Glycoconjugated polymer.: 5.: Synthesis and characterization of a seven-arm star polystyrene with β-cyclodextrin core based on TEMPO-mediated living radical polymerization

beta-Cyclodextrin (-CyD) was modified into a seven-functional initiator (1) for 2,2,6,6-tetramethylpiperidinyloxy- (TEMPO-) mediated living radical polymerization. Styrene (St) was polymerized with 1 under several conditions to afford original products I-IV. Size exclusion chromatography (SEC) traces of I-IV exhibited trimodal molecular weight distributions; hence, they were fractionated into the respective three species, i.e., main products 2, byproducts 3 with lower molecular weights, and byproducts 4 with higher molecular weights. The weight-average molecular weights determined by SEC and static laser light scattering measurement (M-w,M-SEC and M-w,M-SLS,M- respectively) were 1.34 x 10(4) and ;2.98 x 10(4) for 2-I, 4.52 x 10(4) and 6.77 x 10(4) for 2-II, 1.35 x 10(5) and 1.87 x 10(5) for 2-III, and 9.67 x 10(5) and 1.89 x 10(6) for 2-IV. The M-w,M-SLS's were larger than the respective M-w,M-SEC's. In the H-1 NMR spectra of 2, the signals due to polystyrene (PSt) appeared along with the characteristic signals due to the 1 unit. therefore, those of 2 were assignable to a star PSt with an acetylated beta-CyD core. Polymer 2 was treated with sulfuric acid to give. core-cleaved polymer 2'. The M-w,M-SEC's were 2.80 x 10(3), 9.60 x 10(3), 2.70 x 10(4), and 2.61 x 10(5) for 2'-I, 2-II, 2'-III, and 2'-IV, indicating that the arm number of 2, N-PSt, was seven. The byproducts 3 and 4 were characterized and found to be a TEMPO-terminated linear PSt and a star-star coupled polymer, respectively. The seven-arm star PSt with a beta-CyD core, 5, was obtained through deacetylation of 2 using sodium methoxide in dry THF. The M-w,M-SLS values were 3.96 x 10(5), 3.78 x 10(5), 2.40 x 10(5), and 1.94 x 10(6) for 5-I, 5-II, 5-III, and 5-IV. Hence, 5-I and 5-II showed aggregation in a good solvent for PSt with aggregation-numbers (N-A) of 13 and 6, respectively.