Synthesis of Phosphorylated PVA-b-PS Copolymers via ATRP and Its Application to Direct Methanol Fuel Cell Membrane

摘要

Poly(vinyl alcohol) (PVA) is a very attractive material for desalination and pervaporation dehydration, because of its good film- forming property, good chemical and thermal stability, and high water permeability. In particular, PVA membranes have been used in ethanol dehydration to break the ethanol-water azeotrope. Therefore PVA membrane is expected to decrease methanol permeability in direct methanol fuel cell. However, the highest reported proton conductivity of the pure PVA membranes is only 3 5 ?10-5 S/cm To improve the proton conductivity of the PVA membranes, a number of research groups have investigated several combinations of PVA with acid or salts, such as phosphoric acid (H3PO4) , hypophosphorous acid 2 (H3PO2) , sulfuric acid , heteropoly acid (HPA) , etc. Among them, 3 4 1 PVA membranes doped with H3PO4 shows higher proton conductivity, but PVA-H3PO4 blend is very soft, water soluble, and H3PO4 leaches out of the membrane easily and the proton conductivity drops Rapidly , 5 In order to overcome these drawbacks, we synthesized phosphorylated PVA-b-PS copolymer (P-PVA-b-PS) via consecutive telomerization, ATRP, saponification 6, and phosphorylation with phosphorous oxychloride. Then, the copolymer was blended with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) for fuel cell membrane. PPO is one of engineering plastics, which has good physical-chemical properties, good film-forming, and miscible with PS. The fabricated membranes were characterized by ion conductivity, methanol permeability, and thermal stability.