Meso and racemo Additions in Propagation for Radical Polymerization of Dialkyl Fumarates II. Determination of the Absolute Rate Constants

Abstract

ABSTRACT:The propagation process in radical polymerization of dialkyl fumarates (DRF) was investigated. The propagation rate constants (kp) for some DRFs were determined by ESR spectroscopy. It was revealed that k P increased with the introduction of a bulky tert-butyl ester group in the following order: di-tert-butyl fumarate > methyl tert-butyl fumarate > dimethyl fumarate. The absolute rate constants for meso and racemo additions were elucidated by the combination of the kP and the probability of meso addition, which was determined by 13 C NMR spectroscopy.KEY WORDS Dialkyl Fumarate / Radical Polymerization / Electron Spin Resonance / Propagation Rate Constant / meso Addition / racemo Addition / Dialkyl fumarates (DRF) with bulky ester alkyl groups homopolymerize readily to give high molecular weight poly(substituted methylene)s (Scheme 1). 1 -5 We have revealed that the polymerization reactivity ofDRF increases in the following order: di-tert-butyl fumarateThis order is consistent with the increase in the bulkiness of the ester alkyl groups, and has been interpreted as consequence of the decrease in a rate of bimolecular termination between less-flexible poly-(DRF) radicals, relative to a rate of propagation.4·5Rate constants for propagation (kp) and termination (k 1 ) are popularly determined by the analysis of non-steady state by means of a rotating sector. 6 Recently, however, it has been

Synthesis and Characterization of A New Series of “Mesogen-Jacketed Liquid Crystal Polymers” Based on the Newly Synthesized Vinylterephthalic Acid

“…The representative results were shown in Figure 2 which indicated that the samples did not crystallize. The diffraction patterns were similar to those of other MJLCPs, 17,18 showing a diffused halo at larger angles and a relatively sharp peak at lower angles. According to Xu et al 18 and Ober et al, 13 the mesophase could be assigned to the nematic phase.…”

Radical polymerization behavior of ethyl ortho‐(4‐phenyl‐1,3‐dioxolan‐2‐yl)phenyl fumarate

“…The k p values observed here (2.0 -8.5 L/mol s, 60°C) are much higher than those of dialkyl fumarates, for example, dimethyl fumarate (0.058 L/mol s, 60°C) and di-tert-butyl fumarate (0.46 L/mol s, 60°C), 8 indicating that the propagation in this polymerization is promoted by involving an intramolecular hydrogen abstraction of propagating polymer radical. The k p value decreased with increasing monomer concentration.…”

Radical Chain Polymerization

“…Various N-substituted maleimides, dialkyl fumarates (and fumaramides), and vinylene carbonate have been polymerized to higher molecular weights, many in the 10 3 -10 4 range with a few as high as 10 5 [Field and Schaefgen, 1962;Matsumoto and Kimura, 1996;Matsumoto and Otsu, 1995;Matsumoto et al, 1990Matsumoto et al, , 1993Reimschussel and Creasy, 1978]. Dialkyl maleates have not been successfully polymerized, except when a base such as morpholine is present to isomerize the maleate ester to fumarate ester prior to polymerization Yoshioka et al, 1991]. The lack of polymerization for the maleate esters is a consequence of the cis placement of the substituents, which maximizes the steric problem.…”