Polymerization of mono‐, Di‐, and trichloroethyl methacrylates: A study in chain transfer. Issue 1 (30th September 2016)

• Record Type: Journal Article
• Authors: Snow, Arthur W.
• Is Part Of: Journal of polymer science. Volume 55:Issue 1(2017)
• Page Start: 93
• Page End: 106
• Publication Date: 2016-09-30
• Subjects: chain transfer -- chloroethyl methacrylate -- deuterium isotope effect -- vicinal effect; 547
• DOI: 10.1002/pola.28366
• Languages: English
• ISSNs: 0887-624X

Abstract

ABSTRACT: Bulk free radical polymerization of the monomer series CH2 = C(CH3 )C(O)OCH2 CH3‐ n Cl n, n = 1, 2, 3, yields an unexpectedly crosslinked product with a crosslink density that increases with decreasing chlorine content of the respective monomer ( n = 3 < n = 2 < n = 1). This chlorine substituent effect is investigated by correlation with chain transfer constant measurements for four homologous series of chloroalkyl compounds (chloroethyl acetates (CH3 C(O)OCH2 CH3‐ n Cl n, n = 1, 2, 3); chloromethanes (CH4‐ n Cl n, n = 2, 3, 4) and CD2 Cl2 and CDCl3 analogs; butyl chloride isomers ( n‐, iso‐, sec ‐, tert ‐) and tert ‐C4 D9 Cl analog; and nine chloroethanes (C2 H n −6 Cl n, n = 1–6)) in a methyl methacrylate polymerization. The pattern conveyed by the magnitude of chain transfer constants and deuterium isotope effects is consistent with a vicinal chlorine effect (i.e., chlorine activation of a vicinal hydrogen for abstraction) to account for the relative activities of the four series of model compounds and for the propensity of the chloroethyl methacrylates to crosslink in a bulk free radical polymerization. The chloroalkyl moiety's contribution to chain transfer is relatively modest (≤10 −4 ), but, when incorporated as a monomer pendant group in free radical polymerizations, it is effective in broadening molecular weight to the extent of resulting in a crosslinked polymer. Published 2016. † J. Polym. Sci., Part A: Polym. Chem.2017, 55, 93–106 Abstract : Chain transfer to polymer leading to subsequent crosslinking during bulk polymerizations of mono‐, di‐, and trichloroethyl methacrylate monomers is analyzed by crosslink density characterization, by chain transfer measurements on chloroalkyl model compounds and by model compound deuterium isotope effects. A vicinal effect (chlorine activation of a vicinal hydrogen for abstraction) mechanism is proposed and correlated with chain transfer constant measurements from four series of model compounds.