(2003), Synthesis and Properties of Hydrophilic Polymers ..

Dendrimers with hydrophobic core and hydrophilic periphery ..

Photoresponsive Polymer Brushes for Hydrophilic …

AB - Proton exchange type polymer electrolyte membranes (PEM) consisting of ion conducting alkylsulfonic acid and hydrophilic groups such as a hydroxyl group were successfully synthesized by radiation-induced graft polymerization of vinyl acetate (VAc) into a poly(ethylene-co-tetrafluoroethylene) (ETFE) film, followed by saponification and alkylsulfonation with 1,3-propanesulfone. In contrast to the typical S N2 reactions in a solution, the base-catalyzed nucleophilic ring-opening reactions of hydroxyl groups of poly(vinylalcohol) grafts with 1,3-propanesultone in solid state ETFE films hardly proceeds in the hydrophilic solvents, but it does proceed in hydrophobic toluene with a weak base (triethylamine) to yield ETFE-grafted poly(vinylalcohol-co-vinylsulfopropyl ether) (PEM-OH) with various values of ion-exchange capacity (IEC) and molar ratio of hydroxyl to sulfo groups in the grafts. The relative-humidity (RH) dependence of the proton conductivity of the sulfonated membrane was compared with that of poly(styrenesulfonic acid)-grafted ETFE (PEM-PSSA) with a similar IEC (~1.3mmolg -1) at 80°C. The PEM-OH showed a conductivity of 1.0×10 -3Scm -1 under 30% RH, which is higher than those of PEM-PSSA. Further, the PEM-OH with higher IEC (1.9mmolg -1) prepared with a grafting degree of 82% and a sulfonation degree of 41% showed 3.8×10 -3Scm -1 under 30% RH at 80°C. The conductivity is higher than that of PEMs based on sulfonated polyimide and poly(ether sulfone) with a similar IEC. Furthermore, the tensile strength of PEM-OH was 48MPa with the elongation at break of 422%, which are better than those of Nafion. These results strongly indicate that the radiation-grafted PEM with hydroxyl groups is a promising material with excellent mechanical and electrochemical properties, which are important characteristics for a fuel cell operating at a high temperature and low humidity.

Synthesis of lipopolymer with hydrophilic polymer …

A series of experiments enables this goal to be implemented by ensuring sufficiently fast diffusion of the first-stage hydrophilic polymer (using chain-transfer agent to reduce the molecular weight and, more importantly, the degree of branching of the parent poly(vinyl acetate) seed polymer), an initiator which minimized grafting between the first- and second-stage polymers, and modifying the seed poly(vinyl acetate) to increase its hydrophilicity.

We have studied syntheses of lipopolymers with a hydrophilic polymer chain using RAFT polymerization. This process enables us to synthesize various lipopolymers without complicated processes.