Glycoconjugated Polymer II. Synthesis of Polystyrene-block-poly(4-vinylbenzyl glucoside) and Polystyrene-block-poly(4-vinylbenzyl maltohexaoside) via 2,2,6,6-Tetramethylpiperidine-1-oxyl-Mediated Living Radical Polymerization

Abstract

The polymerizations of glycoconjugated monomers, i.e., 4-vinylbenzyl glucoside peracetate (1a) and 4-vinylbenzyl maltohexaoside peracetate (1b), were carried out using 2,2,6,6-tetramethylpiperidine-1-oxyl-terminated polystyrene (PS-TEMPO, Mn=8100 and Mw/Mn=1.17) as a macromolecular initiator in xylene at 120°C ([1]/[PS-TEMPO] = 25). The Mn of the product increased from 9900 to 12700 for the polystyrene-block-poly-1a (2a) and from 14200 to 16200 for the polystyrene-block-poly-1b (2b) with the increasing polymerization time, whereas the Mw/Mn values were constant at 1.13–1.21. The deacetylation of 2a and 2b using sodium methoxide in dry-THF provided amphiphilic block copolymers containing glucose and maltohexaose as hydrophilic segments, i.e., polystyrene-block-poly(4-vinylbenzyl glucoside) (3a) and polystyrene-block-poly(4-vinylbenzyl maltohexaoside) (3b). The solution property of the block copolymers 3a and 3b in toluene (a good solvent for polystyrene) and H2O (a good solvent for saccharides) varied depending on the weight fraction of the glucose residues (fg, wt%) in 3, i.e., 3a with an fgs of 4, 10, and 14 wt% formed reversed micelle-like aggregate in toluene, whereas 3a with an fg of 17 wt% and 3b with an fg of 37 and 50 wt% formed micelle-like aggregates in H2O.