Danaja Štular

Embedment of silver into temperature- and pH-responsive microgel for the development of smart textiles with simultaneous moisture management and controlled antimicrobial activities

Silver nanoparticles were embedded into a temperature- and pH-responsive microgel based on poly-(N-isopropylacrylamide) and chitosan (PNCS) before or after its application to cotton fabric to create a smart stimuli-responsive textile with simultaneous moisture management and controlled antimicrobial activities. Two different methods of silver embedment into the PNCS microgel using two different forms of silver nanoparticles were studied, i.e., in-situ synthesis of AgCl nanocrystals into PNCS microgel particles that had previously been applied to cotton fabric, as well as the direct incorporation of colloidal silver into the microgel suspension prior to its deposition on cellulose fibres. SEM and FT-IR analysis were employed to determine the morphological and chemical changes of the modified cotton fibres, while EDS and ICP MS analysis were used to confirm the presence of the silver nanoparticles. The influence of silver embedment on the swelling/deswelling activity of the PNCS microgel was studied using the temperature- and pH-responsiveness, as determined by the moisture content, water vapour transmission rate and water uptake. The antimicrobial activity against the bacteria Staphylococcus aureus and Escherichia coli was assessed. Regardless of the embedment technique, the presence of silver nanoparticles resulted in impaired moisture management activity of the studied microgel. The PNCS microgel proved to be a suitable carrier of antimicrobial agents, assuring the effective controlled release of silver triggered by changes in the temperature and pH of the surroundings, which granted the cotton fabric excellent antimicrobial activity against Gram-negative E. coli (>99%) and Gram-positive S. aureus (>85%).

Combining polyNiPAAm/chitosan microgel and bio-barrier polysiloxane matrix to create smart cotton fabric with responsive moisture management and antibacterial properties: influence of the application process

Smart cotton fabric with simultaneous temperature and pH responsive moisture management and antibacterial properties was prepared by applying poly-(N-isopropylacrylamide)/chitosan microgel in combination with bio-barrier-forming sol–gel precursor dimethyloctadecyl (3-(trimethoxysilyl)propyl) ammonium chloride. Two application processes were used: one-step, which included deposition of a mixture of PNCS microgel and Si-QAC mixture (PNCS/SiQ (1S)), and two-step, comprising deposition of PNCS microgel followed by Si-QAC (PNCS + SiQ (2S)) and vice versa, i.e., deposition of Si-QAC followed by the PNCS microgel (SiQ + PNCS (2S)). Different analysis, i.e., nuclear magnetic resonance, thermogravimetry and dynamic light scattering were used to characterize the poly-(N-isopropylacrylamide)/chitosan microgel, while scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy analysis were employed to determine the morphological and chemical properties of the modified cotton samples. Their functional properties were assessed by the moisture content, water vapor transmission rate, water retention capacity and antibacterial activity against Escherichia coli. While Si-QAC granted excellent antibacterial activity, it also influenced swelling/deswelling activity of the poly-(N-isopropylacrylamide)/chitosan microgel. Accordingly, it slightly impaired moisture content and water retention capacity at conditions when microgels swell but increased water repulsion from the poly-(N-isopropylacrylamide)/chitosan microgel at conditions that trigger its coil-to-globe transition. The application process greatly influenced the washing fastness of the coatings, and the PNCS + SiQ (2S) application process appeared most promising. In this case, the poly-(N-isopropylacrylamide)/chitosan microgel acted as a carrier for the sol–gel precursor dimethyloctadecyl (3-(trimethoxysilyl)propyl) ammonium chloride, causing its gradual release to the fiber surface triggered by a variation of temperature and pH and thus preserving its excellent antibacterial activity after five laboratory washings. To assure complete synergistic activity of both components in the coating, further optimization of the sol–gel precursor dimethyloctadecyl (3-(trimethoxysilyl)propyl) ammonium chloride concentration is necessary.Graphical Abstract

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.

Preparation of Functional Stimuli-responsive Polyamide 6 Fabric with ZnO Incorporated Microgel

A new functional, stimuli-responsive microgel coating on polyamide 6 (PA6) fabric with simultaneous temperature (T)and pH-responsive moisture management, UV protection and photocatalytic self-cleaning properties was prepared by applying poly-(N-isopropylacrylamide)/chitosan (PNCS) microgel in combination with ZnO nanoparticles to PA6 fabric. Two diff erent application procedures were used: (i) the application of PNCS previously functionalized with a ZnO nanoparticles suspension and (ii) the application of PNCS with the subsequent application of a ZnO nanoparticles suspension. The coatings were fabricated on the untreated PA6 fabric as well as on fabric previously modifi ed by the silica matrix created by the sol-gel precursor iSys MTX in order to increase the adsorption ability and uniformity of the coating. The chemical and morphological properties of the coated PA6 samples were determined by SEM and FTIR analyses. Stimuli responsiveness and functional properties were assessed by the moisture content, water vapour transmission rate, water uptake, UV protection and photocatalytic self-cleaning measurements. The results show that the application procedure as well as the pretreatment of PA6 fabric greatly infl uenced the properties of the coating. Accordingly, the most appropriate procedure included the creation of a silica matrix on the PA6 fi bres followed by the application of PNCS and subsequent application of ZnO. In this case, the modifi ed PA6 fabric exhibited high T and pH responsiveness due to the swelling/de-swelling activity of the PNCS microgel, as well as good UV protection with UPF equal to 18.8 and photocatalytic self-cleaning properties that are even higher than those in the case of the one-component coating with ZnO.

Influence of the structure of a bio-barrier forming agent on the stimuli-response and antimicrobial activity of a “smart” non-cytotoxic cotton fabric

In this study, a stimuli-responsive cotton fabric with controlled antimicrobial properties was prepared using temperature- and pH-responsive microgels based on poly(N-isopropylacrylamide) and chitosan (PNCS microgel) in combination with biological-barrier (bio-barrier) forming polysiloxane matrices. For the polysiloxane matrix, (3-aminopropyl)triethoxysilane (APTES) was used in concentrations of 0.5, 2 and 4%. For comparison, 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride (Si-QAC) was included using a concentration of 0.5%. A two-step application process was used, where PNCS microgel was applied to cotton cellulose firstly, followed by the deposition of APTES or Si-QAC secondly. Morphological and chemical changes in the functionalized samples were studied by SEM and FT-IR, and the influence of the polysiloxane matrix structure on functional properties was studied by the determination of the antibacterial activity, moisture content, water vapour transition rate and water uptake. Additionally, for the first time, the cytotoxicity of the samples in the presence of APTES and Si-QAC was assessed. The results show that different structures of the bio-barrier-forming polysiloxane matrices not only have a great influence on functional antimicrobial and responsive properties but also affect the cytotoxicity. Both polysiloxane matrices produced excellent antimicrobial activity, which was also obtained with 0.5% Si-QAC. However, a much higher concentration of APTES (i.e., 4%) was needed for the same antimicrobial effect. Despite its small concentration, the presence of the Si-QAC caused strong cytotoxicity, whereas the other studied samples were non-cytotoxic. The Si-QAC hindered the dual temperature- and pH-responsive properties, but the latter quality was preserved in the presence of APTES.Graphical abstract

Visual and Functional Properties of Digital Printed and Finished Anaglyph Pictures on Cotton Fabric

The aim of the study was to examine the infl uence of various protective fi nishes on the visual properties of anaglyph images and CMYK primary colours digitally printed on a cotton fabric. Using the impregnation process, one-component waterand oil-repellent, and fl ame retardant fi nishes, as well as their combination were subsequently applied on the printed samples. A visual evaluation was determined for the 3D visual eff ect of printed samples before and after the fi nishing, one and fi ve washings, and after seventy-two hours of exposure to artifi cial light. The colour fastness of prints after repeated washing, exposure to artifi cial light, dry and wet rubbing was determined. The repellence properties of studied fi nishes were studied by measuring the contact angles of water and n-hexadecane, while the vertical fl ammability test was used for the determination of fl ame retardancy. The wash fastness of the studied fi nishes was also taken into observation. The results showed that the presence of fi nishes changed the colour properties of prints; however, it did not impair the 3D eff ect of the anaglyph image, which was maintained even after repeated washings and exposure to artifi cial light. The presence of fi nishes improved the wash fastness of the M and Y colour, and impaired the wash fastness of the C and K colour. The light fastness of unfi nished printed samples was poor, but it improved for the M, Y and K colours after the application of fi nishes. The prints did not infl uence the functional repellent and fl ame retardant properties. However, the impaired wash fastness of fi nishes was observed.