Tunable wettability of polyester fabrics functionalized by chitosan/poly(N-isopropylacrylamide-coacrylic acid) microgels

Functionalization of textiles has been the aim of many studies in the field of intelligent materials. Biomimesis (lotus, pinecone effect etc.), adapting informatics to textile production (integration of computer-controlled electronic sensors), creating new fibres either natural or synthetic (algae biocomposite, ferroelectric polymeric etc.) and convergence of opposites (e.g. hydrophilic with hydrophobic materials) are some of the approaches used for textile functionalization [1-5]. This research focuses on a novel approach for developing advanced textile materials with biopolymer-based functionalities: the use of a hydrophilic stimuli-responsive system based on polyelectrolyte hydrogels for the surface modification of hydrophobic polyester fabrics. The aim was to render textiles responsive to external stimuli such as pH and temperature changes, without affecting dramatically their good intrinsic properties (e.g. mechanical strength). This research involved the following tasks: preparation of surface modifying systems (hydrogels) based on specifically selected polymers; characterization of the surface functionalization; and study of the new functionalities imparted to the textile, expressed as pH/thermo-responsiveness of the material

Advanced microgel-functionalized polyester textiles adaptive to ambient conditions

A new approach toward textile-based multi-functional and stimuli-responsive materials is proposed. Polyelectrolyte microgel technology is combined with conventional functionalization methods of photo- and thermo-crosslinking to activate the surface of polyester textiles, making them interactive with their environment. The microgels consisted of pH/thermo-responsive poly(N-isopropylacrylamide-co-acrylic acid) (PNIAA) microparticles either alone or complexed with oppositely charged macromolecular chains of the pH-responsive natural polysaccharide chitosan. Microgel incorporation into polyester surface layers was achieved either through UV irradiation in the presence of the photoinitiator benzophenone or through low temperature treatment using the natural crosslinker genipin. The adaptivity of the functionalized textiles to\ud ambient conditions of pH, temperature and relative humidity was expressed by changes in the textile physicochemical and water management properties. These changes were found to occur within a physiological pH/temperature range of the human body (pH 4–8 and 20–40°C). More specifically, functionalized polyester textiles exhibited a shift in surface charge from positive to negative values at pH ranging from 5.0 to 6.6, following the trend of the incorporated microgels. Below the microgel Lower Critical Solution Temperature (36ºC), the chitosan-containing functionalized textiles exhibited improved water wettability compared with reference textiles. Above 36ºC, functionalized textiles had lower moisture regains and higher water vapor transmission rates than the reference textiles. Microgel incorporation was found to be sufficiently durable, in some cases even after 30 washing cycles. However, some of the textile advantageous properties (e.g. whiteness, crease recovery) deteriorated due to the functionalization process. Possible applications of the microgel-functionalized polyester textiles lie in the fields of biomedicine and protective clothing

Moisture absorption capacity of polyamide 6,6 fabrics surface functionalised by chitosan-based hydrogel finishes

The present study aims at investigating the moisture absorption capacity of polyamide 6,6 fabrics when their surface is functionalised by chitosan-based hydrogels. For the finishing procedure, bulk hydrogels of chitosan (CS) with different contents of embedded thermosensitive microparticles of poly(N-isopropylacrylamide-co-acrylic acid) (PNIAA) were used. In practice, hydrogel incorporation into the fabric surface layer was achieved by crosslinking primary amine groups of chitosan with the end amine groups of polyamide, using the natural crosslinker genipin. Among other analytical techniques, Scanning Electron Microscopy (SEM) was used to characterize the surface morphology of both hydrogel and fabric samples, Differential Scanning Calorimetry (DSC) to determine the Lower Critical Solution Temperature (LCST) of PNIAA, and X-ray Photoelectron Spectroscopy (XPS) to analyse the fabric surface chemical composition. The fabric moisture contents were determined by weight measurements at different temperatures and relative humidity values (RH). Liquid porosimetry, water vapour transmission (WVT) and dynamic wetting measurements were also performed to assess the fabric pore volume distribution, permeability and wetting times, respectively. It was found that the moisture absorbed by the functionalised polyarnide fabrics can be regulated at different conditions of temperature and relative humidity according to the PNIAA/CS ratio in the hydrogel. For example, at 40 degrees C (i.e. above the PNIAA LCST) and even at high RH (85%), the higher the PNIAAJCS ratio was in the incorporated hydrogel, the lower were the moisture contents of the functionalised fabrics, compared to the reference. In all cases, the presence of CS increased significantly the polyamide fabric wetting times

Application of temperature and pH responsive microhydrogels for functional finishing of cotton fabric

This paper discusses the developing of an innovative strategy for functional finishing of cotton by application of surface modifying systems based on stimuli responsive microparticulate hydrogels. Dual responsive hydrogels in the microscale were prepared using a temperature responsive synthetic polymer (poly-NiPAAm) and a pH responsive biopolymer (chitosan). The physicochemical characterisation and the stimuli responsiveness of the microparticulate systems have been investigated by microscopy and spectrophotometric techniques, and dynamic light scattering. In an attempt to enhance the incorporation of microparticulate hydrogel to cotton surface, carboxymethylation and aminisation methods for cotton activation have been assessed. Surface modified textile material with incorporated microparticles has been characterised by SEM and XPS techniques in order to determine surface morphology and chemical structure. The capability of the material to respond to different stimuli (pH, temperature, humidity) was studied through swelling/shrinking or hydration/dehydration kinetics and equilibrium using a gravimetric method