Study on partition and release of molecules in superabsorbent thermosensitive nanocomposites

Abstract

Nanocomposites are synthesized by in-situ polymerization of conducting polymers: polyaniline (PANI) or poly(N-methylaniline) (PNMANI) inside thermosensitive hydrogels based on poly(N-isopropylacrylamide) (PNIPAM) homopolymer and copolymers with 2-acrylamido-2-methyl propane sulfonic acid (AMPS). Large swelling capacities (up to 25,000%) are measured for a nanocomposite based on a hydrogel containing only 2% of anionic monomer units. Dynamic swelling experiences show that water intake follows a non-Fickian mechanism. Drug release kinetics and partition coefficients (K)of model compounds (Methyl Orange, Ruthenium-tris(2,20-bipyridyl) ion, Dansyl Chloride) and pharmaceuticals (Tryptophan, Propranolol Chloride, Riboflavin) were measured. Log K values were determined by UVevisible or fluorescence spectroscopy, below and above the phase transition temperature of the materials. Large values of log K (>3) were measured for tryptophan while the same material shows small log K (1.5) for riboflavin. Depending on the nanocomposite/solute interactions, the partition increases ordecreases upon phase transition. Several nanocomposites studied show potential for application in the separation of solutes or water purification. Additionally, it is possible to synthesize nanocomposites which show different partition coefficients for the same molecule. In that way, a specific pattern could be measured for each molecule allowing its identification.