Investigation of deuterium substitution effects in a polymer membrane using IR Fourier spectrometry

Experiments on IR Fourier spectrometry of a Nafion polymer membrane swollen in water are described. The dynamics of Nafion swelling is studied in relation to the deuterium content in water. It has turned out that, if the polymer swells in waters with different deuterium contents, a considerable confinement effect is observed, which, in this case, manifests itself in that the transmittance of IR radiation of water that is enclosed within a region with a size of $\sim$ 100 $\mu$m differs from that of water that is inside nanometer pores of the polymer membrane. In addition, the transmittance of Nafion swollen in water measured at a wavelength of $\lambda$ = 1.92 $\mu$m (spectral minimum) experiences a local minimum in the deuterium concentration range 10$^2<C<$ 10$^3$ ppm, irrespective of the soaking time of the polymer in deuterated water. Finally, the effect of the deuterium substitution of the residual water present in the volume of the membrane has been revealed.