Dynamic rheological properties and microstructures of liquid-crystalline poly(p-phenyleneterephthalamide) solutions in the presence of single-walled carbon nanotubes

The rheological properties and microstructures of both poly(p-phenylene terephthalamide)/sulfuric acid(PPTA/H2SO4) and poly(p-phenylene terephthalamide)/ single-walled carbon nanotubes/sulfuric acid (PPTA/SWNT/H2SO4) dopes were investigated with flat plate rotational rheometer, polarized optical microscope and differential scan calorimeter. The results showed that, the two types of dopes presented typical shear thinning behaviour even at low frequencies, at various temperatures as well as at all polymer concentrations, and that the relationships between complex viscosity and freqency and between zero shear viscosity and weight average molecular weight implied the tight PPTA chain contacts, somewhat the feature of flexible polymer entanglements. The protonation due to concentrated sulfuric acid allowed SWNT to be well dispersed in PPTA/SWNT/H2SO4 dopes. At the concentrations of SWNT, approximately over 0.2 wt%, a novel type of single phase nematic liquid crystal was formed. The dopes can be used to fabricate high performance fibers by dry-jet wet spinning process.