Evaluation of form birefringence in chiral nematic mesoporous materials

We present a detailed investigation into the form birefringence of chiral nematic mesoporous materials templated by the self-assembly of cellulose nanocrystals as the potential basis to detect changes in refractive index in an optical sensor using circular dichroism (CD) spectroscopy. The behavior is in excellent agreement with a model of form birefringence in a chiral nematic structure. We characterize the variability introduced by the self-assembly of the biologically-derived cellulose nanocrystals{,} which can partially be accounted for through normalization to address reproducibility in thickness and helical pitch within each sample. As one potential application{,} we show that the refractive index performance of these materials is maintained in strongly absorbing solutions due to the chiral nature of the form birefringence.