Electric field-induced gradient strength in nanocomposite hydrogel through gradient crosslinking of clay

In this paper, mechanically strong organic-inorganic nanocomposite (NC) gradient hydrogels were successfully prepared by the in situ polymerization of acrylamide (Am) and N , N -dimethyl aminoethyl methacrylate (DMAEMA) using an electrophoresis method. Due to its specific colloidal properties, LAPONITE® showed directional movement in direct-current (DC) electric field and thus formed a gradient distribution in the hydrogel. The concentration gradient of LAPONITE® was characterized by UV-vis absorption, FTIR and TGA. The network structures of lyophilized gradient hydrogels were observed from SEM images. The TEM morphology indicated that LAPONITE® had a good gradient dispersion in the NC gradient hydrogel. As a physical crosslinker, LAPONITE® can regulate the cross-linking density of the hydrogel, thus affecting its mechanical properties. The NC gradient hydrogel exhibited a high mechanical strength (a gradient tensile strength ranging from 43.4 to 135.3 kPa and a gradient compression strength ranging from 116 kPa to 1100 kPa, depending on the distance from the anode). This work provided a facile method to develop NC gradient hydrogels with improved mechanical performance. The NC gradient hydrogels can be used as potential candidates in the field of biological and chemical materials. Nanocomposite gradient hydrogels with adjustable mechanical strength and network sizes were synthesized by electric field-induced gradient crosslinking polymerization.