Polyvinyl Alcohol Polymer Films Research Articles

Tailoring the optical properties of dye–polymer composite films based on polyvinyl alcohol doped with phenol red toward flexible optoelectronic applications

The composite films of polyvinyl alcohol (PVA) incorporating varying concentrations of phenol red (PR) dye were fabricated using the solution casting method. Structural characteristics of the prepared films were explored through XRD and FTIR spectroscopy analyses. The inclusion of PR dye within the PVA matrix induced cross-linking, enhancing the amorphous nature of the doped PVA samples, as evidenced by XRD patterns. In the presence of PR dopants, the FTIR peaks for PVA exhibited altered intensities and increased width, indicating physical interactions between the functional groups of PVA and PR dopants. The impact of PR additives on the optical properties of PVA was investigated across the spectral range of 190–2500 nm. The PVA/phenol red composite demonstrated enhanced UV blocking in the 190–400 nm wavelength range, rendering it suitable for applications such as UV notch filters, including laser blocking filters. The indirect and direct optical band-gaps of PVA polymer films were reduced from 5.20 eV and 5.78 eV to 4.30 eV and 5.28 eV, respectively, with an increase in the PR filling ratio from 0 wt% to 1.8 wt%. The dispersion region of the refractive index was analyzed using the single oscillator model (Wemple-DiDomenico). Calculation and discussion of values such as dispersion and oscillation energies (Ed and Eo), permittivity at infinite frequency (ε ∞), and lattice contribution to the dielectric function (ε L) of PVA/PR composite films were conducted. These advancements position PVA/PR composite films for potential applications in flexible optoelectronic devices, including light-emitting diodes and photodetectors.

Enhanced premelting of ice in contact with hydrophilic polymer films

Abstract Premelting is an interfacial phenomenon with practical consequences such as the contribution to the slipperiness of ice. In many situations ice is in contact with opposing materials. We have explored the effect of opposing materials on the premelting behavior of ice by using a resonance shear measurement setup. Interestingly, contact with polyvinyl alcohol polymer films caused enhanced premelting. These results provide information about the nature of ice interfaces and can lead to a better understanding of friction on ice.

The instructive role of mechanical properties of polyvinyl alcohol film in the process of YSZ tape calendering

Aqueous tape calendering offers the advantage of a simple fabrication process, inexpensive equipment, and environmental friendliness. Polyvinyl alcohol (PVA), as a polymer, is a conventional binder for aqueous tape calendering. In this innovative work, we aim to achieve a suitable process for tape calendering, by studying mechanical properties of the PVA polymer film with a series of plasticizers. The results show that the elongation at break of the PVA film reaches a maximum of 828.26%, using a triple plasticizer of glycerol, polyethylene glycol (PEG) 200, and PEG 400. With an optimized ratio of the binder to the plasticizer, a YSZ sheet with a relative density of 98% and a conductivity of 0.043 S cm−1 at 800 °C is obtained by sintering at 1400 °C, demonstrating comparable performance to those of the YSZ electrolytes by dry pressing. SEM reveals that the sintered YSZ body is dense, and has no visible open and closed pores. The mechanical properties characterization of the PVA polymer film adopted in this paper has instructive significant instruction for tape calendering and tape casting methods.

Fabrication of PVA polymer films with improved antibacterial activity by fine-tuning via organic acids for food packaging applications

In this study, organic acids were used as cross-linker with polyvinyl alcohol (PVA) films prepared by a solution-casting method for food packing applications. The effect of incorporating three different organic acids, i.e., malic acid (MA), tartaric acid (TA), and lactic acid (LA), on the physicochemical and biological properties of PVA was explored in detail. The crystalline phase, optical absorption, and functional groups were examined via UV–Vis and Fourier transform infrared spectroscopy. Thermal, microstructural, and surface investigations were conducted by thermogravimetric analysis and scanning electron microscopy, and the antibacterial activity was evaluated. The surface topography and roughness were found to have a strong effect on the bactericidal properties of the films, as confirmed by atomic force microscopy. Among the considered films, PVA/LA exhibited the highest bacterial inhibition, which was largely due to its capacity to modify the local pH and alter the permeability of the microbial layer by disrupting bacteria–substrate interaction. In general, the composite film was found to have attractive properties and can be considered as a food packaging material with low environmental impact based on polyvinyl alcohol.

Experimental study, phenomenological and adaptive neuron analysis of creep property of Momordica augustisepala L nanofiber reinforced polyvinyl alcohol polymer film composite

The viscoelastic property of packaging material affects foods’ postharvest management and biophysical quality preservation of food. This study investigated the creep viscoelastic property of neat polyvinyl alcohol film and polyvinyl alcohol film reinforced Momordica augustisepala nanofiber composite. The applicability and comparison of Burger phenomenological and Adaptive neuron model to analyze the creep data were investigated. The instantaneous modulus and creeping speed of neat and reinforced polyvinyl alcohol were 7.53710 MPa, 10.27580 MPa and 3.00590 MPa.s, 2.85391 MPa.s, respectively. The coefficient of determination of Burger model prediction was 0.99889 and 0.99972 for neat and composite polyvinyl alcohol film, while the coefficient of determination of Adaptive neuron model was 0.99986 for both neat and reinforced polyvinyl alcohol film. The Momordica augustisepala nanofiber improved the creep viscoelastic property of polyvinyl alcohol film and Adaptive neuron model showed superiority over Burger model in prediction of experimental data. The results are vita in material design, life prediction and usage prescription.

Exploring the Structural, Thermal and Dielectric Properties of PVA/Ni0.5Zn0.5Fe2O4 Composites

Nano-Ni0.5Zn0.5Fe2O4 embeded in polyvinyl alcohol (PVA) with different weight ratios (5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 30 wt.%, 40 wt.% and 50 wt.%) were prepared by solution casting. The formation of PVA/Ni0.5Zn0.5Fe2O4 hyprid composite is confirmed through x-ray diffraction, scanning electron micrographs, transmission electron microscopy, and Fourier transform infrared spectroscopy analysis. Thermogravimetric analysis showed that the composite films have thermal stability higher than pure PVA. The complex dielectric constant (e*), electrical conductivity, electric modulus and impedance spectra of these polymer nanocompsites have been studied over the frequency range 1 Hz–20 MHz. The real permittivity (e′) of PVA polymer film enhanced while the real electric modulus (M′) decreased by the addition of Ni0.5Zn0.5Fe2O4 nanoparticles. The imaginary part of permittivity has the same trendline of e′ leading to the increase in its values. These aspects of PVA composites making it a promising material to be used in microwave absorbers depending on the dielectric loss.

Ultrasonic-assisted preparation of graphene oxide carboxylic acid polyvinyl alcohol polymer film and studies of thermal stability and surface resistivity

In this paper, flake graphite, nitric acid and acetic anhydride are used to prepare graphene oxide carboxylic acid (GO-COOH) via an ultrasonic-assisted method, and GO-COOH and polyvinyl alcohol polymer (PVA) are used to synthesize graphene oxide carboxylic acid polyvinyl alcohol polymer (GO-COOPVA) via the ultrasonic-assisted method, and GO-COOPVA is used to manufacture graphene oxide carboxylic acid polyvinyl alcohol polymer film (GO-COOPVA film) via a solidification method, and the structure and morphology of GO-COOH, GO-COOPVA and GO-COOPVA film are characterized, and the thermal stability and surface resistivity are measured in the case of the different amount of GO-COOH. Based on the characterization and measurement, it has been successively confirmed and attested that carboxyl groups implant on 2D lattice of GO to form GO-COOH, and GO-COOH and PVA have the esterification reaction to produce GO-COOPVA, and GO-COOPVA consists of 2D lattice of GO-COOH and the chain of PVA connected in the form of carboxylic ester, and GO-COOPVA film is composed of GO-COOPVA, and the thermal stability of GO-COOPVA film obviously improves in comparison with PVA film, and the surface resistivity of GO-COOPVA film clearly decreases.

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.

Effect of beam expansion loss in a carbon nanotube-doped PVA film on passively mode-locked erbium-doped fiber lasers with different feedback ratios

The effect of beam expansion induced divergent loss in a single-wall carbon nanotube (SWCNT) doped polyvinyl alcohol (PVA) based ultrafast saturable absorber (SA) film thickness on the passive mode-locking (PML) performances of erbium-doped fiber lasers are demonstrated. The variation on the PML pulsewidth of the EDFL is discussed by changing the SWCNT-PVA SA film thicknesses, together with adjusting the pumping power and the intra-cavity feedback ratio. An almost 6 dB increment of divergent loss when enlarging the SWCNT-PVA based SA film thickness from 30–130 µm is observed. When shrinking the SA thickness to 30 µm at the largest pumping power of 52.5 mW, the optical spectrum red-shifts to 1558.8 nm with its 3 dB spectral linewidth broadening up to 2.7 nm, while the pulse has already entered the soliton regime with multi-order Kelly sidebands aside the spectral shoulder. The soliton pulsewidth is as short as 790 fs, which is much shorter than those obtained with other thicker SWCNT doped PVA polymer film based SAs; therefore, the peak power from the output of the PML-EDFL is significantly enlarged accompanied by a completely suppressed residual continuous-wave level to achieve the largest on/off extinction ratio. The main mechanism of pulse shortening with reducing thickness of SWCNT doped PVA polymer film based SA is attributed to the limited beam expansion as well as the enlarged modulation depth, which results in shortened soliton pulsewidth with a clean dc background, and broadened spectrum with enriched Kelly sidebands. The increase of total SWCNT amount in the thicker SA inevitably causes a higher linear absorption; hence, the mode-locking threshold also rises accordingly. By enlarging pumping power from 38.5–52.5 mW, the highest ascent on pulse extinction of up to 32 dB is observed among all kinds of feedback conditions. Nevertheless, the enlargement on the extinction slightly decays with increasing the feedback ratio from 30–90%, as the ascent slope gradually decays due to the more severe gain saturation effect occurring when the mode-locking gradually completes at this stage.

Spectral studies of Donepezil release from streched PVA polymer films

The focus of this research is to obtain poly vinyl alcohol (PVA) polymer foils containing Donepezil in different concentration, in order to be used in controlled drug release as a palliative treatment of mild to moderate Alzheimer’s disease. The influence of polymeric foil stretching degree on drug release was analyzed using spectral measurements.Aiming to evidence the stretching degrees of PVA foils influence on drug release the membranes containing 2% Donepezil were obtained and characterized. The morphology of pure PVA and polymeric films with Donepezil at different stretching degrees was investigated.In vitro evaluation of drug release from the polymeric foils was made for different stretching degrees. The absorbance of the solution was measured at 232nm in each case; the amount of drug release after each time interval was calculated and a cumulative addition was made. The mechanism involved in drug release process was evaluated using Korsmeyer–Peppas empirical equation. Surface roughness and profile of drug release are affected by the stretching degree of PVA foils.The dependence of the release profile on the characteristics of polymer foils containing Donepezil and the manner in which the stretching degree of the PVA with Donepezil films modify the kinetics of drug release were emphasized in this study.

Luminescence properties of Sm, Tb(Sal)3Phen complex in polyvinyl alcohol: an approach for white-light emission

Polyvinyl alcohol polymer films doped with Sm,Tb(Sal)3Phen complexes have been synthesized using solution casting technique. An enhancement in absorption intensity is observed revealing the encapsulation of rare earth ions by salicylic acid (Sal)/1,10 phenanthroline (Phen) complex. Photoluminescence spectra of the co-doped samples were examined by varying the concentration of Tb3+ keeping concentration of Sm3+ ions fixed and vice-versa. It is found that the polymer samples emit a combination of blue, green and orange–red wavelengths tunable to white light when excited with 355 nm radiation. The emission spectra also show a self-quenching effect at higher concentration of Sm3+ ions. An efficient energy transfer was observed from Tb3+ : 5D4 → Sm3+ : 4G9/2. The reason for the enhancement in fluorescence intensities of Sm3+ in the co-doped polymer sample is the intermolecular as well as the intramolecular energy transfer.

Cool White Light Emission in Dysprosium and Salicylic Acid Doped Poly Vinyl Alcohol Film Under UV Excitation

Dysprosium (Dy) and Salicylic acid (Sal) doped Poly Vinyl Alcohol (PVA) films have been successfully prepared by solution cast technique. The absorption, excitation, emission and lifetime analysis of the samples have been carried out. Judd-Ofelt theory has been used to estimate several parameters for DyCl(3) and Dy(Sal)(3)Phen in PVA polymer film which show fair agreement between the experimental and the theoretical values supporting the J-O theory. A combination of blue and yellow emissions in Dy(x)(Sal)(3)Phen co-doped PVA samples makes one perceive cool white light when excited by ultraviolet light. Energy transfer (ET) from Sal to Dy(3+) is investigated by directly observing the luminescence intensity of Dy(3+) in the Dy(x)(Sal)(3)Phen co-doped PVA samples which is much stronger than that in the DyCl(3) in PVA which is further confirmed by lifetime studies with different concentrations of Dysprosium ion (Dy(3+)). The generation of white light with chromaticity coordinates (0.30, 0.34) makes it potential material for white LED and display devices.

Study of enhanced red emission from Sm(Sal) 3Phen ternary complexes in Poly Vinyl Alcohol film

In the present work, dinuclear complexes of salicylic acid (Sal) and 1,10-phenanthroline (Phen) were synthesized with different concentrations of Samarium ion (Sm 3+) in Poly Vinyl Alcohol (PVA) polymer films and their structural and spectroscopic properties were investigated. Judd–Ofelt theory has been employed to estimate the several radiative parameters for SmCl 3 and Sm(Sal) 3Phen complex in PVA polymer film which are in fairly agreement between the experimental and the theoretical values supporting the J–O theory. Photoluminescence properties of the complex have been studied on 355 nm and 400 nm excitations in steady state as well as in time domain. On the basis of the UV–Vis absorption, FT-IR absorption, excitation, emission spectra and decay curves, spectroscopic properties of these films were studied and the photophysics involved was explained in terms of energy transfer and the RE encapsulation effect.

Vibrational Spectra and Dynamics of Electronically Excited Semiconducting Single-Walled Carbon Nanotubes

Femtosecond mid-infrared spectroscopy was applied to study the vibrational spectra and dynamics in the electronic excited states of semiconducting single-walled carbon nanotubes (SWNTs). The experiments were performed by exciting SWNTs dispersed individually in polymethylmethacrylate and polyvinyl alcohol polymer films with 40 fs laser pulses at 800 nm, and the resulting responses were monitored with broadband mid-infrared pulses ranging from 1510 to 1670 cm(-1). The structured spectra observed show vibrational bands with up-shifted frequencies by approximately 10-50 cm(-1) with respect to their ground-state counterparts. The observation provides direct evidence for the theoretically predicted lattice distortions in the electronic excited state. Analysis of the kinetics probed in the mid- and near-infrared regions provide an estimate of the time scales for the vibrational relaxation.

Emission Spectra of Tb3+:PVA Polymer Films

This paper reports on the development and optical analysis of Tb3+‐doped polyvinyl alcohol (PVA) films. A reference PVA film has also been prepared for which X‐ray diffraction (XRD) spectral profile has been carried out; it was found that this polymer possesses a semi crystalline nature. Spectral analysis of the Tb3+:PVA polymer film has been made based on the measurement of the excitation, emission, and decay curves of the emission transitions (5D4→7F6,5,4&3). Under a UV source (254 nm), a bright green emission was noticed from the surface of Tb3+:PVA film. The current study reveals that this terbium polymer film could be suggested as a novel green luminescent material.

Red emission from Eu3+: PVA polymer film

AbstractBright red luminescent Eu3+ doped polyvinyl alcohol (PVA) films were made by solution casting technique. The emission performance of these films was studied from the measurement of excitation, emission, and lifetimes. On irradiation with an UV source, the doped films emitted bright red light. Such luminescent polymer films are expected to find potential applications as new optical materials. Emission process in the system was explained by an energy level scheme. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3273–3276, 2006

Photoluminescence properties of Mn 2+-doped II–VI semiconductor nanocrystals

Our recent photoluminescence studies on ZnS:Mn 2+- and CdS:Mn 2+-nanocrystals dispersed in polyvinyl alcohol polymer films are reviewed. Both nanocrystal samples show Mn 2+ 3d intrashell luminescence with high quantum efficiencies of about 20% at room temperature under the interband excitation. Noticeable characteristics of our nanocrystal samples are that the luminescence involving some trap state is much weaker than the Mn 2+ luminescence, unlike other reports, and that thermal quenching of the Mn 2+ luminescence is remarkably weak, compared with the corresponding bulky crystal powder. These two characteristics lead to the above high quantum efficiencies of the Mn 2+ luminescence at room temperature. In addition, we examine the dominant excitation mechanism of Mn 2+ in the nanocrystals under the interband excitation and the validity of the sp–d mixing model proposed previously to explain the high luminescence quantum efficiency.

Electro-optic properties of CdS embedded in a polymer.

CdS microcrystals under weak confinement conditions embedded in a polyvinyl alcohol polymer film have been optically characterized by linear absorption and time-resolved luminescence spectroscopy. They are studied in the presence of an external electrical field at low and room temperature and different densities of photoexcited carriers. By applying a voltage of 400 V corresponding to an external electric-field strength of 5\ifmmode\times\else\texttimes\fi{}${10}^{4}$ V/cm, the observed absorption change in this material is \ensuremath{\Delta}\ensuremath{\alpha}/\ensuremath{\alpha}\ensuremath{\approxeq}0.07. The electrical field produces a redshift of the absorption band which is explained in terms of the quantum-confined Stark effect. In addition, a restoring of the oscillator strength is observed and explained by screening effects of internal fields in the interface region by the photogenerated electron-hole pairs. At high laser excitation an electric-field-induced change of the nonlinear absorption spectrum of \ensuremath{\Delta}\ensuremath{\alpha}/\ensuremath{\alpha}=0.25 is achieved, giving a considerable modulation of the absorption edge. The electrical field separates the laser excited carriers and the change in the absorption is attributed to a compensation of the many-particle interaction by the external electrical field.

Dispersive kinetics of nonphotochemical hole growth for oxazine 720 in glycerol, polyvinyl alcohol and their deuterated analogues

Dispersive hole growth kinetic data obtained with burn intensities in the nW to μW/cm 2 range are reported for the laser dye oxazine 720 in glycerol glasses and polyvinyl alcohol polymer films. The data are well described by a theory that employs a distribution function for the hole burning rate constant derived from a Gaussian distribution for the tunnel parameter of extrinsic two-level systems. The linear electron-phonon coupling is taken into account in the analysis. An approach for calculating the nonphotochemical hole burning quantum yield as a function of the hole depth is described. Deuteration of the hydroxyl proton of the amorphous hosts reduces the average hole burning quantum yield by a factor of ≈ 20, indicating that large amplitude motion of this proton is an important component of the tunneling coordinate. Temperature-dependent data are used to prove that the dispersive hole burning kinetics are independent of temperature between 1.6 and 7 K (the range studied).