---
schema_version: "secwatch.filing_event.v1"
accession: "0001558370-25-004485"
form_type: "8-K"
ticker: "TSEOF"
cik: "0001519061"
company_name: "Trinseo PLC"
filed_at: "2025-04-04T23:59:59+00:00"
generated_at: "2026-05-23T20:57:55.130533+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.45
calibrated_materiality_score: 0.45
confidence: "high"
source: SEC EDGAR
---

# Trinseo board members De Leener and Tomkins retire; board to shrink to nine

## Summary
- Pierre-Marie De Leener and Mark Tomkins will retire at 2025 AGM and not stand for reelection.
- Board size will decrease to nine members following the annual general meeting.
- De Leener served since Trinseo's 2014 IPO; Tomkins served since 2019.
- Retirements not due to any disagreement with the company on operations or policies.

## SEC filing metadata
- accession: 0001558370-25-004485
- form_type: 8-K
- ticker: TSEOF
- cik: 0001519061
- company_name: Trinseo PLC
- filed_at: 2025-04-04T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.45
- calibrated_materiality_score: 0.45
- confidence: high
- sec_items: 5.02, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1519061/000155837025004485/0001558370-25-004485-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1519061/000155837025004485/tse-20250403x8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001558370-25-004485
- JSON: https://secwatch.observer/filing/0001558370-25-004485.json
- Plain text: https://secwatch.observer/filing/0001558370-25-004485.txt

## Key facts
- Executive change
  Mark Tomkins departed as Director at Trinseo PLC.
  - Action: retire
  - Role: Director
  source text: Pierre-Marie De Leener and Mark Tomkins, two members of the Board of Directors (the “Board”) of Trinseo PLC (the “Company”), notified the Company of their decision to retire from the Board and not stand for reelection at the Company’s 2025 annual general meeting of shareholders.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1519061/000155837025004485/0001558370-25-004485-index.htm
- Executive change
  Pierre-Marie De Leener departed as Director at Trinseo PLC.
  - Action: retire
  - Role: Director
  source text: Pierre-Marie De Leener and Mark Tomkins, two members of the Board of Directors (the “Board”) of Trinseo PLC (the “Company”), notified the Company of their decision to retire from the Board and not stand for reelection at the Company’s 2025 annual general meeting of shareholders.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1519061/000155837025004485/0001558370-25-004485-index.htm

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.