Synthesis and ring‐opening polymerization of 2‐acetoxymethyl‐2‐alkyltrimethylene carbonates and of 2‐methoxycarbonyl‐2‐methyltrimethylene carbonate; a comparison with the polymerization of 2,2‐dimethyltrimethylene carbonate

Abstract

AbstractThe polymerization of 2‐acetoxymethyl‐2‐alkyltrimethylene carbonates (alkyl = methyl: AMTC, alkyl = ethyl: AETC) and of 2‐methoxycarbonyl‐2‐methyltrimethylene carbonate (MMTC) in toluene with sec‐butyllithium as initiator results in the respective polymer with yields between 78% and 88%. The analysis of the polymer microstructure by means of NMR spectroscopy reveals linear chains without branching due to an attack of the active chain end at the ester moiety of the repeating units. Poly(MMTC) and poly(‐AETC) afford crystalline materials upon precipitation from solution while poly‐(AMTC) is amorphous; after quenching from the melt all materials are amorphous. Copolymerization of AMTC, AETC and MMTC with 2,2‐dimethyltrimethylene carbonate (DTC) results in random copolymers. The kinetics of the polymerization of AETC and MMTC revealed that the ester side chain enhances the rate of propagation compared to the polymerization of DTC. The apparent rate constants of propagation in toluene with lithium alcoholate as active sites at 23°C were determined to be kappDTC = 4 ċ 10−3 s−1, kappAETC = 4,28 ċ 10−2 s−1, and kappMMTC = 2,57 ċ 10−2 s−1. Studies of ring‐chain equilibria in solution of tetrahydrofuran revealed that on the basis of the theory of Jacobson‐Stockmayer the characteristic ratios of the polymers are C∞PDTC = 7,1, C∞PMMTC = 8,6, C∞PAETC = 9,9, and C∞PAMTC = 13,4.