A series of thermally stable second-order nonlinear optical (NLO) polymeric materials based on bismaleimide chemistry have been developed. Two maleimide containing chromophores with excellent thermal stability were incorporated into the bismaleimide polymer matrices to form interpolymer networks. Moreover, a full interpenetrating polymer network (IPN) was formed through simultaneous addition reaction of the bismaleimide, and sol-gel process of alkoxysilane dyes (ASD). Atomic force microscopy results indicate that the inorganic networks are distributed throughout the polymer matrices on the molecular scale. The silica particle sizes are well under 200 nm. Second harmonic coefficients, d(33) of 6.9-57.0 pm/V have been obtained for the organic and organic/inorganic materials. Excellent temporal stability was obtained for these NLO materials at 100 degreesC. The dynamic thermal and temporal stabilities of the IPN system were much better than those of the crosslinked organic systems.