Comparison of responsive behaviour of smart PLA fabrics applied with temperature and pH responsive microgel and nanogel

Hydrogels based on poly(N-isopropylacrylamide) (poly-NiPAAm) and chitosan (PNCS hydrogel) in two size ranges were synthesised, i.e. PNCS microgel (PNCS_M) and PNCS nanogel (PNCS_N) with an average particle size of 405 nm and 76 nm, respectively. Hydrogels were applied to poly(lactic acid) (PLA) fabric and the influence of the hydrogel particle size on the functional and handling properties of the fabric was assessed. Morphological and chemical changes were determined using FT-IR, SEM and AFM. The temperature and pH responsiveness of the functionalised PLA were studied based on the water uptake (WU), moisture content (MC) and water vapour transition rate (WVTR); thus, the rate of the liquid spreading through the sample and the overall stiffness of the padded samples were assessed. Both hydrogels improved air and moisture management of the functionalised PLA fabric. In an aqueous dispersion, PNCS_N demonstrated a greater volume change than PNCS_M. Particle size did not influence the LCST of poly-NiPAAm, but it affected morphology of the coated fibres. PNCS_M formed microgel particles on the PLA fibres, and a homogenous layer was observed on the PNCS_N coated fibres. Such deposition hindered swelling of the PNCS_N in comparison to the PNCS_M. The handling properties were better preserved when using smaller particles.