The rmomechanical behavior and chemical sensing cationic poly(diallyldimethylammonium chloride) and anionic poly(sodium 4-styrene sulfonate) assembled into composite polyelectrolyte multilayer thin films and complex membranes

Abstract

Polyelectrolyte composite membranes of cationic PDADMAC and anionic PSS assembled into polyelectrolyte multilayer (PEM) thin film and polyelectrolyte complex (PEC) membranes were used as matrix embedded with several additive molecules. Nano-scale PEM films fabricated using the layer-by-layer deposition method and the loading and release of a hydrophobic model drug curcumin (Cur) was studied for drug delivery and sensing applications. Interestingly, it was found that the loading and release of Cur could be triggered by solvent composition and temperature. In a parallel study, the alternative to the nanoscale PEM was studied in the form of PEC, which were used as stand-alone film with a thickness in micro-scale. PECs prepared by solution-mixing using NaCl as a plasticizer followed by centrifugation and compression molding were investigated. Remarkably, not only the tuning of [NaCl] used during mixing could affect the thermomechanical behavior of salt-free films but also the changes in polyelectrolytes stoichiometry. Cur blended into non-stoichiometric PEC membranes were tested as optical NH3 vapor sensor and it was found that the excess positive stoichiometry gave the best results. To further improve the mechanical properties of both the free-standing PEM and PEC films, cellulose nanocrystals (CNCs) were used as fillers to reinforce the polymer matrix.