Free-Radical Copolymerization of Methacrylonitrile and α-Methylstyrene

Abstract

Copolymerization of methacrylonitrile and «-methylstyrene was studied at 60°with free-radical initiation.Copolymer composition was determined by monitoring rate of loss of monomers from toluene solution, using gas-liquid chromatography. The reactivity ratios are ri(methacrylonitrile) 0.38, r2(«-methylstyrene) 0.54. A simple copolymerization model fits the data, although the ceiling temperature of poly(a-methylstyrene) is 61°. Mean sequences of this monomer in the copolymer are short and have an effectively higher polymerization enthalpy and ceiling temperature than high molecular weight homopolymer. A comparison of these results and previous data for copolymerization of styrene and «-methylstyrene with other reports based on chemical analyses of high molecular weight copolymer suggests that «-methylstyrene may be accumulating in low polymer.

Ring‐Opening Metathesis Copolymerization of Cyclopentene Above and Below Its Equilibrium Monomer Concentration

“…The earliest theoretical description [38] of copolymerizations with significant [M] eq explicitly considered repeat unit sequence effects on the rate of depropagation (i.e., the identity of not only the penultimate repeat unit in the chain, but also the unit preceding the penultimate unit). While such extended sequence effects are relevant for monomers that yield repeat units whose substituents have strongly unfavorable steric interactions, such as α-methylstyrene [3,[5][6][7][8]12] and 1,1-diphenylethylene, [13] they are unlikely to influence ROMP copolymerizations of monomers such as N and C, where each repeat unit contributes five backbone carbons to the chain. Instead, we derive an expression based on population balances from the rate equations, analogous to the classic copolymerization equation [26] based on the terminal model of copolymerization kinetics [24,25] but with depropagation of one monomer included.…”

“…But while monomers cannot homopolymerize below their [M] eq , they may still copolymerize with other monomers. This fact has been recognized since at least 1950, [3] and numerous examples of free-radical, [4][5][6][7][8][9] cationic, [10,11] and anionic [12,13] copolymerizations, where at least one monomer is below its [M] eq , have been demonstrated. Many monocyclic olefins (cyclopentene, cyclohexene, cycloheptene, and derivatives thereof), [14] which are mechanistically amenable to ring-opening metathesis polymerization (ROMP), also exhibit a significant [M] eq .…”

Terpolymerization of Methacrylonitrile, Styrene, and α-Methylstyrene

“…Qualitatively, we note that polymerization rates are faster in a termonomer system than in binary polymerizations. Feeds (Table 2) with relatively low cr-methylstyrene concentrations gave conversions of about 15% total monomers in 24 h at 60 "C. The conversion for higher a-methylstyrene contents was about 9%, but both polymerization rates are considerably faster than those noted previously in binary systems (2,3). This would beexpected to parallel the lower mean sequence lengths of terpolymers.…”

“…The best procedure then involves use of a non-linear least squares fit to a differential equation or use of an integrated form of the copolymer equation. A linear least squares fit of reactivity ratios to analytical data in a differential copolymer equation can lead to errors even when the polymer composition does not vary over the experimental range of monomer conversions (3,4,6,16).…”

Optimal Temperature−Time Programming in a Batch Copolymerization Reactor

“…Kinetic Model. The copolymerization of styrene and α-methylstyrene has been previously studied both in the bulk and in solution. − Similarities with the homopolymerization behavior of styrene or α-methylstyrene are often emphasized. The kinetic model of an emulsion polymerization usually divided into three stages is detailed in ref , where different assumptions and subsequent models are discussed.…”