Studying anomalous diffusion in a liquid crystal/ polymer system using fast FTIR imaging

Abstract

The diffusion of liquid crystal 4-n-pentyl-4′-cyanobiphenyl (5CB) into a poly(butyl methacrylate) (PBMA) matrix has been studied using fast FTIR imaging. The concentration profiles were obtained as a function of time at several temperatures above and below the nematic to isotropic transition temperature (TNI) of 5CB and the Tg of PBMA. The time-dependent progression of the diffusion front position, when fitted to a power law model, exhibited exponential values between 0.40 and 0.52. This, along with the observed progression of a sharp 5CB-diffusion front into the PBMA matrix, indicates the presence of an anomalous diffusion process. It was shown that fast FTIR was able to correctly identify the diffusion process as anomalous, whereas a simple mass uptake analysis would have led to the conclusion that the process proceeded according to Fick's second law. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2261–2268, 1999