Vibrational overtone spectroscopy of several mono- and polyacrylates, azo-initiators and polysiloxanes, vibrationally initiated polymerization of methyl methacrylate and methyl methacrylate-polysiloxane mixtures

Vibrational overtone spectra of several mono- and poly-acrylates, polysiloxanes and various azo-initiators were recorded in the 4500 to 15000 cm-1 range, covering the first through fourth vibrational overtone transitions of the CH stretch. The transition wavenumbers for the fifth overtone absorptions of the CH stretch were calculated using Birge-Sponer extrapolations. The conversion of EGDMA monomer was calculated using first, second, third and fourth vibrational overtones of the CH stretch.; Solvent-induced frequency shifts of the methyl CH stretch absorptions of AIBN were studied and the correlation between frequency shifts and solubility of AIBN was found.; Excitation at the fifth vibrational overtone transition of the CH stretch of AIBN initiates polymerization in a mixture of AIBN and MMA. The reaction is wavelength specific since there is no polymerization detected when the sample is irradiated at a wavelength where both monomer and initiator have no absorption. Excitation at the third vibrational overtone transition of the CH stretch of AIBN initiates polymerization in a mixture of AIBN and MMA. Despite stronger absorbance, the reaction is less efficient than irradiation at the fifth vibrational overtone.; The overall quantum efficiencies for polymerization after 24 hours were estimated for irradiation at both the fifth and third overtones of the CH stretch. After 24 hours the overall quantum yield for the mixtures irradiated at initiator/monomer absorptions (ϕ628 = 9937, ϕ 901 = 47.7) is more than five times larger than for the mixtures irradiated at pure monomer absorption (ϕ602 = 1810, ϕ872 = 12.8). The overall quantum efficiency for the irradiation at the third overtone of initiator/monomer absorption is 200 times smaller than that of the fifth overtone excitation.; The vibrationally initiated cross-linking of vinylmethoxy siloxane oligomer/MMA and dimethylsiloxane methyl-(methacryloxypropyl) siloxane copolymer/MMA mixtures has been studied. It was found that vinylmethoxy siloxane oligomer does not participate in the cross-linking. The resulting product is a mixture of poly-MMA and siloxane oligomer.; The irradiation at the fifth vibrational overtone of the CH stretch of AIBN results in co-polymerization of dimethylsiloxane methyl-(methacryloxypropyl) siloxane copolymer/MMA mixtures. Reaction is wavelength specific.; The conversion of each component in the mixture, sol-gel fractions, degrees of cross-linking and average molecular weights between junction points (measure of cross-linking density) of the final copolymers were studied.