Nonlinear optical polymers with high glass transition temperatures were prepared by covalent functionalisation of polymaleimide copolymers with hydroxyalkyl chromophores via the Mitsunobu reaction. The polymaleimides were obtained by radical polymerisation of maleimide with 4-phenylstyrene (PM1), indene (PM2) or 1-adamantylmethacrylate (PM3). Glass transition temperatures in the range of 222-288 degreesC were obtained. Thin spincoated films of the polymers were corona-poled and analysed by second-harmonic generation; second-order susceptibility values (d(33)) up to 16 pm/V were obtained. Poled order stability measurements over periods of more than 200 h resulted in 72-90% of remaining NLO-response at 125 degreesC.