Studies on electrical conductivity of PVA/graphite oxide nanocomposites: a free volume approach

Poly(vinyl alcohol) and graphite oxide (PVA/GO) polymer nanocomposites of different GO wt% have been prepared. The decreased positron lifetime parameter viz., o-Ps lifetime (τ₃) at the lower concentration of GO indicates the improved interfacial interaction between the surface of GO nanoparticles and side chain of PVA polymer matrix. This is evident from Fourier transform infrared spectroscopy (FTIR) studies. The increased o-Ps lifetime (τ₃) after 0.4 wt% of GO suggests the increased interfacial area at the interface of PVA and GO nanoclusters. The increased electrical conductivity at the lower concentration of GO suggests the conductivity chain formation through the nanoparticle aggregation. The decreased conductivity at higher concentration of GO indicates the reduced conducting pathways for the mobility of charge carriers. Scanning electron microscopy (SEM) studies show the random distribution of GO nanoparticles and the formation of nanoclusters in PVA matrix at the lower and higher concentrations of GO nanoparticles respectively.     

Porous chitosan/graphene oxide biocomposites for tissue engineering

Porous chitosan/graphene oxide (CHT/GO) biocomposites with 0.5, 1, 2, and 3 wt% GO were prepared by freeze‐drying method. The biocomposites were characterized regarding structural, morphological, and thermal properties, degradation, and swelling responses. Raman spectroscopy and scanning electron microscopy (SEM) results indicated good GO dispersion within the polymer host and highly porous structure for the obtained biocomposites. The GO presence has a profound effect on the structural features of the biocomposites generating decrease of swelling degree and enzymatic biodegradation rate. Conversely, the thermal stability of the biocomposites was significantly improved, and the decomposition temperature at which the mass loss is 3% (T _d,3%) was increased with 64°C by adding 3 wt% GO within the CHT. The ability of the biocomposites to form apatite‐like crystals was also investigated. X‐ray diffraction and SEM analyses indicated the formation of apatite deposits on the CHT/GO biocomposites. POLYM. COMPOS., 38:363–370, 2017. © 2015 Society of Plastics Engineers     

Green Route for the Synthesis of Alanine-based Poly(amide-imide) Nanocomposites Reinforced with the Modified ZnO by Poly(vinyl alcohol) as a Biocompatible Coupling Agent

The objective of this article was fabrication and characterization of novel optically active poly(amide-imide)/zinc oxide nanocomposites with different modified ZnO nanoparticle contents under ultrasonic irradiation technique. For better dispersion of ZnO nanoparticles in a polymer matrix, their surface was modified with poly(vinyl alcohol) as a coupling agent. Effects of poly(vinyl alcohol) modifier on dispersity of nanoparticles, morphological structures, and thermal stability of the obtained nanoparticles were studied by several techniques. According to the transmission electron microscopy images of the nanocomposite, the average diameter of particles was around 7–15 nm in the poly(amide-imide).     

Covalent approach for in situ enhancement of interaction between pristine graphene and styrene‐butadiene‐p‐(2,2,2‐triphenylethyl)styrene rubber

A facile method for enhancing the interaction between pristine graphene and nonpolar rubber matrices was developed by preparing a new solution‐polymerized styrene‐butadiene‐p‐(2,2,2‐triphenylethyl)styrene (TPES) rubber (SBTR). SBTR macroradicals were formed by the thermal decomposition of a 1,1,1,2‐tetraphenylethane pendant. The macroradicals were successfully trapped by graphene through the formation of covalent bonds. This was confirmed by rotorless rheometer and X‐ray photoelectron spectroscopy measurements. The dispersion of graphene and interfacial interaction between graphene and the SBTR was significantly increased by increasing the TPES content in SBTR composites, as demonstrated by differential scanning calorimetry, scanning electron microscopy, rubber process analysis, and dynamic mechanical thermal analysis. The mechanical properties of the SBTR/GNS composites were significantly improved by the improved dispersion and the increased surface affinity of SBTR for graphene. The developed approach can be generally applied to the functionalization of other polymer matrices by copolymerizing TPES with other vinyl monomers for pristine graphene‐based composite materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44923.     

Fabrication and Characterization of Electrospun PVA/Mica Fibrous Nanocomposite Mats

This paper focuses on the fabrication of cost effective and high performance poly(vinyl alcohol)/mica fibrous nanocomposites using electrospinning. Effective incorporation of fine particles of mica in poly(vinyl alcohol)/mica nanocomposites was examined and confirmed along with the evidence of good dispersion, by digital optical microscopy and scanning electron microscopy. The presence of mica improved the mechanical properties of the nanocomposites without affecting the thermal stability. The electrospun poly(vinyl alcohol) mats containing 20?wt% mica exhibited tensile strength of 13.29?MPa and tensile modulus of 180.3?MPa as compared to values of 3.92 and 83?MPa, respectively, for poly(vinyl alcohol) fiber mats.     

Electrochemical investigation of Pd nanoparticles and MWCNTs supported Pd nanoparticles-coated electrodes for alcohols (C1–C3) oxidation in fuel cells

Incorporation of palladium nanoparticles (PdNPs) and multi-walled carbon nanotubes (MWCNTs) into chitosan-coated glassy carbon (GC) electrode for alcohols (methanol, ethanol, and isopropanol) electrooxidation has been studied. PdNPs–chitosan and MWCNTs–PdNPs–chitosan nanocomposites are successfully prepared and characterized by transmission electron microscopy images and UV–Vis spectroscopy. Based on the results, PdNPs–chitosan nanocomposite indicates high electrochemical activity and excellent catalytic characteristic for alcohol (C₁–C₃) electrooxidation on a GC electrode in an alkaline medium. The current density of the alcohols oxidation at GC–PdNPs–chitosan electrode is investigated in optimized conditions and compared with that obtained at the GC-modified electrode by Pd with different polymers. Also, our results show that the dispersion of Pd nanoparticles on the MWCNTs significantly improved the performance of the PdNPs/chitosan composite for electrooxidation of the C₁–C₃ alcohols.     

Effect of PVA content on morphology,swelling and mechanical property of crosslinked chitosan/PVA nanofibre

Abstract

Crosslinked chitosan/poly(vinyl alcohol) nanofibres were successfully prepared via electrospinning technique with heat mediated chemical crosslinking. The structure, morphology and mechanical properties of nanofibres were characterised by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and tensile tester respectively. The SEM images demonstrated that crosslinked nanofibres exhibited a smooth surface and regular morphology. With increasing PVA, swelling of nanofabric increased. The mechanical properties of the fibre mats, as determined in a static tensile test, improved with increasing PVA composition owing to strong interaction between chitosan and poly(vinyl alcohol) molecular resulted from intermolecular hydrogen bonds. The crosslinked chitosan/poly (vinyl alcohol) nanofibrous mats have potential use as artificial skin and other tissue scaffold materials.     

Preparation and characterization of PVA-g-GO/PVA/PAN composite membrane for pervaporation desalination

Graphene oxide (GO) has extensive applications in membrane-based separations, but its dispersion in the membrane has always been a problem due to the presence of π–π interactions in GO nanosheets. In this study, a grafting reaction was designed by using poly (vinyl alcohol) (PVA) for GO grafting modification and poly (vinyl alcohol)-g-graphene oxide (PVA-g-GO) nanocomposites were synthesized. The grafting material to GO was the same as the basic separation polymer material. PVA-g-GO showed better dispersibility and hydrophilicity than GO, and a series of composite membranes were prepared using a polyacrylonitrile (PAN) ultrafiltration (UF) membrane as a substrate. PVA-g-GO nanocomposites and membranes were characterized by using X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), water contact angle, scanning electron microscopy (SEM), etc. The addition of PVA-g-GO improved both the separation performance and anti-swelling property of the composite membrane, and the PVA-g-GO/PVA/PAN composite membrane loaded with 2 wt.% PVA-g-GO obtained a high flux of 4.46 kg/m² · h and a high rejection of 99.99% when dehydrating 3.5 wt.% NaCl solution at 30°C by pervaporation.     

In vitro and in vivo investigational studies of a nanocomposite‐hydrogel‐based dressing with a silver‐coated chitosan wafer for full‐thickness skin wounds

A nanocomposite reservoir‐type hydrogel dressing of poly vinyl alcohol (PVA) was fabricated by a freeze–thaw method and loaded with silver‐nanoparticle‐coated chitosan wafers (Ag–CHWs). The Ag–CHWs were synthesized by a sonication technique with silver nitrate (AgNO₃) and chitosan powder. Scanning electron microscopy images showed silver nanoparticles (AgNPs) with a size range of 10 ± 4 nm on the surface of the chitosan wafers, and the antibacterial efficacy (minimum inhibitory concentration) of the Ag–CHWs was measured against Pseudomonas aeruginosa (32 µg/mL), Staphylococcus aureus, (30 µg/mL) and Escherichia coli (32 µg/mL). The antimicrobial PVA hydrogel showed an improved tensile strength (～0.28 MPa) and gel content (～92%) in comparison with the blank hydrogels. Full‐thickness‐excision wound studies of the nanocomposite dressing on Wistar rats revealed enhanced wound contraction, improved inflammation response, re‐epithelization rate, neoangiogenesis, and granulation tissue formation in comparison to the control group. A flexible, biocompatible, nanocomposite reservoir dressing not only established the chitosan as a stabilizer but also proved the efficacious and safe utility of AgNPs toward chronic wound management. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43472.     

Influence of Syzygium cumini leaves extract on morphological,thermal, mechanical,and antimicrobial properties of PVA and PVA/chitosan blend films

In the present work, poly(vinyl alcohol)/Syzygium cumini leaves extract (PSN) and poly(vinyl alcohol)/chitosan/S. cumini leaves extract blend films were prepared by solution casting technique. The films were characterized by using scanning electron microscopy, atomic force microscopy, X‐ray diffraction study, Fourier transform infrared spectroscopy, thermogravimetric analysis, and universal testing machine. The results indicated that the appreciable physical interaction at lower concentrations of S. cumini leaves extract in the PVA and PVA/chitosan films contribute to the smooth uniform morphology, increased the degree of crystallinity, degradation temperature, and improved mechanical properties. Further, films were analyzed with water contact angle analyzer which illustrates that blend films were hydrophilic (PSN‐1) and hydrophobic (PCS‐1) in nature. However, blend films were also subjected to the antimicrobial study, which revealed that inclusion of S. cumini leaves extracts significantly enhanced the antibacterial activity in the PVA and PVA/chitosan film. With all of these results, fabricated blends can find potential applications in packaging material to extend the shelf life of foodstuffs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46188.     

Synthesis and properties of click coupled graphene oxide sheets with three‐dimensional macromolecules

A facile click chemistry approach to the functionalization of three‐dimensional hyperbranched polyurethane (HPU) to graphene oxide (GO) nanosheets is presented. HPU‐functionalized GO samples of various compositions were synthesized by reacting alkyne‐functionalized HPU with azide‐functionalized GO sheets. The morphological characterization of the HPU‐functionalized GO was performed using transmission electron microscopy and its chemical characterization was carried out using Fourier transform‐infrared spectroscopy, nuclear magnetic resonance spectroscopy, and X‐ray photoelectron spectroscopy. The graphene sheet surfaces were highly functionalized, leading to improved solubility in organic solvents, and consequently, enhanced mechanical, thermal, and thermoresponsive and photothermal shape memory properties. The strategy reported herein provides a very efficient method for regulating composite properties and producing high performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43358.     

Effect of octa(aminopropyl) polyhedral oligomeric silsesquioxane (OapPOSS) functionalized graphene oxide on the mechanical,thermal, and hydrophobic properties of waterborne polyurethane composites

A novel graphene nanomaterial functionalized by octa(aminopropyl) polyhedral oligomeric silsesquioxane (OapPOSS) was synthesized and then confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), Raman spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy with energy‐dispersive X‐ray spectroscopy (SEM EDX), atomic force microscopy, and X‐ray diffraction. The obtained functionalized graphene (OapPOSS‐GO) was used to reinforce waterborne polyurethane (WPU) to obtain OapPOSS‐GO/WPU nanocomposites by in situ polymerization. The thermal, mechanical, and hydrophobic properties of nanocomposites as well as the dispersion behavior of OapPOSS‐GO in the polymer were investigated by TGA, a tensile testing machine, water contact angle tests, and field emission SEM, respectively. Compared with GO/WPU and OapPOSS/WPU composites, the strong interfacial interaction between OapPOSS‐GO and the WPU matrix facilitates a much better dispersion and load transfer from the WPU matrix to the OapPOSS‐GO. It was found that the tensile strength of the OapPOSS‐GO/WPU composite film with 0.20 wt % OapPOSS‐GO exhibited a 2.5‐fold increase in tensile strength, compared with neat WPU. Better thermal stability and hydrophobicity of nanocomposites were also achieved by the addition of OapPOSS‐GO. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44440.     

Properties and structural characterization of oxide starch/chitosan/graphene oxide biodegradable nanocomposites

Novel chitosan (CS)/oxidized starch (OST)/graphene oxide (GO) nanocomposites (COST/GO‐n) films are prepared in a casting and solvent evaporation method. Fourier transform infrared spectroscopy, X‐ray diffractions, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, tensile testing, and moisture uptake are used to study the structure and properties of these nanocomposites. To indicate the effect of carboxyl groups of OST, some results of the properties of CS/starch/GO nanocomposite (CST/GO‐n) were selected for control experimentation. Compared with the control CST/GO‐n series, COST/GO‐n films, which have the same component ration showed higher tensile strength (σ_b) and lower elongation at break (ε_b). Additionally, in the COST/GO‐n series, the σ_b increased with an increase of GO loading. However, higher proportion of GO could result in aggregations of GO nanosheets and deterioration of the film properties. Compared with the COST/GO‐0, the values of σ_b and water resistance of the COST/GO‐4 containing 2.0 wt % of GO were improved by 57.7 and 20.1%, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Nanophotothermolysis of Poly-(vinyl) Alcohol Capped Silver Particles

Laser-induced thermal fusion and fragmentation of poly-(vinyl) alcohol (PVA)-capped silver nanoparticles in aqueous medium have been reported. PVA-capped silver nanoparticles with an average size of 15 nm were prepared by chemical reduction technique. The laser-induced photo-fragmentation of these particles has been monitored by UV-visible spectroscopy and transmission electron microscopy. The morphological changes induced by thermal and photochemical effects were found to influence the optical properties of these nanoparticles.     

Effect of flake size on thermal properties of graphene oxide/poly(methyl methacrylate) composites prepared via in situ polymerization

The effect of graphene oxide (GO) flake size on thermal properties of GO/poly(methyl methacrylate) (GO/PMMA) composites prepared via in situ polymerization was investigated. Two styles of GO sheets were synthesized from different sizes of graphite powders by modified Hummers' method and GO/PMMA composites with GO of different sizes were prepared via in situ polymerization. Transmission electron microscopy verified that GO sheets produced from large graphite powders was obviously larger than that from small graphite powders. The similar number of layers and disorder degree of two types of GO sheets were proved by X‐ray diffraction and Raman, respectively. X‐ray diffraction and scanning electron microscopy results of GO/composites proved the homogenous dispersion of both two types of GO sheets in polymer matrix. Dynamic mechanical analysis and thermogravimetric analysis results showed that large GO sheets exhibit better improvement than small GO sheets in thermal properties of the composites. Compared with neat PMMA, the glass transition temperature and decomposition temperature of the composites with large GO sheets (0.20 wt %) were increased by 15.9 and 25.9 °C, respectively. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46290.     

Synthesis and properties of silver nanoparticles in chitosan‐based thermosensitive semi‐interpenetrating hydrogels

In this article, thermosensitive poly(N‐isopropyl acrylamide‐co‐vinyl pyrrolidone)/chitosan [P(NIPAM‐co‐NVP)/CS] semi‐interpenetrating (semi‐IPN) hydrogels were prepared by redox‐polymerization using N,N‐methylenebisacrylamide as crosslinker and ammonium persulfate/N,N,N′,N′‐tetramethylethylenediamine as initiator. Highly stable and uniformly distributed Ag nanoparticles were prepared by using the semihydrogel networks as templates via in situ reduction of silver nitrate in the presence of sodium borohydride as a reducing agent. Introduction of CS improves the hydrogels swelling ratio (SR) and stabilizes the formed Ag nanoparticles in networks. Scanning electron microscopy and transmission electron microscopy revealed that Ag nanoparticles were well dispersed with diameters of 10 nm. The semi‐IPN hydrogel/Ag composites had higher SR and thermal stability than its corresponding semi‐IPN hydrogels. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Antibacterial films with enhanced physical properties based on poly (vinyl alcohol) and halogen aminated-graphene oxide

Graphene oxide (GO) nanosheets as great nanofiller have been utilized for the enhancement of a polymer matrix. In this work, polymeric N-halamine poly[5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin] (PSPH) was covalently grafted onto GO, which was denoted as GO-PSPH. The chlorinated GO-PSPH (GP-Cl) was then mixed with poly (vinyl alcohol) (PVA) solution to obtain the PVA/GP-Cl hybrid films. The as-prepared hybrid films were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectra. Compared with PVA film, the addition of GP-Cl into PVA matrix endowed the film with enhanced thermal and mechanical properties, and the crystallinity, tensile strength, and Young's modulus increased by 45, 21, and 246%, respectively. It can be deduced that the interfacial interaction between PVA matrix and GP-Cl nanosheets was the crucial factor for the physical enhancement. Furthermore, the synergistic effect between GO and polymeric N-halamine greatly improved the antibacterial activities of the hybrid films with 3.95 logs reduction of Staphylococcus aureus and 4.53 logs reduction of Escherichia coli O157:H7 with 30 min of contact time, respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48176.     

Effect of Dodecyal Amine Functionalized Graphene on the Mechanical and Thermal Properties of Epoxy‐Based Composites

Simultaneous surface functionalization and reduction of graphene oxide (GO) was achieved by using dodecyl amine (DA) as surface modifying agent. The DA modified reduced GO (DA‐G) was used for subsequent preparation of DA‐G/epoxy composites by solution mixing. Fourier transform infrared spectroscopy analysis, X‐ray diffraction (XRD) and electrical conductivity measurements were conducted to establish the concurrent functionalization and reduction of GO. The effect of DA‐G on the epoxy composites at 0 to 0.75 wt% loadings was studied by investigating its static and dynamical mechanical properties. XRD study was performed to verify the dispersion of DA‐G in the epoxy polymer. Field emission scanning electron microscopy was used to investigate the fracture surface morphology of the composites and Transmission electron microscopy was employed to further confirm the dispersion of DA‐G in the matrix. It was found that the tensile strength of the composite was increased by 38.8% with the addition of 0.5 wt% of DA‐G. The good adhesion/interaction between DA‐G and epoxy resulted in the increase of storage modulus; however, glass transition temperature (T_g) value of the composites shifted to lower temperature in comparison to the neat epoxy. Thermogravimetric analysis showed small decrease in onset degradation temperature for the composites as compared to neat epoxy except for the composites containing 0.75 wt% of DA‐G. POLYM. ENG. SCI., 56:1221–1228, 2016. © 2016 Society of Plastics Engineers     

Preparation of chitosan nanoparticles and their application to Antheraea pernyi silk

In this study, a chitosan nanoparticle dispersion solution as a novel multifunctional agent was developed to modify Antheraea pernyi silk. An ionization gelation methodology with chitosan and sodium tripolyphosphate (STPP) was used to prepare the chitosan nanoparticle solution, and then, Fourier transform infrared spectra, laser particle size analysis, and transmission electron microscopy (TEM) were used to characterize the structure and size distribution of the chitosan nanoparticles. The peaks at 3390.7, 1633.7, 1538.2, and 1258.1 cm⁻¹ revealed the reaction between the chitosan and STPP molecules in the chitosan nanoparticles. The average size of the nanoparticles in the aqueous dispersion solution was approximately 20 nm. TEM images clearly showed the round spherical morphology and the distribution of the particles in the solid state. The obtained chitosan nanoparticle dispersion solution was then applied to treat silk filaments and fabric. The results indicate that the surface of the chitosan‐nanoparticle‐treated A. pernyi silk fiber was rougher than that of the chitosan‐treated and untreated ones, and a higher specific surface was achieved. In addition, the antibacterial activity, breaking strength, and wrinkle‐resistance properties of the chitosan‐nanoparticle‐treated A. pernyi silk fabric were also enhanced. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Evidence of sidewall covalent functionalization of single-walled carbon nanotubes and its advantages for composite processing

Single-walled carbon nanotubes (SWCNTs) were functionalized in a three-step procedure. The first step is a radical reaction creating a covalent bond between the carbon nanotube surface and grafted p-methoxyphenyl functional groups. In a second step, a deprotection of the methoxy functions generates free alcohol groups and in the final step an esterification is done in order to install a double bond for further polymerization. Evidence that functionalization has actually occurred on the SWCNT sidewalls is furnished through investigations involving several complementary techniques (visual dispersion tests, transmission electron microscopy, thermal gravimetric analysis and adsorption volumetry). We show that surface properties of SWCNTs are changed throughout the chemical treatments and that the obtained level of functionalization is low. Incorporation of functionalized SWCNTs in a polymer (poly(methyl methacrylate)) matrix was done through an in situ polymerization process. Observations of the obtained composites using scanning and transmission electron microscopy illustrate that interactions between the SWCNT surface and the polymer matrix are improved.