Synthesis and characterization of nanocomposite hydrogel by γ-ray irradiation: poly(n-isopropylacrylamide) (PNIPAM) and laponite

Abstract

Three types of poly(n-isopropylacrylamide) (PNIPAM) and laponite nanocomposite hydrogels were prepared. First sample is polymerized from directly gamma irradiated solution with only NIPAM monomer and laponite (Lap/NIPAM/γ-ray gel). High energy of γ-ray initiates polymerization of NIPAM monomer. The hydrogel is synthesized even the solution has no cross-linker (NIPAM/γ-ray gel). Second sample is polymerized from gamma irradiated laponite solution followed by putting NIPAM solution (Lap/γ-ray/NIPAM gel). Third sample was polymerized by putting potassium persulfate (KPS) into the mixed NIPAM and the laponite solution (Lap/NIPAM/KPS gel). The effect of synthetic methods on various properties were investigated. Lap/γ-ray/NIPAM and Lap/NIPAM/KPS gels have better swelling/deswelling property than Lap/NIPAM/γ-ray gel. It is expected that Lap/NIPAM/γ-ray gel have more cross-links and short inter-crosslink chain lengths than Lap/γ-ray/NIPAM and Lap/NIPAM/KPS gels by the analysis of small angle X-ray scattering. Scanning Electron Microscope (SEM) images show the gap between Lap/NIPAM/γ-ray, Lap/γ-ray/NIPAM and Lap/NIPAM/KPS gels. Self-healing property was also shown in Lap/γ-ray/NIPAM and Lap/NIPAM/KPS gels because of the structural difference. The highest storage modulus (G′) of Lap/NIPAM/γ-ray gel in rheology is also the evidence that Lap/NIPAM/γ-ray gel have more cross-links.