Manufacture of ultra high modulus polymer fibres: the polymerization step

Polymers with a rodlike conformation can be spun into ultra high strength fibres which find applications in the manufacture of light weight composites, cables and ropes, and protective clothing, among others. The polymerization of such rodlike molecules, which are made by solution polycondensation, is qualitatively different from flexible molecules. For rodlike polymers, nearly parallel orientation of the reacting pair of is a necessary condition for reaction, and this results in slowing of the reaction due to very slow rotational diffusion of the molecules. Flow can easily orient rodlike molecules due to their anisotropic shape and low rotational diffusivity, and thus has an impact on polymerization kinetics. The role of polymer dynamics on the polymerization kinetics of rodlike molecules is reviewed, as is the effect of dynamics on the molecular weight and the molecular weight distribution of the product. The implications for practical applications are discussed