A series of comb-shaped ring polystyrene samples, RC, composed of a common ring backbone and multiple linear branches with three different lengths were successfully prepared. First, a highly purified ring backbone was synthesized by anionic polymerizations followed by multistep size exclusion chromatography (SEC) and interaction chromatography (IC) fractionations. Second, this backbone was reacted with an excess molar amount of anionic living linear branch chains. Through the coupling reactions, the targeted RC samples were successfully obtained with high grafting efficiency without causing any side reactions. Their chain dimensions in THF were investigated by SEC-MALS measurements, and they were evaluated by estimating the shrinking factor g1/2 (= Rg,comb/Rg,linear). All RC samples prepared in this study exhibited smaller Rg and g1/2 values than those of the corresponding linear combs, LC. Moreover, combs with short branches exhibited an evidently larger g1/2 than the Gaussian chains due to the intramolecular excluded volume effects, being originated from the local high segment density in the vicinity of the branch points. In contrast, g1/2 for combs having long branches agreed reasonably well with the values based on the Gaussian approximation. This result suggests that the intramolecular excluded volume effect is weakened with increasing branch chain length, and consequently the comb behaves like a star polymer. Thus, characteristic chain dimensions of comb-shaped ring samples have been clarified, which strongly depend on the branch chain length and the backbone architecture.
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