Dependence of the electrooptical response time of a polymer/liquid crystal (LC) composite film on the ionic conductivity and dielectric property of the matrix polymer has been investigated. Poly(2-methyloxycarbonyl-bicyclo[2.2.1]hepta-2,5-diene-co poly(ethyl-ene glycol) methacrylate) was synthesized by photo-polymerization. Ionic conductivity and relative dielectric constant were found to be greatly dependent on the content of poly(ethylene glycol) methacrylate in the copolymer. The results indicate that the matrix polymer with high conductivity and dielectric constant has led to the short response time.