Synthesis, thermal and optical properties of crosslinked poly(isobornyl methacrylate-co-butyl acrylate) copolymer films

• Series of crosslinked poly(IBOMA-co-BA) copolymer films were prepared.
• The copolymer films have excellent chemical resistance and thermal stability.
• The crosslinked films have significantly increased glass transition temperature.
• The refractive indices of films are tunable in a wide range.
• The crosslinked films exhibit very low birefringence.

Novel crosslinked poly(IBOMA-co-BA) copolymers were prepared by free-radical copolymerization from isobornyl methacrylate (IBOMA) and butyl acrylate (BA), using 4,4′-isopropylidenediphenol dimethacrylate (BD) as crosslinking agent and 2,2′-azobisisobutyronitrile (AIBN) as thermal initiator. The chemical structures, physical and optical properties of the resultant copolymers were characterized by FTIR, 1H NMR, differential scanning calorimetry, thermogravimetry analysis, refractive index and birefringence measurements. It was found that the crosslinking modification could effectively improve the resistance to organic solvents, and significantly increase the glass transition temperatures and thermal stability of the copolymers. More importantly, the transparent copolymer films with three-dimensional network structures exhibited very low birefringence. In addition, with the incremental increase of the BD content in copolymers from 15 wt% to 60 wt%, the refractive indices of films could be tunable over a range of 1.475–1.546. The excellent chemical resistance, thermal and optical properties endow this series of polymer materials with promising application in light-waveguide device field.