Unprecedented Double Insertion of Cyclohexene Oxide in Ring-Opening Copolymerization with Cyclic Anhydrides Catalyzed by a Tin(II) Alkoxide Complex

• Published in: Macromolecules 2020-11, Vol.53 (22), p.9869-9877
• Main Authors: Ungpittagul, Thasanaporn, Jaenjai, Tiphanan, Roongcharoen, Thantip, Namuangruk, Supawadee, Phomphrai, Khamphee
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.0c01738

Typical ring-opening copolymerization (ROCOP) of cyclic anhydrides (A) and epoxides (B) catalyzed by most metal complexes underwent strict alternating monomer insertions giving (AB) n polyesters. In this contribution, a novel polyester containing (ABB) n polymer sequences was prepared via the ROCOP of cyclic anhydrides and cyclohexene oxide (CHO) using a tin­(II) alkoxide complex. Quantum calculations revealed that the preference for the (ABB) n sequence was enhanced by the energetic preference of the second CHO insertion. The copolymer with (ABB) n content as high as 70% was obtained from the ROCOP of succinic anhydride and CHO with an enhanced T g of 65 °C (>20 °C higher than the (AB) n analogue). The ROCOP of maleic anhydride and CHO also gave a copolymer with high (ABB) n content at 48% and improved T g of 89 °C (38 °C higher). The improved thermal properties were a result of the more rigid (ABB) n polymer backbone compared with conventional alternating (AB) n copolymer analogues. In addition, terpolymerization with ε-caprolactone (ε-CL) was achieved by sequential addition of ε-CL affording the block copolymer with the (ABB) n backbone.