[Form 4] Trinseo PLC Insider Trading Activity

Rhea-AI Filing Summary

Trinseo PLC (TSE) director Matthew Farrell made open-market purchases totaling 100,000 ordinary shares across August 12-14, 2025, raising his beneficial ownership to 250,225 shares. The reported weighted-average prices were $2.29 on 08/12, $2.45 on 08/13 and $2.43 on 08/14, with per-trade price ranges disclosed for each date. The purchases were reported on Form 4 and executed by an attorney-in-fact; full per-price breakdowns are available upon request as noted in the filing.

Positive

• Director purchased 100,000 shares over three days, increasing reported beneficial ownership to 250,225 shares
• Purchases disclosed at low weighted-average prices ($2.29, $2.45, $2.43) with execution price ranges provided
• Form 4 properly filed and includes explanatory notes and signature via attorney-in-fact

Negative

• None.

Insights

Financial Analyst

TL;DR: Director bought 100,000 shares over three days, increasing ownership to 250,225 shares at low single-digit dollar prices.

The reported insider purchases are a clear, material disclosure of director confidence, totaling 100,000 shares acquired over August 12-14, 2025. The weighted-average prices—$2.29, $2.45 and $2.43—show consistent buying near the same price level. An increase to 250,225 shares is significant for monitoring insider alignment with shareholders; the filing provides per-date weighted averages and notes ranges for the exact execution prices.

Corporate Governance Expert

TL;DR: The Form 4 shows routine, properly disclosed open-market purchases by a director via agent, with documentation available on per-trade pricing.

From a governance perspective, the filing meets Section 16 disclosure requirements and includes explanatory notes about weighted-average prices and available per-price details. The purchases were reported as direct beneficial ownership increases and were signed by an attorney-in-fact, which is standard practice when an agent executes transactions on behalf of an insider. No amendments or additional restrictions are indicated in the form.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

FARRELL MATTHEW

(Last) (First) (Middle)

C/O TRINSEO PLC

440 EAST SWEDESFORD ROAD, SUITE 301

(Street)

WAYNE PA 19087

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Trinseo PLC [ TSE ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
08/12/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Ordinary Shares	08/12/2025		P		25,000	A	$2.29(1)	175,225	D
Ordinary Shares	08/13/2025		P		26,391	A	$2.45(2)	201,616	D
Ordinary Shares	08/14/2025		P		48,609	A	$2.43(3)	250,225	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Price reflects the weighted average purchase price for the purchase transaction made on the date reported above. Purchase prices ranged from $2.26 to $2.32. The reporting person will provide, upon request by the Staff, the Company, or a security holder of the Company, full information regarding the number of shares purchased at each separate price.

2. Price reflects the weighted average purchase price for the purchase transaction made on the date reported above. Purchase prices ranged from $2.36 to $2.50. The reporting person will provide, upon request by the Staff, the Company, or a security holder of the Company, full information regarding the number of shares purchased at each separate price.

3. Price reflects the weighted average purchase price for the purchase transaction made on the date reported above. Purchase prices ranged from $2.38 to $2.46. The reporting person will provide, upon request by the Staff, the Company, or a security holder of the Company, full information regarding the number of shares purchased at each separate price

	/s/ Angelo Chaclas, Attorney-in-Fact	08/14/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What did Trinseo (TSE) director Matthew Farrell purchase?

He purchased 100,000 ordinary shares in open-market transactions reported on Form 4.

When were the insider purchases executed?

Purchases occurred on August 12, 2025 (25,000 shares), August 13, 2025 (26,391 shares) and August 14, 2025 (48,609 shares).

What prices were paid for the shares?

Weighted-average prices reported were $2.29 on 08/12, $2.45 on 08/13 and $2.43 on 08/14; price ranges per date are disclosed in the filing.

How many shares does the reporting person own after these transactions?

The filing reports 175,225 shares after the 08/12 purchase, 201,616 after 08/13, and 250,225 after 08/14, with final beneficial ownership of 250,225 shares.

Who signed the Form 4 filing?

The filing was signed by Angelo Chaclas, Attorney-in-Fact on behalf of the reporting person on 08/14/2025.