Photoreactivity of vinyl ether/oxirane-based resin systems

We evaluated the reactivity in homopolymerization and as comonomers in dioxirane/polyol visible-light curable systems the following vinyl ethers (VEs): mono-, di-, and tri(ethylene glycol) divinyl ethers (EGDVE, DEGDVE, and TEGDVE, respectively); 1,6-hexanediol divinyl ether (HDDVE); cyclohexanedimethanol divinyl ether (CHDMDVE); glycidyl vinyl ether (GVE); 4-(1-propenyloxymethyl)-1,3-dioxolan-2-one (POMDO); and 1,4-butanediol vinyl ether (BDVE). The dioxirane/polyols (80/20) were Cyracure UVR 6105 or ERL 4206 dioxiranes with polytetra-hydrofuran [PTHF; number-average molecular weight (M-n) = 250]. Reactivities were evaluated by photodifferential scanning calorimetry with visible light. For VE homopolymerization, the relative reactivity ranking (based on exotherm peak maximum time) was TEGDVE > EGDVE > DEGDVE > HDDVE > CHDMDVE > BDVE > GVE > POMDO. For VEs in UVR 6105/PTHF, the ranking was GVE > TEGDVE > CHDMDVE > BDVE > EGDVE > DEGDVE = HDDVE = POMDO. In ERL 4206/PTHF, the ranking was: GVE > TEGDVE > BDVE > DEGDVE > HDDVE > EDGDVE > CHDMDVE = POMDO. The incorporation of an electron-donating reaction promoter, ethyl-4-dimethylaminobenzoate, generally shortened induction times and exotherm peak maximum times and increased rate constants for homopolymerizations and ternary polymerizations. Experimentally determined polymerization reactivities were compared with previously reported semiempirical quantum mechanical calculations of activation energies and heats of reaction. The results of laboratory and computational studies for selected compounds were in general agreement. (C) 2002 Wiley Periodicals, Inc.