Glycoconjugated Polymer. 3. Synthesis and Amphiphilic Property of Core-Glycoconjugated Star-Shaped Polystyrene

Abstract

Coupling reactions of 2,2,6,6-tetramethylpiperidinyloxy-terminated polystyrene (PS-TEMPO) using divinylbenzene (DVB) as a linking agent were performed in the presence of 4-vinylbenzyl glucoside peracetate (1a) and 4-vinylbenzyl maltohexaoside peracetate (1b). To prepare core-glycoconjugated star-shaped polymers with various amphiphilic properties, the molar ratio of 1 and DVB in the feed (F1, [1]/[DVB]) was changed from 0.13 to 0.38 for the coupling reaction. Star-shaped polystyrenes having 1a and 1b units in their cores (2a and 2b, respectively) were obtained by purification using preparative SEC. The weight-average molecular weights determined by static laser light scattering measurements (Mw,SLS), the polydispersity indices determined by size exclusion chromatography (Mw/Mn), the number of polystyrene arms (Narm), and the core-composition ratio (f1, [1 unit]/[DVB unit]) were 2.89 × 105−3.31 × 105, 1.36−1.38, 18, and 0.09−0.23 for 2a and 2.28 × 105−2.60 × 105, 1.29−1.35, 11−14, and 0.05−0.17 for 2b, respectively. Amphiphilic star-shaped polystyrenes with cores containing glucose and maltohexaose as hydrophilic segments (3a and 3b, respectively), which were obtained by the deacetylation of 2a and 2b, exhibited an encapsulation ability toward water-soluble molecules, such as methyl orange (MO), in chloroform. The amounts of encapsulated MO remarkably increased with the increasing hydrophilic property of 3. A positive Cotton effect was observed in the circular dichroism spectrum for the MO/3 system in the adsorption area of MO, indicating that MO existed in a chiral segment, i.e., the glycoconjugated core.