| Autor: |
R. E. Singler, N. S. Schneider, M. N. Alexander, P. L. Sagalyn, C. R. Desper |
| Rok vydání: |
1978 |
| Předmět: |
|
| DOI: |
10.1016/b978-0-12-160850-7.50031-9 |
| Popis: |
The poly(organophosphazenes) of general structure [(RO) 2 PN] n , where RO may be an alkoxy or an aryloxy group, are generally crystalline and exhibit both a first order transition to a mesomorphic phase at a temperature designated T(l) and the transition to the isotropic melt at a temperature T M which is 150 to 250°C higher. An investigation of the behavior at T(l) and T M by scanning calorimetric and thermal expansion methods is presented. It is shown that the thermal history of the sample at temperatures above T(l) has a strong influence on the endotherm at T(l) implying that it is possible to alter the structure of the mesomorphic phase and, in turn, the crystalline structure formed on cooling. The results of x-ray diffraction studies indicate that the T(l) transition involves a transformation from the crystalline structure to a metrically hexagonal lattice exhibiting lateral order but longitudinal disorder and that side chain packing controls the interchain distance. Preliminary broad line NMR data show that the disorder above T(l) is dynamic rather than positional and arises from the onset of rapid side chain and backbone motions. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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