Poly(methyl methacrylate)‐block‐poly(2,2‐dimethyltrimethylene carbonate); site transformation from a group transfer polymerization to an anionic ring‐opening polymerization

Abstract

AbstractPoly(methyl methacrylate)‐block‐poly(2,2‐dimethyltrimethylene carbonate) was prepared by a group transfer polymerization (GTP) of methyl methacrylate (MMA), followed by an anionic metal‐free polymerization of 2,2‐dimethyltrimethylene carbonate (DTC). It was shown that the anionic metal‐free polymerization of DTC can be initiated either by the system silyl ether/tris(dimethylamino)sulfonium trimethylsilyldifluoride (TASF) or by the system 1‐methoxy‐1‐trimethylsilyloxy‐2‐methyl‐1‐propene (MTS) in combination with TASF. The latter can be considered as a model compound for the living PMMA end in a GTP polymerization. The transformation of the trimethylsilyl ketene acetal end into an anionic species was achieved by desilylation with TASF. In the presence of DTC the resulting enolate reacts as carbanion with the carbonyl group of the carbonate moiety. Thus, at the linkage of the two blocks a disubstituted malonic acid derivative is formed. GPC analysis of the copolymers reveals a unimodal and rather narrow distribution of molecular weights. The block structure expected from the way of preparation is confirmed by 13C NMR analysis. The 1H NMR analysis gives the composition of the block copolymers and reveals that the larger the PMMA block, the less efficient is the initiating ability, leading to a larger PDTC block as expected from the monomer to initiator ratio; correspondingly more homo‐PMMA is formed. Thermal analysis of the block copolymers shows a melting transition of the PDTC block which is by about 20°C lower than that of the homopolymer: the glass transition temperature of the PMMA block is hidden under the melting transition of the PDTC block.