ISSN:
1022-1352
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
For poly(TMPS)Poly(oxydimethylsilanediyl-1,4-phenylene-dimethylsilanediyl). fractions and blends of fractions, it has been established experimentally that the isothermal spherulitic growth rate, G, and physical properties are strongly interrelated. Correlations also depend strongly upon molecular weight. Below the melt viscosity entanglement molecular weight Mc, G is very dependent upon molar mass whenever crystallized fractions are chain folded, brittle and lacking in tiemolecules. Above Mc, G is essentially constant, and polymers are tough and durable because of trapped entanglements, tie-molecules and the like, that are mostly located at lamellar interfaces. Growth rate measurements and other physical properties of poly(TMPS) are inconsistent with the claim that reptation is a viable process in the crystallization of this polymer. Selective chemical etching of poly(TMPS) crystal surfaces of moderate MW (≈35 × 103 Daltons) show an increase in crystallinity from ≈75% to 95% as the surface is removed, thus testifying to a less than ordered surface morphology. Notably, in melt crystallized high MW fractions, approaching 106 Daltons and beyond, the morphology is much less well organized than it is in moderate to low MW fractions. Trends in the physical properties of polyethylenes, polyisoprene and poly-(ethylene oxide) MW fractions are analogous in behavior to melt crystallized poly(TMPS) fractions over comparable molecular weights ranges, and consistent with a morphology that is dependent upon polymer chain length.
Additional Material:
14 Ill.
Type of Medium:
Electronic Resource
