Calorimetric investigation of polymerization reactions. V. Crosslinked copolymerization of methyl methacrylate with ethylene dimethacrylate

Abstract

The crosslinked copolymerization of methyl methacrylate with ethylene dimethacrylate (EDMA) in bulk and in toluene has been investigated by differential scanning calorimetry. The appearance of a second peak, in addition to that arising from the gel effect, noted in curves of bulk copolymerization rate (fraction of EDMA mE = 0.20) is explained by the formation of microgels during the copolymerization. With mE = 0.50–1.00, copolymerization proceeds heterogeneously at first, providing opaque microgels, which become transparent polymer in a later stage at a weight fraction of toluene wT ≦ 0.20 and independent polymer particles at wT ≧ 0.30. A diagram is given which illustrates three types of copolymerization depending on initial composition of monomers and toluene. Final conversions for mE ≦ 0.10 agree well with predictions. Copolymerization at mE ≧ 0.20 ceases because of reduction of segmental mobility due to dense network formation in microgel, though the whole system is not yet in glassy state. Data of final conversions in solution copolymerization also support the above mechanism.

Polymerization Behavior of Hydrophilic-Rich Phase of Dentin Adhesive

“…Previous investigations have also reported a bimodal rate of polymerization for the methacrylate system (Horie et al 1975;Anseth et al 1994;Yu et al 2001). Horie et al (1975) suggested that there could be an accumulation of pendant double bonds during polymerization due to their reactivity being lower than the free monomers.…”

“…Horie et al (1975) suggested that there could be an accumulation of pendant double bonds during polymerization due to their reactivity being lower than the free monomers. During later stage of the polymerization, these pendant double bonds could form higher cross-linked regions called microgels.…”

“…During later stage of the polymerization, these pendant double bonds could form higher cross-linked regions called microgels. The trapped pendant double bonds trigger a secondary gel effect within the microgels, allowing the reaction to continue through the postpolymerization and resulting in the secondary rate maxima (Horie et al 1975).…”

Co-polymerization of Acrylates

“…Introducing cross-links into a latex film can increase its physical and chemical stability as well as improve its tensile strength and abrasion resistance [65]. As a consequence, there is a deep and growing interest within the coating industry in cross-linked water-borne coatings.…”

“…Ethylene glycol dimethacrylate (EGDM) has been widely used as a cross-linking agent in the synthesis of hydrophilic or hydrophobic co-polymer networks [55]. Some aspects of the co-polymerization of MMA with EGDM have been investigated since 1945 [14,[56][57][58][59][60][61][62][63][64][65][66]. Some authors estimated the efficiency of cross-linking [57,63] or determined the glass transition temperature of the co-polymer [58] (Table 3).…”