Effect of sizes of vinyl modified narrow-dispersed silica cross-linker on the mechanical properties of acrylamide based hydrogel.

Polymeric hydrogel with the incorporation of nano to submicro-meter sized materials forms an exhilarating new generation of composite hydrogels. Most of the applications of hydrogels are in aqueous environments in which they swell to a very high degree. This emanates from low density of the polymer chains, making them highly inferior in terms of physical strength and their prospective applications. In order to address the weak mechanical properties, hydrogels have successfully prepared with high tensile strength and toughness by reinforcing the acrylamide (AAm) network with 3-methacryloxypropyltrimethoxysilane (MPTS) modified silica particles (MSiO2) as chemical cross-linker. The MSiO2 cross-linkers are prepared from narrow-dispersed silica particles (SiO2) of 100 nm, 200 nm, and 300 nm diameters to investigate the effect of cross-linker sizes on the mechanical strengths of hydrogels. The presence of MSiO2 remarkably increases the stretching ability and toughness of hydrogels compared to conventional hydrogels. The tensile strength, toughness, and Young's modulus of the hydrogel decrease from 30 to 11 kPa, 409 to 231 kJ/m3, and 0.16 to 0.11 kPa, respectively, while the SiO2 particle size increase from 100 to 300 nm and the concentration of AAm and MSiO2 (%) are kept constant. The compressive strength and toughness of the hydrogel decrease from 34 to 18 kPa and 6 to 4 kJ/m3, respectively, but the Young's modulus increases from 0.11 to 0.19 kPa. This work is excellent proof of regulating mechanical strength of hydrogel by adjusting the particle size of MSiO2 cross-linkers.