The use of stable carbene‐CO2 adducts for the polymerization of trimethylene carbonate

ABSTRACT The synthesis of poly(trimethylene carbonate) via carbene catalyzed ring‐opening polymerization (ROP) was investigated. The N‐heterocyclic carbenes were protected as CO2‐adducts to improve their handling (e.g., carbene generation without base). The influence of catalyst structure, different solvents and microwave radiation on conversion, molecular weight and end groups was investigated to gain an insight into the reaction mechanism. Different NHC structures were investigated for their catalytic activity toward the ROP of trimethylene carbonate. The analytic studies were performed by using NMR spectroscopy, SEC and ESI‐IMS mass spectrometry. It was found that the reaction can be performed in acetonitrile, toluene, THF and CH2Cl2. Synthesis in CH2Cl2 allows the best control over the resulting polymer with regards to polydispersity and molecular weight. Microwave radiation accelerates the reaction at 80 °C. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 820–829 Poly(trimethylene carbonate) was synthesized via carbene carboxylates catalyzed ring‐opening polymerization. These pre‐catalysts are more air and moisture stable than their free counterparts. They show a slower reaction than the free carbenes. Different catalyst structures and reaction parameters were investigated. The polymerizations work well in several solvents and can be accelerated by moderate microwave radiation but the control over the endgroups needs improvement. The polymers were analyzed using Electrospray Ionization coupled to Ion Mobility Separation, which allows the endgroup analysis of even complex polymer samples.