High-Pressure Kinetics of Vinyl Polyperoxides

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 R-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 °C, degradation of the poly(styrene peroxide) formed is about 2.5 times less than that observed above 50 °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 RO2 • 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.

High-Pressure Kinetics of Oxidative Copolymerization of Styrene with -Methylstyrene

“…The saturation pressure of oxygen for styrene (STY) and α ‐methylstyrene (AMS) was found to be 2 and 300 psi, respectively 11. During the oxidative polymerization, STY shows auto‐deceleration with a break point, whereas AMS12 exhibits auto‐acceleration with the formation of a knee point 11.…”

Degradable Polymers Prepared from Alkyl Sorbates and Oxygen under Atmospheric Conditions and Precise Evaluation of Their Thermal Properties

“…For example, a peroxide polymer is formed in a high yield during the oxidative polymerization of styrene, but the simultaneous formation of benzaldehyde and formaldehyde is unavoidable and influences the polymerization kinetics and the reaction mechanism including a radical chain transfer. 8,12,27,28 The accurate evaluation of the thermal properties of peroxide polymers is often hin- dered by contamination with decomposition products despite a large number of studies on the synthesis and characterization of peroxide polymers.…”

Kinetic and thermochemical study of the oxidative polymerization of α-substituted styrenes

“…A detailed examination of the mechanism of oxidative polymerization revealed that the polyperoxides formed during oxygen copolymerization undergo facile degradation above 50°C [32]. To avoid side reactions, we have studied kinetics of oxidative polymerization at 40-50°C.…”

“…The [M] and [I] are monomer and initiator concentration, and k a is the overall rate constant for the oxidative copolymerization. [32] of the electrondonating methyl group. In addition to the reactivity of ÀMO 2 toward the monomer, we have to also consider the electron richness of the vinyl p bond in the monomer.…”

“…In presence of AIBN, the PCAMSP formation yields an E a of 22 kcal/mol. For AIBN-initiated polymerization, E i = 30 kcal/mol is reported [32,33]. The activation energies for the termination (E t ) for St oxidation is 1.8 kcal/mol [34].…”