ISSN:
0449-2951
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Since the observations of Edgar and Hill on polyhexamethylene adipamide/polyhexamethylene terephthalamide copolymers, a linear melting point/composition relationship has become widely accepted as a criterion for isomorphous replacement. In a series of binary copolymers based on homopolymers prepared from hexamethylene diamine and p-phenylene dipropionic (3P3), 3-(p-carboxymethyl) phenyl butyric (2P4), 2-(p-carbomethoxy) phenyl propionic (3PO2), hydroquinone diacetic (2OPO2), terephthalic (T), adipic (6), or sebacic (10) acids, only the 6.3P3/6.3PO2 system showed a linear softening point/composition curve, although the differences in repeating unit length were certainly no greater and often much less than with adipic and terephthalic acids. X-ray examination, however, revealed that all the systems behaved in the same basic manner, the second component dissolving in the lattice of the first until a certain critical concentration was reached when the lattice changed fairly abruptly to that of the second component in which the first component was now dissolved. The changeover point generally, but not always, coincided with the position of a minimum in the softening point/composition curve. Infrared and density measurements did not show any reduction in crystallinity at this point. These copolyamides, thus, afford no exception to the assumption that close similarity in length of repeating units is a necessary, but perhaps not the only, prerequisite for the occurrence of segmental change. The form of the softening point/composition curve is, therefore, not a reliable criterion for isomorphous replacement and it seems likely that this conclusion applies equally to the melting point/composition curve.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1964.100021004
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