کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5184468 | 1381048 | 2011 | 10 صفحه PDF | دانلود رایگان |
Microsingle crystals of poly(para-phenylene terephthalamide), abbreviated PPTA, were obtained by water-vapor induced precipitation of PPTA rigid-flexible copolymers in sulfuric acid solution. Electron diffraction was performed and yielded hk0 patterns. The crystal structure of a model compound, N, NⲠpara (4-methoxycarbonyl) phenylene dibenzamide, abbreviated 3ARB-COOMe, is also reported. Its structure is compatible with that of the polymer, in which aromatic rings are all coplanar and form a 30° angle with amide groups. A reinvestigation of form II, based on electron diffraction data and molecular modeling simulations, is reported. The proposed space group is P112, and corresponds to a parallel chain arrangement, with terephthaloyl groups facing one another, and carbonyl groups pointing in opposite directions along the b-axis in adjacent hydrogen-bonded sheets. Chain conformation is the same as in form I, as previously established. The 3ARB-COOMe conformation is suggested as a possible polymorph or as defects in the crystal phase.
Journal: Polymer - Volume 52, Issue 18, 18 August 2011, Pages 4083-4092