Influence of cross-linker concentration on the water contained within the pores of poly(vinyl alcohol)-borax hydrogels: a vibrational spectroscopic study

Abstract

The water content and solvent structure of six poly(vinyl alcohol)-based hydrogels possessing different proportions of borax have been studied as a function of cross-linker concentration. The differing proportions of borax in the matrices cause mesoscopic structural changes in the polymer hydrogel network which lead to differences in water content. The FTIR data show non-monotonic variations in the intensities of the various bands. For the Raman data, the region sensitive to the OH vibrations has been fitted with four Gaussian peaks corresponding to the stretching modes of liquid water. The wavenumber positions of the peaks are dependent on the water content. The non-monotonic behavior of the peak parameters suggests that the structure of entrapped water molecules is dependent on the local mesoscopic structure. From the measurements, cross-linker proportions are seen to affect, both, polymer network and the solvent.