Synthesis and characterizations of block copolymer of poly(n-butyl acrylate) and gradient poly(methyl methacrylate-co-N,N-dimethyl acrylamide) made via nitroxide-mediated controlled radical polymerization

摘要

Methyl methacrylate (MMA)/N,N-dimethyl acrylamide (DMA) gradient copolymers with various chemical composition were synthesized by nitroxide-mediated controlled radical polymerization (NMP). Molecular weight (MW) characterization via gel permeation chromatography demonstrated that these materials were made in a "controlled" manner. The reactivity ratios values r(1)(MMA) = 2.36 and r(2)(DMA) = 0.33 were experimentally determined using the linear least-squares numerical method, results in good agreement with the literature. Characterization of the glass transition temperature, T-g, by differential scanning calorimetry (DSC) of gradient copolymers exhibited one T-g, with a value intermediate to the T-g of pure poly(methyl methacrylate) (PMMA) and poly(N,N-dimethyl acrylamide) (PDMA). In contrast, di- and triblock copolymers made of poly(n-butyl acrylate) (PBA) as central block and PMMA/PDMA gradient copolymer as external block yielded two T-g, one corresponding to the T-g of PBA and the other intermediate to the T-g of PMMA and PDMA, indicating microphase separation which was confirmed by dynamic mechanical analysis and TEM observations of films of di- and triblock copolymers showing lamellae structure.