ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Relaxation distribution functions for concentrated solutions of six polyisobutylene samples, using three different solvents, have been derived from measurements by the methods of the single transducer, wave propagation, and stress relaxation following cessation of steady-state flow. The ranges of molecular weight, concentration, and temperature were about 0.3 to 2.5 × 106, 5 to 40%, and -5 to 40°C., respectively. When plotted with reduced variables with a reference state of unit density and viscosity at a standard temperature, data at different temperatures superpose; data at different concentrations superpose except for the two samples of highest molecular weight, where there are perceptible deviations. The reduced distribution functions for all the samples lie close together at long times where there is a drop associated with the finite lengths of the molecules. The theory of Rouse for viscoelastic properties of dilute solutions, when modified for concentrated solutions by assuming that all segmental mobilities are equally affected by interlacing of neighboring molecules, agrees with the reduced mechanical properties at long times fairly well. However, it does not predict the plateau region characteristic of distribution functions of polymers of high molecular weight. The existence of this plateau in concentrated solutions and undiluted polymers represents an abnormal prolongation of the longest relaxation times in these systems, which is attributed to molecular coupling by entanglement as discussed by Bueche with respect to steady flow viscosity.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1954.120147504
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