Synthesis and swelling-release behavior of superabsorbent nanocomposites

Official URL: https://risc01.sabanciuniv.edu/record=b2708489_(Table of contents)

Superabsorbent polymers (SAPs) are functional polymers in various application fields from the hygiene industry to construction and agriculture. As versatility and high water absorption capacity are significant merits, SAPs usually suffer from low water retention capacity (fast release) and weak mechanical properties. To address these drawbacks, a set of new superabsorbent polymer – Halloysite nanotubes (HNT) nanocomposites were synthesized via free radical polymerization of acrylamide, 2-acrylamido-2-methylpropane-1-sulfonic acid and acrylic acid in the presence of vinyltrimethoxysilane (VTMS) as the crosslinker. FTIR and TGA characterizations confirm the polymerization of SAP and the successful incorporation of HNT into the SAP polymer matrix. The effect of different amounts of HNT nanofiller addition into nanocomposite polymer matrix was investigated with swelling-release performance tests, crosslink density calculations, and rheology measurement. It is found out that equilibrium swelling ratios are correlated, and therefore can be tuned via crosslinking densities of nanocomposites, while water retention capacities are governed by storage moduli. A maximum swelling of 537 g/g was observed 5% HNT was incorporated, in which the crosslinking density is the lowest. Among the SAP nanocomposites prepared, the highest storage modulus was observed when 1% of nanofiller was included, which coincides with the longest water retention nanocomposite. The water release duration of SAPs was prolonged up to 27 days with 1% HNT addition in parallel with the approached maximum storage modulus. Finally, three different incorporation mechanisms of HNT nanofiller into SAP nanocomposite structure were proposed and confirmed with rheology measurements. Moreover, another SAP data set were synthesized with other Poly(ethylene glycol) diacrylate crosslinking agents to observe the effect of crosslinker chain length and amount on crosslinking density and the correlation between crosslinking density and equilibrium swelling capacity. This study provides a rapid synthesis method for SAP nanocomposites with enhanced water retention capacities and explains the relationship between swelling-crosslink density and water retention-mechanical properties of SAP nanocomposites. In addition, the second SAP set with tunable crosslinking densities was prepared with PEGDA crosslinkers and was explained the swelling-crosslink density correlation in detail.