Premium
Low‐frequency thermomechanical spectrometry of polymeric materials: Tactic poly(methyl methacrylates)
Author(s) -
Gillham J. K.,
Stadnicki S. J.,
Hazony Y.
Publication year - 1977
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.1977.070210208
Subject(s) - tacticity , materials science , polymer , methyl methacrylate , amorphous solid , glass transition , poly(methyl methacrylate) , polymer chemistry , composite material , extrapolation , shear modulus , analytical chemistry (journal) , crystallography , chemistry , organic chemistry , monomer , polymerization , mathematical analysis , mathematics
A computerized and automated torsional pendulum has been used to characterize amorphous poly(methyl methacrylates) at about 1 Hz in the temperature sequence 473° → 93° → 473°K. The effects of thermal prehistory, temperature cycling, water content, and tacticity are demonstrated. In particular, a comparison of the out‐of‐phase shear modulus ( G″ ) versus temperature for “syndiotactic,” “atactic,” and “isotactic” polymer specimens shows that the intensity of the glassy‐state β loss peak decreases with increasing isotactic content while the temperature of its location remains the same. Extrapolation suggests that completely isotactic polymer would not display a β loss peak. The shape and location of the G″ data at low temperatures indicate that the basic mechanism of the β process is the same for the three polymer samples and support the validity of the extrapolation. The effect of tacticity is reflected also in the glass transition region; the isotactic sample has its T g about 65°C lower with greater intensity than the syndiotactic polymer.