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Investigation of the T u (>T g ) relaxation in homopolymers and block copolymers of styrene by torsional braid analysis
Author(s) -
Gillham J. K.
Publication year - 1979
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760191015
Subject(s) - polystyrene , copolymer , materials science , styrene , polymer chemistry , glass transition , relaxation (psychology) , polymer , amorphous solid , crystallography , composite material , chemistry , psychology , social psychology
Investigation of the T u (>T g ) relaxation in amorphous polymers of styrene by the technique of torsional braid analysis is reviewed. For the most part the relaxation behaves like the glass transition ( T g ) in its dependence on molecular weight, on average molecular weight in binary polystyrene blends, and on composition in a polystyrene homogeneously plasticized throughout the range of composition. Diblock and triblock copolymers also display a T > T g relaxation above the T g , of the polystyrene phase. Two results in particular suggest that the T u relaxation is molecularly based. (1) The T u temperature is determined by the number average molecular weight for binary blends of polystyrene when both components have molecular weights below M c . (the critical molecular weight for chain entanglements). (2) Homopolymers, and diblock and triblock copolymers of styrene, have a T > T g relaxation at approximately the same temperature when the molecular weight of the styrene block is equal to that of the homopolymer.