Tailoring of temperature- and pH-responsive cotton fabric with antimicrobial activity: Effect of the concentration of a bio-barrier-forming agent.

A stimuli-responsive cotton fabric was designed using temperature and pH-responsive poly-N-isopropylacrylamide (poly-NiPAAm) and chitosan (PNCS) microgel as a carrier of antimicrobially active 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride (Si-QAC), which forms a bio-barrier on the fibre surface. The influence of Si-QAC on the moisture management and thermoregulation abilities of the PNCS microgel was investigated. Using a pad-dry cure method, Si-QAC was applied to a 100% cotton fabric model in concentrations ranging from 0.05-4% to determine the antimicrobial activity of Si-QAC against two types of bacteria, gram-positive Staphylococcus aureus and gram-negative Escherichia coli. Based on these results, three different concentrations of Si-QAC were selected (0.5, 2 and 4%) and tested with in situ embedment of the agent into PNCS microgel particles for further functionalization of the cotton fabric. The functional properties of the studied samples were assessed by measuring the moisture content, water vapour transmission rate, water uptake and antibacterial activity, and FT-IR and SEM were used to study the chemical and morphological properties of the fibres. The results show that regardless of the concentration, the presence of Si-QAC caused a reduction in the change in the volume of the PNCS microgel particles under conditions that would normally cause swelling. Accordingly, the moisture management and thermoregulation properties of the PNCS microgel were best preserved when the lowest Si-QAC concentration (0.5%) was used. Despite the low concentration, at the conditions required, enough Si-QAC was released from the microgel particles onto the surface of the fibres to form a bio-barrier with excellent antimicrobial activity.