A novel photosensitive adhesive composition including the following components (A), (B), (C), and (D): Component (A): a polymer having a structural unit of the following formula (1) and a structure of the following formula (2) at a terminal, Component (B): a polymer having the structural unit of formula (1), and a carboxy group or hydroxy group at a terminal, Component (C): a radical photopolymerization initiator, and Component (D): a solvent, wherein the content by mass of the component (B) is larger than that of the component (A), ##STR00001##
(wherein X is a C.sub.1-6 alkyl group, a vinyl group, an allyl group, or a glycidyl group, m and n are each independently 0 or 1, Q is a divalent C.sub.1-16 hydrocarbon group, Z is a divalent C.sub.1-4 linking group, the divalent linking group being bonded to an O group in formula (1), and R.sup.1 is a hydrogen atom or a methyl group.)

A novel photosensitive adhesive composition including the following components (A), (B), (C), and (D): Component (A): a polymer having a structural unit of the following formula (1) and a structure of the following formula (2) at a terminal, Component (B): a polymer having the structural unit of formula (1), and a carboxy group or hydroxy group at a terminal, Component (C): a radical photopolymerization initiator, and Component (D): a solvent, wherein the content by mass of the component (B) is larger than that of the component (A),

##STR00001##

(wherein X is a C.sub.1-6 alkyl group, a vinyl group, an allyl group, or a glycidyl group, m and n are each independently 0 or 1, Q is a divalent C.sub.1-16 hydrocarbon group, Z is a divalent C.sub.1-4 linking group, the divalent linking group being bonded to an O group in formula (1), and R.sup.1 is a hydrogen atom or a methyl group.)

The present invention relates to fuel cells that incorporate seal means, in particular seal means for sealing a bipolar plate to a membrane in a PEM fuel cell stack. The resulting fuel cell stack exhibits superior leak resistance and reduced ion leaching in water.