Electron spin resonance spectroscopic studies on microheterogeneity of crosslinked polymers. IV. Correlation between void evaluation of crosslinked resin and microgelation in monomethacrylate/dimethacrylate copolymerizations

Electron spin resonance spectroscopic studies on the microheterogeneity of crosslinked polymers were performed to ascertain the correlation of the voi d evaluation of monomethacrylate/dimethacrylate (DMA) cured resins with the microgel formation before gelation in their crosslinking copolymerizations . Lauryl methacrylate (LMA) was added to methyl MA (MMA)/ethylene DMA (EDMA ) copolymerization because the addition of LMA reduces the occurrence of in tramolecular crosslinking by the steric hindrance of bulky long-chain alkyl groups, leading to the formation of a less densely crosslinked microgel co re and a less microheterogeneously crosslinked resin. Then MMA/vinyl laurat e (VL)/EDMA terpolymerization was performed because the polymerizability of conjugated methacryloyl groups belonging to MMA and EDMA is markedly high compared with the unconjugated vinyloxycarbonyl group of VL. Thus, enhanced microheterogeneity for MMA/VL/EDMA terpolymerization would be induced as c ompared with MMA/EDMA copolymerization. Finally, allyl MA (AMA) and vinyl M A C(SIMA) crosslinkers were used in place of EDMA because in the polymeriza tions of AMA and VMA having two types of carbon-carbon double bonds of diff erent reactivities there was no microgelation observed up to the gel-point conversion. (C) 2001 John Wiley & Sons, Inc.