Synthesis and characterization of pH and temperature double-sensitive nanocomposite hydrogels consisting of poly(dimethylaminoethyl methacrylate) and clay

The monomer dimethylaminoethyl methacrylate (DMAEMA) was cross-linked by clay Laponite XLG and Laponite XLS, respectively, in situ free-radical polymerization to prepare nanocomposite gels (named as G-NC gels and S-NC gels). From the analysis of yield, transparency, Fourier transform infrared spectroscopy, x-ray, and scanning electron microscopy, it was proved that the clay Laponite XLS is an appropriate cross-linker for preparing PDMAEMA NC gels with better homogeneous and higher yield due to the uniform dispersion of clay in gels. The resulting S-NC gels show obvious temperature and pH double sensitiveness, and the lowest critical solution temperatures of gels with a low clay content are close to the temperature of the human body, which makes this gel a potential candidate for application in drug release. Comparing with the gels cross-linked by a chemical cross-link agent, the S-NC gels exhibit a considerable improvement in the mechanical properties, swelling ratio, and deswelling rate. The properties of S-NC gels could be adjusted by controlling the content of clay.