined above. We have adopted the following compensation practices, which are intended to promote strong corporate governance and alignment with shareholder’s interests:

Compensation and Talent Development Committee Practices

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How We Make Compensation Decisions

Our compensation committee is responsible for, among other matters: (1) reviewing key executive compensation goals, policies, plans and programs; (2) reviewing the compensation of our executive officers; (3) reviewing and approving employment agreements and other similar arrangements between the Company and our executive officers; and (4) administering our equity-based plans and other incentive compensation plans.

Our Chief Executive Officer reviews annually each NEO’s performance (other than his own) and recommends to the compensation committee appropriate base salary, annual cash incentive awards and long-term equity incentive awards (to the extent applicable with respect to a particular year) for these NEOs. Based upon the recommendations of our Chief Executive Officer, and after considering the objectives of our executive compensation program, as described above, as well as the factors described below under “Use of Benchmarking Comparison Data,” the compensation committee approved the annual compensation packages of our executive officers. In 2025, the compensation committee also approved Mr. Bozich’s compensation, including his base salary, annual cash incentive award and long-term equity and cash incentive awards. See “—Narrative Disclosure to Summary Compensation Table and Grants of Plan Based Awards Table; Other Narrative Disclosure” for a description of each NEO’s employment agreement terms.

In making decisions with respect to any element of an NEO’s compensation, the compensation committee considered the total compensation that may be awarded to the executive, including salary, annual cash incentive awards and long-term incentive compensation. In addition, in reviewing and approving employment agreements for our NEOs, the compensation committee considered the other benefits to which the officer is entitled by the agreement, including compensation payable upon termination of the executive’s employment under a variety of circumstances. Our goal is to award compensation that is competitive to attract and retain highly qualified leaders and that motivates them to drive strong business performance. We believe that our compensation programs align executive and shareholder interests, while allowing compensation to vary based on each executive’s individual contributions to the Company and to the Company’s overall performance.

Use of Independent Compensation Consultant

The compensation committee has retained Willis Towers Watson as its independent compensation consultant. Willis Towers Watson provides the compensation committee with advice on a broad range of executive compensation matters. The scope of their services includes, but is not limited to, the following:

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During fiscal 2025, Willis Towers Watson attended all of the regularly scheduled meetings of the compensation committee.

The compensation committee considered the range of services provided by Willis Towers Watson in its decision to approve its fees and selection as its independent compensation consultant in 2025. The compensation committee assessed the independence of Willis Towers Watson pursuant to applicable SEC rules and concluded that no conflict of interest exists that would prevent Willis Towers Watson from independently representing the compensation committee.

Use of Benchmarking Comparison Data

The compensation committee selects a peer group of companies, with assistance from Willis Towers Watson, for use in making compensation decisions with respect to the total mix and amount of compensation. This peer group consists of companies in the chemicals manufacturing and similar industries. The compensation committee reviewed various market-based metrics of the peer group that it deemed appropriate, which included enterprise value, revenue, market capitalization, and EBITDA margins, to establish compensation benchmarks. For 2025, the compensation committee added Koppers Holdings and removed Westlake to better align the peer list with companies of similar revenue size as Trinseo. The compensation committee may annually review the companies included in our peer group and may add or eliminate companies as it determines is appropriate. The peer group selected for fiscal 2025 compensation decisions consisted of the following 23 companies:

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During fiscal 2025, the compensation committee of the Board reviewed our executive compensation peer group and concluded our peer group adequately aligned our executive officers’ pay opportunities with our compensation philosophy.

Shareholder Approval of Executive Compensation

In 2025, the compensation of our NEOs was approved by shareholders with approximately 96% of votes cast in favor. Based on this shareholder support of our executive compensation program, we and the compensation committee believe our compensation program and practices are well aligned with our shareholders’ wishes. We believe the continued strong shareholder support of our say-on-pay proposals indicates our practices accurately represent the desires of our shareholders.

2025 Compensation Structure & Performance

The principal components of our executive compensation program include both short-term and long-term compensation. Short-term compensation consists of an executive’s annual base salary and annual cash incentive award. Long-term compensation generally includes grants of share-based incentives as determined by the compensation committee. Certain elements of compensation of our NEOs were determined through direct negotiation with the executives at the time of their hiring.

Base Salary

Setting appropriate levels of base pay allows us to attract and retain an executive leadership team that will continue to meet our commitments to customers, sustain profitable growth and create value for our shareholders. The base salaries for our NEOs are determined based on the scope of their responsibilities and our compensation committee members’ collective knowledge of competitive compensation levels, following its review of competitive market data from Willis Towers Watson based on our peer group and survey data. Base salaries are reviewed annually by the compensation committee and adjusted from time to time to reflect individual responsibilities, performance and experience, as well as market compensation levels. In 2025, executive leadership was not eligible for merit increase due to the at market pay position and performance of the company.

Annual Cash Incentive Plan

Our annual cash incentive plan (“ACI Plan”) is designed to create a pay for performance culture by aligning the compensation program to the achievement of our strategic and business objectives and with shareholder interests. Our business objectives are to: (1) generate strong Adjusted EBITDA and free cash flow results relative to our industry; (2) provide a safe working environment by meeting or exceeding our metrics for injuries, spills, and process safety incidents, and demonstrating progress on Sustainability goals; (3) implement Trinseo’s strategy to transform into a specialty materials and sustainable solutions provider; (4) promote Company culture, talent development, recruitment and retention. The actual amount that will be paid in respect of an ACI Plan award is based on a combination

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of the achievement of Company performance goals as well as individual performance. The performance goals and metrics are reviewed and approved by the compensation committee at the beginning of the year. At the end of the year, the amount paid to each NEO is based on the achievement of the Company performance goals and an assessment of the executive’s overall performance.

For 2025, the ACI Plan was designed to align our executives’ compensation with the Company’s business plan and priorities for the year, and reward performance based on the following components:

Financial Performance. We believe that Adjusted EBITDA is a key measure of our financial performance, removing the impacts of our capital structure (such as interest expense), asset base (such as depreciation and amortization) and tax structure as well as other non-recurring items. We define Adjusted EBITDA, which is considered a non-GAAP measure, as net income (loss) from continuing operations before interest expense, net provision for income taxes; depreciation and amortization expense; loss on extinguishment of long-term debt; asset impairment charges; gains or losses on the disposition of businesses and assets, restructuring charges; acquisition related costs and benefits, and other items. Our ACI Plan Adjusted EBITDA performance metric for the ACI Plan awards was set consistent to our 2025 business plan that was approved by the Board (the “2025 Plan”), but is adjusted to exclude results from the Company’s Americas Styrenics segment and the impacts of raw material timing. As in prior years, we exclude the earnings of our Americas Styrenics segment because as a joint venture the Company does not have direct control of its day-to-day operations. Additionally, we also exclude the impacts of raw material timing because timing impacts are generally outside of our executives’ control but can have a significant positive or negative impact on the Company’s financial performance.

Free Cash Flow is also an important measure of our Company’s financial performance. We define Free Cash Flow, which is a non-GAAP measure, as cash provided by operating activities less capital expenditures. Our free cash flow performance metric for the ACI Plan (the “ACI Plan Free Cash Flow”) was set in accordance with expectations under the 2025 Plan, and uses our reported Free Cash Flow as adjusted to exclude the impact of certain items, including certain delayed vendor payments, accounts receivable discounting, and PIK interest deferrals. We exclude these items because we believe this eliminates management actions which could artificially influence the ACI Plan Free Cash Flow calculation.

See “Item 7 — Management’s Discussion and Analysis of Financial Condition and Results of Operations—Non-GAAP Performance Measures” and “Item 7 — Management’s Discussion and Analysis of Financial Condition and Results of Operations—Cash Flows—Free Cash Flow” of this Annual Report on Form 10 K for more information on our approach to calculating Adjusted EBITDA and Free Cash Flow. See Pay Versus Performance—Use of Non-GAAP Measures for a reconciliation of Adjusted EBITDA and Free Cash Flow, which are non-GAAP measures, to Net Income (Loss) and Cash provided by operating activities.

Responsible Care. Industry-leading environmental, health and safety metrics, are important measures for establishing performance objectives and measuring the performance of our NEOs. We are a Responsible Care® company and our environmental, health and safety policy states that protecting people and the environment is part of everything we do and every decision we make. The 2025 ACI Plan includes three environmental, health and safety metrics that we track for our Company – (i) Total Recordable Incident Rate, a metric used in the chemicals industry to measure injury rates versus operating hours, (ii) Spills, defined as loss of containment of any physical device used to contain a chemical or plastic resin as part of our manufacturing processes, and (iii) Process Safety Incidents as defined by the American Chemistry Council. Incentive payouts with respect to these metrics are determined based on our achievement rating for Responsible Care® performance and in accordance with the threshold, target and maximum levels set forth in the table below.

Individual Goals. In addition, each NEO had individual performance goals that included, depending on the NEO: corporate Adjusted EBITDA; Free Cash Flow; capital spending; margins and profitability; cost savings and cash preservation; corporate finance restructuring; sustainable solutions; human capital management; and workplace safety. The results achieved against each of these individual goals were assessed by the CEO or the compensation committee and a percentage rating was assigned to each NEO.

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COMPENSATION DISCUSSION AND ANALYSIS

The table below shows the weight and targets of the component metrics, along with the payout opportunity for the ACI Plan.

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ACI Plan Adjusted EBITDA

Based on our 2025 audited financial results, our compensation committee determined that our financial performance component resulted in a payout of 0% of the ACI Plan Adjusted EBITDA component, as set forth in the table below. All payout values in this table are shown as a percentage of Target performance.

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The ACI Plan Adjusted EBITDA represents the Company’s reported Adjusted EBITDA excluding $6 million, $(10) million and $(3) million in earnings/losses from our joint ventures, in the first half, second half and full year, respectively, and the $(2) million, $(21) million and $(23) million impact of raw material timing, respectively.

ACI Plan Free Cash Flow

The ACI Plan Free Cash Flow represents our reported Free Cash Flow of ($153) million which resulted in payout of 0% of target.

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Responsible Care Metrics

All payout values for the Responsible Care® portion of the bonus in this table are shown as a percentage of the Target performance payout. Our achievement rating for the Responsible Care® portion of the bonus qualified plan participants for 24.5% of the Responsible Care® component of the ACI Plan, as set forth below. All payout values in this table are shown as a percentage of the Target performance payout.

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COMPENSATION DISCUSSION AND ANALYSIS

The table below shows the contribution of each performance metric under our ACI Plan to the actual bonus award earned by our NEOs. All values in this table are shown as a percentage of the Target performance payout.

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Long-Term Equity Incentive Compensation

Our compensation committee approved long-term incentive awards to certain key employees, not including the NEOs, which were awarded in February 2025 under the Company’s Amended & Restated 2014 Omnibus Incentive Plan (the “Equity Plan”). In 2025 these awards consisted of long-term equity and cash awards Mr. Bozich received a long-term incentive award comprised of three types of awards:  RSUs (30%), PSUs (40%) and restricted cash units (“RCUs”) (30%). Mr. Stasse, Mr. Chaclas, Ms. van Kessel and Ms. Reverberi received a long-term incentive award comprised of three types of awards: RSUs (50%), PSUs (20%) and RCUs (30%). The total award for each NEO is based on a target percentage of their base salary, as shown in the table below. These awards are subject to time-based vesting conditions, with RSUs and RCUs vesting in three equal annual installments beginning on the first anniversary of the date of grant and PSUs partially vesting on each of the first, second and third year anniversary of the date of grant, subject to the Company’s relative total shareholder return (“TSR”) performance. In each case, vesting is generally subject to the NEO’s continuous employment with us on the applicable vesting date. The size of all RSU, PSU and RCU awards was determined by dividing a target grant value by the 30 day average closing price of the Company’s shares on the grant date, which does not correspond with the grant date fair value of these awards. For disclosure of the grant date fair value of the awards, See the “Summary Compensation Table” and “Grants of Plan-Based Awards Table” below.

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Performance-Vested Restricted Stock Units

The Board grants PSUs as part of each NEO’s target equity compensation package to increase the percentage of at-risk, long-term incentive-based compensation. We believe the use of PSUs, as part of an overall equity compensation package, provides alignment between our executive compensation program and the creation of shareholder value through the Company’s long-term strategic initiatives. In addition, our Board considers the stock options to be performance-based because a stock option will only have value to the extent that our share price increases after the date the stock option is granted.

PSUs granted in 2025 vest over four performance periods, consisting of three one-year performance periods and one three-year performance period, which are each measured independently. Subject to the executive’s continued employment over the full three-year performance period, vesting is calculated during each performance period based on the Company’s relative TSR performance, assuming the reinvestment of dividends, against the performance of all chemical and basic materials companies in the S&P 600 Small Cap Index (the “Performance Peer Group”) during the fiscal year. PSUs which vest during each performance period will be delivered, in aggregate, following the third anniversary of the grant date (the “final vesting date”).

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Table of Contents

COMPENSATION DISCUSSION AND ANALYSIS

The number of 2025 PSUs that will vest during each performance period, based on the achievement of relative TSR performance goals, will be as follows: