SYNTHESIS, DYNAMIC-MECHANICAL AND MORPHOLOGICAL BEHAVIOR OF STYRENE BUTYL METHACRYLATE DIBLOCK COPOLYMERS/

In order to investigate the structure-property relationship of styrene /butyl methacrylate (PS/PBMA) diblock copolymers, two ranges of polyme rs with (M) over bar(n) approximate to 100000 and (M) over bar(n)>2000 00, respectively, with polydispersity indexes (M) over bar(W)/(M) over bar(n)<1.15 are synthesized with varying ratios of the block lengths. The molecular weights of these polymers are determined by size exclus ion chromatography (SEC). Thermal behavior and morphology are characte rized by dynamic-mechanical analysis (DMA) and transmission electron m icroscopy, respectively. Whereas for unsymmetrical diblock copolymers with an overall molecular weight of (M) over bar(n) approximate to 100 000 only one broadened glass transition due to their disordered state is found, nearly symmetrical diblock copolymers show a partial miscibi lity which can be ascribed to the proximity of the order-disorder tran sition and the annealing temperature of the samples. In the case of un symmetrical high molecular weight diblock copolymers a partial miscibi lity is observed as well. The high molecular weight diblock copolymers with (M) over bar(n)>200000 at all compositions show microphase-separ ated structures in contrast to the diblock copolymers with an overall molecular weight of (M) over bar(n) approximate to 100000. Compared wi th styrene/isoprene diblock copolymers a relatively wide range for lam ellar structures is found.