Accession Number : ADA117262
Title : Property-Structure-Processing Relations in Polymeric Materials.
Descriptive Note : Final rept.,
Corporate Author : CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF CHEMISTRY
Personal Author(s) : Yen,L ; Meitz,D ; Markovitz,H ; Berry,G C
PDF Url : ADA117262
Report Date : 31 Jul 1981
Pagination or Media Count : 80
Abstract : In recent years, macromolecules with a rodlike chain conformation have been processed from liquid crystalline solutions to prepare fibers and sheets with exceptional stiffness and strength. In this study, the polymerization kinetics of a rodlike chain have been determined. The chain studied, poly(1,4 phenylene benzobisoxazole), PBO, is rigid and rodlike, forms liquid crystalline solutions, anc can be fabricated to give high modulus fibers. The investigation showed that the effective reactivity of the chain decreased sharply with increasing chain length. Presumably, this reflects a diffusion-limited polymerization rate for the condensation of rigid rodlike chains--the reactive end group is not free to diffuse without corresponding motion of the entire molecule, in distinction to the situation with flexible-chain polymers. One result of the unusual polymerization kinetics is that the molecular weight distribution is unusually narrow for a step-growth polymer owing to the relative decrease in the production of long chains and the depletion of short chains in the overall population. The second part of this investigation was addressed to the rheological properties of polymeric fluids containing suspended particles.
Descriptors : *Polymers, *Molecular structure, *Polymerization, *Reaction kinetics, *Rheology, Macromolecules, Chemical radicals, Crystal structure, Liquid crystals, Solutions(General), Azoles, Reactivities, Diffusion, Molecular weight, Distribution, Particles, Dispersions, Viscosity, Shear properties, Time dependence
Subject Categories : Polymer Chemistry
Atomic and Molecular Physics and Spectroscopy
Distribution Statement : APPROVED FOR PUBLIC RELEASE