The synthesis and characterization of a novel epoxy-based photocrosslinkable nonlinear optical (NLO) polymer exhibiting enhanced thermal stability is reported. The synthesized polymers show spectroscopic properties (NMR, IR, UV) in accordance with the proposed structures. A glass transition temperature (T-g) of 112 degrees C and a thermal degradation temperature (T-d) of 310 degrees C were recorded. The poled polymer film exhibits stable second-order nonlinear optical activity (d(33) = 19.5 pm/V) over a period of 500 h as characterized by the temporal response of the second harmonic signal at room temperature.