Solvent effects on the rate of polymerization of 2-hydroxyethyl methacrylate photoinitiated with aliphatic azo compounds

Abstract

SUMMARY: The rate of polymerization (R p ) of 2-hydroxyethyl methacrylate, at low conversion, using aliphatic azo compounds as photoinitiators is considerably faster in water than in acetonitrile as a solvent. Active radical production in different solvents was analysed in detail. The quantum yield of active radicals showed only a minor dependence on the medium properties. These differences are due to changes in primary radical recombination reactions and they are unrelated to changes of R p observed in different media. By employing intermittent illumination techniques, it is shown that the increased R p in aqueous solution is due to a reduced rate of termination. Similar propagation rate constants were obtained in acetonitrile and water, whereas the termination rate constant increases by one order of magnitude when acetonitrile is employed instead of water. These results are discussed in terms of the effect of the cosolvent on the medium viscosity and the macroradical conformation.

Effect of solvent on the free radical polymerization of N,N‐dimethylacrylamide

“…Hence, for the same monomer and identical I a , the increase in R P observed in aqueous medium will be a consequence of changes in the k p / k t ratio and/or Φ i . Values of the active radical quantum yield of 0.38 and 0.40 at 25 °C were previously measured for the photodecomposition of AAPH in water and AIBN in acetonitrile, respectively, and the photodecomposition yield of these azo compounds is almost independent of the solvent 25. These facts show that the strong increase of the polymerization rate of NDMAm cannot be due to changes of the photoinitiation quantum yield.…”

Influence of the amine structure on the polymerization of methyl methacrylate photoinitiated by aromatic ketone/amine

“…The differences in the polymerization rates for the different amines must be due to changes in Φ i because we found that the addition of triethylamine or N,N ‐dimethylaniline up to 0.1 M did not modify the polymerization rate of MMA photoinitiated by AIBN. This azo compound produces radicals by a noncatalytic photocleavage 13. Therefore, the amine does not modify the propagation or the termination steps.…”

New UV-Curable Prepolymer: Synthesis, Characterization, and Kinetics Analysis

“…[3] The epoxy acrylate prepolymer is used extensively used in UV-curing coatings because of its good integrated performances such as outstanding adhesion, hardness, nonyellowing, mechanical properties and chemical resistance. [6][7][8][9][10][11][12][13] The main aim of the present work is to synthesize highly reactive, low-cost, high performance, high-shelf life and high viscosity prepolymer, 2-hydroxy-3-[p-(1-{p- [2-hydroxy -3-(vinylcarbonyloxy)propoxy]phenyl}-1-{pmethoxyphenyl)ethyl)phenoxy]propyl acrylate (HEPPA) in high yield as compared to commercially available prepolymer, bisphenol-A -glycerolate (1glycerol/phenol) (BISGA). [5] The composition of the UV-cured formulation influences the kinetics of photopolymerization, rate of polymerization, degree of conversion and the properties of the UV-cured polymer.…”