Patent ID: 8017257

Claim:
A polymer comprising repeating units represented by the following formula (U1) and repeating units represented by the following formula (U2): wherein Q 1 is a perfluoroalkylene group which may have an etheric oxygen atom, Q 2 is a single bond or a perfluoroalkylene group which may have an etheric oxygen atom, R f1 is a perfluoroalkyl group which may have an etheric oxygen atom, X 1 is an oxygen atom, a nitrogen atom or a carbon atom, a is 0 when X 1 is an oxygen atom, 1 when X 1 is a nitrogen atom, or 2 when X 1 is a carbon atom, Y 1 is a fluorine atom or a monovalent perfluoroorganic group, and s is 0 or 1; Q 3 is a single bond or a perfluoroalkylene group which may have an etheric oxygen atom, R f2 is a perfluoroalkyl group which may have an etheric oxygen atom, X 2 is an oxygen atom, a nitrogen atom or a carbon atom, b is 0 when X 2 is an oxygen atom, 1 when X 2 is a nitrogen atom, or 2 when X 2 is a carbon atom, Y 2 is a fluorine atom or a monovalent perfluoroorganic group, and t is 0 or 1.