X0306 4 2016-05-12 0 0001519061 Trinseo S.A. TSE 0001606937 Thomas Stephen F. 200 CLARENDON STREET BOSTON MA 02116 1 0 1 0 ORDINARY SHARES 2016-05-12 4 S 0 8000000 42.90 D 18669567 I See Footnotes Represents ordinary shares of Trinseo S.A. held by Bain Capital Everest Manager Holding SCA ("BCEM Holding"). The governance, investment strategy and decision-making process with respect to the investments held by all of the Bain Capital funds is directed by the Global Private Equity Board of Bain Capital Investors, LLC ("BCI"). Mr. Thomas is Managing Director of BCI. By virtue of these relationships described in these footnotes, Mr. Thomas may be deemed to share voting and dispositive power with respect to all of the shares of Trinseo S.A. held by BCEM Holding. Mr. Thomas disclaims beneficial ownership of such securities except to the extent or of his pecuniary interest therein. Stephen F. Thomas 2016-05-16