In situ diffusion studies using spatially resolved infrared microspectroscopy

Spatially resolved infrared microspectroscopy is used in conjunction with the contact method to conduct in situ diffusion experiments of photocured polymer-dispersed liquid crystals (LCs). The system analyzed consists of a low-molecular-weight liquid crystal (E7) diffusing into a photopolymerizable monomer (NOA65), The measured concentration profiles were generated by monitoring the hydroxyl band of the monomer as a function of time and spatial position. The diffusion coefficients were calculated from least-squares fitting of the data. The system followed Pick's second law of diffusion. The diffusion coefficient for this system is (1.97 +/- 0.2)*(10(-8)) cm(2)/s. The morphology of the system after polymerization exhibited three distinct regions: nematic LC molecularly mixed in the cross-linked network of the polymer, nematic LC droplet gradient in the polymer matrix, and polymer fibers scattered in the continuous nematic LC.