Yotaro Morishima

Self-association behavior in water of an amphiphilic diblock copolymer comprised of anionic and dendritic blocks

Well-defined amphiphilic diblock copolymers (PAMPS-b-PG2) composed of a hydrophilic linear polyelectrolyte and hydrophobic blocks bearing pendent dendritic moieties was synthesized via reversible addition–fragmentation chain transfer (RAFT) controlled radical polymerization of 3,5-bis[3′,5′-bis(benzyloxy)benzyloxy]benzyl 11-acrylamidoundecanoate (G2) using a poly(sodium 2-(acrylamido)-2-methylpropanesulfonate) (PAMPS) based macro-chain transfer agent. Degrees of polymerization of PAMPS and PG2 blocks were 71 and 3, respectively. The polydispersity index was 1.25 as estimated from GPC. Hydrophobic association of the PG2 blocks in aqueous solutions was suggested from restricted motions of the dendritic moieties as observed by 1H NMR in D2O. A fluorescence spectrum of 8-anilino-1-naphthalenesulfonic acid, ammonium salt hydrate indicated that the fluorescence probe was solubilized in the hydrophobic domain formed from the polymer aggregate in water. The formation of polymer aggregates was indicated by light scattering data. The hydrodynamic radius (Rh) of the polymer aggregate was independent of the polymer concentration.

Polymer Micelles II. Effects of Alkyl-Chain Length on the Self-Assembly of Copolymers of Acrylic Acid and Alkyl Acrylate in Aqueous Media.

アクリル酸 (AA) とアクリル酸エチル (EA), n-ブチル (BA), またはドデシル (DA) との2元共重合体の水溶液中における会合挙動に及ぼすアルキル鎖長の影響を光散乱, レオロジー, および泡特性によって調べた. 共重合体の水中での見かけ重量平均分子量は, アルキル鎖が長いほど高かった. AA/EAおよびAA/BA共重合体の水溶液は高濃度でも粘性流体であるのに対し, AA/DA共重合体は, 濃度10wt%でゲル的挙動を示した. さらに泡特性解析から, AA/DA共重合体は気-液界面に配向し, 界面活性剤水溶液の泡膜を安定化することがわかった. 以上の結果から, AA/アクリル酸アルキル共重合体においてアルキル鎖長がドデシル基のように長い場合には水中で高度に分子間会合し3次元網目構造を形成し, また, 界面活性剤とも十分に強く会合することが明らかになった.