Satoshi Takase

Preparation and Properties of Sulfonated or Phosphonated Polybenzimidazoles and Polybenzoxazoles

Five series of copolybenzazoles, polybenzimidazoles and polybenzoxazoles, containing sulfonic acid or phosphonic acid were prepared and their basic properties were compared, although the backbone structures were not exactly corresponding each other. The sulfonic acid-containing polybenzimidazoles showed higher thermal stability and hydrolysis resistance than the sulfonic acid-containing polybenzoxazoles. However, Proton conductivity of the sulfonic acid-containing polybenzoxazoles was superior to that of the sulfonic acid-containing polybenzimidazoles. The phosphonic acid-containing polybenzimidazoles showed similar or higher thermal stability and lower proton conductivity than the sulfonic acid-containing correspondents. The characteristics of the polybenzimidazole systems seem to be explained by the salt formation between ionic functional groups and imidazole rings.

Sulfonation of Novel Fluorine-containing Poly(arylene ether nitrile)s for Polymer Electrolyte Membranes

Sulfonation reaction of fluorine-containing poly(arylene ether nitrile) derived from 4-phenoxy-2,3,5,6-tetrafluorobenzonitrile (PTFB) and 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (6FBA) by concentrated sulfuric acid at 30°C yielded quantitative introduction of one sulfonic group into phenoxy ring in the polymer at para-position with 68 mol% and at meta-position with 32 mol% due to the influence of fluorines at the ortho-positions of adjacent benzene ring. Membrane properties of the resulting polymer, thermal stability, proton conductivity and water uptake, were investigated for the application in fuel cells. While the membrane derived from the polymer showed similar level of proton conductivity at humidified condition to NAFION®112, its dimensional stability based on water uptake was lower than that of NAFION®112.

Controlled sulfonation of poly(arylene ether sulfone)s and poly(arylene ether ketone)s with different molecular structures for polymer electrolyte membranes

ABSTRACT Poly(arylene ether sulfone) copolymers derived from 9,9-bis(4-hydroxyphenyl)fluorene, bisphenol S and 4,4′-difluorodiphenylsulfone and poly(arylene ether ketone) copolymers derived from 4-phenoxybiphenyl, diphenyl ether and isophthaloyl chloride were prepared as precursor polymers for sulfonation reaction in which sulfonic groups are introduced quantitatively into specified positions. Sulfonation reaction for these two series of copolymers by concentrated sulfuric acid was successfully carried out to give sulfonated polymers with controlled positions and degree of sulfonation. Thermal stability, moisture absorption and proton conductivity for these two series of copolymers were measured and the results were compared to those of perfluorosulfonic acid polymers.