Regularities of postpolymerization in a vinyl monomer-metallocene-radical initiator system

Abstract

The polymerization of methyl methacrylate in the presence of metallocenes and radical initiators has been shown to proceed as radical coordination polymerization, with the propagation of some chains fol lowing a coordination mechanism involving metallocenes. The polymerization products are capable of initi ating monomer polymerization in the absence of an initiator. The catalytic activities of "metallocene" poly mers are determined by the history of their synthesis.

Modeling of elementary reactions and kinetics of radical‐initiated methyl methacrylate polymerization in the presence of ferrocene

“…The process of methyl methacrylate bulk polymerization runs in the presence of benzoyl peroxide, and ferrocene is characterized by some interactions between the components of the mixture . In addition to the typical reactions for free radical polymerization (initiation, chain propagation, chain termination, and chain transfer), there are also the following interactions between (1) ferrocene and benzoyl peroxide, (2) ferrocene and monomer, and (3) ferrocene and poly(methyl methacrylate) macroradicals; and the reaction of coordination sites formation and chain propagation on these active sites (reactions 1–9, Scheme ; the structures are indicated in a form suitable for further kinetics modeling).…”

“…For this purpose, the following data were used: the experimentally determined values of the polymerization rate W and the poly(methyl methacrylate) molar masses M n and M w at 5% conversion of methyl methacrylate (Table ); the time dependences of methyl methacrylate conversion (Figures and ); the conversion dependences of molar masses M n and M w 38,39 (Figure ) and the poly(methyl methacrylate) stereoregularity st (Figure ) during its production in the presence of benzoyl peroxide and ferrocene; the time dependence of the methyl methacrylate conversion during its polymerization on poly(methyl methacrylate) macroinitiators, obtained in the presence of benzoyl peroxide and ferrocene (Figure ). To reduce the uncertainty connected with a large number of required parameters, the inverse problem was divided into two stages.…”

“…the time dependence of the methyl methacrylate conversion during its polymerization on poly(methyl methacrylate) macroinitiators, obtained in the presence of benzoyl peroxide and ferrocene (Figure ). To reduce the uncertainty connected with a large number of required parameters, the inverse problem was divided into two stages.…”

“…Along with this, in the experimental studies, the facts appeared that could not be explained by increasing of the rate of polymerization initiation. The most significant of these facts are (1) the increasing of syndiotacticity of poly(methyl methacrylate) obtained in the presence of metallocenes; (2) the ability of poly(methyl methacrylate) obtained in the presence of metallocenes (ferrocene, zirconocene dichloride, and titanocene dichloride) to be as a macroinitiator, that is to initiate the polymerization of a new portion of monomer at a constant rate to the full monomer conversion, showing the signs of living polymerization; (3) unrepresentative for free radical polymerization conversion propagation of polystyrene average molar masses; (4) broad polystyrene molar mass distribution in case of ferrocene and bimodal polystyrene molar mass distribution in case of titanocene dichloride and zirconocene dichloride even for small monomer conversions …”

“…The analysis of the experimental facts, the review of polysites of polymerization systems based on the data of molar mass distribution, and the results of quantum chemical modeling of metallocenes interactions with components of polymerization system have led to the conclusion that in radical‐initiated polymerization along with free radicals, the living active sites of the chain propagation are being formed and do function, and on them a coordinating mechanism of monomer addition to the chain is realized being a ligand of the coordination active site …”