PH-responsive swelling behavior, elasticity and molecular characteristics of poly(N,N-dimethylaminoethyl methacrylate) gels at various initial monomer concentrations

The equilibrium swelling degree and the modulus of elasticity of pH-responsive poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) gels prepared at various initial monomer concentrations were investigated both in buffer solutions and in aqueous salt solutions. As pH of the solution is increased, PDMAEMA gels first remain in the swollen state up to pH 7.7, then exhibit pH-sensitive phase transitions at 8.0 in which PDMAEMA gels attain a collapsed state. The swelling kinetic measurements of PDMAEMA gels showed that pH sensitivity of PDMAEMA is quite stable and the swelling process is reproducible in accordance with pH changing. The swelling behavior of PDMAEMA gels was analyzed by Flory-Rehner theory and the results were combined by the results of compression measurements to calculate the molecular characteristics of gels. The resulting pH-responsive PDMAEMA gels were elastic and displayed good swelling behavior both in buffer solutions and in aqueous salt solutions, therefore, they can be used as a kind of carrying material in drug delivery systems.