Melt Viscosity of Main-Chain Thermotropic Liquid Crystalline Polymers without Flexible Spacers

Abstract published in Advance ACS Abstracts, September 1, 1995. 0024-929719512228-7085$09.00/0 were determined by Celanese using inherent viscosity mea- surements in dilute solution in pentafluorophenolhexafluoro- isopropyl alcohol (PFPMFIP), and they are listed in Table 1 along with their melting points as determined by DSC at 20 "C/min. The thermal characterization was performed from -50 to +360 "C on annealed samples,6s7 where the annealing was carried out at temperatures between room temperature and 310 "C. While annealing below 290 "C gave rise to a secondary endotherm, superimposed upon that associated with the mesophase transition, all transitions were completed by 310 "C, the temperature used for the viscosity measurements. It has been reported that these polymers have an exponent close to 1.0 in the Mark-Houwink-Sakurada eq~ation,~.~ therefore the weight-average molecular weight is about the same as the viscosity-average molecular weight. The nemat- ic-isotropic transition