No abstract

Telechelic poly(methy1 methacrylate) having a terminal OH and COOH group was prepared by anionic polymerization with the initiator made by the reaction between 4-[2-(tert-butyldimethylsiloxy)-ethyl]-a-methylstyrene and n-butyllithium, followed by termination with carbon dioxide and hydrolysis of the tert-butyldimethylsiloxy group. The resulting polymer was characterized by osmometry, GPC, lH NMR, and potentiometric titration. It was confirmed that the polymer was pure and had a fairly narrow molecular weight distribution. IntroductionAcryl polymers such as poly(methy1 methacrylate) [abbreviated poly(MMA)l have been used widely as resin for paint and varnish. This is because the polymers have high weathering resistance and high transparency. Now, solvent-based paint is being replaced with a solvent-free powder 0ne,~,3 since organic solvents cause the serious problem of air pollution. The important factors of powder paints are the pour point and the glass-transition temperature of the resin, both of which depend on molecular eight.^^^ Hence the polymers for powder paint should have narrow molecular weight distributions. To obtain a hard coating, we need polymers having reactive groups. In particular, a,w-difunctional polymers, so-called telechelic polymers, are effective, since they can form a network structure through end-cross-linking.The present objective is to prepare telechelic poly-(MMA) having as narrow a molecular weight distribution as possible. We think the best way is to carry out an anionic polymerization of MMA using an initiator having a protected functional group followed by functional termination.697 There are scarcely any reports on preparation of telechelic poly( MMA), though numerous telechelic polymers have been in~estigated.~-l~ It is well-known that anionic initiators such as n-butyllithium (n-BuLi) make an attack not only on the vinyl group of MMA but also on the ester group.15J6 The latter, unfavorable side-reaction is suppressed by using bulky carbanion instead of small ne.^^-^^ It is very interesting that the addition of lithium chloride has a beneficial effect on the living character of the poly(methy1 methacrylate) anion.21 From a practical point of view, however, this method may be unprofitable for our purpose, since it is not so easy to remove the added salt from the resulting polymer-salt mixture, and the residual salt, especially chlorine, may have an adverse influence upon coating. Incidentally, the a-methylstyrene derivative can be quantitatively metalized by alkyllithium through equilibrium oligomerization near or above the ceiling temperature.22-28 It is relatively easy to purify monomers of the a-methylstyrene type because of their low ability to undergo thermal polymerization.28 The tert-butyldimethylsilyl group has been found to be effective for the protection of the hydroxyl group in anionic polymerizati~n.~~ Taking

No abstract

Novel telechelic poly (methyl methacrylate) having OH and COOH groups in the chain was prepared by anionic polymerization with the difunctional initiator made by the reaction betweem 4-[2-(tert-butyldimethylsiloxy)ethyl]-«-methylstyrene and sodium napththalene, followed by termination with carbon dioxide and hydrolysis of the tert-butyldimethylsiloxy group. The resulting polymer was characterized by osmometry, GPC, NMR, and potentiometric titration. OH groups were introduced quantitatively, but the number of the terminal COOH groups per molecule was 1.7 S0.1 which is less than the theoretical value, 2. The latter result was because part of the initiator was doubly charged and the rest had one charge plus a nonactive end, and/or the initiation efficiency in the reaction between the initiator and methyl methacrylate was low. The characterization assures that the multifunctionality of the polymer necessary for self-crosslinking is presented.samples were precipitated from THF solution into excesses of n-hexane and methanol, respectively. The precipitated samples were further purified by reprecipitation in benzene/n-hexane or benzene/methanol systems. The purified polymers were freezedried from the benzene solutions for 24 h.

No abstract