Homogeneous synthesis of diblock copolymers with a poly (N, N-dimethylacrylamide) block by anionic polymerization in pyridine

摘要: Diblock copolymers containing poly (N, N-dimethylacrylamide) blocks were prepared by anionic polymerization using living polymers of tert-butyl methacrylate and 2-vinyl-and 4-vinylpyridine as macroinitiators. Syntheses were conducted at-40 C in pyridine in the presence of small amounts of THF (9: 1). During synthesis of the second block, active end groups of precursor polymers were modified by diethylzinc (Et 2 Zn: macroinitiator= 15: 1). Homopolymerization of tert-butyl methacrylate and 2-vinyl-and 4-vinylpyridines in the same mixed solvent was conducted with the use of adduct of oligostyryllithium with 1, 1-diphenylethylene (1: 1) in the presence of lithium chloride. The polymers thus prepared had M w/M n= 1.1-1.2. Homopolymers of N, N-dimethyl-and N, N-diethylacrylamides were prepared under similar conditions in the presence of Et 2 Zn (Et 2 Zn: initiator= 15: 1). The homopolymerization and block copolymerization of the latter monomers proceeded under homogeneous conditions in a pyridine: THF (9: 1) mixture and produced polymers consisting predominantly of heterotactic stereostructures. The polymers were characterized by exclusion chromatography and NMR spectroscopy.