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Synthesis of soluble, liquid crystalline aramids via transition metal π‐Complexation
Author(s) -
Dembek Alexa A.,
Burch Robert R.,
Feiring Andrew E.
Publication year - 1994
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19940770132
Subject(s) - lyotropic , terephthaloyl chloride , polymer chemistry , materials science , polymerization , condensation polymer , polymer , crystallography , chemistry , composite material , liquid crystalline
An organo‐soluble, liquid crystalline organometallic polymer, ( p ‐phenyleneterephthalamide)Cr(CO) 3 [(PPTA)Cr(CO) 3 ], is prepared by polycondensation of ( p ‐phenylenediamine)Cr(CO) 3 with terephthaloyl chloride. Polarizing optical microscopy of this high molecular weight metallo‐aramid shows a nematic liquid crystalline texture in N, N‐ dimethylacetamide (DMAc), demonstrating that metal π‐complexation maintains the lyotropic, rigid‐rod character of PPTA. A PPTA copolymer with 50% of the diamine rings Cr(CO) 3 π‐complexed is also soluble and lyotropic in DMAc. Tensile properties of films of the 100% Cr(CO) 3 complexed aramid are isotropic in the plane of the film, while those of the 50% complexed analog are highly anisotropic. The organometallic substituent is a site for polymer functionalization: exchange of a carbonyl for a trimethylphosphine ligand, and subsequent polymerization affords the phosphine‐functionalized (PPTA)Cr(CO) 2 P(CH 3 ) 3 , which has a much higher critical concentration for liquid crystal formation. Oxidative decomplexation of the Cr(CO) 3 group yields the parent PPTA, demonstrating the reversibility of the organometallic modification approach.