The electro‐optic properties of polymer films are measured by an original technique whereby a periodic sequence of poling and probing steps permits alternation of the application of orientation and dephasing potentials. Relaxation dynamics of the electro‐optic coefficient of Red–Acid–Magly crosslinkable polymer films is studied as a function of the temperature of the samples. The time constant of the decay &tgr; as measured at several temperatures is found to follow a Vogel–Fulcher–Tamann—Hesse dependence, for temperatures above glass transition. Poling the samples in the presence of a pulsed electric field leads to ar33electro‐optic coefficient as high as 6 pm/V. ©1995 American Institute of Physics.