Photoinduced pitch gradients and the reflection behaviour of the broadband films: influence of dye concentration, light intensity, temperature and monomer concentration

The broadband polarising films with pitch gradients induced by the diffusion of nematic liquid crystal (N-LC) monomer in chiral nematic liquid crystals (N*-LCs) during the photopolymerisation process have been studied theoretically and experimentally. It was found that the bandwidth of such films broadened sharply after polymerisation. To elucidate the mechanism of photoinduced pitch gradients, the fractured surface and the surface morphology of the polymer network of the sample films were observed by scanning electron microscopy (SEM). The influence of dye concentration, ultraviolet (UV) intensity, polymerised temperature and N-LC monomer concentration on the broadband reflection performance of chiral nematic liquid crystal (N*-LC) films was analysed theoretically.