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Molecular weight and concentration effects on gel/sol transitions in a segmented rigid‐rod polyimide solution
Author(s) -
Lee Sung Koo,
Cheng Stephen Z. D.,
Wu Zongquan,
Lee Chul Joo,
Harris Frank W.,
Kyu Thein,
Yang JenChang
Publication year - 1993
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.4990300117
Subject(s) - polyimide , polymer , glass transition , kinetics , sol gel , materials science , polymer chemistry , chemical engineering , composite material , nanotechnology , layer (electronics) , physics , quantum mechanics , engineering
Gel/sol and order/disorder transitions can be observed in a segmented rigid‐rod polyimide solution at different concentrations and molecular weights. This polyimide was synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 2,2′‐bis(trifluoromethyl)‐4,4′‐diaminobiphenyl in refluxing 3‐cresol in a one‐step process. Above about 140°C, the polymers are completely soluble in 3‐cresol in a concentration range up to 12(w/w)%. During cooling, the hot solutions undergo a mechanical sol/gel transition to form thermally reversible gels. In the gel state, an ordered structure develops. Both the gel/sol and order/disorder transitions are dependent upon concentration, temperature, and molecular weight, but the two transitions exhibit different kinetics. Possible mechanisms of these transitions are discussed.