Effect of DMAEMA content and polymerization mode on morphologies and properties of pH and temperature double-sensitive cellulose-based hydrogels

Double responsive cellulose/ poly 2-(dimethylamino) ethyl methacrylate (PDMAEMA) hydrogels were prepared through in situ radical polymerization. The results from Fourier transform infrared spectroscopy, scanning electron microscopy, mechanical property testing, swelling experiments as well as thermogravimetric analysis demonstrated that 2-(dimethylamino) ethyl methacrylate (DMAEMA) content and polymerization modes played a decisive role in hydrogel's structure. Firstly, with increasing DMAEMA content, the texture of hydrogel became softer. The incorporation of relatively hard cellulose and the increase in crosslink density markedly strengthened the three-dimensional network structure of hydrogels, and the tensile strength, compression and bending properties of the composite's hydrogels were fine with the content of DMAEMA in a certain range. When the DMAEMA content increased to 6 g/g(cellulose), the mechanical strength decreased obviously. An increase in the DMAEMA content resulted in a faster initial swelling rate and higher equilibrium swelling ratio (ESR). Secondly, freezing in hydrogel formation was beneficial to formation of interpenetrating network structure, which can raise its initial swelling rate and higher ESR. Freeze–thaw had a certain destructive effect on the micropore structure. Thirdly, three-dimensional structure and the increase of DMAEMA content can also improve the pH and temperature response sensitivity of hydrogels. Thus, the mechanical, swelling and responsive properties of this hydrogel could be adjusted by the DMAEMA content and polymerization modes.