Relationship Between the Free Radical Polymerization Rates of Methacrylates and the Chemical Properties of their Monomeric Radicals

Abstract

In this study, the rate of photopolymerization (Rp) of 21 alkyl methacrylates is correlated with the chemical properties of their monomeric radicals by making use of the enthalpic and polar effects of these radicals. Based on these properties, a general non‐linear expression is derived by optimizing the radicals and evaluating both their stability and polar effects, via the radical electrophilicity, using density functional theory. The expression performs quite well in predicting Rp for 16 of the 21 methacrylates with an R2 value of 0.9384, but does not hold for too unstable and/or too nucleophilic radicals. Increasing the stability or decreasing the nucleophilicity of the monomeric radical results in a higher polymerization rate; in addition, the influence of the polar effects becomes larger for more stable radicals. Methacrylates containing a pendant phenyl, where π–π stacking plays an important role, are experimentally found to have a higher polymerization rate than predicted.

DFT Modeling of the Alternating Radical Copolymerization and Alder-Ene Reaction between Maleic Anhydride and Olefins

“…The reasons of the formation of alternate polymers by MA and olefins are still unclear in detail. The methods of quantum chemistry based on the density functional theory were successfully used for the analysis of different radical polymerization processes [50][51][52], including homo-and copolymerization of acrylates [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71], acrylamides [70,72,73], and acrylonitrile [74]. However, as far as we know, DFT-based methods have not been extensively used for visualization and comprehensive analysis of the free radical alternating copolymerization of donor and cyclic acceptor monomers, except the publications of Matsumoto et al, devoted to the copolymerization of N-methylmaleimide (MMI) with olefins [75], and MA with 2,4-dimethylpenta-1,3-diene [76].…”

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

“…4). In case of compound 5 (0.052/0.043) and 4 (0.045/0.031) the values were slightly higher as or comparable to the often used 2-hydroxyethyl methacrylate (HEMA), as measured by a different work group (0.032) [34]. Interestingly, equipping the amide α-carbon with a methyl group (1→4) led to a ~70% decrease of R p,max from 0.147/0.102 to 0.045/0.031, indicating the special role of the internal double bond.…”