Poly[(2-(2-(4-cyanophenyl)ethenyl)-5-methoxy-1,4-phenylene)vinylene] (PCEMPV) and a series of copolymers containing 1,4-phenylenevinylene (PV) units were synthesized through a water-soluble precursor route, and their electrical and second- and third-order nonlinear optical properties were studied. The PCEMPV films could not be doped with I-2 but could be doped with FeCl3 to show an electrical conductivity of 5.0 x 10(-3) S/cm. The conductivities of FeCl3-doped copolymer films ranged from 8.0 x 10(-3) to 6.5 S/cm depending on their copolymer compositions. The electro-optic properties of corona-poled copolymer films containing 32 mol % of the CEMPV unit were investigated by using a reflection measurement technique, and they showed electo-optic coefficients of 1.2 +/- 0.3 pm/V. No significant decay of the electro-optic responses was observed for over 2600 h at room temperature. Most significant is the fact that these polymers showed no detectable decay and no tendency of relaxation for 150 h even at 100 degrees C. The third-order nonlinear optical susceptibility, chi((3))(-omega;omega,omega,-omega), was also investigated by the degenerate four wave mixing (DFWM) technique at 602 nm. The chi((3)) values of PCEMPV and 32-poly(PV-co-CEMPV) were 8.3 x 10(-11) and 3.0 x 10(-10) esu, respectively.