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In Situ Diffusion Studies Using Spatially Resolved Infrared Microspectroscopy

Volume 50, Number 11 (Nov. 1996) Page 1339-1344

Challa, Sudarsana R.; Wang, Shi-Qing; Koenig, Jack L.


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 Fick's second law of diffusion. The diffusion coefficient for this system is (1.97 ± 0.2)(10-8) cm2/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.