Cationic Ring-Opening Polymerization of Seven-Membered Cyclic Carbonate with Water−Hydrogen Chloride through Activated Monomer Process

Controlled ring-opening polymerization of a seven-membered cyclic carbonate, 1,3-dioxepan-2-one (7CC), with H 2 O/HCl·Et 2 O initiator system was investigated. The molecular weight ( M n ) of the obtained polymer could be controlled by the amount of H 2 O in the range of 10 3 −10 4 maintaining a low polydispersity ratio ( M w / M n = 1.11−1.17). The second portion of the monomer after completion of the first polymerization was converted quantitatively to give the corresponding polymer with a low M w / M n . The kinetic and 1 H NMR spectroscopic studies suggested that the nucleophilic attack of H 2 O to the monomer activated with hydrogen chloride afforded α-hydroxyl-ω-carbonic acid, followed by decarboxylation reaction to give α,ω-dihydroxyl compound. It was suggested that the chain growth in this system was the attack of the terminal hydroxyl group to the monomer activated with hydrogen chloride.