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

The diffusion of liquid crystal 4-n-pentyl-4'-cyanobiphenyl (5CB) into a po ly(butyl methacrylate) (PBMA) matrix has been studied using fast FTIR imagi ng. The concentration profiles were obtained as a function of time at sever al temperatures above and below the nematic to isotropic transition tempera ture (T-NI) of 5CB and the T-g of PBMA. The time-dependent progression of t he diffusion front position, when fitted to a power law model, exhibited ex ponential values between 0.40 and 0.52. This, along with the observed progr ession of a sharp 5CB-diffusion front into the PBMA matrix, indicates the p resence of an anomalous diffusion process. It was shown that fast FTIR was able to correctly identify the diffusion process as anomalous, whereas a si mple mass uptake analysis would have led to the conclusion that the process proceeded according to Fick's second law. (C) 1999 John Wiley & Sons, Inc.