Mechanical Properties of a pH Sensitive Hydrogel

Abstract

An experimental protocol was developed to determine the basic mechanical properties of a poly(2-hydroxyethyl methacrylate (HEMA)) hydrogel at various levels of pH equilibrium. An Instron micromechanical testing machine was modified such that tensile tests could be carried out in temperature controlled pH solution. Values of Young’s modulus were measured for a range of pH values from 2 to 12 and the experimental data was compared with theoretical predictions of rubber elasticity. Although theory overpredicted the decrease in modulus by 0.05 MPa, the global decrease in modulus with increased swelling was experimentally confirmed. 1