Preparation and characterization of CS-g-PNIPAAm microgels and application in a water vapour-permeable fabric

Chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAAm) was synthesised using sonication with and without the crosslinker, N,N′-methylenebisacrylamide (MBA). FTIR, variable-temperature 1H NMR spectroscopy, atomic force microscopy, UV-vis spectrophotometry, differential scanning calorimetry, and dynamic light scattering were used to characterize the microgels' chemical constituents, structures, morphologies, lower critical solution temperatures (LCSTs), and thermo- and pH-responsiveness. The chemical structures of the two CS-g-PNIPAAm materials were found to be similar and both exhibited dual responsiveness towards temperature and pH. The microgel containing MBA had a higher LCST, smaller diameter, and more compact structure, but exhibited opposite pH- and similar thermo-responsiveness. Although the structure of the microgel particles prepared without crosslinking was unstable, the stability of the crosslinked microgel particles enabled them to be finished onto fabric. Because the microgel prepared with MBA retains thermosensitivity, it can be used to impart controllable water vapour permeability properties. The incorporation of the MBA-crosslinked CS-g-PNIPAAm microgel particles in cotton fabric was accomplished by a simple pad-dry-cure procedure from an aqueous microparticle dispersion. The water vapour permeation of the finished fabric was measured at 25 and 40 °C and 50 and 90% relative humidities. The finished fabric displayed an obviously high water vapour permeability at 40 °C.