Polymer Bulletin, Vol.74, No.5, 1935-1948, 2017
Synthesis of isotactic poly[alpha-(hydroxymethyl)acrylate] by anionic polymerization of the protected monomer
Isotactic poly[methyl alpha-(hydroxymethyl)acrylate] was prepared via anionic polymerization of the respective monomer protected with trimethylsilyl group (1-TMS) initiated with isopropyl alpha-lithioisobutyrate (Li-iPrIB) in toluene at -78 A degrees C. The polymerization proceeded in high isotactic specificity similarly to the case of alpha-(alkoxymethyl)acrylate, although the monomer conversion was low (18 %) due to the self-terminating reaction accompanying the elimination of trimethylsilanolate anion. The monomer conversion could be improved to ca. 75 % in the polymerizations with an excess amount of LiOSiMe3, which would interact with and stabilize the propagating species to suppress the self-terminating reaction. This was a sharp contrast to the polymerization of alpha-(methoxymethoxymethyl)acrylate (1-MOM), an acetal protected monomer, where the addition of LiOSiMe3 enhanced the self-termination. Consequently, the structure of protective group affects the polymerization behavior. For the resulting poly(1-TMS), the deprotection by acid hydrolysis quantitatively afforded isotactic poly[methyl alpha-(hydroxymethyl)acrylate].