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

International audienceMethyl 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 r1(MMA) = 2.36 and r2(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, Tg, by differential scanning calorimetry (DSC) of gradient copolymers exhibited one Tg, with a value intermediate to the Tg 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 Tg, one corresponding to the Tg of PBA and the other intermediate to the Tg 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