Fabrication of superhydrophobic polymethylsilsesquioxane nanostructures on cotton textiles by a solution-immersion process

Superhydrophobic cotton textiles are prepared by a simple, one-step and inexpensive phase separation method under ambient conditions by which a layer of polymethylsilsesquioxane (PMSQ) nanostructures is covered onto the cellulose fibers. By changing the silane precursor concentration, PMSQ nanostructures with various shapes, morphologies and sizes were fabricated. Nanostructures were characterized using SEM, EDS, and attenuated total reflectance FTIR. The wettability of the modified cellulose surfaces was characterized with contact-angle goniometry and sliding angle technique, respectively. The water contact angle of modified cotton is measured to be higher than 150°, which is high enough to exhibit the lotus effect as a result of the superhydrophobicity. Tunable water-repellent properties of the fabric are also demonstrated, with sliding contact angles varying from "sticky" to "slippery" depending upon different nanostructures on the surface of the fibers. It is expected that this simple technique will accelerate the large-scale production of superhydrophobic cellulosic materials with new industrial applications.     

Preparation of superhydrophobic electroconductive graphene-coated cotton cellulose

A simple and versatile method based on cotton cellulose coated with graphene is reported for the fabrication of superhydrophobic and electroconductive textiles. Graphene oxide was deposited on cotton fibers by a dip-pad-dry method followed by reduction with ascorbic acid to yield a fabric with a layer of graphene. The fabric was then reacted with methyltrichlorosilane to form polymethylsiloxane (PMS) nanofilaments on the fibers surface. The surface chemistry and morphology were characterized by UV–visible reflectance spectrophotometry, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy. The water contact angle (CA)/shedding angle (SHA) and resistivity measurements were used for assessing hydrophobicity and conductivity, respectively. The graphene-coated fabric showed hydrophobicity with the CA of 143.2° ± 2.9° and SHA of 41°. The formation of PMS nanofilaments displayed superhydrophobicity with CA of 163° ± 3.4° and SHA of 7°, which indicated the self-cleaning ability. Conductivity of the graphene-coated fabric was confirmed by the electrical resistivity of 91.8 kΩ/sq which increased to 112.5 kΩ/sq after the formation of PMS nanofilaments.     

Synthesis of fluorinated hyperbranched polymers capable as highly hydrophobic and oleophobic coating materials

A series of coating materials were prepared from two classes of hyperbranched polymers containing short fluorocarbon chains (HPEFs/HPUFs). The obtained hyperbranched polymers were characterized by FT-IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR, GPC and TG analyses. HPEFs/HPUFs exhibited very low surface free energies (13.67-24.49 mJ/m²) which almost are independent of their internal backbone but dependent on the terminal fluorocarbon chains. Highly hydrophobic and/or oleophobic surfaces of cotton woven fabric can be achieved from these polymers by solution-immersion coating method. The static and dynamic wettabilities of the HPEFs/HPUFs treated fabrics have been investigated. The static contact angles reached to 146°, 122° and 102° for water, hexadecane and decane, respectively. The lowest contact angle hysteresis reached to 5.9°.     

Biomimetic fabrication of lotus-leaf-like structured polyaniline film with stable superhydrophobic and conductive properties

Superhydrophobic surfaces were successfully prepared on Ti/Si substrates via the fabrication of conductive polyaniline (PANI) nanowire film. The PANI nanowire film was synthesized by electrodeposition of aniline into the pores of an anodic aluminum oxide (AAO) template on Ti/Si substrate followed by the removal of the template. The surface showed conductivity and superhydrophobicity, even in many corrosive solutions, such as acidic or basic solutions over a wide pH range. Field emission scanning electron microscopy (FE-SEM) demonstrated that the binary geometric structures at micro- and nanometer scale bestowed the prerequisite roughness on the surfaces. The chemical surface modification made the PANI nanowire film superhydrophobic. The results demonstrated that the PANI nanowire film will have good potential applications in the preparation of conductive superhydrophobic surfaces.     

Biomimetic superhydrophobic UHMWPE/nanosilica films with different sticky behavior on several metals

A kind of organic–inorganic composite film with biomimetic superhydrophobic performance was prepared on several metals including steel, aluminum, and copper. The organic matrix was ultrahigh‐molecular‐weight polyethylene (UHMWPE), and the inorganic filler was nanosilica. Scanning electron microscope observation indicated addition of nanosilica greatly changed the topography of the UHMWPE film. Special convexities were formed on the surfaces of the composite films, which made the composite films rougher than that of pure UHMWPE film. The nanosilica randomly scattered on the surface of the convexities and formed hierarchical structure similar to that of some plant leaves with superhydrophobic characteristics. Interestingly, it was found that there were remarkable differences between the sliding angles (SA) of water droplet on the composite films on different metals although the contact angles (CA) of water droplet on these films were quite close. The CA on the composite films on steel was about 157°, and the SA was larger than 90°, which demonstrated obvious superhydrophobic and sticky characteristic. But to the films on aluminum and copper, the CAs on them were larger than 160° and the SAs were between 3° and 4°, which meant excellent superhydrophobic and roll‐off performance. Scanning electron microscope observation indicated that there were some micro‐orifices in the film on steel and these micro‐orifices were connected to some extent. It was believed that these micro‐orifices provided capillary force and restrained sliding of water droplet. A sticky model based on capillary mechanism was proposed. Copyright © 2017 John Wiley & Sons, Ltd.     

Epoxy phosphonate crosslinkers for providing flame resistance to cotton textiles

Two new monomers (2‐methyl‐oxiranylmethyl)‐phosphonic acid dimethyl ester ( 3 ) and [2‐(dimethoxy‐phosphorylmethyl)‐oxyranylmethyl]‐phosphonic acid dimethyl ester ( 6 ) were prepared and used with dicyandiamide ( 7 ) and citric acid ( 8 ) to impart flame resistance to cotton plain weave, twill, and 80:20‐cotton/polyester fleece fabrics. Monomers 3 and 6 were prepared from methallyl chloride ( 1 ) and 3‐chloro‐2‐chloromethylpropene ( 4 ) respectively via a two‐step phosphorylation epoxidation sequence in 79.3 and 67.5% overall yields. ¹H and ¹³C nuclear magnetic resonance (NMR) and gas chromatographic mass spectrometry (GCMS) data were used to confirm their structures. Decomposition of monomers 3 and 6 in nitrogen by thermogravimetric analysis (TGA) occurred at 110 and 220°C, respectively. The mixtures of 3 : 7 : 8 and 6 : 7 : 8 (in 2:1:1 ratio) exhibited peak‐curing temperatures by differential scanning calorimeter (DSC) at 125 and 150°C and the temperatures were deemed suitable for curing treated fabrics without marring them. Flame‐retardant treatments were applied by the pad‐dry‐cure methods. All untreated fabrics showed limiting oxygen index (LOI) values of about 18% oxygen in nitrogen. For formulations with monomer 3 , LOI values for the three types of treated fabrics were greater than 25.5% when add‐on values for the formulation were 17.4, 12.7, and 21.1%. For formulations comprising monomer 6 , LOI values were greater than 28.6% when add‐on values for the formulation were 18.3, 13.1, and 16.7%. With the formulation comprising monomer 3 , the three fabrics passed the vertical flame test when add‐on values were 21.6, 12.7, and 23.5%, respectively; and with the formulation comprising monomer 6 , they passed the vertical flame test when add‐on values were 13.8, 8.4, and 18.0%. In all cases char lengths of fabrics that passed the vertical flame test were less than 50% of original length and after‐flame time was 0 sec and after‐glow time was less than 2 sec. Published in 2007 by John Wiley & Sons, Ltd.     

Asymmetrically superhydrophobic cotton fabrics fabricated by mist polymerization of lauryl methacrylate

A graft-polymerization process with atomized lauryl methacrylate as monomer is used to fabricate fluorine-less and asymmetrically superhydrophobic cotton fabrics. The polymers synthesized in the process can form nanoscale hierarchical structures on the cotton surface, and the surface morphology can be controlled by choosing a suitable solvent or by varying the feeding quantity of the monomer mist stream. After applying the surface modification to cotton fabrics, an asymmetrically superhydrophobic surface is achieved without any additional nanosized particles, and the solvent damages on the cotton fabrics are controllable at a very low level. Surface characterization reveals that the modified side of the cotton fabric has laundering-durable and mechanically stable superhydrophobicity with a water contact angle of more than 150°, whereas the opposite inherits the hydrophilic property of pristine cotton fabric. The modified cotton fabrics are found to have medium-level water-absorbing ability between pristine cotton and PET fabrics, as well as good vapor transmissibility similar to pristine cotton fabric. These properties are of great significance in textile and medical applications.     

Fabrication of highly transparent superhydrophobic coatings from hollow silica nanoparticles

We herein report a simple and effective method to fabricate excellent transparent superhydrophobic coatings. 3-Aminopropytriethoxysilane (APTS)-modified hollow silica nanoparticle sols were dip-coated on slide glasses, followed by thermal annealing and chemical vapor deposition with 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (POTS). The largest water contact angle (WCA) of coating reached as high as 156° with a sliding angle (SA) of ≤2° and a maximum transmittance of 83.7%. The highest transmittance of coated slide glass reached as high as 92% with a WCA of 146° and an SA of ≤6°. A coating simultaneously showing both good transparency (90.2%) and superhydrophobicity (WCA: 150°, SA: 4°) was achieved through regulating the concentration of APTS and the withdrawing speed of dip-coating. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were used to observe the morphology and structure of nanoparticles and coating surfaces. Optical properties were characterized by a UV-visible spectrophotometer. Surface wettability was studied by a contact angle/interface system. The effects of APTS concentration and the withdrawing speed of dip-coating were also discussed on the basis of experimental observations.     

ZnO-TiO2 hybrid nanocrystal-loaded,wash durable,multifunction cotton textiles

Life-threatening diseases, especially those caused by pathogens and harmful ultraviolet radiation (UV-R), have triggered increasing demands for comfortable, antimicrobial, and UV-R protective clothing with a long service life. However, developing such textiles with exceptional wash durability is still challenging. Herein, we demonstrate how to fabricate wash durable multifunctional cotton textiles by growing in situ ZnO-TiO₂ hybrid nanocrystals (NCs) on the surface of cellulosic fabrics. The ZnO-TiO₂ hybrid NCs presented high functional efficiency, owing to their high charge transfer/separation. Ultrafine fiber surface pores, utilized as nucleating sites, endowed the uniform growth of NCs and their physical locking. The resulting fabrics presented excellent UV protection factors up to 54, displayed bactericidal efficiency of 100% against Staphylococcus aureus and Escherichia coli, and optimum self-cleaning efficacy. Moreover, the functionalized textiles exhibited robust washing durability, maintaining antibacterial and anti-UV-R efficiency even after 30 extensive washing cycles.

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A facile strategy to fabricate silver-functionalized superhydrophobic cotton fabrics with long-term antibacterial properties

Cellulose - Silver-functionalized textiles, as the most common protective medical materials, have attracted considerable attention. However, poor antibacterial durability and relatively tedious...     

Hexamethyldisiloxane‐modified ZnO‐SiO2‐coated superhydrophobic textiles for antibacterial application

A superhydrophobic cotton textile with high antibacterial properties has been fabricated. The cotton textile was coated through the in situ growth of ZnO‐SiO₂ nanoparticles in presence of chitosan as the template agent via a hydrothermal process at 95 °C. This process was followed by the coating of additional layers of hexadecyltrimethoxysilane (HDTMS). The obtained cotton textile showed antibacterial property against Staphylococcus epidermis and Escherichia coli with inhibition zones up to 18.26 and 8.48 mm, respectively. Scanning electron microscopy (SEM) revealed that the coating had a rough surface, which was attributed to the distribution of ZnO‐SiO₂ nanorods of hexagonal shape. This rough surface creates a superhydrophobic layer that repels the bacteria, as proven by the large water contact angle of approximately 150°. Nevertheless, the HDTMS layers prolong the durability of hydrophobicity for up to 3 h.     

Photoreactive azido-containing silica nanoparticle/polycation multilayers: durable superhydrophobic coating on cotton fabrics

In this study, we report the functionalization of silica nanoparticles with highly photoreactive phenyl azido groups and their utility as a negatively charged building block for layer-by-layer (LbL) electrostatic assembly to produce a stable silica nanoparticle coating. Azido-terminated silica nanoparticles were prepared by the functionalization of bare silica nanoparticles with 3-aminopropyltrimethoxysilane followed by the reaction with 4-azidobenzoic acid. The azido functionalization was confirmed by FTIR and XPS. Poly(allylamine hydrochloride) was also grafted with phenyl azido groups and used as photoreactive polycations for LbL assembly. For the photoreactive silica nanoparticle/polycation multilayers, UV irradiation can induce the covalent cross-linking within the multilayers as well as the anchoring of the multilayer film onto the organic substrate, through azido photochemical reactions including C-H insertion/abstraction reactions with surrounding molecules and dimerization of azido groups. Our results show that the stability of the silica nanoparticle/polycation multilayer film was greatly improved after UV irradiation. Combined with a fluoroalkylsilane post-treatment, the photoreactive LbL multilayers were used as a coating for superhydrophobic modification of cotton fabrics. Herein the LbL assembly method enables us to tailor the number of the coated silica nanoparticles through the assembly cycles. The superhydrophobicity of cotton fabrics was durable against acids, bases, and organic solvents, as well as repeated machine wash. Because of the unique azido photochemistry, the approach used here to anchor silica nanoparticles is applicable to almost any organic substrate.     

Facile preparation of superhydrophobic and oleophobic surfaces via the combination of Cu(0)‐mediated reversible‐deactivation radical polymerization and click chemistry

The fabrication of novel hydrophobic, superhydrophobic, and oleophobic surfaces on glass using nanosilica particles modified with polymer brushes prepared via surface initiated Cu(0)‐mediated reversible‐deactivation radical polymerization was demonstrated. Monomers including n‐butyl acrylate, 2,2,2‐trifluoroethyl methacrylate, and 1,1,1,3,3,3‐hexafluoroisopropyl acrylate were used to synthesize a series of nanosilica–polymer organic/inorganic hybrid materials. Products were analyzed using infrared spectroscopy, thermogravimetric analysis, scanning and transmission electron microscopy. The coated nanosilica showed core–shell structures that contains polymer brushes up to 67 wt %. The application of these particles for modifying surface wettability was examined by covalently attaching them to glass via a recently developed one‐pot “grafting to” methodology using “thio‐bromo click” chemistry. Atomic force microscopy topographic images show up to 25 times increase in roughness of the coated glass compared to blank glass sample. Contact angle measurements showed that nanosilica coated with PBA and PTFEM produced hydrophobic glass surfaces, while a superhydrophobic and oleophobic surface was generated using nanosilica functionalized with PHFIPA. This novel methodology can produce superhydrophobic and oleophobic surfaces in an easy and fast way without the need for tedious and time‐consuming processes, such as layer‐by‐layer deposition, high temperature calcination, and fluorinated oil infusion. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018     

Synthesis of superhydrophobic fluoro-containing silica sol coatings for cotton textile by one-step sol–gel process

Journal of Sol-Gel Science and Technology - Superhydrophobic coatings were successfully fabricated on cotton textiles through a simple one-step sol–gel process. A fluorinated copolymer...     

Fabrication of asymmetrically superhydrophobic cotton fabrics via mist copolymerization of 2,2,2‐trifluoroethyl methacrylate

We report here a simple strategy for fabricating asymmetrically superhydrophobic cotton fabric via a mist copolymerization of three monomers, 2,2,2‐trifluoroethyl methacrylate (TFMA), 2‐isocyanatoethyl methacrylate (IEM), and divinylbenzene (DVB). The copolymer layer on the cotton surface was confirmed by X‐ray photoelectron spectroscopy (XPS) analysis and attenuated total reflection (ATR) accessory, and the nanoscale hierarchical structures in the polymeric layer were demonstrated by observation of field emission scanning electron microscope (FE‐SEM). Surface characterization reveals that the modified surface is superhydrophobic, but the opposite side of the modified cotton fabric has the hydrophilic nature of cotton. More experimental data suggest that the good water adsorptivity and vapor transmissibility of the original cotton fabric were inherited after the surface modification. These properties are of great significance in textile and medical applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1862–1871     

Study of antimicrobial properties of cotton medical textiles treated with citric acid and dried/cured by microwaves

The purpose of this study was to examine antibacterial and antifungal activity of antibacterial finish based on Citric acid on cotton medical textiles. The ability to effectively reduce the number of gram-negative, gram-positive bacteria and yeast was evaluated, specifically comparing the antibacterial activity after two different drying/curing methods. Citric acid (CA) and diethyl–tetradecyl–[3–(trimethoxysilyl)-propyl] ammonium chloride (Quat) were used for hygiene and disinfection purposes of medical textiles in this study. It was applied by pad-dry process and its fixation to cellulose hydroxyls was enhanced either by high curing temperatures or microwaves (MW). Determination of antibacterial activity of finished products was performed according to ISO 20743:2007 standard before the washing and after the 10 washing cycles. Antibacterial activity was tested against gram-negative bacteria, Escherichia coli, gram-positive-Staphylococcus aureus and yeast, Candida albicans. Obtained results are confirming the possibility of eco-friendly CA application, for the purpose of antimicrobial finishing of cotton medical textiles. Prevention of nosocomial infections with the Citric acid is possible using both curing methods (convection and microwave) and furthermore, the treatment is durable up to 10 washing cycles. Citric acid, as one of the suitable active substances is crosslinked to the cellulose hydroxyls by the formation of ester linkages. Its antimicrobial effectiveness against the chosen microorganisms proved to be the best against S. aureus. Applied finish bath has additional crease proof effectiveness providing sufficient both antimicrobial and crease proof effectiveness, so as the durability against 10 washing cycles.     

Hydrophobic and oleophobic surface modification using fluorinated bis-urea and bis-amide gelators

A series of fluorinated bis-urea and bis-amide derivatives were synthesized from fluorinated amines and explored as surface modifiers for nonwoven substrates. A majority of these derivatives showed excellent gelation properties both in organic solvents as well as in supercritical carbon dioxide (scCO₂) at concentrations ranging from 0.3 to 3 wt%. Gelation in the presence of a nonwoven substrate led to a gel-impregnated surface, which upon drying produced a composite with porous microstructure morphology on the surface. The composites thus produced showed high water and hexadecane contact angles, indicative of excellent hydrophobic and lyophobic properties. The superior hydrophobic and oleophobic behaviors observed in these composites are attributed to a combination of increased surface roughness and the presence of fluoroalkyl functionalities in the gelator backbone.