1H NMR T_2 relaxation in contact lens hydrogels as a probe of water mobility

摘要

NMR proton T_2 relaxation time measurements have been performed as a function of temperature for a set of nine commercially available cotact lens hydrogels of varying compositio and equilibrium water content(EWC).The study was undertaken to quantify the behaviour of the water in each material in terms of its average mobility and binding.The resulting complex T_2 behaviour was analysed using a model that incorporates chemical exchange between water protons and exchangeable polymer protons.Using htis analysis it is shown that the water in these hydrogels is perturbed only slightly with respect to bulk water by the polymer.Analysis of the fit parameters suggests that the average water mobility correlates approximately with overall water content,approaching that of bulk water as the EWC is increased.No significant dependence of this mobility on polymer composition was found for the range of materials studied.