THE STRUCTURE OF WHOLLY AROMATIC POLYESTERS WITH BULKY SIDE-CHAINS - POLY(PHENYLENE PHENYL-TEREPHTHALATE)

Citation
Sn. Chvalun et al., THE STRUCTURE OF WHOLLY AROMATIC POLYESTERS WITH BULKY SIDE-CHAINS - POLY(PHENYLENE PHENYL-TEREPHTHALATE), Journal of macromolecular science. Physics, B37(4), 1998, pp. 451-462
Citations number
23
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Polymer Sciences
ISSN journal
0022-2348
Volume
B37
Issue
4
Year of publication
1998
Pages
451 - 462
Database
ISI
SICI code
0022-2348(1998)B37:4<451:TSOWAP>2.0.ZU;2-B
Abstract
The thermotropic polyester prepared from phenyl-terephthalic acid and hydroquinone is highly crystalline, despite the probable random 2- and 3-disposition of the phenyl substituents. The x-ray pattern of melt-s pun fibers contains 18 Bragg reflections that are indexed by a monocli nic unit cell with dimensions a = 28.0 Angstrom, b = 4.89 Angstrom, c = 12.48 Angstrom (fiber axis), and gamma = 114.8 degrees, containing m onomer units of four chains. In the ac-plane, the chains are arranged in pairs with the phenyl side chains interdigitated; successive pairs of chains are staggered by about c/2. We have used molecular mechanics modeling to simulate arrays of chains with random 2- and 3-dispositio n of the side chains on the terephthalic acid units and have compared the results with those for a similar structure in which all the substi tuents were at the 2-position. The refined model for random substituti on is distorted, but the average separations of the monomer units are within experimental error of the observed unit cell dimensions, and th eir standard deviations are very similar to those derived from the lin e broadening data. The potential energy of the random substitution mod el is only about 1 kcal/mol of monomer higher than that for the model with all 2-substitution, indicating the random substitution is not a p roblem for the formation of an ordered structure.