Structure of water in polyvinylalcohol based ferrogel: effect of carbonyl iron concentration

Abstract

Three PVA-borax ferrogels with micron-sized carbonyl iron particles (as the magnetically-sensitive dopant) have been synthesized, alongwith a similar undoped hydrogel. The structural arrangement of the solvent (water) molecules has been studied, as a function of carbonyl iron concentration, using X-ray Diffraction (XRD) and, Raman and Fourier Transform Infra-red (FT-IR) spectroscopy. The presence and concentration of the dopant particles leads to significant changes in the water content and structural arrangement of the solvent molecules within the matrices. Increase in the concentration of the magnetic dopant causes decrease in the number of water molecules possessing average size and average inter-molecular distance. The decrease of the two parameters is unequal leading to a non-monotonic behaviour of the relative ratio of the number of molecules having average inter-molecular spacing of water to those possessing average molecular size. De-convoluted Raman spectra show relative changes in the intensities of the four O-H stretching modes of water. The dopant concentration is found to affect the number density of the bound and un-bound water molecules within the ferrogel matrices. The observed structural arrangement of the solvent molecules is explained on the basis of changes in pore size and re-arrangement of water owing to the presence and concentration of the dopant particles within the pores of the ferrogel polymer network.