Effect of glycerol on structure–property relations in chitosan/poly(ethylene oxide) blended films investigated using wide‐angle X‐ray diffraction

Polymer blending is an effective method for providing desirable polymeric materials with properties useful for the packaging industry. In the study reported, blends of chitosan/poly(ethylene oxide) (PEO) were prepared in various weight ratios with and without glycerol. Line profile analysis of the X‐ray diffraction patterns of these blended films was carried out. Microstructural parameters such as crystallite size and lattice strain were determined using paracrystalline modelling of X‐ray data. These values were correlated with physico‐mechanical and optical properties of the chitosan/PEO blends with and without glycerol to understand the holistic behaviour of the blends. Two prominent Bragg reflections at 2θ ≈ 19° and 23° were observed in the wide‐angle X‐ray diffraction patterns of the glycerol‐based chitosan/PEO blended films of various ratios. Interruption of PEO crystallization with chitosan results in an amorphous polymer network and hence a reduction in crystallite size by almost 97.7%. For glycerol‐based blends, the crystallite size/area decreases to 94.4% of the virgin crystallite size. The X‐ray profile analysis supports the results for the physico‐mechanical properties of the blends. The results show that the addition of 20 wt% of glycerol results in an increase of the elongation at break by more than 150%, meaning that these chitosan/PEO films could be applied in flexible packaging. Copyright © 2010 Society of Chemical Industry     

Mechanical,thermal, and electrical conducting properties of CNTs/bio‐degradable polymer thin films

The objective of this study is to increase mechanical, thermal, and electrical properties of plasticizer free thermoplastic bio polymer, BIOPLAST GS 2189 (BP), a blend of poly lactic acid (PLA) and potato starch. This polymer is highly suitable for sheet molding, film processing; blown film extrusion and injection molding and fully biodegradable. Structural, mechanical, thermal, and electrical properties of these films were manipulated by reinforcement of multiwalled carbon nanotubes (CNTs) in BP. Thin films of various (1–5 wt %) percentages of CNTs/BP were prepared by using a high‐speed spin coating technique. These as‐prepared films are ～60–100 µm in thickness. The thickness measurements of these films were carried out using micrometry and optical microscopy. The maximum tensile strength (200%) and modulus (150%) was observed for 4 wt % loading of CNTs in BP as compared with the neat BP thin film. The X‐ray diffraction results show that the addition of CNTs in BP increases the crystallinity of BP. Electrical conductivity of this film also increased by 48% as compared with the neat BP polymer films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Design and application of flexible insert for microinjection compression molding polymer microlens arrays with tunable height

A flexible insert is assembled using easily available porous plate and flexible polymer film. Then, applying microinjection compression molding technology, a fast and efficient method is proposed for successive, mass and one‐step replication of polymer microlens arrays (MLAs). Orderly MLAs with convex microlenses are successfully prepared without a given micro‐feature on the insert corresponding to that on the MLAs. Interestingly, the flexible films are deformed to arc‐like profiles that match with the shape of the microlenses with different curvatures under the action of different mold compression forces. Hence, by only changing the compression force, a series of high quality MLAs with tunable height and so geometrical‐morphology are molded by one flexible insert. The molded MLAs exhibit average heights of 61.61–86.28 µm by varying the compression force from 90 to 120 kN. The molded MLAs exhibit favorable geometrical‐morphology uniformity and optical properties. The proposed method is an accessible approach to avoid expensive equipment and complicated procedure for manufacturing the mold microfeature. POLYM. ENG. SCI., 58:213–219, 2018. © 2017 Society of Plastics Engineers     

Polyketone nanofiber: an effective reinforcement for the development of novel UV‐curable,highly transparent and flexible polyurethane nanocomposite films

This study deals with the fabrication of a novel polyketone nanofiber‐reinforced UV‐curable polyurethane acrylate nanocomposite. An aliphatic polyketone nanofibrous mat was proficiently prepared by electrospinning using a solvent mixture of methylene chloride and trifluoroacetic acid. The outstanding characteristics of polymer nanofibers including a small pore size, a high aspect ratio and molecular orientation and an excellent mechanical performance offer the use of nanofibers as reinforcement in making nanocomposites. We fabricated a novel highly transparent and flexible nanocomposite film based on casting, electrospinning and UV‐curing processes. This method allowed significant enhancement of the mechanical properties using a very small amount (approximately 3.5 gsm) of polyketone nanofiber. The yield strength and Young's modulus of the nanocomposite were improved by up to 61% and 60%, respectively, compared to a UV‐cured polyurethane acrylate film. The reinforcing effect of nanofibers was accomplished without sacrificing the transparency and flexibility of polyurethane acrylate. The morphologies of the nanofibers and fiber–resin interface as well as the characteristics of the nanocomposite films were also studied. The effective use of nanofibers as a reinforcement and the preparation of a nanocomposite along with its characterization in comparison to a UV‐cured polyurethane acrylate film are also discussed. © 2020 Society of Chemical Industry     

Syntheses and properties of polyimides derived from diamines containing 2,5‐disubstituted pyridine group

A series of novel homo‐ and copolyimides containing pyridine units were prepared from the heteroaromatic diamines, 2,5‐bis (4‐aminophenyl) pyridine and 2‐(4‐aminophenyl)‐5‐aminopyridine, with pyromelltic dianhydride (PMDA), and 3,3′, 4,4′‐biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two‐step thermal imidizaton method. The poly(amic acid) precursors have inherent viscosities of 1.60–9.64 dL/g (c = 0.5 g/dL in DMAC, 30°C) and all of them can be cast and thermally converted into flexible and tough polyimide films. All of the polyimides show excellent thermal stability and mechanical properties. The polyimides have 10% weight loss temperature in the range of 548–598°C in air. The glass transition temperatures of the PMDA‐based samples are in the range of 395–438°C, while the BPDA‐based polyimides show two glass transition temperatures (T_g1 and T_g2), ranging from 268 to 353°C and from 395 to 418°C, respectively. The flexible films possess tensile modulus in the range of 3.42–6.39 GPa, strength in the range of 112–363 MPa and an elongation at break in the range of 1.2–69%. The strong reflection peaks in the wide‐angle X‐ray diffraction patterns indicate that the polyimides have a high packing density and crystallinity. The polymer films are insoluble in common organic solvents exhibiting high chemical resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1844–1851, 2006     

Fabrication and characterization of planar and channel polymer waveguides. II. Poly(p‐phenylene benzobisthiazole) (PBZT) films

Solutions of poly(p‐phenylene benzobisthiazole) (PBZT) in methane sulfonic acid (MSA) were prepared and studied. Solutions with concentrations less than 0.04 wt % PBZT were characterized by dilute solution viscometry. Planar PBZT waveguides were spin‐coated from a 0.5 wt % PBZT solution onto oxidized silicon wafers. The optical attentuation of the resulting polymer waveguides was measured and found to depend on both the thickness of the oxide layer on the silicon substrate and also the wavelength of the incident light. The lowest optical loss recorded for PBZT in this investigation was 4.81 ± 1.39 dB/cm at 834 nm. This work thus demonstrates the successful fabrication of PBZT into thin‐film planar waveguides. The PBZT films prepared here also show improved optical characteristics over PBZT films prepared previously by either extrusion or spin coating. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1448–1456, 2000     

Characterization of flexible polyurethane foams based on soybean‐based polyols

Two series of flexible polyurethane foams were fabricated by substituting conventional petroleum‐based polyols with increasing amounts of soy‐based polyols (SBP) having different hydroxyl numbers. The mechanical properties of the foams were characterized by stress–strain analysis in the compression mode and DMA in tension mode, the cellular morphology was analyzed by SEM and the microphase‐separation of the foams was noted by SAXS. Our results showed that the cellular morphology and mechanical properties of the flexible foams were affected significantly by the foam fabrication method and SBP hydroxyl numbers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Multilayer method as a tool for depth dependent polymer film photodegradation studies

A new polymer film destructive depth profiling protocol is presented for the analysis of photo‐ and thermally degraded thin films on the depth scale of less than 100 microns. The method, demonstrated here on thin films of poly(vinyl chloride) (PVC), provides a means of preparation of thin laminates of high optical quality comprised of many (>20) thin layers of individual thickness less than 15 microns. The constituent layers are fused together under appropriate pressure, temperature and time treatment to yield a film assembly of high optical quality that behaves like a uniform single layer during photodegradation exposure, but which may still be separated after treatment. Compared to previous techniques, this new method is relatively simple and non‐labor intensive. Film adhesive properties are controlled to within ± 5% Concentration depth profiles of polymer photolysis products were reconstructed by analyzing each of the separated layers using UV‐visible spectrophotometry. The continuity of these film assemblies with respect to mechanical properties, adhesive properties and the depth distribution of key photolysis reagents and products was confirmed using photothermal and reference microscopy techniques. Optical absorption depth profiles examined in UV‐ photodegraded poly(vinyl chloride) (PVC) films exhibited the classic dependencies expected in the presence of nitrogen and oxygen atmospheres.     

Poly(urethane acrylate)‐based gel polymer films for mechanically stable,transparent, and highly conductive polymer electrolyte applications

Polymer electrolytes are attractive for the applications in conventional electrochemical devices and emerging flexible devices. In this study, we developed a poly(urethane acrylate)‐based gel polymer electrolyte with excellent mechanical stability, optical transparency, and a high ionic conductivity. These polymer electrolytes showed excellent dimensional stability and an elastomer‐like behavior with a Shore A hardness in the range of 20–40. The optical transmittance values of these polymers films were over 80% in the visible range. Their ionic conductivities were controlled via changes in the concentration of the linker, dimethylol propionic acid (DMPA), and the lithium salt incorporated into the polymer. The maximum ionic conductivity reached 3.7 mS/cm at room temperature (～23 °C) when the DMPA/poly(ethylene glycol) molar ratio was 0.25, and the ionic conductivity was found to be proportional to the salt concentration. We believe that these polymer electrolytes will be useful in various electrochemical applications where flexibility, high ionic conductivity, and transparency in the electrolytes are necessary. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45009.     

Fabrication of surface‐relief gratings on an azobenzene‐containing epoxy‐based polymer film using atomic force microscopy

Many studies have been reported on the photo‐fabrication of surface‐relief gratings (SRGs) in azo‐polymer films using the interference of two laser beams of appropriate polarization. However, there are few reports in the literature concerning the electro‐fabrication of SRGs on such types of polymer films. The goal of the work reported was the electro‐patterning of an azobenzene‐containing epoxy thermoplastic film. An epoxy‐based polymer functionalized with an azo‐chromophore was synthesized and characterized using thermal analysis. The reversible optical storage properties and photo‐induced dichroism were studied. SRGs were fabricated on a film of the synthesized azobenzene‐containing polymer using contact mode current‐sensing atomic force microscopy which locally applied an electric field that aligned the azobenzene moieties. The anisotropic mass transport of the azo‐polymer film was observed after applying an electric field. Additionally, the effect of the relief formation in the polymeric film surface was investigated by means of atomic force microscopy and electrostatic force microscopy. Copyright © 2010 Society of Chemical Industry     

Syntheses and properties of novel polyimides derived from 2‐(4‐Aminophenyl)‐5‐aminopyrimidine

2‐(4‐Aminophenyl)‐5‐aminopyrimidine (4) is synthesized via a condensation reaction of vinamidium salts and amidine chloride salts, followed by hydrazine palladium catalyzed reduction. A series of novel homo‐ and copolyimides containing pyrimidine unit are prepared from the diamine and 1,4‐phenylenediamine (PDA) with pyromellitic dianhydride (PMDA) or 3,3′,4,4′‐biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two‐step thermal imidization method. The poly(amic acid) precursors had inherent viscosities of 0.97–4.38 dL/g (c = 0.5 g/dL, in DMAc, 30°C) and all of them could be cast and thermally converted into flexible and tough polyimide films. All of the polyimides showed excellent thermal stability and mechanical properties. The glass transition temperatures of the resulting polyimides are in the range of 307–434°C and the 10% weight loss temperature is in the range of 556–609°C under air. The polyimide films possess strength at break in the range of 185–271 MPa, elongations at break in the range of 6.8–51%, and tensile modulus in the range of 3.5–6.46 GPa. The polymer films are insoluble in common organic solvents, exhibiting high chemical resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5871–5876, 2006     

Enhanced antioxidant activity of fish gelatin–chitosan edible films incorporated with procyanidin

Gelatin and chitosan are edible polymers, which may be used in combination with antioxidant extracts as films to extend shelf life of foods. In this work, fish gelatin–chitosan edible films with procyanidin (PC) are successfully prepared. The effects of PC on the antioxidant, microstructure, physical properties, and antimicrobial activity of the films and solutions are studied. The results suggest that the addition of PC makes the gelatin–chitosan film possess the highest 2,2‐azinobios‐(3‐ethylbenzothiazoline‐6‐sulfonic acid) radical scavenging activity up to 95.63% at 1.00 mg/mL. As to mechanical properties, drop in tensile strength (27.17 ± 2.35%) and gain in elongation at break (33.42 ± 2.48%) are found for film with 1.00 mg/mL of PC. Owing to the simultaneous antioxidant and antimicrobial activities displayed for these films based on blends of gelatin and chitosan and additivated with PC could provide an alternative as active packaging material for food applications such as fish, meat, and cheese. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45781.     

Graphene‐based electrodes for flexible electronics

As ‘flexibility’ has emerged as an important issue in next‐generation electronics, many efforts to find new classes of materials have been devoted to realizing stretchable, bendable and foldable electronic devices. For these devices to be realized, graphene has been considered as one of the most promising candidates for flexible electrodes due to its extraordinary electrical, optical and mechanical properties. Particularly, recent developments in the fabrication and modification of graphene point to a bright future for graphene electrodes in flexible electronics. This mini‐review summarizes the recent progress in graphene films as flexible electrodes for various applications such as solar cells, organic light‐emitting diodes, touchscreens, transistors and supercapacitors. © 2015 Society of Chemical Industry     

Effect of the processing methods on the performance of polylactide films: Thermocompression versus solvent casting

Polylactide (PLA) films were prepared by the thermocompression and solvent‐casting methods, and selected properties, such as the mechanical, water‐vapor‐barrier, thermal, and thermomechanical properties, were tested. The solvent‐cast films contained 13.7% solvent, which functioned as a plasticizer, as evidenced by the results of the measurements of dry matter and thermogravimetric analysis as well as dynamic mechanical analysis. The PLA films prepared by the thermocompression method were strong and brittle, with maximum tensile strength (σ_max) and maximum elongation at break (?_max) values of 44.0 ± 2.2 MPa and 3.0 ± 0.1%, respectively; however, the solvent‐cast films were more ductile, with σ_max and ?_max values of 16.6 ± 1.0 MPa and 203.4 ± 20.8%, respectively. The water vapor permeability of the PLA films was lower than that of plastic films such as low‐density polyethylene and high‐density polyethylene but higher than that of commonly used biopolymer films. In addition, both types of tested PLA films were water‐resistant and not soluble in water. The thermocompressed films showed higher thermal stability than the solvent‐cast films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3736–3742, 2006     

New class of bioinspired lenses with a gradient refractive index

The recognition that eye lenses in nature often employ a gradient refractive index to enhance the focusing power and to correct aberrations has motivated us to construct a synthetic lens using the layered concept encountered in biological lenses. The result is a highly flexible technology for the fabrication of gradient‐refractive index lenses that is based on a method of polymer forced assembly. Polymeric nanolayered films with incremental differences in the refractive index are assembled according to a prescribed design and molded into the desired shape. The exceptional flexibility of the process lies in the wide range of lens shapes and index profiles that can be realized. A lens with any refractive index distribution can be achieved within the refractive index range of available coextrudable optical materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1834–1841, 2007     

Highly robust and transparent flexible cover window films based on UV-curable polysilsesquioxane nano sol

Flexible cover window films based on the ultraviolet-curable polysilsesquioxane are prepared to have enhanced mechanical, optical properties, and bending performance. To figure out the factors determining those properties, post–treatment conditions are varied into the light source, temperature, and relative humidity. Then, the effect of such variables is examined in respect of surface hardness, yellow index (YI), and bending cycle reliability of flexible hard coating. Also, the effect of photoinitiator type in terms of their chemical structure is also investigated. Notably, the relative humidity and thermal treatment are more effective to enhance the mechanical properties rather than light exposure. Indeed, compared to that of reference condition, the cover windows treated with 99% relative humidity and thermal aging at 85°C exhibit improved surface hardness by 24.4 and 19.5%, respectively. However, only the relative humidity is rather effective to enhance the optical properties such as the YI by lowering to the most 2.6. The YI is also improved by varying the chemical structure of the photoinitiator. By virtue of post–treatment and a different photoinitiator, we could achieve flexible cover window films with bending reliability at bending radius of 3 mm for 100,000 cycles, showing good mechanical and optical properties simultaneously.     

Aqueous Solution‐Processable,Flexible Thin‐Film Transistors Based on Crosslinked Chitosan Dielectric Thin Films

The hydrophilic character of chitosan (CS) limits its use as a gate dielectric material in thin‐film transistors (TFTs) based on aqueous solution‐processable semiconductor materials. In this study, this drawback is overcome through controlled crosslinking of CS and report, for the first time, its application to aqueous solution‐processable TFTs. In comparison to natural CS thin films, crosslinked chitosan (Cr‐CS) thin films are hydrophobic. The dielectric properties of Cr‐CS thin films are explored through fabrication of metal–insulator–metal devices on a flexible substrate. Compared to natural CS, the Cr‐CS dielectric thin films show enhanced environmental and water stabilities, with a high breakdown voltage (10 V) and low leakage current (0.02 nA). The compatibility of Cr‐CS dielectric thin films with aqueous solution‐processable semiconductors is demonstrated by growing ZnO nanorods via a hydrothermal method to fabricate flexible TFT devices. The ZnO nanorod‐based TFTs show a high field‐effect mobility (linear regime) of 10.48 cm² V^?1 s^?1. Low temperature processing conditions (below 100 °C) and water as the solvent are utilized to ensure the process is environmental friendly to address the e‐waste problem.     

Exceptionally good,transparent and flexible FeS2/poly(vinyl pyrrolidone) and FeS2/poly(vinyl alcohol) nanocomposite thin films with excellent UV‐shielding properties

Composites of nanocrystalline iron disulfide (FeS₂) coated with poly(vinyl pyrrolidone) (PVP) or poly(vinyl alcohol) (PVA) have been successfully synthesized using a solvothermal process, in which PVP and PVA serve as soft templates. Transparent, flexible thin films of these nanocomposites were prepared from homogeneous solution using a solution‐casting approach. X‐ray diffraction and thermogravimetric analysis and energy‐dispersive X‐ray, Fourier transform infrared and UV‐visible absorption spectroscopic techniques were employed to study the structural and optical properties of these nanocomposite films. UV‐visible spectra in transmission mode reveal the UV‐shielding efficiency of these nanocomposite films and the films are found to be exceptionally good for UV‐shielding applications in the wavelength range 200 to 400 nm. The present work aims at developing transparent and flexible UV‐shielding materials and colour filters using cost‐effective and non‐toxic inorganic–polymer nanocomposites. © 2012 Society of Chemical Industry     

Synthesis of poly(butyl acrylate)‐poly(methyl methacrylate) core–shell nanomaterials of anti‐crease‐whitening properties

Core–shell nanomaterials of poly(butyl acrylate)‐poly(methyl methacrylate) were synthesized using a differential microemulsion polymerization method for being used as polyacrylate‐based optical materials, which meet the requirement of anti‐crease‐whitening and proper mechanical strength. The effects of reaction temperature and surfactant amount on the particle sizes, as well as the effect of reaction temperature on the conversion and solid content were investigated to reveal the dependence of the application properties on the reaction conditions. The spherical morphology of core–shell nanoparticles was also studied via transmission electron microscopy. The resulting polymers with a core–shell monomer ratio of butyl acrylate/methyl methacrylate at 32/10 (vol/vol) demonstrated the optimal balanced properties in the anti‐crease‐whitening and mechanical property, confirmed by the visible light transmittance measurement and the dynamic analysis of the viscoelastic properties of the synthesized core–shell nanomaterials. The smaller the particle size, the better the transparency of the resulting polymer films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39991.     

Stability of high‐bandwidth graded‐index polymer optical fiber

The properties of poly(methyl methacrylate) (PMMA)‐based graded‐index polymer optical fiber (GI POF), including the thermal stability, thermal humidity, and mechanical properties, were studied for polymer optical fiber research and applications. The glass‐transition temperature of the fiber core was 103°C in the presence of the dopant, which was close to that of the PMMA matrix without the dopant. A special refractive‐index profile derived from the distribution of the dopant was stable at 60°C. Moreover, GI POF exhibited good mechanical properties. The excellent performance indicated that GI POF could be applied not only for indoor use but also for outdoor use. However, PMMA‐based GI POF exhibited poor hot‐water/humidity resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2330–2334, 2004