Polymerization kinetics of rigid-rod-like molecules. II. Polymerization of poly (1,4-phenylene-2,6-benzobisthiazole) in the nematic state

The kinetics of the polymerization to form the rod-like poly(1,4-phenylene-2,6-benzobisthiazole) in the nematic phase are discussed. The kinetics are not affected by a phase transformation from isotropic to nematic, provided that transformation occurs early in the polymerization. Suppressed diffusion rate parallel to the molecular axes appears to control the kinetics over much of the conversion, resulting in a constant rate of increase of the intrinsic viscosity with polymerization time. At high conversions, additional constraints due to restricted rotational diffusion may occur. The molecular-weight distribution is close to most-probable.