Pt. Mather et al., THERMALLY CROSS-LINKABLE THERMOTROPIC COPOLYESTERS - SYNTHESIS, CHARACTERIZATION, AND PROCESSING, Polymer, 38(24), 1997, pp. 6009-6022
The synthesis, characterization, and processing of thermotropic copoly
mers composed of hydroxybenzoic acid (HBA), hydroxynaphthoic acid (HNA
), and systematically varying amounts of hydroquinone (HQ) and crossli
nkable terephthalic acid (XTA) are described. The XTA monomer contains
a benzocyclobutene (BCB) group that lies dormant during synthesis and
initial steps of processing, but that can be thermally activated to i
ntroduce covalent crosslinking between laterally adjacent macromolecul
es. The XTA-containing HBA/HNA copolymers all remain thermotropically
liquid crystalline, and can be processed into oriented fibres by melt
spinning. Rheological characterization reveals an increase in the visc
osity and transition from liquid-like to solid-like behaviour as the c
rosslinking proceeds. X-ray diffraction reveals the changes in local o
rganization with increasing XTA content. The microstructures of the XT
A-containing copolymers (up to 20% XTA) in the condensed state are sim
ilar to those seen in HBA/HNA copolymers. (C) 1997 Elsevier Science Lt
d.