Vibrational spectroscopy studies of interdiffusion in polymer laminates and diffusion of water into polymer membranes

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FTIR-ATR studies of diffusion and perturbation of water in polyelectrolyte thin films. Part 4. Diffusion, perturbation and swelling processes for ionic solutions in SPEES/PES membranes

We report diffusion rates and equilibrium concentrations of water in a polyelectrolyte SPEES/PES film using ATR/FTIR spectroscopy. The data for water obtained by fitting spectral intensities to a dual mode diffusion model in the presence of different counter ions (at 0.2 mol dm(-3)) follow the order Li+ > Cs+ > Na+ > Ca2+ > K+. Diffusion is progressively slower for higher concentrations of NaCl (0.2-0.85 mol dm(-3)) and the NO3- counter anion leads to a faster diffusion rate than for Cl- at the same concentration. Both water uptake and diffusion rates are broadly consistent with expectations based on the differential degrees of swelling, caused by changes in the SO3-/SO3- interpolymer chain repulsive forces leading to a decrease in volume diffusion compared with the value for pure water. Direct spectral measurements of the degree of swelling confirm that the process does occur, although the order of the swelling amounts does not map directly onto that of the diffusion rates. This is probably because the interfacial dissociation processes are hydration dependent. (C) 2002 Elsevier Science Ltd. All rights reserved

ATR-FTIR study of the diffusion and interaction of water and electrolyte solutions in polymeric membranes

We present a comparative review of the most up to date ATR-FTIR measurements of water diffusion into three polymers, PET, PVC and SPEES-PES. New data on the diffusion of water from electrolyte solutions into SPEES-PES have been added and we discuss reasons for changes in transport coefficient due to ionic screening of interchain repulsions. Finally, we point out, and attempt to interpret, the differences in perturbation of the water IR bands in the three different polymer types. Some suggestions for further elucidation of the effect have been made

Materials analysis using confocal Raman microscopy

The recent development of Raman microscopes with high optical throughput and very sensitive CCD cameras has led to Raman spectroscopy again competing effectively with FTIR methods for materials analysis. Modem Raman instruments, designed to operate confocally without serious alignment or energy trade-off problems, allow depth profiling of optically transparent polymers and polymer matrices to be routinely obtained with a spatial resolution of 1-2 mu m. The use of such an instrument is illustrated by describing recent work on polymeric material problems including, 1 The distribution and redistribution of small molecules in polymeric matrices. 2 The monitoring of adhesion primer diffusion at a polymer/silica interface. 3 The determination of the extent of interdiffusion and interaction at a polymer/polymer interface. 4 A comparison of confocal and micotoming approaches to polymer laminate analysis. The range of possible applications is increasing rapidly. It is clear that Raman microscopy will become a very important tool for future materials analysis, both in the polymer area and many other areas