Transparent polymeric materials with high heat resistance and low water absorption were designed based on the alternating copolymers of N-substituted maleimide (RMI) with isobutene (IB). The N-substituent of the maleimide significantly affected the glass transition temperature (T-g) and water absorption of the copolymers. Poly(N-cyclohexylmaleimide-alt-IB) [poly(CHMI-IB)] showed a T(?)g value as high as 192 degrees C and relatively low water absorption. Furthermore, the incorporation of a small amount of lauryl methacrylate in the copolymers was confirmed to reduce the water absorption of the copolymer drastically, although it decreased the T-g of the copolymers at the same time. Poly(CHMI-IB), containing 4 mol % lauryl methacrylate, showed a good balance of excellent transparency, high heat resistance, acceptable mechanical properties, and low water absorption. The heat deflection temperature was as high as 141 degrees C. The water absorption at 23 degrees C after immersion for 14 days was 0.56% and the dimensional change after 7 days was 0.06%. They are half and one-quarter of those of poly(methyl methacrylate), respectively.