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Origin of stress and birefringence generation at hot‐stretching of poly(methyl methacrylate) containing low‐molecular‐weight compound
Author(s) -
Yamaguchi Masayuki,
Miyashita Maho
Publication year - 2021
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.49707
Subject(s) - birefringence , materials science , relaxation (psychology) , stress (linguistics) , liquid crystal , methyl methacrylate , deformation (meteorology) , poly(methyl methacrylate) , stress relaxation , methacrylate , polymer chemistry , composite material , optics , polymer , creep , polymerization , optoelectronics , psychology , social psychology , linguistics , philosophy , physics
The simultaneous measurements of stress and birefringence during hot‐stretching, and after the cessation of stretching, were performed using a miscible blend of poly(methyl methacrylate) (PMMA) and 10 wt% of 4‐cyano‐4′‐pentylbiphenyl (which is commonly known as 5CB). The birefringence of the blend exhibited anomalous behavior during stretching, that is, it initially decreased, then rapidly increased to a positive value. A concave curve with a minimum birefringence was prominent at low temperatures, during which PMMA determined birefringence. After passing the yield point, which corresponded to the minimum birefringence, the birefringence increased in proportion to the applied stress. That is to say, the stress‐optical coefficient remained constant. In this region, the 5CB molecules oriented themselves with the PMMA chains, that is, there was nematic interaction. After stretching ceased, the stress initially decreased rapidly; during this period, the stress‐optical coefficient was determined mainly by the deformation of PMMA, that is, glassy component. Subsequently, the orientation relaxation of 5CB, which occurred with the orientation relaxation of PMMA chains in the stage with a long time region, determined the birefringence. These results demonstrated that nematic interaction does not occur when inelastic deformation is governed.