ISSN:
0360-6376
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
By adapting the rotating sector technique to provide an intermittent source of cobalt-60 radiation the activation volumes for all reaction steps of the bulk polymerization of styrene have been shown to be independent of pressure up to 208 MPa. The activation volumes determined for polymerization, initiation, propagation and termination were, respectively, ΔV≠pol = -20.5 ± 0.22, ΔV≠i = +2.0 ± 0.18, ΔV≠p = -18.6 ± 0.44, and ΔV≠t = +5.8 ± 0.55 cm3 mol-. The values for the effect of pressure on the degree of polymerization ΔDP and the radical lifetime Δτ were, respectively, -22.6 ± 0.16 and -3.9 ± 0.29. The average radical lifetime increased from 4.5 s at atmospheric pressure to 6.3 s at 208 MPa. Because ΔV≠t is less than ΔV≠t and both are positive, the molecular weight increased with pressure at a faster rate than the polymerization rate. Although fewer radical chains were initiated per second under pressure the macroradical concentration increased with pressure because of the longer average lifetime of the radicals.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1981.170190706
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