Enhanced mechanical properties of multilayer nano‐coated electrospun nylon 6 fibers via a layer‐by‐layer self‐assembly

We reported the mechanical properties of the polyelectrolyte multilayer nano‐coated electrospun fiber mats with different number of layers. Multilayer nano‐coatings composed of layers of PSS and PAH were successfully deposited onto electrospun nylon 6 fibers via layer‐by‐layer self‐assembly. Compared with pure nylon 6 fibers, the morphology of polyelectrolyte multilayer coated nylon 6 fibers was uniform and smooth. The mechanical properties of polyelectrolyte multilayer coated random and aligned nylon 6 fibers were remarkably enhanced. Moreover, it was found that the higher degree of alignment resulted in higher tensile strength, suggesting the combined effects of the alignment, the surface nanocoating and the formation of internal networks of polyelectrolytes on nylone 6 fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Gas‐sensor fabrication by a layer‐by‐layer technique using polydiacetylene

In order to increase the sensitivity of a polydiacetylene (PDA) sensor, PDA, and poly(sodium 4‐styrene‐sulfonate) (PSS) were alternately stacked to form a layer‐by‐layer (LBL) film on the quartz. In this study, N‐(2‐aminoethyl)pentacosa‐10,12‐diynamide (AEPCDA) was used as a constituent of the PDA and n‐butylamine was used as a target compound. The formed‐film sensor showed higher sensitivity than the vesicle solution. There was a large difference in sensitivity depending on the method used to form the LBL film. Unlike the vesicle solution state, the formed‐film sensor exhibited excellent reversibility in the color change caused by heat. The LBL film formed worked very well as a sensor that detects the actual gas, n‐butyl amine, showing its potential for practical applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44997.     

Layer‐by‐layer films based on charge transfer interaction of ϕ‐conjugated poly(dithiafulvene) and incorporation of gold nanoparticles into the films

Layer‐by‐layer (LBL) self‐assembled ultrathin films were prepared via consecutively alternating immersion of substrates into solutions of electron donor, poly(dithiafulvene) (PDF), and electron acceptor, poly(hexanyl viologen) (6‐VP). The charge transfer (CT) interaction formed at solid–liquid interfaces between the backbones of the electron acceptor and donor polymers was the driving force of the alternative deposition. The sandwich heterostructure of the LBL film led to electrical anisotropy in the directions parallel and perpendicular to the film surfaces. Incorporation of gold nanoparticles into the LBL films was investigated by reducing gold ions with the PDF layers already deposited on the film surfaces, or depositing PDF‐protected gold colloidal solution as the electron donor layers directly. The influence of the gold nanoparticles on the electrical anisotropy of the LBL films was also illustrated in this research. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1608–1615, 2007     

Development of multilayer polyelectrolyte thin‐film membranes fabricated by spin assisted layer‐by‐layer assembly

Polyelectrolyte multilayer (PEM) thin films consisting of alternate layers of two PEM systems, that is poly(diallyl dimethyl ammonium chloride)/poly(vinyl sulfate) (PDAC/PVS) and poly(allyl amine hydrochloride) (PAH)/ are successfully deposited on polysulfone (PSF) support using spin‐assisted layer‐by‐layer assembly. The films are characterized using atomic force microscope, Fourier transform Infrared, and contact angle measurement. The salt (NaCl) rejection and water flux of the [PDAC/PVS] and [PAH/PVS] membranes are also evaluated using a crossflow permeation test cell. The permeation test shows that 120 bilayers of [PAH/PVS] on PSF substrate provide salt rejection of 53% and water flux of 37 L/m² h, whereas that of PDAC/PVS on PSF substrate provide salt rejection of 21% and water flux of 90 L/m² h for a 2000‐ppm NaCl solution feed at a pressure of 40 bar and temperature of 25°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Combination Intumescent and Kaolin‐Filled Multilayer Nanocoatings that Reduce Polyurethane Flammability

Chitosan (CH), ammonium polyphosphate (APP), CH and poly(acrylic acid) (PAA)‐stabilized kaolin (KAO) clay are deposited as quadlayers onto the surface of flexible polyurethane foam (PUF) via layer‐by‐layer assembly in order to improve the fire resistance of the foam. The effectiveness of this nanocoating on flame suppression is compared to control films without KAO and bilayer coatings. PUF coated with only five CH/APP/CH/PAA‐KAO quadlayers (around 184 nm thick) maintains its open porous structure and self‐extinguishes upon exposure to a butane torch flame for 10 s. Cone calorimetry reveals that this coating reduces the peak heat release rate and total smoke release by 66.8% and 59.3%, respectively, compared with uncoated foam. Thermogravimetric analysis under nitrogen indicates the combination of intumescent components and clay promotes char formation and improves the thermal stability of the polyurethane substrate. This multilayer coating has the potential to improve the fire safety for PUF, commonly used in home furnishings, and a variety of other polymeric substrates.     

Manipulating the phase morphology in PPS/PA66 blends using clay

By adding a small amount of clay into poly(p‐phenylene sulfide) (PPS)/polyamide 66 blends, the morphology was found to change gradually from sea–island into cocontinuity and lamellar supramolecular structure, as increasing of clay content. Clay was selectively located in the PA66 phase, and the exfoliated clay layers formed an edge‐contacted network. The change of morphology is not caused by the change of volume ratio and viscosity ratio but can be well explained by the dynamic interplay of phase separation between PPS and PA66 through preferential adsorption of PA66 onto the clay layers and through layer–layer repulsion. This provides a means of manipulating the phase morphology for the immiscible polymer blends. The mechanical and tribological properties of PPS/PA66 blends with different phase morphologies (different clay contents) were studied. Both tensile and impact strength of the blends were found obviously increased by the addition of clay. The antiwear property was greatly improved for the blends with cocontinuous phase form. Our work indicates that the phase‐separating behavior of polymer blends contained interacting clay can be exploited to create a rich diversity of new structures and useful nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Layer‐by‐layer assembly of halogen‐free polymeric materials on nylon/cotton blend for flame retardant applications

Thin films of environmentally safe, halogen free, anionic sodium phosphate and cationic polysiloxanes were deposited on a Nyco (1:1 nylon/cotton blend) fabric via layer‐by‐layer (LbL) assembly to reduce the inherent flammability of Nyco fabric. In the coating process, we used three different polysiloxane materials containing different amine groups including, 35–45% (trimethylammoniummethylphenythyl)‐methyl siloxane‐55‐65% dimethyl siloxane copolymer chloride salt (QMS‐435), aminoethylaminopropyl silsesquioxane‐methylsilsesquioxane copolymer oligomer (WSA‐7021) and aminopropyl silesquioxane oligomers (WSA‐991), as a positive polyelectrolyte. Thermo‐gravimetric analysis showed that coated fabric has char yield around 40% at 600 °C whereas control fabric was completely consumed. The vertical flame test (VFT) on the LbL‐coated Nyco fabric was passed with after flame time, 2 s, and the char length of 3.81 cm. Volatile and nontoxic degradation products of flame retardant‐coated fabric were analyzed by pyrolysis gas chromatography mass spectroscopy (Py‐GCMS). Surface morphology of coated fabrics and burned fabric residues were studied by scanning electron microscopy. Copyright © 2014 John Wiley & Sons, Ltd.     

Multilayer assembly of ionic starches on old corrugated container recycled cellulosic fibers

In this study, old corrugated container recycled fibers were treated with polyelectrolyte multilayers consisting of biopolymer cationic starch with two degrees of substitution (DS) each in combination with one anionic starch. Pulp zeta potential, paper strength and the thin layer ellipsometry technique were applied to examine the influence of cationic starch DS on the formation of polyelectrolyte multilayers. The results indicated a significant interaction between the DS of cationic starch and the number of ionic starch layers formed. When low‐DS cationic starch was used, the pulp zeta potential and the paper strength increased significantly in assembling the first cationic layer. However, in depositing high‐DS cationic starch a greater zeta potential and a stronger influence on the paper strength were observed with a larger number of starch layers. This was confirmed by thin layer ellipsometry when a greater thickness of multilayers was achieved by employing high‐DS cationic starch to form a higher number of layers. © 2017 Society of Chemical Industry     

Electrochemistry and electrocatalysis with hemoglobin in hollow polyelectrolyte fibrous mats

To form the PS/PAH fibers, positively charged poly(allylamine hydrochloride) (PAH) was coated on the surface of polystyrene (PS) fibers. Then, the ordered Hb‐PS/PAH film was prepared by the self‐assembly of hemoglobin (Hb) on the surface of fibers and characterized by electrochemical and spectroscopic methods. Cyclic voltammetry of the self‐assembled Hb‐PS/PAH films modified on glassy carbon electrode (GCE) displayed a quasi‐reversible electrochemical response in pH 5.0 buffers. Moreover, the Hb‐PS/PAH films also exhibited the electrocatalytic activity to the reduction of H₂O₂. Consequently, the Hb‐PS/PAH films are favorable for the direct electrochemistry of heme containing proteins, suggesting their potential application as the promising sensitive biosensor. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Ways of strengthening biodegradable soy‐dreg plastics

Biodegradable plastics (GSD) based on soy dreg (SD) were prepared by compression‐molding, with glycerol as the plasticizer and glutaraldehyde (GA) as the cross‐linker. The structure and properties of the GSD sheets were investigated by Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), scanning electron microscope (SEM), and tensile test methods. The results indicate that when GA content was 6.8%, the tensile strength (σ_b) of the sheet reached the maximum value of 14.5 MPa. Moreover, the strength and water resistance of the sheets coated with castor‐oil‐based polyurethane/nitrochitosan interpenetrating network (IPN) coating were significantly enhanced to 24.6 MPa in the dry state and 9.8 MPa in the wet state. Simultaneously, the test of biodegradability of the GSD sheet in a mineral salts medium containing microorganisms and agar proved that GSD could be fully biodegradable. This work has provided a novel way to utilize low‐cost SD to prepare biodegradable plastics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 422–427, 2003     

Microstructured conducting polymer coatings on plastic strip for contact electrodes: Formulation and tuning of sheet resistance

Mechanically strong and flexible strips of cellulose acetate were used to support a thin coating of poly(3,4 ethylenedioxythiophene) : poly(styrene sulfonic acid) PEDOT : PSS, an intrinsically conducting polymer (ICP), formulated with an aqueous dispersion of judiciously chosen copolymer of vinyl acetate and ethylene (VAE), to impart adhesion of the coating onto the substrate. Incorporation of a few drops of an organic acid to the formulation resulted in a substantial reduction of the sheet resistance of the coated surface. When the coated strips were post‐treated with a salt solution, a further fine tuning of the sheet resistance by a factor of 10 was achieved. The coated strips combine high conductivity with flexibility and mechanical strength. The performance of the coated strips has been evaluated in relationship to composition, coating thickness, and sheet resistance for application as contact electrodes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 234–237, 2007     

Preparation and characteristics of nitrile rubber (NBR) nanocomposites based on organophilic layered clay

The effect of clay modification on organo‐montmorillonite/NBR nanocomposites has been studied. Organo‐montmorillonite/NBR nanocomposites were prepared through a melt intercalation process. NBR nanocomposites were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), dynamic mechanical thermal analysis (DMTA) and a universal testing machine (UTM). XRD showed that the basal spacing in the clay increased, which means that the NBR matrix was intercalated in the clay layer galleries. On TEM images, organo‐montmorillonite (MMT) particles were clearly observed, having been exfoliated into nanoscale layers of about 10–20 nm thickness from their original 40 µm particle size. These layers were uniformly dispersed in the NBR matrix. The DMTA test showed that for these nanocomposites the plateau modulus and glass transition temperature (T_g) increased with respect to the corresponding values of pure NBR (without clay). UTM test showed that the nanocomposites had superior mechanical properties, ie strength and modulus. These improved properties are due to the nanoscale effects and strong interactions between the NBR matrix and the clay interface. Copyright © 2003 Society of Chemical Industry     

Effect of clay on properties of polyimide‐clay nanocomposites

Effect of clay on mechanical, thermal, moisture absorption, and dielectric properties of polyimide‐clay nanocomposites was investigated. Nanocomposites of polyimide (ODA‐BSAA) hybridized with two modified clay (PK‐802 and PK‐805) were synthesized for comparison. The silicate layers in the polymer matrix were intercalated/exfoliated as confirmed by wide‐angle X‐ray diffraction and transmission electron microscopy. Thermal stability, moisture absorption, and storage modulus for these nanocomposites are improved as hybridized clay increases. Reduced dielectric constants due to the hybridization of layered silicates are observed at frequencies of 1 kHz–1 MHz and temperatures of 35–150°C. The tetrahedrally substituted smectite (PK‐805) resulted in higher mechanical strength and dielectric constants than those of octahedrally substituted smectite (PK‐802), which could be attributed to their stronger ionic bonding between clay layer and polymer matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 318–324, 2007     

Copolymerization of glycidyl methacrylate with styrene and applications of the copolymer as paper‐strength additive

A copolymer of glycidyl methacrylate and styrene (PGS) was synthesized by emulsion polymerization. The effect of the polymer on paper dry‐ and wet‐strength improvement was investigated. The polymer contains phenyl groups that provide hydrophobic character to fibers so as to improve paper wet performance, and glycidyl groups that react with nucleophilic groups in fibers and other polymers to increase paper strength. Results showed that other polymers, such as polyallylamine, polyacrylic acid, and modified polyacrylamide, could be used together with PGS for paper‐strength improvement. Furthermore, three kinds of partially carboxymethylated pulps (CMP) were prepared and used for PGS treatment. Compared with original pulp sheet, the sheets containing CMPs were strengthened greatly both in dry and in wet strength after PGS treatment. It was confirmed that higher CMP content got higher strength improvement at the same addition level of PGS. The results showed that carboxyl groups in pulp participate in the reaction with PGS and the cocrosslinkings between fibers and polymers were formed for improving paper strength. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 334–339, 2001     

Processing and properties of polymeric nano‐composites

Polymeric nano‐composites are prepared by melt intercalation in this study. Nano‐clay is mixed with either a polymer or a polymer blend by twin‐screw extrusion. The clay‐spacing in the composites is measured by X‐ray diffraction (XRD). The morphology of the composites and its development during the extrusion process are observed by scanning electron microscopy (SEM). Melt viscosity and mechanical properties of the composites and the blends are also measured. It is found that the clay spacing in the composites is influenced greatly by the type of polymer used. The addition of the nano‐clay can greatly increase the viscosity of the polymer when there is a strong interaction between the polymer and the nano‐clay. It can also change the morphology and morphology development of nylon 6/PP blends. The mechanical test shows that the presence of 5–10 wt.% nano‐clay largely increases the elastic modulus of the composites and blends, while significantly decreases the impact strength. The water absorption of nylon 6 is decreased with the presence of nano‐clay. The effect of nano‐clay on polymers and polymer blends is also compared with Kaolin clay under the same experimental conditions.     

Role of clays in fouling-resistant clay-embedded polyelectrolyte multilayer membranes for wastewater effluent treatment

This study aimed to investigate the effects of cation exchange capacity (CEC) and location of clay nanoplatelets on the structure and performance of clay-embedded polyelectrolyte multilayer (c-PEM) membranes for wastewater effluent treatment. Two kinds of clay nanoplatelets, montmorillonite and kaolin, were deposited on the ultrafiltration membrane by employing layer-by-layer (LbL) assembly with poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). Negatively charged clay platelets or PAA interacted with positively charged PAH to form a bilayer in the c-PEM membrane. The filtration effect of clay platelets was successively distinguished from PEM by reducing the number of (PAH/PAA) bilayers from four to one, while keeping the clay layer at the outermost layer of assembly. When the clay platelets were deposited only as the outermost layer of the LbL multilayers, the c-PEM membrane with one clay layer and one bilayer assembly showed significant flux barrier and fouling resistance. Clay platelets as the outermost layer physically increased the flow path length and decreased the number of pores, as well as effectively blocked the organic contaminants in the wastewater. Meanwhile, when the clay layer was embedded in the middle of the PEM, the synergistic effect of clay platelets and PEM for wastewater treatment was difficult to obtain because the presence of clay platelets defected the buildup of fully interdigitated c-PEM and the adsorption of clay platelets was decreased. For the clays having low CEC, a higher number of LbL multilayers were required to deposit the clay platelets and to improve the performance of membrane. The high CEC clays (montmorillonite) turned out to be better than the low CEC clays (kaolin) in the structure and performance of the c-PEM membrane for wastewater effluent treatment.     

Highly luminescent film functionalized with CdTe quantum dots by layer‐by‐layer assembly

Robust and facile strategies are required to fabricate film with high luminescence for application in the fields of biomaterials. In this study, the luminescent electrospinning cellulose fibrous mats were decorated with CdTe quantum dots (QDs) and poly(diallyl dimethyl ammonium chloride) (PDDA) using layer by layer (LBL). The characterizations of the LBL films coated mats were executed by X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, fluorescent spectroscopy, X‐ray diffraction, thermal gravimetric analysis, and differential scanning calorimetry. The luminescent intensities were linearly increased with adding the amount of deposited bilayers. The green fabricated (QDs/PDDA)_n coated mat through physical interactions is a promising luminescent material. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41893.     

Spray‐On Polymer–Clay Multilayers as a Superior Anticorrosion Metal Pretreatment

Pretreatment coatings applied to metals are essential in the overall performance of anticorrosion coating systems. Hexavalent chromium, a widely used pretreatment for aluminum is now considered harmful. Therefore, a need for environment‐friendly yet efficient and scalable pretreatment coatings has emerged. Here, the authors present the spray‐assisted layer‐by‐layer (LbL) assembly and anticorrosion performance of a highly ordered polymer–clay nanocomposite coating. This approach is an entirely water‐based process, allowing for application over large surface areas. This novel pretreatment coating (25 wt% clay) presents a brick‐and‐mortar multilayered structure, where the montmorillonite clay (MMT) acts as a physical oxygen barrier, while preventing the dissolution of corrosion products—thus delaying corrosion. The branched polyethylenimine polymer (BPEI) mortar provides surface buffering once the corrosion process initiates. The anticorrosion properties of the LbL coating are evaluated using electrochemical measurements and salt‐spray testing. This BPEI/MMT system presents good anticorrosion properties, making it a potential alternative pretreatment.

     

Effect of the Co‐SiO2 Mesoporous Layer Coating Step on the Performance of Liquid Fuel Dimethyl Amino Ethyl Azide Dehydration

A cobalt‐doped silica (Co‐SiO₂) layer was successfully synthesized in a sol‐gel process as the mesoporous layer overlaid in three‐, six‐, and ten‐step coating on a mullite support. The microporous layer was coated over the mesoporous layer in six steps by adopting the sol‐gel method. The membranes were applied in pervaporation experiments to dehydrate dimethyl amino ethyl azide (DMAZ) containing 5 wt % water. In dehydration tests, the membrane permeate flux decreased and its separation factor increased. During the first initial hours, it reached a steady state and subsequently remained constant.     

Self‐assembly of novel architectural nanohybrid multilayers and their selective separation of solvent‐water mixtures

A new architectural nanohybrid multilayer has been explored and built on various substrates. The building blocks of positive and negative charged polyelectrolyte‐coated nanoparticles (NPs) could be obtained by tuning the electrical properties of the amphoteric oxide NPs in acid and basic environments. The nanohybrid films were, thereafter, formed by layer‐by‐layer (LbL) assembly of polycation‐ and polyanion‐coated NPs. It was demonstrated that this approach could incorporate single component NPs into both polycation and polyanion layers, and in turn improve the NP loading, maintain good dispersion of NPs within the film. For separation applications, a dynamic LbL assembly was attempted as a means of fabricating such nanohybrid multilayers on both 2‐D and 3‐D polymeric porous substrates. The nanohybrid multilayer membrane renders both much higher selectivity and flux in the separation of solvent‐water mixtures. Moreover, such assembly of nanohybrid multilayers allows us to efficiently simplify the procedures by reducing 30–40‐fold process cycles. © 2011 American Institute of Chemical Engineers AIChE J, 2012