Unperturbed dimensions of some aryloxy polyphosphazenes

✍ Scribed by A.L. Andrady; J.E. Mark

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 338 KB
• Volume: 17
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(81)90131-2

✦ Synopsis

Three aryloxyphosphazene copolymers, [P(ORXOR')-N-] with R = phenyl, and R' = p-ethylphenyl, 2,4-dichlorophenyl or 2-naphthyl, were each separated into four fractions using fractional precipitations from tetrahydrofuran (THF) solutions, with n-pentane as non-solvent. Two fractions from each were characterized using osmometry and viscometry, in THF at 25 °, thereby providing values of the number-average molecular weight, second viria! coefficient, and intrinsic viscosity. This information was used to obtain values of the characteristic ratio (r2)o/nl 2 of the unperturbed dimensions relative to the number of skeletal bonds and the square of their length. The values of this ratio show a remarkably large dependence on the nature of side-groups, in agreement with the results of two previous investigations. The observed large variations could be due to experimental difficulties associated with solution properties of this class of polymers. If real, however, the differences could be due to the fact that, when the two bond angles of the repeat unit of these chains are significantly different, then the most likely regular conformations of these chains correspond to extremely different spatial extensions. Markedly different values of the unperturbed dimensions could thus conceivably result from changes in conformationai population arising from relatively small changes in intramolecular interactions, stereochemical composition, chemical composition, or chemical sequence distribution.