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Arrangement of substituted, rigid‐rod aramids in the highly‐ordered solid state
Author(s) -
Glomm Bernhard H.,
Grob Markus C.,
Neuenschwander Peter,
Suter Ulrich W.
Publication year - 2000
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20000801)201:13<1476::aid-macp1476>3.0.co;2-9
Subject(s) - crystallinity , aramid , materials science , steric effects , crystallography , crystal structure , phenylene , ring (chemistry) , crystal (programming language) , polymer chemistry , composite material , polymer , fiber , chemistry , stereochemistry , organic chemistry , computer science , programming language
Fibers of various rigid‐rod, fully aromatic polyamides, produced by polycondensation of differently substituted p‐ phenylenediamines and terephthaloyldichlorides, were spun from nematic solution and analyzed with wide‐angle X‐ray diffraction (WAXD). A post‐spin heat treatment was employed to improve the degree of orientation and crystallinity of the fibers. The dominating crystal structures were similar to those found in poly( p‐ phenylene‐terephthalamide) (PPTA) and described in the literature, i. e., “Modification I” and “Modification II”. With the exception of only one case, the investigated fibers do not suffer a structural transformation upon heat treatment comparable to that found in PPTA. Steric and electronic effects of the ring substitution lead in most cases to a small disturbance of the solid‐state structure in the fibers. Major structural changes caused by ring substitution are rare. Effects of the ring substitution pattern in the chains on the fiber crystal structure, their structural order, and their orientational properties could be observed. While the substitution of the aromatic rings seems to affect the competition between the basic crystal structures “Modification I” and “Modification II” (in analogy to PPTA) and the observed crystal structures agree with the results of detailed atomistic modeling predictions, no simple pattern seems to exist that would help predict, which candidate crystal structure is most stable.