New morphologies in rubber-modified polymers

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Abstract
New morphologies, especially “core-shell” and multilayered structures (“onion structure”) have been obtained for polymer blends containing block copolymers. For triblock copolymers Cop A-B-C, having three sequences of different types, in this case, poly(styrene-b-isoprene-b-methyl methacrylate), the conditions are given for the formation of core-shell structures. A scheme is presented showing the structures of the mesomorphic phases, as a function of the composition of the copolymer. Multilayered and core-shell structures have also been obtained by a suitable combination of two diblock copolymers, Cop A-B, i.e., poly(styrene-b-isoprene), with a corresponding homopolymer, i. e., polystyrene. One of the copolymers can act as an emulsifier for the second one forming the dispersed phase of the blend. An extension of the classical mesomorphic structures is presented, and it is shown that the emulsifying effect of block copolymers is quite general.