To provide a polymer comprising as a structural unit a monomer unit containing a hydroxy group or other hydrophilic radical and other functional group in the molecule which is useful in medical, cosmetic and electric industries. A polymer comprising as a structural unit a monomer unit shown by the general formfula [1]
(wherein R 1 and R 2 are, independently, a hydrogen atom or a halogen atom, R 3 is a hydrophilic radical and R 4 is a cyano group or a carboxyl group which may be esterified).