Water-borne Macrophotoinitiators And Their Application In Photoinitiated Polymerization

Water-borne UV curing systems have been developed rapidly because of its advantages over the traditional UV curing system, such as low VOC, nontoxicity, non-inflammability and low cost. As one of the important components of water-borne UV curing system, water-borne macrophotoinitiator have been paid much attention. In this work, a series of water-borne macrophotoinitiators(HMPP-PEG-HMPP) were prepared by using polyethylene glycol(PEG) and a small molecular photoinitiator 2-hydroxy-2-methyl-1-phenylpropanone(HMPP). The HMPP-PEG-HMPPs were then applied to the aqueous solution polymerization of acrylamide, emulsion and dispersion polymerizations of methyl methacrylate(MMA). The details and conclusions are as follows:1, A series of HMPP-PEG-HMPPs were synthesized by using 2-hydroxy-2-methyl-1-phenylpropanone(HMPP), isophrone diisocyanate(IPDI) and polyethylene glycol(PEG) with different molecular weight as raw materials in one pot with two steps. Fourier transform infrared spectroscopy(FTIR), ~1HNMR and high performance liquid chromatography(HPLC) were used to confirm the structure of HMPP-PEG-HMPP. The maximum absorption wavelengths of HMPP-PEG-HMPPs are similar to that of the low molecular weight photoinitiator HMPP, but the photolysis rate of HMPP-PEG-HMPP is slightly lower than that of HMPP. The theoretical migration rate of HMPP-PEG-HMPP from a UV-cured matrix is much lower compared to that of HMPP, and decreases with the increase of HMPP-PEG-HMPP molecular weight. HMPP-PEG-HMPP serves as both a photoinitaitor and an emulsifier(or stabilizer), and its cloud point, turbidity and HLB value increases with the increase of polyethylene glycol(PEG) molecular weight. The kinetics of the aqueous solution polymerization of acrylamide initiated by HMPP-PEG-HMPP follow the general laws of free-radical polymerization. The PMMA emulsion prepared by HMPP-PEG6k-HMPP was not stable, and serious aggregation was observed.2, Monodispersed PMMA microspheres were prepared by photoinitiated dispersion polymerization of MMA in the medium of ethanol/water with HMPP-PEG-HMPP acting as both stabilizer and photoinitiator. Under the experimental conditions, HMPP-PEG6k-HMPP content, the ratio of ethanol/water in dispersion medium, MMA concentration and UV irradiation intensity had no obvious effect on the size and polydispersity of PMMA microspheres. Water contact angle and XPS spectrum indicated that the content of HMPP-PEG-HMPP on the surface of microspheres was about 21.53%.