Synthesis of Water-Soluble Polymethacrylates by Living Anionic Polymerization of Trialkylsilyl-Protected Oligo(ethylene glycol) Methacrylates

2-[2-[( tert -Butyldimethylsilyl)oxy]ethoxy]ethyl methacrylate ( 2 ) and 2-[2-[2-[( tert -butyldimethylsilyl)oxy]ethoxy]ethoxy]ethyl methacrylate ( 3 ) were polymerized anionically in THF at −78 °C for 2−24 h. The anionic initiator systems included 1,1-diphenyl-3-methylpentyllithium/lithium chloride and diphenylmethylpotassium/diethylzinc. The polymerization of novel tert -butyldimethylsilyl-protected oligo(ethylene glycol) methacrylates, 2 and 3, proceeded quantitatively in each case. The resulting polymers possessed the predicted molecular weights based on the molar ratios of monomers to initiators, and narrow molecular weight distributions ( M w / M n < 1.1). The stability of the propagating carbanion of poly( 2 ) and poly( 3 ) was ascertained by the quantitative efficiencies of the sequential block copolymerizations using tert -butyl methacrylate (tBMA). Well-defined block copolymers, poly( 2 )- block -poly(tBMA) and poly( 3 )- block -poly(tBMA), were obtained. The trialkylsilyl protecting groups of poly( 2 ) and poly( 3 ) were quantitatively hydrolyzed using 2 N HCl in aqueous THF at 0 °C for 2 h to give tailored poly[di(ethylene glycol) methacrylate] and poly[tri(ethylene glycol) methacrylate], respectively. Both polymethacrylates obtained after deprotection were readily soluble in water due to the high polarity of the hydrophilic oligo(ethylene glycol) pendant units with terminal OH functionality.