PROTECTION AND POLYMERIZATION OF FUNCTIONAL MONOMERS .23. SYNTHESIS OF WELL-DEFINED POLY(2-HYDROXYETHYL METHACRYLATE) BY MEANS OF ANIONIC LIVING POLYMERIZATION OF PROTECTED MONOMERS

Anionic polymerizations of 2-[(trimethylsilyl) oxy]ethyl methacrylate (1), 2-[(tert-butyldimethylsilyl)oxy]ethyl methacrylate (2), and 2-[(methoxymethyl)oxy]ethyl methacrylate (3), the protected forms of 2-hydroxyethyl methacrylate (HEMA), were carried out in THF at -78 degrees C with 1,1-diphenylhexyllithium or 1,1-diphenyl-3-methylpentyllithium in the presence of LiCl. The resulting poly(1-3)s were found to possess predictable molecular weights and very narrow molecular weight distributions. The sequential polymerizations of tert-butyl methacrylate with the anionic propagating ends of poly(1-3) gave block copolymers in quantitative efficiency. Thus, the anionic polymerizations of 1-3 proceeded without transfer and termination reactions to afford stable living polymers. Complete hydrolysis of the protective groups of poly(1-3)s produced linear poly(HEMA) quantitatively. Novel well-defined di- and triblock copolymers containing hydrophobic [polystyrene, poly(4-octylstyrene), polyisoprene] and hydrophilic segments [poly(HEMA)] were also prepared by sequential polymerization of the corresponding hydrophobic comonomers with 1, followed by deprotection.