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High-Pressure Kinetics of Vinyl Polyperoxides

Kishore, K and Paramasivam, S and Sandhya, TE (1996) High-Pressure Kinetics of Vinyl Polyperoxides. In: Macromolecules, 29 (22). pp. 6973-6978.

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Official URL: http://pubs.acs.org/doi/abs/10.1021/ma951769c

Abstract

This is the first report on studies carried out in detail on high-pressure oxygen copolymerization (> 50 psi) of the vinyl monomers styrene and alpha-methylstyrene (AMS). The saturation pressure of oxygen for AMS oxidation, hitherto obscure, is found to be 300 psi. Whereas the ease of oxidation is more favorable for styrene, the rate and yield of polyperoxide formation are higher for AMS. This is explained on the basis of the reactivity of the corresponding alkyl and peroxy radicals. Below 50 degrees C, degradation of the poly(styrene peroxide) formed is about 2.5 times less than that observed above 50 degrees C, so much so that it gives a break in the rate curve, and thereafter the rate is lowered. Normal free radical kinetics is followed before the break point, after which the monomer and initiator exponents become unusually high. This is interpreted on the basis of chain transfer to the degradation products. The low molecular weight of polyperoxides has been attributed to the (i) low reactivity of RO(2)(.) toward the monomer, (ii) chain transfer to degradation products, (iii) facile cleavage of O-O bond, followed by unzipping to nonradical products, and (iv) higher stability of the reinitiating radicals. At lower temperatures, (i) predominates, whereas at higher temperatures, chiefly (ii)-(iv) are the case.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to American Chemical Society.
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 12 Aug 2009 06:06
Last Modified: 19 Sep 2010 05:27
URI: http://eprints.iisc.ernet.in/id/eprint/19287

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