Solution properties of polymers.

Abstract

Osmometry, viscometry, light scattering and Gel permeation chromatograph are normally used to measure the physical properties of polymer solutions and determine their average molecular weights. Nine monodisperse polystyrene standards with different molecular weights were used to obtain a conventional calibration curve for GPC. Another five polystyrene standards were used to obtain a universal calibration curve. By use of both calibration curves and the chromatogram of polymer sample from GPC, the number-average molecular weight, M¯n, and the weight-average molecular weight, M¯w, were consequently computed. Three polystyrene standards were characterized by osmometry, viscometry, light scattering, and GPC. Determinations of molecular weights were generally in agreement with their given molecular weight except for polystyrene of very high molecular weight. Commercial polybutadiene, polyisoprene, and two types of polystyrene-butadiene were also characterized by means of osmometry, viscometry, light scattering and GPC. M¯n for the synthetic rubbers as determined by osmometry was found to be in the range from 45,000 to 100,000. Because of some slight turbidity of polystyrene-butadiene-THF solution, the molecular weight determined by light scattering was found to be extremely high and finally deleted. From GPC analyses, it was found that synthetic rubber polymers had a relatively broad molecular weight distribution.