Spin Self‐Assembled Clay Nanocomposite Passivation Layers Made from a Photocrosslinkable Poly(vinyl alcohol) and Na+‐Montmorillonite Enhance the Environmental Stability of Organic Thin‐Film Transistors

We investigated the effects of the multilayer polymer‐clay nanohybrid passivation films on the stability of pentacene organic thin‐film transistors (OTFTs) exposed to air and UV irradiation. Well‐ordered multilayer films were deposited by the spin‐assisted layer‐by‐layer assembly method using photocrosslinkable poly(vinyl alcohol) with the N‐methyl‐4(4′‐formylstyryl)pyridinium methosulfate acetal group (SbQ‐PVA) and Na⁺‐montmorillonite in a water‐based solution process. When photocrosslinked, these SbQ‐PVA/clay multilayers were found to serve as excellent barriers to O₂ and UV‐light. Moreover, when used as passivation layers, they enhanced the stability of pentacene OTFT devices exposed to air and UV radiation.     

Metal nanocomposite films prepared in situ from PVA and silver nitrate. Study of the nanostructuration process and morphology as a function of the in situ routes

Cast‐hybrid films composed of polyvinyl alcohol (PVA) and silver nitrate were treated according to three different ways, thermal annealing, UV‐irradiation, and chemical reduction by a borohydride solution, to obtain PVA/silver nanocomposite films. The nanostructuration process was studied as a function of the treatment conditions, and discussed as a function of the mobility state of the polymer chains in the nanocomposite matrix during treatment. A homogeneous dispersion of crystalline silver nanoparticles was obtained by thermal annealing above T_g and below T_m and UV‐lamp irradiation below T_g. For these two treatments, the major processing parameters were the annealing temperature and time and the UV‐exposure time, respectively. For low‐conversion rate in Ag(0), the films evolved upon ageing at room temperature. Totally different morphology and Ag(0) conversion were achieved by chemical reduction in a borohydride solution. All the silver ions were reduced into Ag(0), and crystalline silver nanoparticles layers parallel to the film surface were observed after the treatment. This morphology was related to the high‐swollen state of the polymer matrix during treatment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2062–2071, 2008     

Poly(vinyl alcohol) Chains Grafted onto the Surface of Copper Oxide Nanoparticles: Application in Synthesis and Characterization of Novel Optically Active and Thermally Stable Nanocomposites Based on Poly(amide-imide) Containing N-trimellitylimido-L-valine Linkage

Green polymer nanocomposites (NCs) show unique properties of combining the advantages of nanofillers and organic polymers. In this study, in order to control the dispersion of nanoparticles (NPs) in a polymer matrix, first, poly(vinyl alcohol) (PVA) as a green modifier was grafted on the surface of the CuO NPs to obtain CuO-PVA nanohybrid. Then poly(amide-imide) (PAI) was synthesized by the direct step growth polymerization of N-trimellitylimido-L-valine and 4,4′-methylenebis(3-chloro-2,6-diethylaniline) in ionic liquid medium. Finally, CuO-PVA hybrids were incorporated into the PAI matrix using ultrasonic technique for the preparation of PAI/CuO-PVA NCs. The obtained PAI/CuO-PVA NCs were characterized by different methods. The results of thermogravimetric analysis showed that thermal stability of the NCs was enhanced by incorporation of CuO-PVA nanohybrid compared to the pure PAI.     

Application of CuO nanoparticles modified with vitamin B1 for the production of poly(vinyl alcohol)/CuO nanocomposite films with enhanced optical,thermal and mechanical properties

In this Investigation, the CuO nanoparticles (NPs) were treated by vitamin B₁ as a biomolecule modifier. The CuO NPs were used as an appropriate filler for fabrication of poly(vinyl alcohol) (PVA) nanocomposites (NCs). Then, NCs with various ratios (3, 5, and 7wt%) of modified CuO were fabricated under ultrasonic irradiation and their properties were compared with pure PVA. Several techniques were used for characterization of NCs. Field emission scanning electron microscopy and transmission electron microscopy analysis indicated that NPs have proper compatibility with the PVA matrix. Thermal gravimetric analysis results confirmed that NCs displayed higher thermal stability than neat PVA. Also, the addition of the NPs into the PVA matrix improved the optical and mechanical behaviors. Finally, the contact angle measurements verified that the hydrophilicity decreased for different ratios of modified NPs loaded in the polymer matrix. Copyright © 2017 John Wiley & Sons, Ltd.     

Photoinduced shape fixity and thermal-induced shape recovery properties based on polyvinyl alcohol bearing coumarin

In this paper, polyvinyl alcohol (PVA) bearing coumarin with different degrees of substitution (DS) are synthesized by esterifying hydroxyl of PVA with 7-carboxylmethoxycoumarin. The grafted polymer has photosensitive property and presents photocrosslinking due to the photodimerization between pendant coumarin groups, which affords PVA–coumarin sample photoinduced shape fixity properties. PVA–coumarin can be cross-linked after being illuminated under UV light of 360 nm; this provides the possibility that the sample has shape memory properties only if the cross-linking extent is suitable. The shape memory properties were induced by thermal as most shape memory polymer do. In fact, the shape fixity and recovery has strong relationship with DS, irradiation time, and thickness of sample. The effect of DS on the grafted polymer structure and properties has been studied by differential scanning calorimetry, thermogravimetric analysis, and UV spectra.     

Dynamics of cyclodimerization and viscoelasticity of photo‐crosslinkable PVA

We investigated the interfacial properties of poly(vinyl alcohol) carrying UV‐crosslinkable pendant quaternized stilbazole (styrylpyridinium), PVA‐SbQ. The extent and dynamics of PVA‐SbQ cyclodimerization reactions and crosslinking induced by UV irradiation were monitored in situ and in real time by quartz crystal microgravimetry (QCM). Sensograms reflecting time‐dependent changes in density and viscoelasticity of crosslinking films followed a Boltzmann sigmoidal model, depending on precursor film composition and irradiation power. The shifts in QCM frequency and energy dissipation upon PVA‐SbQ cyclodimerization correlated with three photo‐crosslinking phases involving soft‐to‐rigid transitions, namely, induction (initiation), main crosslinking (interaction), and termination. PVA‐SbQ films crosslinked to different degree were used as protein carriers and a slower release profile was determined for the films that underwent more extensive crosslinking. Overall, this study demonstrates for the first time the dynamics of PVA‐SbQ crosslinking and its impact in system viscoelasticity and protein release. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 345–355     

Gamma Radiation‐Induced Crosslinked PVA/Chitosan Blends for Wound Dressing

Crosslinked polyvinyl alcohol (PVA) and chitosan polymer blends have been prepared by using gamma irradiation. Chitosan was used in the blends to prevent microbiological growth, such as bacteria and fungi on the polymer. The physical properties of the blend, such as gelation, water absorption, and mechanical properties were examined to evaluate the possibility of its application for wound dressing. A mixture of PVA/chitosan, with different ratios, were exposed to gamma irradiation doses of 20, 30, 50 KGy, to evaluate the effect of irradiation dose on the physical properties of the blend. It was found that the gel fraction increases with increasing irradiation dose and PVA concentration in the blend. Swelling percent increased as the composition of chitosan increased in the blend. The PVA/chitosan blend has a water content in the range between 40% and 60% and water absorption between 60% and 100%. The water vapor transmission rate value (WVRT) of the PVA/chitosan blend varies between 50% and 70%. The examination of the microbe penetration shows that the prepared blend can be considered as a good barrier against microbes. Thus, the PVA/chitosan blend showed satisfactory properties for use as a wound dressing.     

Gold Nanoparticles Grown on Ionic Liquid‐Functionalized Single‐Walled Carbon Nanotubes: New Materials for Photothermal Therapy

Gold nanoparticles were grown on single‐walled carbon nanotubes (SWNTs) coated with a thiol‐functionalized ionic liquid resulting in the formation of core‐shell structures referred to as SWNT‐IL‐Au nanohybrid materials. The nanohybrid materials were characterized by high‐resolution transmission electron microscopy (HR‐TEM), Raman‐, and UV/Vis absorption spectroscopy. The nanohybrid materials were found to enter lysosomes in HeLa cells and show negligible cytotoxicity. Interestingly, they have an enhanced NIR absorption that is effectively transferred into heat to cause localized hyperthermia, resulting in rapid cell death; overall, the material appears to have excellent properties for photothermal therapeutic applications.     

Synthesis of water‐soluble perylenediimide‐functionalized polymer through esterification with poly(vinyl alcohol)

A new material has been prepared by covalent attachment of a perylene derivative, N‐(carboxyphenyl)‐N′‐(8‐pentadecyl)perylene‐3,4:9,10‐bis(dicarboximide) (PDI‐COOH), to poly(vinyl alcohol) (PVA) by esterification. The perylenediimide (PDI)‐modified PVA polymers are soluble in water and dimethylsulfoxide (DMSO). This solubility is conferred to the insoluble perylene derivative by the water‐soluble polymer. The materials have been characterized by hydrogen‐nuclear magnetic resonance, Fourier transform infrared spectra, X‐ray diffraction, and X‐ray photoelectron spectroscopy confirming the covalent attachment of the PDI to the polymer chains. The significant changes in the crystalline parameters and the thermal stability observed for the polymer after the esterification also confirm the covalent linkage with PDI. In addition, the PDI‐modified PVA shows good fluorescence both in solution (quantum yield ～0.2–0.25) and in solid suggesting that the PDI retains largely its photochemical and photophysical properties after immobilization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3613–3622, 2010     

Synthesis and characterization of new organic–inorganic nanohybrid film (TBA)PWFe/PVA/CTS as an efficient and reusable amphiphilic catalyst for ODS of real fuel

In this work, we report a new catalytic oxidative desulfurization (CODS) system based on (TBA)PWFe/PVA/CTS nanohybrid film as a highly active catalyst. The nanohybrid material was successfully fabricated by the composition of tetra (n‐butyl) ammonium salt of Fe‐substituted phosphotungstate, ((n‐C₄H₉)₄N)₄[PW₁₁Fe(H₂O)O₃₉] abbreviated as (TBA)PWFe, polyvinyl alcohol (PVA), and chitosan (CTS). The composite was characterized using various analytical techniques including FT‐IR, UV–vis, XRD, and SEM. The results revealed the hydrogen‐bonding interaction between inorganic (TBA)PWFe clusters and organic polymers. The catalytic activity of (TBA)PWFe/PVA/CTS was evaluated in the CODS of real gas oil. Also, the solutions of heterocyclic thiophenic compounds (HTCs) in n‐heptane were tasted as simulated fuels. It was found that the removal efficiency of HTCs in the presence of (TBA)PWFe/PVA/CTS catalyst reached as high as 95% at 60 °C after 2 h. The significant catalytic performance of the nanohybrid film might be attributed to its amphiphilicity and multifunctional active sites, which enhances adsorption and oxidation of sulfur compounds. Moreover, the (TBA)PWFe/PVA/CTS composite can be easily recovered and reused by simple filtration, making it a suitable catalyst for cleaner processing.     

Preparation,characterization and thermal behavior of poly(vinyl alcohol)/organic montmorillonite nanocomposites through solid-state shear pan-milling

In this study, the solid-state shear pan-milling was employed to prepare a series of polymer/layered silicate (PLS) nanocomposites. During the process of pan-milling at ambient temperature, poly(vinyl alcohol)/organic montmorillonite (PVA/OMMT) can be effectively pulverized, resulting in coexistence of intercalated and exfoliated OMMT layers. The obtained PLS nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM analysis indicated that OMMT dispersed homogeneously in PVA matrix and XRD results illustrated that pan-milling had an obvious effect on increase in the interlayer spacing of OMMT, and resulted in coexistence of intercalated and exfoliated OMMT layers formed. Thermal gravimetric analysis showed that thermal stability of PVA was improved owing to the incorporation of OMMT. Thermal decomposition kinetics of PVA/OMMT nanocomposites with different milling cycles of OMMT was also studied. Two types of OMMT are chosen to compare the effect of hydrophilicity of OMMT on PVA/OMMT nanocomposites.     

Preparation and photochromic properties of pyrazolones/polyvinyl alcohol composite films

Novel photochromic composite films have been successfully fabricated by dispersing pyrazolone derivative:1,3-Diphenyl-4-(3-chlorobenzal)-5-hydroxypyrazole 4-phenylsemicarbazone (1a) into hydrosol of polyvinyl alcohol (PVA). The microstructure, photochromic behaviors and thermal bleaching properties were investigated by Raman spectroscopy, X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and ultraviolet-visible absorption spectroscopy (UV-vis). The results showed that 1a was not only blended but also well dispersed in the PVA polymer films with a suitable content of chromophore. Upon UV light irradiation, the composite films gradually changed from colorless to yellow and recovered fully to the initial state upon thermal bleaching. The time constants of photochromic reactions were almost the same as those of 1a observed in their crystalline state, indicating that the photochromic phenomenon is barely disturbed by the polymer matrix.     

Photochemical stability of poly(vinyl alcohol) in the presence of collagen

The photochemical stability of poly(vinyl alcohol) (PVA) in the presence of 1%, 3% and 5% of collagen has been studied by Fourier Transform Infrared (FTIR) Spectroscopy, UV-vis spectroscopy, and Differential Scanning Calorimetry (DSC). PVA samples containing 1%, 3% and 5% of collagen were irradiated with UV light wavelength λ = 254 nm in air.The results have shown that PVA in the presence of 1%, 3% and 5% of collagen is less stable under UV radiation than pure PVA. A small amount of collagen in PVA enhances photooxidation in the PVA. The amount of crystallinity in PVA containing 1%, 3% and 5% of collagen decreases faster with UV irradiation time than that for pure PVA films.     

Role of photoadduct of K4Fe(CN)6 and C3H4N2 in improving thermal stability of polyaniline composite

This paper involves the synthesis of polyaniline composite with photoadduct of potassium hexacyanoferrate and imidazole via photochemical route by oxidative polymerization technique by ammonium persulphate. The photoadduct has been synthesized by photoirradiation followed by substitution with imidazole ligand. The photoaquation, substitution and successful synthesis has been proved by recording pH, UV visible spectra before and after irradiation and XRD of photoadduct. The as synthesized composite has been subjected to various characterizations like elemental analysis, UV–Visible spectra, FTIR, XRD, SEM, and TG/DTG. XRD of photoadduct shows crystalline structure which has been retained in the composite, changing the amorphous structure of polyaniline into the crystalline one, hence proving the insertion of photoadduct in the polymer chain. Various parameters like crystallite size (L), interplanar distance (d), micro strain (ε), dislocation density (δ) and distortion parameters (g) were calculated from XRD data. Thermal analysis shows the high thermal stability of composite which can be due to strong interaction between polymer chain and the photoadduct which restricts the thermal motion of polyaniline and thus enhances the thermal stability of composite.     

An ultrafast and clean method to manufacture poly(vinyl alcohol) bead foam products

Poly (vinyl alcohol) (PVA) foam is a promising environment‐friendly packaging material due to the good biodegradability and excellent mechanical properties. Besides, PVA can be produced on a large scale viathe non‐petroleum routes. However, the preparation of complex‐shaped PVA foam products has not been realized, because PVA is a water‐soluble and semi‐crystalline polymer with a high melting temperature (226°C), which cannot be welded through the conventional bead foaming technology. In this article, a clean and efficient strategy based on microwave foaming and sintering was innovatively developed to manufacture the PVA bead foam products. First, the expandable PVA beads were prepared through polar solvent‐plasticization, followed by supercritical carbon dioxide (scCO₂)‐impregnation in solid‐state. The impregnated beads were then surface plasticized with polar solvent by simple coating. Thus, the incorporated polar solvent in the internal and superficial regions of PVA beads was rapidly heated upon exposure to the microwave irradiation, which simultaneously induced the CO₂ foaming and interfacial melting, respectively. In this way, the expansion and welding of PVA beads were completed in a one‐step procedure. Meanwhile, the complex‐shaped PVA bead foam products with excellent elasticity and intra‐bead adhesive strength were prepared within a short period of 30 seconds. Therefore, the microwave heating can be considered as an efficient strategy for preparing the high‐performance polymer bead foam products, especially for these high‐melting temperature or glass‐transition temperature polymers.     

Thermal and mechanical properties of UV irradiated collagen/chitosan thin films

The thermal and mechanical properties of collagen/chitosan blends before and after UV irradiation have been investigated using thermal analysis and mechanical (Instron) techniques. Comparisons were made with the thermal and mechanical properties of both collagen and chitosan films. Air-dried collagen, chitosan and collagen/chitosan films were exposed to UV irradiation (wavelength 254 nm) for different time intervals. Thermal properties of collagen/chitosan blends depend on the composition of the blend and are not significantly altered by UV irradiation.Mechanical properties such as ultimate tensile strength and ultimate percentage of elongation were much better for collagen films than for collagen/chitosan films. The results have shown that the mechanical properties of the blends were greatly affected by the duration of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the blend. Increasing UV irradiation leads to an increase in Young's modulus of the collagen/chitosan blend.     

Physio-chemical influence of high electron-phonon coupling induced by 120 MeV Ag9+ SHI irradiation on exfoliated MoS2 - PVA nanocomposite films for achieving remarkable electrical conductivity for potential application in organic electronics

Swift heavy ion (SHI) irradiation technology is known to enhance the optical, electronic, mechanical, and electrical properties in polymer nanocomposites by the virtue of electron-phonon coupling. In the present work, Molybdenum disulphide (MoS₂), a two-dimensional metal dichalcogenide, has been exfoliated via liquid-phase exfoliation using N-methyl-2- pyrrolidone (NMP) as the solvent that yielded nanosheets of around 2–4 layers as depicted by HR-TEM images. MoS₂ - PVA free-standing films were prepared by wet chemical technique i.e. solution casting method and irradiated by focussed high-energy Ag⁹⁺ ion beam at fluence range of 1E10 - 3E11 ions/cm². As a consequence, the structural modification was observed by X-Ray diffraction studies that showed the shift of (002) plane of MoS₂ while Raman studies indicated the decrease of degree of disorderness at fluence 1E10 ions/cm². SHI irradiation has found to induce a two-order increase in the electrical conductivity yielding a 9.7 E-3 S/cm against that of the pristine films at 2.6E-5 S/cm. The enhanced conductivity is attributed to the induced dispersion and annealing of MoS₂ nanosheets in the PVA matrix due to the interaction of 120 MeV Ag⁹⁺ ion beam irradiation as explained by Thermal spike model.     

Effects of Various Factors on the Modification of Carbon Nanotubes with Polyvinyl Alcohol in Supercritical CO2 and Their Application in Electrospun Fibers

Supercritical（SC） CO2 anti-solvent induced polymer epitaxy（SAIPE） method was used to help prepare nanohybrid carbon nanotubes（CNTs） wrapped with polyvinyl alcohol（PVA） nanocrystals.With the variation of a series of experimental conditions or peripheral effects,such as PVA concentration,CNTs concentration,and SC CO2 pressure,the optimal experimental variables for PVA-nanocrystals growing on CNTs have been found.The adsorption of polymer on CNTs via multiple weak molecular interactions has been studied by Fourier transform infrared（FTIR） spectroscopy and Raman spectroscopy.The mechanism about the formation of PVA nanocrystals on CNTs can be suggested through the experimental phenomena.These CNTs wrapped with PVA nanocrystals can be directly used as nanofillers to fabricate PVA composite fibers reinforced with CNTs by electrospinning.     

Comparison of thermal‐ and photo‐polymerization of lauryl methacrylate monolithic columns for CEC

Lauryl methacrylate‐based (LMA) monolithic columns for CEC, prepared using either thermal initiation or by UV‐irradiation in the presence of AIBN have been compared. Thermal polymerization was carried out at 70°C for 20 h. For UV initiation, the effects of the time exposure to UV light and irradiation energy were investigated. For each initiation process, the influence of composition of porogenic solvent (1,4‐butanediol/1‐propanol ratio) on the physical and electrochromatographic properties of the resulting monoliths was also evaluated. Photochemically lauryl methacrylate stationary phases initiated showed higher permeabilities and better efficiencies than those prepared by thermal initiation. After optimization of polymerization mixture, photopolymerized columns provided a permeability of 4.25×10^?13 m² and a minimum plate height of 13.4 μm for a mixture of polycyclic aromatic hydrocarbons. Similar column‐to‐column and batch‐to‐batch reproducibilities, with RSD values below 11.6 and 11.0 % for the thermal‐ and UV‐initiated columns, respectively, were obtained.     

Water‐soluble polymer‐grafted platinum nanoparticles for the subsequent binding of enzymes. synthesis and SANS

Functionalized platinum nanoparticles (PtNPs) possess catalytic properties towards H₂0₂ oxidation, which are of great interest for the elaboration of electrochemical biosensors. To improve the understanding of phenomena involved in such systems, we designed platinum‐polymer‐enzyme model nanostructures according to a bottom–up approach. These structures have been elaborated from elementary building units based on polymer‐grafted PtNPs obtained from surface initiated‐atom transfer radical polymerization. This paper describes the polymerization of ter‐butyl methacrylate from PtNPs and its subsequent hydrolysis to obtain a water‐soluble corona, followed by an activated ester modification to introduce an enzyme (glucose oxidase). The structure of the objects, the molecular weight and the grafting density of the polymer chains were principally elucidated by small angle neutron scattering (SANS). After the grafting of the enzyme, the final hybrid structures were characterized by both microscopy and SANS to attest for the covalent grafting of the enzyme. Composition and enzyme activity of the nanohybrid objects, have also been determined by UV spectroscopy. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012