In-situ study of the structure and dynamics of thermo-responsive PNIPAAm grafted on a cotton fabric

Stimuli-responsive polymeric materials can adapt to various surrounding environments, converting chemical and biochemical changes into optical, electrical and thermal signals, or changing wettability and adhesion properties upon external stimuli. Herein we report a cotton fabric modified with a thermo-responsive polymer, Poly(N-isopropylacrylamide) (PNIPAAm). 1H solid-state NMR techniques were used to characterize the molecular structure and dynamics of the PNIPAAm brushes, while still grafted on the cotton fabric surfaces, avoiding un-grafting destructive procedures. The results demonstrate that the motion of the grafted PNIPAAm brushes is restricted as the temperature rises above the low critical solution temperature (LCST), which was estimated to be ~34 °C. Variable temperature (VT) experiments were used to investigate the nature of the hydrophilic-hydrophobic transitions of the grafted polymer. The 1H solid-state NMR techniques used proved to be an extremely sensitive and precise way to probe in-situ the LCST transition of the PNIPAAm brushes, while still grafted on cotton fibres. This work presents a high potential synthesis and analysis route towards stimuli-responsive cotton fibres which can find exceptional applications as novel intelligent fabrics for the textile related industries.