Exhibit 4.2


 


TRINSEO PLC





AMENDED AND RESTATED





2014 OMNIBUS INCENTIVE PLAN





 


(As Assumed, Amended and Restated





as of October 8, 2021)


 


WHEREAS:


 


A.           On
May 30, 2014, Trinseo S.A., a public limited company (société anonyme) incorporated under the laws of Luxembourg
adopted the Trinseo S.A. 2014 Omnibus Incentive Plan (as so adopted and amended, from time to time, in respect of periods prior to the
Effective Time (as defined below), the “Original Plan”).


 


B.          On
October 8, 2021, the re-domiciliation of Trinseo S.A. from Luxembourg to Ireland pursuant to a merger by acquisition under the European
Communities (Cross-Border Mergers) Regulations 2008 of Ireland (SI 157/2008), as amended, and the Luxembourg law of 10 August 2015,
as amended, was completed (the “Merger”). Pursuant to the Merger: (i) Trinseo PLC, a public limited company incorporated
under the laws of Ireland, by operation of law and universal succession of title, became entitled to the assets of Trinseo S.A. and assumed
the liabilities of Trinseo S.A. from the effective time of the Merger (the “Effective Time”); (ii) ordinary shares
of $0.01 each (nominal value) were allotted and issued by the Trinseo PLC to the shareholders of Trinseo S.A. (other than Trinseo S.A.
as holder of shares in itself), on a one-for-one basis, at the Effective Time as consideration for the transfer of the assets and liabilities
of Trinseo S.A.; and (iii) Trinseo S.A. ceased to exist following completion of the Merger.


 


C.            In
connection with the Merger, among other matters, at the Effective Time, the Original Plan and all awards then outstanding under the Original
Plan were assumed by Trinseo PLC and the Original Plan was amended and restated on the terms set out herein and renamed the Trinseo PLC
Amended And Restated 2014 Omnibus Incentive Plan (the Original Plan as so assumed, amended and restated at the Effective Time and as may,
from time to time, be amended in respect of periods following the Effective Time, the “Plan”).


 


D.           Save
as otherwise expressly provided herein, the Plan shall apply to all awards granted prior to or following the Effective Time.


 


1.            DEFINED
TERMS


 


Exhibit A, which is incorporated by
reference, defines the terms used in the Plan and sets forth certain operational rules related to those terms.


 


2.            PURPOSE


 


The Plan has been established to advance the interests
of the Company by providing for the grant to Participants of Stock-based Awards.


 


3.            ADMINISTRATION


 


The Administrator has discretionary authority,
subject only to the express provisions of the Plan, to interpret the Plan; determine eligibility for and grant Awards; determine, modify
or waive the terms and conditions of any Award; determine the form of settlement of Awards (whether in cash, shares of Stock or other
property); prescribe forms, rules and procedures relating to the Plan; and otherwise do all things necessary or appropriate to carry
out the purposes of the Plan. Determinations of the Administrator made under the Plan will be conclusive and will bind all parties.


 






    


     


    

 


4.             LIMITS
ON AWARDS UNDER THE PLAN


 


(a)           Number
of Shares. The maximum number of shares of Stock that may be delivered in satisfaction of Awards under the Plan is 6,000,000 shares.
Up to the total number of shares available for Awards to employee Participants may be issued in satisfaction of ISOs, but nothing in this
Section 4(a) will be construed as requiring that any, or any fixed number of, ISOs be awarded under the Plan. The limits
set forth in this Section 4(a) shall be construed to comply with Section 422 of the Code. For purposes of this Section 4(a),
the shares of Stock withheld by the Company in payment of the exercise price or purchase price (including any nominal value payable in
respect of an Award provided always that such nominal value must be paid by the Participant or some other person permitted to do so by
Irish law as provided for in Section 6(a)(9)) of the Award, in satisfaction of tax withholding requirements with respect to the Award,
or purchased by the Company using proceeds from Awards are prohibited from being returned back to the Plan’s share reserve for future
issuance. The gross number of SAR awards granted under the Plan, as opposed to the net number of shares actually delivered under the SAR
Award, will be deducted from the number of shares remaining available for issuance pursuant to the Awards granted under the Plan. For
the avoidance of doubt, any shares of Stock underlying Awards settled in cash or that otherwise expire or become unexercisable without
having been exercised or that are forfeited to or repurchased or redeemed by the Company due to the failure to vest may be returned to
the Plan for future issuance. To the extent consistent with the requirements of Section 422 and the regulations thereunder, and with
other applicable legal requirements (including applicable stock exchange requirements), Stock issued under awards of an acquired company
that are converted, replaced or adjusted in connection with the acquisition shall not reduce the number of shares of Stock available for
Awards under the Plan.


 


(b)          Type
of Shares. Stock delivered by the Company under the Plan may be newly issued Stock or treasury Stock acquired by the Company.
No fractional shares of Stock will be delivered under the Plan.


 


(c)            Individual
Limits. The following additional limits will apply to Awards of the specified type granted, or in the case of Cash Awards, payable
to any person in any calendar year:


 


(1)            Stock
Options: 900,000 shares of Stock.


 


(2)            SARs:
900,000 shares of Stock.


 


(3)           Awards
other than Stock Options, SARs or Cash Awards: 450,000 shares of Stock.


 


(4)            Cash
Awards: $5,000,000.


 


In applying the foregoing limits, (i) all
Awards of the specified type granted to the same person in the same calendar year will be aggregated and made subject to one limit; (ii) the
limits applicable to Stock Options and SARs refer to the number of shares of Stock subject to those Awards; (iii) the share limit
under clause (3) refers to the maximum number of shares of Stock that may be delivered, or the value of which could be paid in cash
or other property, under an Award or Awards of the type specified in clause (3) assuming a maximum payout; and (iv) the dollar
limit under clause (4) refers to the maximum dollar amount payable under an Award or Awards of the type specified in clause (4) assuming
a maximum payout. The foregoing provisions will be construed in a manner consistent with Section 162(m), including, without limitation,
where applicable, the rules under Section 162(m) pertaining to permissible deferrals of exempt awards.


 






    


     


    

 


5.            ELIGIBILITY
AND PARTICIPATION


 


The Administrator will select Participants from
among key Employees and Directors of, and consultants and advisors to, the Company and its Affiliates who are in a position to contribute
significantly to the success of the Company and its Affiliates. Eligibility for ISOs is limited to individuals described in the first
sentence of this Section 5 who are employees of the Company or of a “parent corporation” or “subsidiary corporation”
of the Company as those terms are defined in Section 424 of the Code. Eligibility for Stock Options other than ISOs is limited to
individuals described in the first sentence of this Section 5 who are providing direct services on the date of grant of the Stock
Option to the Company or to a subsidiary of the Company that would be described in the first sentence of Treas. Regs. §1.409A-1(b)(5)(iii)(E).


 


6.            RULES
APPLICABLE TO AWARDS


 


(a)           All
Awards.


 


(1)           Award
Provisions. The Administrator will determine the terms of all Awards, subject to the limitations provided herein. By accepting
(or, under such rules as the Administrator may prescribe, being deemed to have accepted) an Award, the Participant will be deemed
to have agreed to the terms of the Award and the Plan. Notwithstanding any provision of this Plan to the contrary, awards of an acquired
company that are converted, replaced or adjusted in connection with the acquisition may contain terms and conditions that are inconsistent
with the terms and conditions specified herein, as determined by the Administrator.


 


(2)          Term
of Plan. No Awards may be made after ten years from the Date of Adoption, but previously granted Awards may continue beyond that
date in accordance with their terms.


 


(3)           Transferability.
Neither ISOs nor, except as the Administrator otherwise expressly provides in accordance with the third sentence of this Section 6(a)(3),
other Awards may be transferred other than by will or by the laws of descent and distribution. During a Participant’s lifetime, ISOs
(and, except as the Administrator otherwise expressly provides in accordance with the third sentence of this Section 6(a)(3), SARs
and NSOs) may be exercised only by the Participant. The Administrator may permit the gratuitous transfer (i.e., transfer not for
value) of Awards other than ISOs, subject to such limitations as the Administrator may impose.


 


(4)           Vesting, etc.
The Administrator will determine the time or times at which an Award will vest or become exercisable and the terms on which a Stock
Option or SAR will remain exercisable. Except in the event of the Participant’s death or disability or a five percent (5%) carve-out
of the number of shares of Stock that may be delivered in satisfaction of Awards under the Plan (as defined in Section 4(a)), all
Awards will only vest or become exercisable after a minimum of twelve months from the grant date. Without limiting the foregoing, the
Administrator may at any time accelerate the vesting or exercisability of an Award, regardless of any adverse or potentially adverse tax
or other consequences resulting from such acceleration. Unless the Administrator expressly provides otherwise, however, the following
rules will apply if a Participant’s Employment ceases:


 






    


     


    

 


(A)            Immediately
upon the cessation of the Participant’s Employment and except as provided in (B) and (C) below, each Stock Option and
SAR that is then held by the Participant or by the Participant’s permitted transferees, if any, will cease to be exercisable and
will terminate and all other Awards that are then held by the Participant or by the Participant’s permitted transferees, if any,
to the extent not already vested will be forfeited.


 


(B)            Subject
to (C) and (D) below, all Stock Options and SARs held by the Participant or the Participant’s permitted transferees, if
any, immediately prior to the cessation of the Participant’s Employment, to the extent then exercisable, will remain exercisable
for the lesser of (i) a period of three months or (ii) the period ending on the latest date on which such Stock Option or SAR
could have been exercised without regard to this Section 6(a)(4), and will thereupon immediately terminate.


 


(C)           All
Stock Options and SARs held by a Participant or the Participant’s permitted transferees, if any, immediately prior to the cessation
of the Participant’s Employment due to his or her death or by the Company due to his or her Permanent Disability, to the extent
then exercisable, will remain exercisable for the lesser of (i) a period of twelve (12) months or (ii) the period ending on
the latest date on which such Stock Option or SAR could have been exercised without regard to this Section 6(a)(4), and will thereupon
immediately terminate.


 


(D)            All
Stock Options and SARs (whether or not exercisable) held by a Participant or the Participant’s permitted transferees, if any, immediately
prior to the cessation of the Participant’s Employment will immediately terminate upon such cessation of Employment if the termination
is for Cause or occurs in circumstances that in the sole determination of the Administrator would have constituted grounds for the Participant’s
Employment to be terminated for Cause.


 


(5)          Additional
Restrictions. The Administrator may cancel, rescind, withhold or otherwise limit or restrict any Award at any time if the Participant
is not in compliance with all applicable provisions of the Award agreement and the Plan, or if the Participant breaches any agreement
with the Company or its Affiliates with respect to non-competition, non-solicitation or confidentiality. Without limiting the generality
of the foregoing, the Administrator may recover Awards made under the Plan and payments under or gain in respect of any Award in accordance
with any applicable Company clawback or recoupment policy, as such policy may be amended and in effect from time to time, or as otherwise
required by applicable law or applicable stock exchange listing standards, including, without limitation, Section 10D of the Securities
Exchange Act of 1934, as amended.


 


(6)           Taxes.
The Company or any Affiliate shall have the authority and right to deduct or withhold or require a Participant to remit to the Company
or any Affiliate, an amount sufficient to satisfy Tax-Related Items with respect to any taxable event concerning a Participant arising
as a result of the Plan or to take such other action as may be necessary in the opinion of the Company or any Affiliate, as appropriate,
to satisfy withholding obligations for the payment of Tax-Related Items, including but not limited to (i) withholding from the Participant’s
wages or other cash compensation; (ii) withholding from the proceeds for the sale of shares of Stock underlying the Award either
through a voluntary sale or a mandatory sale arranged by the Company on the Participant’s behalf; or (iii) in the Administrator’s
sole discretion and in satisfaction of the foregoing requirement withhold shares of Stock otherwise issuable under an Award (or allow
the return of shares of Stock ) having a fair market value equal to the sums required to be withheld. To avoid negative accounting treatment,
the number of Shares which may be withheld with respect to the issuance, vesting, exercise or payment of any Award or which may be repurchased
from the Participant of such Award in order to satisfy the Participant's Tax-Related Items liabilities with respect to the issuance, vesting,
exercise or payment of the Award may be limited to the number of shares of Stock which have a fair market value on the date of withholding
or repurchase equal to the aggregate amount of such liabilities based on the maximum applicable withholding rates. No Stock shall be delivered
hereunder to any Participant or other person until the Participant or such other person has made arrangements acceptable to the Company
for the satisfaction of the Tax-Related Items withholdings obligations with respect to any taxable event concerning the Participant or
such other person arising as a result of the Plan in a manner consistent with Irish law.


 






    


     


    

 


(7)           Dividend
Equivalents, Etc. The Administrator may provide for the payment of amounts (on terms and subject to conditions established by
the Administrator) in lieu of cash dividends or other cash distributions with respect to Stock subject to an Award whether or not the
holder of such Award is otherwise entitled to share in the actual dividend or distribution in respect of such Award, except for Awards
of Stock Options or SARs, for which such payments shall be prohibited. Any entitlement to dividend equivalents or similar entitlements
will be established and administered either consistent with an exemption from, or in compliance with, the requirements of Section 409A.
Dividends or dividend equivalent amounts payable in respect of Awards shall be subject to the identical time-based vesting and performance
conditions as the underlying Award and cannot be paid unless and until all vesting and performance conditions of the underlying Award
are met. Dividends or dividend equivalent amounts payable in respect of Awards that are subject to restrictions may be subject to such
additional limits or restrictions as the Administrator may impose, consistent with the requirements of the Articles.


 


(8)           Rights
Limited. Nothing in the Plan will be construed as giving any person the right to continued employment or service with the Company
or its Affiliates, or any rights as a stockholder except as to shares of Stock actually issued under the Plan. The loss of existing or
potential profit in Awards will not constitute an element of damages in the event of a termination of Employment for any reason, even
if the termination is in violation of an obligation of the Company or any Affiliate to the Participant.


 


(9)           Purchase
Price. At the time of the Award, the Administrator shall determine the price, if any, to be paid by the Participant for each share
of Stock subject to the Award. The price to be paid by the Participant shall not be less than the nominal value of a share of Stock (or
such higher amount required by applicable Irish law). The purchase price of shares of Stock acquired pursuant to the Award shall be paid
or redeemed by a non-Irish incorporated Subsidiary on behalf of the Participant as designated by the Administrator or by the Participant
through one or more of the following methods (a) in cash or(b) in any other form of legal consideration that may be acceptable
to the Administrator in its discretion and in compliance with applicable Irish law.


 


(10)         Coordination
with Other Plans. Awards under the Plan may be granted in tandem with, or in satisfaction of or substitution for, other Awards
under the Plan or awards made under other compensatory plans or programs of the Company or its Affiliates. For example, but without limiting
the generality of the foregoing, awards under other compensatory plans or programs of the Company or its Affiliates may be settled in
Stock (including, without limitation, Unrestricted Stock) if the Administrator so determines, in which case the shares delivered will
be treated as awarded under the Plan (and will reduce the number of shares thereafter available under the Plan in accordance with the
rules set forth in Section 4). In any case where an award is made under another plan or program of the Company or its Affiliates
and such award is intended to qualify for the performance-based compensation exception under Section 162(m), and such award is settled
by the delivery of Stock or another Award under the Plan, the applicable Section 162(m) limitations under both the other plan
or program and under the Plan will be applied to the Plan as necessary (as determined by the Administrator) to preserve the availability
of the Section 162(m) performance-based compensation exception with respect thereto.


 






    


     


    

 


(11)         Section 162(m).
In the case of any Performance Award (other than a Stock Option or SAR) intended to qualify for the performance-based compensation
exception under Section 162(m), the Administrator will establish the applicable Performance Criterion or Criteria in writing no later
than ninety (90) days after the commencement of the period of service to which the performance relates (or at such earlier time as is
required to qualify the Award as performance-based under Section 162(m)) and, prior to the event or occurrence (grant, vesting or
payment, as the case may be) that is conditioned on the attainment of such Performance Criterion or Criteria, will certify whether it
or they have been attained. The preceding sentence will not apply to an Award eligible (as determined by the Administrator) for exemption
from the limitations of Section 162(m) by reason of the post-initial public offering transition relief in Section 1.162-27(f) of
the Treasury Regulations.


 


(12)         Section 409A.
Each Award will contain such terms as the Administrator determines, and will be construed and administered, such that the Award either
qualifies for an exemption from the requirements of Section 409A or satisfies such requirements.


 


(13)         Fair
Market Value. In determining the fair market value of any share of Stock under the Plan, the Administrator will make the determination
in good faith, and consistent with the rules of Section 422 and Section 409A when applicable.


 


(b)          Stock
Options and SARs.


 


(1)          Time
And Manner Of Exercise. Unless the Administrator expressly provides otherwise, no Stock Option or SAR will be deemed to have been
exercised until the Administrator receives a notice of exercise (in form acceptable to the Administrator), which may be an electronic
notice, signed (including electronic signature in form acceptable to the Administrator) by the appropriate person and accompanied by any
payment required under the Award. A Stock Option or SAR exercised by any person other than the Participant will not be deemed to have
been exercised until the Administrator has received such evidence as it may require that the person exercising the Award has the right
to do so. The Administrator may impose conditions on the exercisability of Awards, including limitations on the time periods during which
Awards may be exercised or settled.


 


(2)           Exercise
Price. The exercise price (or the base value from which appreciation is to be measured) of each Award requiring exercise will
be no less than the higher of (a) the nominal value of the Stock subject to the Award and (b) 100% (or in the case of an ISO
granted to a ten-percent shareholder within the meaning of subsection (b)(6) of Section 422, 110%) of the fair market value
of the Stock subject to the Award, determined as of the date of grant, or such higher amount as the Administrator may determine in connection
with the grant. Except in connection with a corporate transaction involving the Company (which term shall include, without limitation,
any stock dividend, stock split, extraordinary cash dividend, recapitalization, reorganization, merger, consolidation, split-up, spin-off,
combination, or exchange of shares) or as otherwise contemplated by Section 7 of the Plan, the terms of outstanding Stock Options
or SARs, or any substitution of such Awards under Section 6(a)(10), as applicable, may not be amended to reduce the exercise prices
of such Stock Options or the base values from which appreciation under such SARs are to be measured other than in accordance with the
stockholder approval requirements of the New York Stock Exchange. Unless otherwise submitted to and approved by the Company’s shareholders,
any substitution or buyout of Stock Options or SARs for cash, as applicable, shall be prohibited when the exercise price for such Stock
Option is below the current fair market value or when the base value from which appreciation under such SARs are to be measured is below
the current fair market value.


 






    


     


    

 


(3)          Payment
Of Exercise Price. Where the exercise of an Award is to be accompanied by payment, payment of the exercise price will be by cash
or check acceptable to the Administrator or by such other legally permissible means, if any, as may be acceptable to the Administrator.


 


(4)           Maximum
Term. Stock Options and SARs will have a maximum term not to exceed ten (10) years from the date of grant (or five (5) years
from the date of grant in the case of an ISO granted to a ten-percent shareholder described in Section 6(b)(2) above); provided,
however, that, if a Participant still holding an outstanding but unexercised NSO or SAR ten (10) years from the date of grant (or,
in the case of an NSO or SAR with a maximum term of less than ten (10) years, such maximum term) is prohibited by applicable law
or a written policy of the Company applicable to similarly situated employees from engaging in any open-market sales of Stock, and if
at such time the Stock is publicly traded (as determined by the Administrator), the maximum term of such Award will instead be deemed
to expire on the thirtieth (30th) day following the date the Participant is no longer prohibited from engaging in such open market sales.


 


7.            EFFECT
OF CERTAIN TRANSACTIONS


 


(a)           Mergers, etc.
Except as otherwise provided in an Award agreement, the following provisions will apply in the event of a Covered Transaction:


 


(1)          Assumption
or Substitution. If the Covered Transaction is one in which there is an acquiring or surviving entity, the Administrator may (but,
for the avoidance of doubt, need not) provide (i) for the assumption or continuation of some or all outstanding Awards or any portion
thereof or (ii) for the grant of new awards in substitution therefor by the acquiror or survivor or an affiliate of the acquiror
or survivor.


 


(2)         Cash-Out
of Awards. Subject to Section 7(a)(5) below the Administrator may (but, for the avoidance of doubt, need not) provide
for payment (a “cash-out”), with respect to some or all Awards or any portion thereof, equal in the case of each affected
Award or portion thereof to the excess, if any, of (A) the fair market value of one share of Stock (as determined by the Administrator
in its reasonable discretion) times the number of shares of Stock subject to the Award or such portion, over (B) the aggregate exercise
or purchase price, if any, under the Award or such portion (in the case of an SAR, the aggregate base value above which appreciation is
measured), in each case on such payment terms (which need not be the same as the terms of payment to holders of Stock) and other terms,
and subject to such conditions, as the Administrator determines; it being understood that if the exercise or purchase price (or base value)
of an Award is equal to or greater than the fair market value of one share of Stock, the Award may be cancelled with no payment due hereunder.


 


(3)          Acceleration
of Certain Awards. Subject to Section 7(a)(5) below, the Administrator may (but, for the avoidance of doubt, need not)
provide that any Award requiring exercise will become exercisable, in full or in part and/or that the delivery of any shares of Stock
remaining deliverable under any outstanding Award of Stock Units (including Restricted Stock Units and Performance Awards to the extent
consisting of Stock Units) will be accelerated in full or in part, in each case on a basis that gives the holder of the Award a reasonable
opportunity, as determined by the Administrator, following exercise of the Award or the delivery of the shares, as the case may be, to
participate as a stockholder in the Covered Transaction.


 






    


     


    

 


(4)           Termination
of Awards Upon Consummation of Covered Transaction. Except as the Administrator may otherwise determine in any case, each Award
will automatically terminate (and in the case of outstanding shares of Restricted Stock, will automatically be forfeited) upon consummation
of the Covered Transaction, other than Awards assumed pursuant to Section 7(a)(1) above.


 


(5)           Additional
Limitations. Any share of Stock and any cash or other property delivered pursuant to Section 7(a)(2) or Section 7(a)(3) above
with respect to an Award may, in the discretion of the Administrator, contain such restrictions, if any, as the Administrator deems appropriate
to reflect any performance or other vesting conditions to which the Award was subject and that did not lapse (and were not satisfied)
in connection with the Covered Transaction. For purposes of the immediately preceding sentence, a cash-out under Section 7(a)(2) above
or acceleration under Section 7(a)(3) above will not, in and of itself, be treated as the lapsing (or satisfaction) of a performance
or other vesting condition. In the case of Restricted Stock that does not vest and is not forfeited in connection with the Covered Transaction,
the Administrator may require that any amounts delivered, exchanged or otherwise paid in respect of such Stock in connection with the
Covered Transaction be placed in escrow or otherwise made subject to such restrictions as the Administrator deems appropriate to carry
out the intent of the Plan.


 


(b)           Changes
in and Distributions With Respect to Stock.


 


(1)           Basic
Adjustment Provisions. In the event of a stock dividend, stock split or combination of shares (including a reverse stock split),
recapitalization or other change in the Company’s capital structure that constitutes an equity restructuring within the meaning
of FASB ASC 718, the Administrator will make appropriate adjustments to the maximum number of shares of Stock that may be delivered under
the Plan, to the maximum number of shares of Stock that may be delivered in satisfaction of ISOs under the Plan, and to the maximum share
limits described in Section 4(c) and will also make appropriate adjustments to the number and kind of shares of stock or securities
subject to Awards then outstanding or subsequently granted, any exercise or purchase prices (or base values) relating to Awards and any
other provision of Awards affected by such change.


 


(2)           Certain
Other Adjustments. The Administrator may also make adjustments of the type described in Section 7(b)(1) above to take
into account distributions to stockholders other than those provided for in Section 7(a) and 7(b)(1), or any other event, if
the Administrator determines that adjustments are appropriate to avoid distortion in the operation of the Plan, having due regard for
the qualification of ISOs under Section 422, the requirements of Section 409A , and for the performance-based compensation rules of
Section 162(m)  where applicable.


 


(3)          Continuing
Application of Plan Terms. References in the Plan to shares of Stock will be construed to include any stock or securities resulting
from an adjustment pursuant to this Section 7.


 


8.            LEGAL
CONDITIONS ON DELIVERY OF STOCK


 


The Company will not be obligated to deliver any
shares of Stock pursuant to the Plan or to remove any restriction from shares of Stock previously delivered under the Plan until: (i) the
Company is satisfied that all legal matters in connection with the issuance and delivery of such shares have been addressed and resolved;
(ii) if the outstanding Stock is at the time of delivery listed on any stock exchange or national market system, the shares to be
delivered have been listed or authorized to be listed on such exchange or system upon official notice of issuance; and (iii) all
conditions of the Award have been satisfied or waived. The Company may require, as a condition to exercise of the Award, such representations
or agreements as counsel for the Company may consider appropriate to avoid violation of the Securities Act of 1933, as amended, or any
applicable state or non-U.S. securities law. Any Stock required to be issued to Participants under the Plan will be evidenced in such
manner as the Administrator may deem appropriate, including book-entry registration or delivery of stock certificates. In the event that
the Administrator determines that Stock certificates will be issued to Participants under the Plan, the Administrator may require that
certificates evidencing Stock issued under the Plan bear an appropriate legend reflecting any restriction on transfer applicable to such
Stock, and the Company may hold the certificates pending lapse of the applicable restrictions.


 






    


     


    

 


9.            AMENDMENT
AND TERMINATION


 


The Administrator may at any time or times amend
the Plan or any outstanding Award for any purpose which may at the time be permitted by law, and may at any time terminate the Plan as
to any future grants of Awards; provided, that, except as otherwise expressly provided in the Plan, the Administrator may not, without
the Participant’s consent, alter the terms of an Award so as to affect materially and adversely the Participant’s rights under
the Award, unless the Administrator expressly reserved the right to do so at the time the Award was granted. Any amendments to the Plan
will be conditioned upon stockholder approval only to the extent, if any, such approval is required by law (including the Code and applicable
stock exchange requirements), as determined by the Administrator.


 


10.          OTHER
COMPENSATION ARRANGEMENTS


 


The existence of the Plan or the grant of any
Award will not in any way affect the Company’s right to award a person bonuses or other compensation in addition to Awards under
the Plan.


 


11.          MISCELLANEOUS


 


(a)          Waiver
of Jury Trial. By accepting an Award under the Plan, each Participant waives any right to a trial by jury in any action, proceeding
or counterclaim concerning any rights under the Plan and any Award, or under any amendment, waiver, consent, instrument, document or other
agreement delivered or which in the future may be delivered in connection therewith, and agrees that any such action, proceedings or counterclaim
will be tried before a court and not before a jury. By accepting an Award under the Plan, each Participant certifies that no officer,
representative, or attorney of the Company has represented, expressly or otherwise, that the Company would not, in the event of any action,
proceeding or counterclaim, seek to enforce the foregoing waivers. Notwithstanding anything to the contrary in the Plan, nothing herein
is to be construed as limiting the ability of the Company and a Participant to agree to submit disputes arising under the terms of the
Plan or any Award made hereunder to binding arbitration or as limiting the ability of the Company to require any eligible individual to
agree to submit such disputes to binding arbitration as a condition of receiving an Award hereunder.


 


(b)           Limitation
of Liability. Notwithstanding anything to the contrary in the Plan, neither the Company, nor any Affiliate, nor the Administrator,
nor any person acting on behalf of the Company, any Affiliate, or the Administrator, will be liable to any Participant or to the estate
or beneficiary of any Participant or to any other holder of an Award by reason of any acceleration of income, or any additional tax (including
any interest and penalties), asserted by reason of the failure of an Award to satisfy the requirements of Section 422 or Section 409A
or by reason of Section 4999 of the Code, or otherwise asserted with respect to the Award.


 






    


     


    

 


12.           MISCELLANEOUS
ESTABLISHMENT OF SUB-PLANS


 


The Administrator may from time to time establish
one or more sub-plans under the Plan for purposes of satisfying applicable securities, or other regulatory or tax laws of various jurisdictions.
The Administrator will establish such sub-plans by adopting supplements to the Plan setting forth (i) such limitations on the Administrator’s
discretion under the Plan as it deems necessary or desirable and (ii) such additional terms and conditions not otherwise inconsistent
with the Plan as it deems necessary or desirable. All supplements so established will be deemed to be part of the Plan, but each supplement
will apply only to Participants within the affected jurisdiction (as determined by the Administrator).


 


13.            GOVERNING
LAW


 


(a)            Certain
Requirements of Corporate Law. Awards will be granted and administered consistent with the requirements of applicable law of Ireland
relating to the issuance of stock and the consideration to be received therefor, and with the applicable requirements of the stock exchanges
or other trading systems on which the Stock is listed or entered for trading, in each case as determined by the Administrator.


 


(b)            Other
Matters. Except as otherwise provided by the express terms of an Award agreement, under a sub-plan described in Section 12
or as provided in Section 13(a) above, the provisions of the Plan and of Awards under the Plan and all claims or disputes arising
out of or based upon the Plan or any Award under the Plan or relating to the subject matter hereof or thereof will be governed by and
construed in accordance with the domestic substantive laws of the State of Pennsylvania without giving effect to any choice or conflict
of laws provision or rule that would cause the application of the domestic substantive laws of any other jurisdiction.


 


(c)            Jurisdiction.
By accepting an Award, each Participant will be deemed to (a) have submitted irrevocably and unconditionally to the jurisdiction
of the federal and state courts located within the geographic boundaries of the United States District Court for the District of Pennsylvania
for the purpose of any suit, action or other proceeding arising out of or based upon the Plan or any Award; (b) agree not to commence
any suit, action or other proceeding arising out of or based upon the Plan or an Award, except in the federal and state courts located
within the geographic boundaries of the United States District Court for the District of Pennsylvania; and (c) waive, and agree not
to assert, by way of motion as a defense or otherwise, in any such suit, action or proceeding, any claim that it is not subject personally
to the jurisdiction of the above-named courts that its property is exempt or immune from attachment or execution, that the suit, action
or proceeding is brought in an inconvenient forum, that the venue of the suit, action or proceeding is improper or that the Plan or an
Award or the subject matter thereof may not be enforced in or by such court.


 






    


     


    




 


EXHIBIT A


 


Definition of Terms


 


The following terms, when used in the Plan, will
have the meanings and be subject to the provisions set forth below:


 


“Administrator”: The Compensation
Committee, except that the Compensation Committee may delegate (i) to one or more of its members (or one or more other members of
the Board (including the full Board)) such of its duties, powers and responsibilities as it may determine; (ii) to one or more officers
of the Company the power to grant Awards to the extent permitted by applicable law; and (iii) to such Employees or other persons
as it determines such ministerial tasks as it deems appropriate. In the event of any delegation described in the preceding sentence, the
term “Administrator” will include the person or persons so delegated to the extent of such delegation.


 


“Affiliate”: Any corporation
or other entity that stands in a relationship to the Company that would result in the Company and such corporation or other entity being
treated as one employer under Section 414(b) and Section 414(c) of the Code, provided that, for purposes of
determining treatment as a single employer under Section 414(b) and Section 414(c) of the Code, “50%”
shall replace “80%” in the applicable stock ownership requirements under such sections of the Code and the regulations thereunder.


 


“Articles”: The articles of association of the Company.


 


“Award”: Any or a combination of the following:


 


(i)            Stock
Options.


 


(ii)           SARs.


 


(iii)          Restricted
Stock.


 


(iv)          Unrestricted
Stock.


 


(v)           Stock
Units, including Restricted Stock Units.


 


(vi)          Performance
Awards.


 


(vii)          Cash
Awards.


 


(viii)         Awards
(other than Awards described in (i) through (vii) above) that are convertible into or otherwise based on Stock.


 


“Board”: The Board of Directors of the Company.


 


“Cash Award”: An Award denominated in cash.


 


“Cause”: In the case of any
Participant who is party to an employment or severance-benefit agreement that contains a definition of “Cause,” the definition
set forth in such agreement will apply with respect to such Participant under the Plan for so long as such agreement is in effect. In
the case of any other Participant, “Cause” will mean, as determined by the Administrator in its reasonable judgment, (i) a
substantial failure of the Participant to perform the Participant’s duties and responsibilities to the Company or subsidiaries or
substantial negligence in the performance of such duties and responsibilities; (ii) the commission by the Participant of a felony
or a crime involving moral turpitude; (iii) the commission by the Participant of theft, fraud, embezzlement, material breach of trust
or any material act of dishonesty involving the Company or any of its subsidiaries; (iv) a significant violation by the Participant
of the code of conduct of the Company or its subsidiaries or of any material policy of the Company or its subsidiaries, or of any statutory
or common law duty of loyalty to the Company or its subsidiaries; (v) material breach of any of the terms of the Plan or any Award
made under the Plan, or of the terms of any other agreement between the Company or subsidiaries and the Participant; or (vi) other
conduct by the Participant that could reasonably be expected to be harmful to the business, interests or reputation of the Company.


 






    


     


    

 


“Code”: The U.S. Internal Revenue
Code of 1986 as from time to time amended and in effect, or any successor statute as from time to time in effect.


 


“Compensation Committee”: The Compensation Committee
of the Board.


 


“Company”: Trinseo PLC, a company incorporated
in Ireland or, where the context requires, with respect to periods prior to the Effective Time, Trinseo S.A.


 


“Covered Transaction”: Any
of (i) a consolidation, merger, or similar transaction or series of related transactions, including a sale or other disposition of
stock, in which the Company is not the surviving corporation or that results in the acquisition of all or substantially all of the Company’s
then outstanding ordinary shares by a single person or entity or by a group of persons and/or entities acting in concert, (ii) a
sale or transfer of all or substantially all the Company’s assets, or (iii) a dissolution or liquidation of the Company. Where
a Covered Transaction involves a tender offer that is reasonably expected to be followed by a merger described in clause (i) (as
determined by the Administrator), the Covered Transaction will be deemed to have occurred upon consummation of the tender offer.


 


“Date of Adoption”: The earlier of the dates (both
prior to the Effective Time) that the Plan was approved by the Company’s shareholders or adopted by the Board, as determined by
the Compensation Committee.


 


“Director”: A member of the Board.


 


“Employee”: Any person who is employed by the Company
or an Affiliate.


 


“Employment”: A Participant’s
employment or other service relationship with the Company and its Affiliates. Employment will be deemed to continue, unless the Administrator
expressly provides otherwise, so long as the Participant is employed by, or otherwise is providing services in a capacity described in
Section 5 to the Company or an Affiliate. If a Participant’s employment or other service relationship is with an Affiliate
and that entity ceases to be an Affiliate, the Participant’s Employment will be deemed to have terminated when the entity ceases
to be an Affiliate unless the Participant transfers Employment to the Company or its remaining Affiliates. Notwithstanding the foregoing
and the definition of “Affiliate” above, in construing the provisions of any Award relating to the payment of “nonqualified
deferred compensation” (subject to Section 409A) upon a termination or cessation of Employment, references to termination or
cessation of employment, separation from service, retirement or similar or correlative terms will be construed to require a “separation
from service” (as that term is defined in Section 1.409A- 1(h) of the U.S. Treasury Regulations, after giving effect to
the presumptions contained therein) from the Company and from all other corporations and trades or businesses, if any, that would be treated
as a single “service recipient” with the Company under Section 1.409A-1(h)(3) of the U.S. Treasury Regulations.
The Company may, but need not, elect in writing, subject to the applicable limitations under Section 409A, any of the special elective
rules prescribed in Section 1.409A- 1(h) of the U.S. Treasury Regulations for purposes of determining whether a “separation
from service” has occurred. Any such written election will be deemed a part of the Plan.


 






    


     


    

 


“ISO”: A Stock Option intended
to be an “incentive stock option” within the meaning of Section 422. Each Stock Option granted pursuant to the Plan will
be treated as providing by its terms that it is to be an NSO unless, as of the date of grant, it is expressly designated as an ISO.


 


“NSO”: A Stock Option that
is not intended to be an “incentive stock option” within the meaning of Section 422.


 


“Participant”: A person who
is granted an Award under the Plan.


 


“Performance Award”: An Award
subject to Performance Criteria. The Administrator in its discretion may grant Performance Awards that are intended to qualify for the
performance-based compensation exception under Section 162(m) and Performance Awards that are not intended so to qualify.


 


“Performance Criteria”: Specified
criteria, other than the mere continuation of Employment or the mere passage of time, the satisfaction of which is a condition for the
grant, exercisability, vesting or full enjoyment of an Award. For purposes of Awards that are intended to qualify for the performance-based
compensation exception under Section 162(m), a Performance Criterion will mean an objectively determinable measure or measures of
performance relating to any or any combination of the following (measured either absolutely or by reference to an index or indices and
determined either on a consolidated basis or, as the context permits, on a divisional, subsidiary, line of business, project or geographical
basis or in combinations thereof): sales; revenues; assets; expenses; earnings before or after deduction for all or any portion of interest,
taxes, depreciation, amortization or equity expense, whether or not on a continuing operations or an aggregate or per share basis; return
on equity, investment, capital, capital employed or assets; one or more operating ratios; operating income or profit, including on an
after-tax basis; net income; borrowing levels, leverage ratios or credit rating; market share; capital expenditures; cash flow; stock
price; stockholder return; sales of particular products or services; customer acquisition or retention; acquisitions and divestitures
(in whole or in part); joint ventures, strategic alliances, licenses or collaborations; spin-offs, split-ups and the like; reorganizations;
recapitalizations, restructurings, financings (issuance of debt or equity) or refinancings; manufacturing or process development; or environmental
health and/or safety metrics. A Performance Criterion and any targets with respect thereto determined by the Administrator need not be
based upon an increase, a positive or improved result or avoidance of loss. To the extent consistent with the requirements for satisfying
the performance-based compensation exception under Section 162(m), the Administrator may provide, by the deadline that otherwise
applies to the establishment of the terms of any Award intended to qualify for such exception, that one or more of the Performance Criteria
applicable to such Award will be adjusted in an objectively determinable manner to reflect events (for example, the impact of charges
for restructurings, discontinued operations, mergers, acquisitions, extraordinary items, and other unusual or non- recurring items, and
the cumulative effects of tax or accounting changes, each as defined by U.S. or international generally accepted accounting principles)
occurring during the performance period that affect the applicable Performance Criterion or Criteria.


 






    


     


    

 


“Permanent Disability”: In
the case of any Participant who is party to an employment or severance-benefit agreement that contains a definition of “Permanent
Disability” (or similar term), the definition set forth in such agreement will apply with respect to such Participant under the
Plan for so long as such agreement is in effect. In the case of any other Participant, “Permanent Disability” shall mean a
disability that would entitle a Participant to long-term disability benefits under the Company’s long-term disability plan to which
the Participant participates. Notwithstanding the foregoing, however, in the case of any Award that is subject to Section 409A and
is payable upon a Participant’s Permanent Disability, the Participant shall be treated as having a Permanent Disability only if
the Participant’s condition also satisfies the definition of “disability” in Treasury Regulation 1.409A-3(i)(4).


 


“Restricted Stock”: Stock subject
to restrictions requiring that it be redelivered or offered for sale to the Company if specified conditions are not satisfied.


 


“Restricted Stock Unit”: A
Stock Unit that is, or as to which the delivery of Stock or cash in lieu of Stock is, subject to the satisfaction of specified performance
or other vesting conditions.


 


“SAR”: A right entitling the
holder upon exercise to receive an amount (payable in cash or in shares of Stock of equivalent value) equal to the excess of the fair
market value of the shares of Stock subject to the right over the base value from which appreciation under the SAR is to be measured.


 


“Section 162(m)”: Section 162(m) of
the Code.


 


“Section 409A”: Section 409A of the Code.


 


“Section 422”: Section 422 of the Code.


 


“Stock”: Ordinary shares of the Company, nominal
value $0.01 per share and “stockholder” shall be interpreted accordingly where referring to holders of Stock in the Company.


 


“Stock Option”: An option entitling
the holder to acquire shares of Stock upon payment of the exercise price.


 


“Stock Unit”: An unfunded and
unsecured promise, denominated in shares of Stock, to deliver Stock or cash measured by the value of Stock in the future.


 


“Tax-Related Items” means
(i) federal, state, and local taxes and taxes imposed by any jurisdiction (including but not limited to, income tax, social security
or insurance contributions, payroll tax, fringe benefits tax, payment on account, employment tax obligations, stamp taxes, and any other
taxes that may be due) required by law to be withheld and (ii) any employer tax liability shifted to a Participant.


 


“Unrestricted Stock”: Stock not subject to any restrictions
under the terms of the Award.