| Polymerizable surfactant, also referred as a surfmer, can be used not only to counteract negative effects caused by non-reactive surfactants, including foaming, destabilization of the latex particles or the dispersion, decrease of gloss and water resistance of the film formed, reduction of the wet adhesion characteristics of the binder, etc., but also to provide some positive features, such as reducing the total amount of surface-active matter necessary, mak ing latexes redispersable, or functionalizing the latex particle surface. In this work, we tried to design and synthesize a series of polymerizable epoxy resin(PER) surfactants with highly reactive polymerizable groups and good compatibility with epoxy resin matrix which could be used in UV- irradiated system. The synthesis process, physicochemical properties and polymerizability of the corresponding PER surfactants were measured. Then the PER surfactants were further used as dispersion stabilizers and applied into heterophase polymerization. The details are as follows:1. A long operation cycle is required to determine the epoxide value by the commonly used hydrochlo ric acid-acetone method(referred as the hydrochloric acid-acetone-standing method). And the error and consistency of the results were well-below expectation when the samples were a mixture of epoxy resin and et hylene glycol(PEG) instead of pure epoxy resin. To shorten the test cycle and achieve real-time monitoring, ultrasonication was first introduced to this method. And a series of experiments with various constituents of epoxy resin-PEG, including pure epoxy resin E-44, a mixture of E-44 and low molecular weight PEG(PEG-200) and a mixture of E-44 and high molecular weight PEG(PEG-4k), were carried out to test the efficiency of this new method. The results showed that, compared to the hydrochloric acid-acetone-standing method, the hydrochloric acid-acetone-ultrasonication method provides a much faster and more accurate measurement of the epoxide value of a pure epoxy resin(within 2 min) and the mixture of epoxy resin with polyethylene glycol(PEG-4k, within 5 min) by enhancing the dissolution of epo xy resin and its mixture with polyethylene glycol, as well as the reaction between epoxide groups and HC l. As a result, real-time monitoring of the reaction between an epoxy resin and other materials such as PEG becomes feasible. Ultrasonication-assisted dissolution and reaction may be extended to other chemical(titration) analysis methods.2. Bisphenol A epoxy resin(E-44) was first reacted with highly reactive acrylic acid(AA) to form an envisaged epoxy monoacrylate(EmA), with the one remaining epoxide group reacting with hydrophilic polyethylene glycol(PEG-1k/2k/4k/6k) to obtain a series of polymerizable epoxy resin(PER) surfactants containing terminal unsaturated carbon-carbon double bond at the lipophilic end. The procedures were monitored by chemical titrations, infrared spectroscopy and 1HNMR and the results indicated that slightly excess AA at the first step of the reaction is helpful with the synthesis of targeted final products. The HLB value and cloud point of the PER surfactants increase with the increase of PEG’s molecular weight and are slightly higher than the non-polymerizable nonionic surfactant OP-10, except for S-1 with the lowest PEG molecular weight of 1k. The critical micellar concentration(CMC) and solubilization of PER surfactants to toluene and methyl methacrylate also increase with the increase of PEG’s chain length. The light transmittance measurement shows that the water solubility of the PER surfactants increases but the phase inversion point of their water solutions starts at a lower concentration with the increase of PEG’s molecular weight. The polymerizability of PER surfactants in the copolymerization with epoxy diacrylate(Ed A) under UV radiation was further evaluated and it was found that about 75-80 wt% of PER surfactants participated in the copolymerization, except for S-1. In addition, the PER surfactants can be used as multifunctional cross-linkers to prepare polyacrylamide hydrogels.3. The commonly used dispersion stabilizers, such as polyvinylpyrrolidone(PVP), carboxymethyl cellulose(CMC), polyacrylic acid(PAA), PEG and in situ block and graft copolymers(e.g., PEG-b-PMMA) are physically adsorbed onto or embedded into microspheres. When the external conditions(p H, shear, temperature, solvent, etc.) changes, the adsorption and embedded effect may be destroyed and the stabilization therefore reduced or even disappeared. To solve this problem, the as-prepared PER surfactants, rather than the traditional dispersion stabilizers were applied in dispersion polymerizatio n of methyl methacrylate(MMA). The effect of the amount of monomer, alcohol-water ratio and amount and type of PER surfactants on the polymerization process and kinetics were investigated. The results showed that PMMA microspheres with gradient dispersity in size and smooth surface can be obtained when 20 wt% MMA, alcohol-water ratio of 40/40(w/w), 4 wt%(vs MMA) S-4 or S-6(the PER obtained with PEG-4k and PEG-6k) dispersion stabilizers were applied. When neutralization is carried out at the end of reaction, the PMMA microspheres with hollow surface can be prepared. It was a surprise, however, that the PER surfactant almost did not participate in the copolymerization with MMA. Further studies are needed to find out the reasons behind s uch an unexpected phenomenon. |
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