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Well-defined poly(2,6-dimethyl-4,4 1 -phenylene oxide)-g-poly(styrenesulfonic acid) (PPO-g-PSSA) graft copolymer was synthesized via living radical polymerization. For the graft copolymer, poly(2,6-dimethylphenylene oxide) (PPO) was brominated first, and the brominated PPO (PPO-Br) was used as a macroinitiator in the atom transfer radical polymerization (ATRP) of styrenesulfonic acid sodium salt. The number of grafts per PPO chain and the molecular weight of the graft were controlled by adjusting the degree of bromination, and conversion in ATRP, respectively. The graft copolymers obtained were transformed into proton exchange membranes for direct methanol fuel cell (DMFC) application. The performance of the membranes was measured in terms of water uptake, proton conductivity, methanol permeability, and thermal stability. The water uptake, ion exchange capacity (IEC), and proton conductivity of the membranes increased with PSSA block content. Very low methanol permeability and good proton conductivity were observed by adjusting grafting frequency and PSSA block content.

Poly(vinyl alcohol-b-styrene) (poly(VA-b-St)) diblock copolymer containing high syndiotactic poly (vinyl alcohol) (PVA) was synthesized by the saponification of poly(vinyl pivalate-b-styrene) (poly(VPi-b-St)). For the block copolymer, poly(vinyl pivalate) (PVPi) with trichloromethyl end group was obtained via telomerization of vinyl pivalate with carbon tetrachloride as a telogen and 2,2-azobisisobutyronitrile (AIBN) as an initiator. Then resulting poly(vinyl pivalate) with trichloromethyl end group was used as an efficient macroinitiator for the synthesis of poly(VPi-b-St) using atom transfer radical polymerization (ATRP) in the presence of CuCl/2,2'-bipyridine at 130 o C. The poly(vinyl pivalate) macroinitiator, poly(VPi-b-St), poly(VA-b-St) were characterized by GPC, FT-IR and 1 H-NMR. And the analysis showed that integrity of the block copolymer was maintained during saponification reaction.

In an attempt to develop direct methanol fuel cell (DMFC) membrane with low methanol permeability, we synthesized successfully poly(vinyl phosphateb-styrene) copolymers from poly(vinyl alcohol-b-styrene) by reaction with phosphorus oxychloride and subsequent hydrolysis. We obtained the ratio of the differently bound phosphorus by 31 P Solid-state NMR Spectroscopy because the majority of block copolymer is not soluble or does not make homogeneous solution in a NMR solvent. The total amount of acid groups as well as the ratio of singly and doubly bound phosphorus by 31 P Solid-state NMR and pH titration was slightly different due to the cross-linked nature of the sample. Therefore, solid-state NMR spectroscopy is the most powerful technique to characterize cross-linked polymers like DMFC membrane.