Poly Vinyl Alcohol Composite Films Research Articles

Passively mode-locked erbium-doped fiber laser by a Mo2TiC2 MXene saturable absorber

Mono- and few-layer MXenes have gained widespread use as a nonlinear material platform for saturable absorbers (SAs) when generating ultrafast mode-locked pulses. However, the manufacturing processes associated with these materials are intricate and require considerable expertise. Consequently, it would be intriguing to investigate whether bulk and/or nanoscale-layered MXenes can be used as a nonlinear optical material platform. In this study, we experimentally demonstrated a Mo2TiC2 MXene-based SA by depositing nanoscale-layered Mo2TiC2 MXene particles and a polyvinyl alcohol composite film onto a side-polished fiber device. The fabricated SA exhibited a modulation depth of 5.67% and a saturation intensity of 0.135 MW/cm2. By integrating the Mo2TiC2 MXene-based SA within an erbium-doped fiber ring cavity, we generated mode-locked pulses featuring a pulse width of 1.74 ps at a wavelength of 1557.9 nm. This investigation highlights the potential of nanoscale-layered Mo2TiC2 MXene to function as an efficient material platform for nonlinear photonics applications.

Improvement of biodegradable polymer film properties by incorporating functionalized few-layer graphene

Functionalized few-layer graphene (FFG) prepared employing an eco-friendly liquid exfoliation method using coffee waste extract was added to three biological and one synthetic polymers. Chitosan/FFG, polyvinyl alcohol (PVA)/FFG, sodium alginate/FFG, and gelatin/FFG composite films were developed using variable concentrations of FFG (0–1 wt% of polymer). The developed films were characterized for water content, swelling degree, thickness, thermal and mechanical properties, water vapor permeability, and indoor soil burial degradation. In comparison to the pure chitosan, PVA, sodium alginate, and gelatin films, the inclusion of FFG significantly increased the tensile strength up to 439%, 247%, 190%, and 195%, respectively. Moreover, the Young’s modulus of the developed composite films was improved up to 515%, 253%, 144%, and 341%, respectively. The elongation at break of chitosan and PVA films declined with FFG concentration, while the maximum elongation at break existed for sodium alginate/FFG and gelatin/FFG films. The water vapor permeability of chitosan, PVA, sodium alginate, and gelatin composite films decreased by 87%, 67%, 50%, and 55%, respectively, with the addition of only 1% FFG. The incorporation of FFG reduced both the water content and swelling degree of all composite films. In addition, the composite films showed similar degradation after addition of FFG in the 60-day soil burial test.

Graphene Nanoplatelet and Multiwalled Carbon Nanotube Doping Effect on the Structural and Physical Properties of PolyVinyl Alcohol Composites

Polyvinyl alcohol (PVA) composite thin films were prepared using graphene nanoplatelets (GNPs) and multiwalled carbon nanotubes (MWCNTs) as carbon fillers (CFs). The resulting electrical, optical, mechanical, and structural changes caused by adding the CFs to the pure PVA matrix were characterized. The improvement of electrical, optical, and mechanical properties was interpreted in terms of the percolation theory. Depending on this interpretation, the percolation threshold values, and the critical exponential values of the related properties were calculated. It turns out that the measured mechanical and optical changes were compatible with the site percolation theory while the electrical conductivity was compatible with the classical percolation theory. X-ray diffraction (XRD) measurements were performed to correlate the physical properties with the structure of the PVA composite films. They revealed that the degree of crystallinity of the composites increased with the CF reinforcement and that MWCNT was more effective in improvement of the crystallinity of the PVA composites than GNP.

SPR studies in PVA composite films of SiO2@NaYF4:Er3+/Yb3+ UCNPs via AuNPs concentration variation and their temperature sensing applications

The composite film of mesoporous silica coated NaYF4:Er3+/Yb3+ upconversion nanoparticles and gold nanoparticles (AuNPs) in Poly vinyl alcohol (PVA) medium were prepared. The effect of the concentrations of AuNPs with 0 µl, 50 µl, 100 µl and 150 µl on the structure and upconversion luminescence intensity were studied. The phenomenon of enhancement in upconversion luminescence intensity due to AuNPs were explained via surface plasmon resonance (SPR) phenomenon. Apart from this the XRD, FE-SEM and AFM studies were done for estimation of structure and surface morphology etc. The impurities were estimated through FTIR analysis. The optical properties of these polymer composite films were studied via UV–vis absorption spectra and upconversion luminescence spectra analysis. A low temperature sensing ability of these films have been demonstrated for the suitability of these films in bio-medical applications.

Simultaneously Monitoring Humidity and Temperature Based on Waveguide Bragg Grating Sensor Chip

Herein, we proposed and demonstrated a novel relative humidity (RH) sensing chip with temperature compensation, which is based on waveguide Bragg grating (WBG) assisted with polyvinyl alcohol (PVA) and polydimethylsiloxane (PDMS) composite film. Half of the cladding of the WBG region was corroded with hydrofluoric acid, which results in a split of the Bragg peak into two peaks. The PVA-PDMS composite film coated on the surface of the corroded region shows a high sensitivity to RH due to the hydrophilic hydroxyl groups of PVA film. PDMS not only enhances the stability of the composite film, but also reduces the RI of the PVA film, which restricts the energy loss of the light passing through. In our experiment, average RH sensitivities of -12.2 pm/RH% and 0 pm/RH% in the RH range of 50%-90%, and temperature sensitivities of 9.6 pm/°C and 9.8 pm/°C were obtained by the two peaks shift, respectively. We testified that the simultaneous measurement of RH and temperature can be achieved by the sensitivity matrix method. Furthermore, the proposed sensor possesses remarkable stability and excellent repeatability. Such a cost-effective, integrated, easily fabricated, and reflection power detection-based humidity sensor promises great application prospects in the fields of agriculture, food industry, biological field and other production activities.

Thermal transfer improvement in polyvinyl alcohol films by mixing with boron nitride nanotubes synthesized using a radio-frequency inductively coupled thermal plasma

Boron nitride nanotubes (BNNTs)/polyvinyl alcohol (PVA) composite films were fabricated to enhance heat transfer capabilities. The incorporation of just 1 wt% of BNNTs into PVA resulted in a remarkable six-fold improvement in heat transfer properties. The BNNTs used in the composite films were synthesized using a thermal plasma method, exhibiting high aspect ratio with diameters ranging from 3 nm to 6 nm. The BNNTs improved the formation of heat transfer networks throughout the PVA films, resulting in enhanced heat transfer properties as compared to both pure PVA and BN nano-powder/PVA composite films. In addition, the addition of BNNTs did not adversely affect the mechanical properties of the BNNTs/PVA composite film such as durability and mechanical strength.

Fabrication of CNTs-reinforced poly(vinyl alcohol) nanocomposite film with tailored structural, surface chemical and optical properties

Purpose This study aims to fabricate multiwalled carbon nanotubes (MWCNTs)-mediated polyvinyl alcohol (PVA) composite films using the solution casting approach. Design/methodology/approach The prepared films were evaluated for diverse structural, surface, optical and electrical attributes using advanced analytical techniques, i.e. electron microscopy for surface morphology, Fourier transform infrared spectroscopy for tracing chemical functionalities, x-ray diffraction (XRD) for crystal patterns, water contact angle (WCA) analysis for surface wettability and UV visible spectroscopy for optical absorption parameters. The specimens were also investigated for certain rheological, mechanical and electrical properties, where applicable. Findings The surface morphology results expressed a better dispersion of MWCNTs in the resultant PVA-based nanocomposite film. The XRD analysis exhibited that the nanocomposite film was crystalline. The surface wettability analysis indicated that with the inclusion of MWCNTs, the WCA of the resultant nanocomposite film improved to 89.4° from 44° with the pristine PVA film. The MWCNTs (1.00%, w/w) incorporated PVA-based film exhibited a tensile strength of 54.0 MPa as compared to that of native PVA as 25.3 MPa film. There observed a decreased bandgap (from 5.25 to 5.14 eV) on incorporating the MWCNTs in the PVA-based nanocomposite film. Practical implications The MWCNTs’ inclusion in the PVA matrix could enhance the AC conductivity of the resultant nanocomposite film. The prepared nanocomposite film might be useful in designing certain optoelectronic devices. Originality/value The results demonstrated the successful MWCNTs mediation in the PVA-based composite films expressed good intercalation of the precursors; this resulted in decreased bandgap, usually, desirable for optoelectronic applications.

Enhanced microwave absorption properties of magnetite nanoparticles decorated multi walled carbon nanotubes loaded polyaniline/polyvinyl alcohol nanocomposites

AbstractElectromagnetic radiation interference (EMI) or pollution is increased significantly in proportion to the expansion of electronic and communication industries, which lead to the disturbance of the functioning of electronic gadgets and medical equipments, in addition to the human health damage. The Microwave absorbing (MA) composite comprised of polyvinyl alcohol (PVA), polyaniline (PANI), carbon nanotube (MWCNT) and iron oxide (Fe3O4) has been developed with various proportions, denoted as PVA/PANI/MWCNT/Fe3O4 (1%, 3%, 5%). Fe3O4 was prepared using a hydrothermal method, and PVA/PANI/MWCNT/Fe3O4 (1%, 3%, 5%) nanocomposites was made by solvent casting techniques. The PVA composite films were also subjected to a range of analyses including IR, TGA, DTA, DTG, SEM, TEM, dielectric measurements and EMI shielding effectiveness (EMI SE), to describe their characteristics. The results of various studies indicate that the PVA/PANI/MWCNT/Fe3O4 (1%, 3%, 5%) composites possess enhanced thermal and dielectric characteristics, for instance the PVA/PANI/MWCNT/5% Fe3O4 blend nanocomposites possess 10% initial decomposition at 220°C and dielectric constant of 3.2 × 107 at 1 MHz. The total EMI SE value for the synthetic PVA/PANI/MWCNT/Fe3O4 was found at 9.2 and 10 GHz is 48 and 54 dB, respectively, exhibiting synergistic properties of the composites toward EMI shielding. The microwave absorption spectra indicate two absorption peaks in the region around 8 to 12 GHz, with the absorption reflection loss (RL) value of −20 dB at 10 GHz for the PVA/PANI/MWCNT/5% Fe3O4 nanocomposites.

Bilayer PVA composite film with structural color for high-performance and multifunctional sensing

Intelligent E-skins attract lots of attention for their potential in health monitoring, human-computer interaction, and soft-body robotics. In this work, a colorful multifunctional E-skin sensor with a Janus structure was constructed by solution casting of polyvinyl alcohol (PVA) with clay and carbon nanoparticles on a patterned PDMS template. The halloysite nanotubes (HNTs) and carbon nanoparticles (C) derived from Chinese ink were introduced into PVA to obtain a nano-reinforced layer (top) with structural color and multi-functional layer (bottom) for detection of pressure, temperature, and humidity. Uniformly dispersed HNTs greatly improves the mechanical properties of PVA (up to 46.8 MPa at 303.9% strain). The difference in water absorption of the two layers provides excellent sensitivity to humidity, so it can be used as contactless password unlocking, closing and blooming of bionic flowers, and humidity alarm. The device can achieve object capture and release within 12 s by turning on and off the xenon light. Furthermore, the sensor responds distinctly to pressure and can track human activities such as drinking motion and finger bending, which can also detect the temperature by resistance change. This work provides a materials design strategy for E-skin aimed to applications in robotics, artificial intelligence, prosthetics, and health monitoring.

High intrinsic thermal conductive polymer films by engineered interchain hydrogen bond interactions

AbstractA series of polyvinyl alcohol (PVA) composite films containing different hydrogen bond acceptors 4,4′‐dihydroxydiphenyl (BP), 1,1′‐biphenyl‐4,4′‐diyl dihexanoate (DHB) and benzene‐1,3,5‐triyl tribenzoate (TBB) were prepared by casting method. Due to the existence of strong intermolecular interaction, the highest in‐plane thermal conductivity of the above films is 1.298 Wm−1 K−1, which is about 65% higher than pure PVA films. Fourier Transform infrared spectroscopy (FT‐IR) and wide‐angle X‐ray diffraction (WXAD) demonstrated that the TBB acts as a thermal bridge to enhance the internal interaction force and make the internal structure more regular. Strong molecular contact forces were demonstrated by mechanical tensile testing. The thermal expansion rate of the system was explored through molecular dynamics. Thermal expansion experiments proved that hydrogen bond can effectively reduce the free volume. Molecular dynamics simulations were also performed in this work. The number and density of hydrogen bonds inside different polymers were calculated, and the phonon thermal transport was quantitatively analyzed. The thermal bridge and intermolecular contact force were discovered to effectively restrict the molecular chain's activity and reduce its free volume. The results of the experiments and molecular dynamics reveal that strong intermolecular interactions and thermal bridges can significantly improve polymer intrinsic thermal conductivity.

Optically transparent polyvinyl alcohol composite film obtained by self-reinforcing and self-toughening with electrospun polyvinyl alcohol nanofibers: A solution processing strategy

Optically transparent polyvinyl alcohol (PVA) films with high tensile strength and toughness are urgently needed in optical field. However, the combination of good optically transparency and excellent mechanical properties is still an obstacle for the PVA films. Herein, PVA composite film obtained by self-reinforcing and self-toughening with electrospun PVA nanofibers possessing various solubility via a solution strategy is proposed to tackle this challenge. The uniaxially aligned PVA nanofibers were electrospun by a narrow roller; thereafter, the PVA composite films were fabricated by solution impregnation technique and mould pressing. Owing to the strong interface binding, entangled molecular chains, and close refractive index between PVA nanofiber and PVA matrix, the as-prepared PVA-based composite film showed satisfactory light transmittance of above 85% in the 400–800 nm wavelength range with the tensile strength and elongation at break achieving 70 MPa and 160.1%. This work proposed a new solution-based strategy to efficiently fabricate PVA composite films for optical applications.

Thermally conductive polyvinyl alcohol composite films via introducing hetero-structured MXene@silver fillers

Thermally conductive polyvinyl alcohol composite films via introducing hetero-structured MXene@silver fillers

Physicochemical Characterization, Biocompatibility, and Antibacterial Properties of CMC/PVA/Calendula officinalis Films for Biomedical Applications.

This study reports a carboxymethyl cellulose (CMC)/polyvinyl alcohol (PVA) composite film that incorporates Calendula officinalis (CO) extract for biomedical applications. The morphological, physical, mechanical, hydrophilic, biological, and antibacterial properties of CMC/PVA composite films with various CO concentrations (0.1%, 1%, 2.5%, 4%, and 5%) are fully investigated using different experiments. The surface morphology and structure of the composite films are significantly affected by higher CO concentrations. X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR) analyses confirm the structural interactions among CMC, PVA, and CO. After CO is incorporated, the tensile strength and elongation upon the breaking of the films decrease significantly. The addition of CO significantly reduces the ultimate tensile strength of the composite films from 42.8 to 13.2 MPa. Furthermore, by increasing the concentration of CO to 0.75%, the contact angle is decreased from 15.8° to 10.9°. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay reveals that the CMC/PVA/CO-2.5% and CMC/PVA/CO-4% composite films are non-cytotoxic to human skin fibroblast cells, which is favorable for cell proliferation. Remarkably, 2.5% and 4% CO incorporation significantly improve the inhibition ability of the CMC/PVA composite films against Staphylococcus aureus and Escherichia coli. In summary, CMC/PVA composite films containing 2.5% CO exhibit the functional properties for wound healing and biomedical engineering applications.

Improved mechanical and antibacterial properties of polyvinyl alcohol composite films using quaternized cellulose nanocrystals as nanofillers

Cellulose nanocrystals (CNC) are natural, renewable, and biocompatible materials that have been widely used as new sustainable reinforcing nanofillers in polymer composites. We present polyvinyl alcohol (PVA)/CNC composites with improved mechanical and antibacterial properties using CNC-based nanofillers. The surface esterified CNC (ECNC) was prepared by 6-bromohexanoyl chloride via surface esterification. Subsequently, the alkyl bromide group of the ECNC was transferred to quaternary ammonium groups for preparing quaternized CNC (ECNC-Qn) by introducing tertiary amino groups with different carbon chain lengths (C8–C16). Then, ECNC-Qn were blended with a PVA matrix to prepare PVA/ECNC-Qn nanocomposite films via a solvent casting procedure. Diverse features, including light transmission, mechanical properties, and antibacterial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria were investigated. Compared with pure PVA films, the PVA/ECNC-Qn nanocomposite films had higher tensile strength and higher antibacterial activity. Specifically, the maximum tensile strength and elongation at break of PVA/ECNC-Qn nanocomposite films were 45.4 MPa and 318.4%, respectively, which were 37.2% and 94.3% higher than those of pure PVA film, respectively. Moreover, the ECNC-Q8 exhibited the highest antibacterial efficiency, leading to the best antibacterial activity for PVA/ECNC-Q8 nanocomposite films among all films. This study demonstrates an efficient method for preparing a functional, environment-friendly PVA composite film. The prepared PVA/ECNC-Qn nanocomposite films exhibited considerable application potential in the packaging field, owing to their good mechanical and antibacterial barrier properties.

Ultra‐High Nonlinear Saturable Absorption Responses and Ultra‐Fast Carrier Dynamics of Organic DAST

AbstractThird‐order nonlinear optical (NLO) absorption properties and ultra‐fast carrier dynamics of organic 4‐N,N‐dimethylamino‐4'‐N'‐methyl‐stilbazolium tosylate (DAST) at the wavelength of 520 nm are investigated by femtosecond open‐aperture Z‐scan technique and transient absorption spectroscopy, respectively. Z‐scan measurements indicate that DAST solution exhibits ultra‐high nonlinear saturable absorption (SA) responses with a figure of merit of 4.57 × 10−13 esu cm and a saturation strength of 3.20 GW cm−2, far superior to those of the most known 2D SA materials under similar excitations. Transient absorption results reveal that the outstanding SA performances of the solution‐phase DAST are rooted in ultra‐fast ground‐state bleaching based on the Pauli blocking effect. The subsequent excited state carrier relaxation processes are dominated by rapid intraband carrier cooling and defect‐assisted interband Auger recombination. Moreover, high‐quality DAST−polyvinyl alcohol composite films prepared by solution casting exhibit similar ultra‐high SA responses and reliable long‐term stability without any degradation of their SA responses even after exposure to air moisture for 100 days. These findings establish an experimental and theoretical foundation for the development of high‐performance ultra‐fast optoelectronic devices based on organic NLO materials in the future.

Fluorine-terminated functionalized liquid metal/silicon carbide binary nanoparticles for polyvinyl alcohol composite films with high in-plane thermal conductivity and ultra-low dielectric constant

Highly thermally conductive and low dielectric constant are among the most sought-after properties of flexible polymer-based thermal-management materials (TMMs). However, it remains a formidable challenge to develop efficient thermal dissipation materials with fascinating comprehensive performance. In this work, we present an interfacial engineering strategy using trifluoropropyltriethoxysilane (TFPTES) to act as a thermal linker at granular silicon carbide-liquid metal (SiC-LM) binary interfaces (SiC-LM@F) in the polyvinyl alcohol (PVA) matrix, in which the LMs merely partially anchored to the surface of binary filler by a controllable ball milling technology. The strong hydrogen bonding and/or compact “shoulder-to-shoulder” contact between the binary components and matrix interfaces confer an expressway for the propagation of interfacial phonons. For this, the developed PVA/SiC-LM@F composite film demonstrates a high in-plane TC of 10.2 W m−1 K−1 and ultra-low dielectric constant of 1.49 at 106 Hz at 40 wt% SiC-LM@F loading content, which is more superior to those of the other counterparts in this experiment. Additionally, the obtained PVA/SiC-LM@F composite film also reveals favorable tensile strength, excellent electric insulation, and efficient cooling capacity. This interfacial engineering strategy is expected to offer a versatile solution to the design and construction of advanced thermal-management materials (TMMs).

Fabrication Mechanisms of Lignin Nanoparticles and Their Ultraviolet Protection Ability in PVA Composite Film.

Lignin is an indispensable and essential compound present in plants. It is a renewable resource and a green alternative to traditional petroleum energy. The rational utilization of lignin can reduce the environmental damage caused by traditional industrial development. The preparation of lignin nanoparticles (LNPs) using the self-assembly method is one of the most favorable ways to achieve high value-added utilization of lignin. However, the process requires an in-depth understanding of the sphere-forming mechanism of lignin self-assembly and the interaction of self-assembly forces. We used the same raw materials and two different preparation methods to prepare LNPs. The results revealed that the variation in the order of the dropwise addition of lignin solution and deionized water produced LNPs with varying average sizes. The sphere-forming mechanisms of the two kinds of lignin nanoparticles were discussed for the preparation of UV-resistant polyvinyl alcohol (PVA) polymeric films. During lignin spherification, the faster the solution reaches the supersaturation state, the faster the spherogenesis rate is, the smaller the size is, and the narrower the particle size distribution is. The lignin micro/nanospheres are produced by exploiting the π–π bonding interactions in lignin itself. The lignin micro/nanospheres are then mixed with PVA to form a film to obtain a lignin–PVA composite film material with an anti-UV effect.

Enhancement of the Dielectric Properties of Polyvinyl Alcohol by Adding TiO2Nanoparticles

High dielectric constant nanocomposite polymer films based polyvinyl alcohol (PVA) with different weight ratios of nanoparticles (NPs) TiO2(1.0, 2.5, 5.0, and 10) are prepared by the casting method. The structure of TiO2NPs is studied using TEM and XRD spectra, where the FTIR spectra show a strong interaction between PVA and TiO2NPs. The addition of TiO2NPs to the composites improves their mechanical properties. The dielectric parameters and AC conductivity are explored in the 10 Hz to 107 Hz frequency range at different temperatures. PVA composite films filled with 5.0 wt% TiO2NPs exhibit the highest dielectric constant (ε′) reaching up to 26 at 25 °C and 100 Hz. The origins of the enhanced dielectric properties are investigated using theoretical predictions of the effectiveε′of composites. The activation energy of a dielectric relaxation process is computed. As the temperature rises, the relaxation time lengthens slightly. A conduction mechanism is described based on thermally activated electron hops at the Fermi edge.

Rice straw cellulose microfiber reinforcing PVA composite film of ultraviolet blocking through pre-cross-linking

Rice straw cellulose microfiber (CMF) was obtained through the gentle low-temperature phase transition method. Then, NaIO4 was utilized to modify CMF by selective oxidation to prepare aldehyde CMF (a-CMF) to improve the reactivity of the CMF. Finally, the a-CMF reinforced polyvinyl alcohol (PVA) composite films were prepared through a pre-cross-linking and solvent casting approach. The cross-linking network formed by a-CMF and PVA through the aldolization reaction significantly improved the mechanical properties of the a-CMF/PVA composite film. The tensile strength of a-CMF-2/PVA was 37.54 ± 0.77 MPa, which was higher than 25.88 ± 2.97 MPa of the pure PVA. SEM results showed that the fracture surface of the a-CMF/PVA composite film with the cross-linking network was smooth. In addition, prepared a-CMF-2/PVA composite films had a transmittance of over 80 % in the visible light range, and also possessed excellent UV blocking property.

Preparation of a Conductive Cellulose Nanofiber-reinforced PVA Composite Film with Silver Nanowires Loading

We report herein a flexible, light and electrically conductive composite film based on polyvinyl alcohol (PVA) matrices. Cellulose nanofibers (CNFs) were used as reinforcement to improve the mechanical properties of the PVA. Addition of silver nanowires (AgNWs) was crucial in enhancing the thermal stability and conductivity of the resulting PVA/CNF-AgNWs composite. The CNFs were obtained through a mechanical defibrillation process and the AgNWs were synthesized via a solvothermal method. A simple casting method combined with a drop cast process was chosen for producing AgNW film on the surface of the composite. The PVA/CNF-AgNWs composite film obtained was superior to the PVA/CNF composite film in terms of thermal stability, tensile strength (up to 38.12 ± 0.53 N/mm 2) and conductivity (8.92 × 10−2 vs 9.46 × 10−12 S/m). These results highlight the potential application of the PVA/CNF-AgNWs composite as a candidate film for the production of flexible electronics.