Abstract
AbstractThe polymerization of 2,2‐dimethyltrimethylene carbonate (1) was initiated with borontrifluoride etherate, trifluoromethanesulfonic acid (triflic acid), methyl triflate and ethyl fluorosulfate. The reaction was studied at 20, 50, 80 and 120°C in 1,2‐dichloroethane and nitrobenzene. Methyl triflate and triflic acid turned out to be the most reactive initiators. Yet, due to “black biting” degradation, yields > 80% were never obtained. With BF3 etherate yields up to 98% and molecular weights (M̄n) up to 5200 g/mol were found. From 1H NMR and IR spectra it can be deduced that methyl triflate alkylates the exocyclic oxygen (carbonyl group) and the resulting carbenium ion reacts with its counterion by ring‐opening of the alkyl‐oxygen bond. The oligomers and polymers formed in this way initially possess methyl (or ethyl) carbonate groups at one end and triflate groups at the other end of the chain. Elemental analyses and IR spectra prove that no carbon dioxide is lost in the course of the cationic polymerization. DSC measurements showed that crystallinity and melting points of poly(1) largely depend on the polymerization conditions in contrast to the glass transition temperature.
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