Kinetic and ESR studies on the radical polymerization of ?-n-(??-methylbenzyl) ?-ethyl itaconamates derived from racemic and (s)-?-methylbenzylamines

Abstract

The polymerization of α-N-(α′-methylbenzyl) β-ethyl itaconamate derived from racemic α-methylbenzylamine (RS-MBEI) by initiation with dimethyl 2,2′-azobisisobutyrate (MAIB) was studied in methanol kinetically and with ESR spectroscopy. The overall activation energy of polymerization was calculated to be 47 kJ/mol, a very low value. The polymerization rate (Rp ) at 60 °C was expressed by Rp = k[MAIB]0.5±0.05[RS-MBEI]2.9±0.1. The rate constants of propagation (kp ) and termination (kt ) were determined by ESR. kp was very low, ranging from 0.3 to 0.8 L/mol s, and increased with the monomer concentration, whereas kt (4–17 × l04 L/mol s) decreased with the monomer concentration. Such behaviors of kp and kt were responsible for the high dependence of Rp on the monomer concentration. Rp depended considerably on the solvent used. S-MBEI, derived from (S)-α-methylbenzylamine, showed somewhat lower homopolymerizability than RS-MBEI. The kp value of RS-MBEI at 60 °C in benzene was 1.5 times that of S-MBEI. This was explicable in terms of the different molecular associations of RS-MBEI and S-MBEI, as analyzed by 1H NMR. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4137–4146, 2000