Exploring the role of Muscovite in poly(alkyl methacrylate)-based ternary nanocomposite cryogels with selective functional groups: formation via cryogelling with the aid of inorganic clay

Abstract

Easy fabrication of inorganic clay muscovite (MUS) embedded poly(2-acrylamido-2-methyl-1-propane sulfonic acid-co-diethylaminoethyl methacrylate-co-hydroxyethyl methacrylate) (PADH) nanocomposite cryogels with dual temperature/pH dependent catalytic potential was reported. Nanocomposite cryogels were fabricated by a method involving cryogelation and free radical crosslinking of aqueous systems containing MUS ranging from 0% to 1.50% (w/v). The changes in the properties of polybasic PADH networks were investigated to explain how the network parameters and gel properties were affected by the addition of clay, with the formation of a single terpolymer-MUS structure. The potential of the addition of different amounts of MUS to strengthen the prepared terpolymer matrix was investigated by uniaxial compression tests. By lowering the polymerization temperature or increasing the MUS content, the PADH/MUS nanocomposite cryogels became more elastic and compressible with stronger entanglement of terpolymer chains between the clay layers. With the addition of 1.50% (w/v) MUS, the swelling capacity was reduced by 50%, resulting in a two-fold increase in compression elasticity. The nanocomposite gels showed a strong pH-dependence, and when the pH of the swelling medium decreased from 9.8 to 2.1, there was a significant increase in the degree of swelling with increasing protonation of tertiary amine groups. Under an acidic environment, the swelling capacity of the nanocomposite gel containing 1.10% (w/v) MUS increased by 49.5%. In temperature dependent swelling between 15 and 75 °C, all ternary PADH/MUS-Ngels showed a tendency to swell at low and high swelling temperatures, by the predominance of DEAEM units at low temperatures and HEMA monomers at high temperatures, respectively. As the temperature was increased to 55 °C, the swelling decreased and reached a minimum, and then the nanocomposite gels tended to swell again. The obtained results provide an insight into the effect of MUS addition on the properties of poly(alkyl methacrylate)-based ternary nanocomposite gels and demonstrate a simple and efficient way to produce multiple response systems with enhanced elasticity.