Molecular weight of polymers from electrical resistivity of solutions

✍ Scribed by Purdon, J. R. ;Morton, M.

• Publisher: John Wiley and Sons
• Year: 1962
• Weight: 757 KB
• Volume: 57
• Category: Article
• ISSN: 0022-3832
• DOI: 10.1002/pol.1962.1205716536

✦ Synopsis

Abstract

An investigation has been carried out to further establish the usefulness of electrical resistivity techniques for the study of polymerization kinetics, and to determine the extent of molecular weight dependence of electrical resistivity. The resistivity increment, (__p − p__0)/~__p__0~, which may be regarded as the fractional increase in resistivity of a system due to the presence of polymer, was found to be directly proportional to the concentration of polymer in solution. Based on the assumption that conductance in polymeric systems occurs by migration of ionic impurities, the resistivity increment was shown to be identical to the specific local viscosity. A marked dependence of (__p − p__0)/~__p__0~ upon molecular weight was found. The relationships observed provide expressions for determination of molecular weight from resistivity data in the systems: polystyrene‐styrene, polystyrene‐cyclohexane, and poly(methyl methacrylate)‐benzene. Furthermore, these relationships indicate the existence of a “critical packing volume” for the polymer chains in solution. This effect permits a determination of the unperturbed end‐to‐end chain dimension of the polymer (polystyrene) which agrees reasonably well with the published value.