PVA Films Research Articles

Fluorescence Enhancement of Nonemissive Monodeprotonated Luteolin in a Poly(vinyl alcohol) Film.

Solid polymer matrixes can modulate the electronic states of embedded chromophores and have been widely used in flexible optoelectronic and optical materials. Luteolin is one of the most common natural flavonoids, and its neutral and monodeprotonated forms are nonemissive in aqueous solution induced by ultrafast excited-state proton transfer (ESPT) followed by nonradiative relaxation. In this study, we have incorporated luteolin into poly(vinyl alcohol) (PVA) films and studied their fluorescence behaviors. Neutral and one monodeprotonated luteolin coexist in the PVA film. Weak steady-state fluorescence of neutral luteolin peaking at about 440 nm is observed for the first time. In addition, the monodeprotonated luteolin in PVA film exhibits obvious fluorescence peaking at 500 nm, with a fluorescence quantum yield of as high as 0.4 and a fluorescence lifetime of as long as 2.4 ns. Time-dependent density functional theory calculations have determined that the ESPT of neutral luteolin is barrierless but that of monodeprotonated luteolin needs to surmount a barrier, explaining their distinct emission properties. These results indicate the modulation ability of the PVA film in both ground-state deprotonation and ESPT, broadening the application areas of the solid polymer matrix.

Photoluminescent Y2O3:Eu3+@PVA composite dispersions and films for anti-counterfeiting ink applications

The development of high-tech anti-counterfeiting inks to detect counterfeit products is a crucial task for almost every aspect of modern life around the world. Herein, we report the synthesis of photoluminescent xY2O3:Eu3+@PVA (x = 0, 1, 2.5, 5, 10, 15, and 20 wt%) composite dispersions and films and demonstrate their potential for anti-counterfeiting inks applications. Laser-synthesized m-Y2O3:Eu3+ nanoparticles (daver = 20.3 ± 6.9 nm) with strong red luminescence due to 5D0 → 7F0-4 transitions of Eu3+ were used as a pigment to create luminescent composites. Detailed photoluminescence properties of the obtained composite dispersions and films as a function of m-Y2O3:Eu3+ content were investigated in combination with SEM, EDX, UV–Vis and IR spectroscopy data. Tuning of the CIE coordinates of xY2O3:Eu3+@PVA is observed by changing the excitation wavelength. The results of SEM showed that the photoluminescent nanoparticles were uniformly distributed in the PVA film. Photoluminescent m-Y2O3:Eu3+-doped PVA composite inks can be applied via spray, brush, and screen-printing techniques to create security features on various surfaces, including glass, ceramics, paper, plastics, and currency notes. These inks remain stable for at least four months and offer a distinctive luminescent signature that is challenging to replicate, owing to the unique photoluminescence spectrum of Eu3+ in the monoclinic Y2O3 polymorph.

Mechanical and Thermal Characteristics of Films from Glycerol Mixed Emulsified Carnauba Wax/Polyvinyl Alcohol

Poly(vinyl alcohol) (PVA)-based films have drawn significant attention owing to their potential applications in various industries. The application of wax to PVA films enhanced their resistance to dissolution and water infiltration. Nevertheless, waxed PVA films often exhibit inadequate mechanical properties owing to crack formation. In this study, we evaluated the impact of glycerol as a plasticizer in varying concentrations of Carnauba wax (CW). The addition of glycerol to the PVA/CW blend led to enhanced mechanical properties compared to the blend without glycerol. The functional group and morphology of the blends confirm glycerol compatibility with PVA/CW films. Glycerol was fully dispersed to form a consistent polymer matrix and equally improved the film’s contact angle. Furthermore, the thermal property from differential scanning calorimetry and thermogravimetric analysis highlights the plasticizing effect of glycerol in PVA/CW films, potentially broadening their use in food packaging and wrapping applications.

Site Effect of Electron Acceptors on Ultralong Organic Room-Temperature Phosphorescence.

Herein, we successfully observe the site effect of electron acceptors on ultralong organic room-temperature phosphorescence (UORTP) in the case of 7H-benzo[c]carbazole (BCz) derivatives: cyanophenyl on the nitrogen site can promote intersystem crossing (ISC) efficiency and enhance phosphorescence intensity by facilitating n-π* transitions but make a slight change to the phosphorescence wavelength; cyanophenyl on the naphthalene site can cause a remarkable red shift of phosphorescence wavelength by reducing the T1 energy level of BCz derivatives and also enhance phosphorescence intensity by promoting ISC but weaken phosphorescence intensity by lowering the molecular symmetry. Three BCz derivatives (1-BCzPhCN, 2-BCzPhCN, and 3-BCzPhCN) with the electron acceptor cyanophenyl at different sites (nitrogen site and naphthalene site) were synthesized through a combination of the nucleophilic substitution reaction and the Suzuki coupling reaction. The phosphorescence properties of 1-BCzPhCN, 2-BCzPhCN, and 3-BCzPhCN in toluene solution, in a copolymerized MMA film, and in a PVA film were measured and analyzed. 1-BCzPhCN emits intrinsic green ultralong phosphorescence at ∼500, ∼536, and ∼580 nm, while 2-BCzPhCN and 3-BCzPhCN give out intrinsic yellow ultralong phosphorescence with a red shift of 27 and 40 nm, showing that cyanophenyl on the naphthalene site leads to a remarkable red shift of the intrinsic phosphorescence wavelength, but cyanophenyl on the nitrogen site makes a slight difference to the intrinsic phosphorescence wavelength. Under the same condition, the phosphorescence intensity is usually ranked as 1-BCzPhCN/3-BCzPhCN > 2-BCzPhCN, demonstrating that cyanophenyl on the nitrogen site promotes ISC and enhances phosphorescence intensity, but cyanophenyl on the naphthalene site reduces molecular symmetry and accelerates nonradiative dissipation. Time-dependent density functional theory calculations verify that cyanophenyl on the naphthalene site shifts the phosphorescence wavelength by reducing the T1 energy level, and cyanophenyl on the nitrogen site facilitates n-π* transitions to strengthen the phosphorescence intensity. Moreover, three BCz derivatives were doped into DMAP and BBP, separately. The BCz derivatives exhibited different phosphorescence colors and shifts due to interactions with the host materials. We believe this work will give an insight into the structure-property relationship of organic phosphorescence molecules and pave a way for design of colorful UORTP materials.

Luminescent study of Eu(OOCC6H5)3·3(H2O) complex dispersed on polyvinyl alcohol films: Crystal structure, interaction and quenching effect

This study presents the preparation of a mononuclear complex of europium and benzoic acid and its interaction with polyvinyl alcohol films. The europium complex was prepared from europium (III) chloride hexahydrate (EuCl3 · 6H2O), and sodium benzoate (C7H5NaO2), and it was established that the ligand is attached to the metal ion through the carbonyl group anchored by bidentate interaction, obtaining a mononuclear complex powder with the formula Eu(OOCC6H5)3·3(H2O) (identified as EuBA3). First, the crystal structure solution for the complex powder was carried out, showing a monoclinic P2 space group with two molecules in the unit cell, the resulting crystal structure was deposited in the CCDC service with number 2370755. Afterward, the complex was deposited on polyvinyl alcohol films, to study the interactions between them, the morphological and luminescent properties were also evaluated. This work details the synthesis, of a complex made of europium and sodium benzoate and its luminescent properties as a complex deposited at different concentrations on polyvinyl alcohol films, the results obtained showed a shift in the excitation wavelength from the EuBA3 powder complex when incorporated into the PVA films. The concentration of the complex in the film increases until reaching a maximum followed by a decrease due to quenching.

Enhancing PVA mulching films: Leveraging modified lignin as a bio-based crosslinking agent for improved mechanical strength, UV barrier, and biodegradability

In contemporary agriculture, eco-friendly mulching films present a promising alternative to conventional plastic mulching films. However, their potential is constrained by challenges related to limited biodegradation and barrier performance. Addressing these limitations, innovative lignin-carboxylated materials were employed as bio-based crosslinking agents to enhance diverse properties in the fabrication of PVA films. Alkali lignin was modified with diethylenetriaminepentaacetic acid (DTPA) to enhance its chemical reactivity. The abundance of carbonyl groups in modified lignin (Lig-DTPA) plays a significant role in establishing strong compatibility with PVA through covalent bonds. This interaction yielded remarkable enhancements, elevating both tensile strength and tensile modulus by an impressive 50.9 % and 60.1 %, respectively. The introduction of Lig-DTPA at 3 % into the PVA composite films resulted in excellent UV-blocking properties. Moreover, at 3 % ratios, the presence of lignin became visibly dispersed as clear spots across the film, indicating a relatively uniform state within the matrix. The study revealed a direct correlation: as the lignin content increased, the film exhibited heightened water solubility and enhanced biodegradability. The PVA/Lig-DTPA film displays promising potential for utilization as a mulching film material, offering anti-ultraviolet functionality and a high degradation rate. Furthermore, its versatility extends to potential applications in packaging materials, including seedling bowls, transplanting pots, and coating films for transportation purposes.

Expanding the Color Range of Photoresponsive Multicolor Luminescent System Through Host-Guest Interaction.

Photoresponsive multicolor luminescent systems offer interesting functions, which have led to applications in anticounterfeiting and biological imaging. However, expanding the color range of these materials remains a challenging task. Herein, a carbazole-modified dithienylethene derivative (DTE-CZ) that exhibits modulated fluorescence color changes through the photocyclization reaction and photolysis reaction is synthesized. DTE-CZ emits orange fluorescence, and it can release a fluorophore which emits blue fluorescence by the photolysis reaction, resulting in the color change. Upon complexation of DTE-CZ with cucurbit[10]uril (CB[10]), the fluorescence wavelength will have a blue shift and the photolysis reaction will be inhibited. Benefiting from the influence of CB[10] and the photolysis reaction of free guests, the color range of the photoresponsive system which is composed of free guests and host-guest complexes is further extended. White light emission along with a color shift from yellow-green to blue was achieved by adjusting the ratio of free guests to host-guest complexes. Finally, the photoresponsive multicolor systems are utilized to construct a photostimulated PVA film and an information encryption system. This work provides an alternative strategy for the preparing of photoresponsive multicolor luminescent system and modulation of its color range.

Highly efficient phosphate adsorption using calcium silicate hydrate-embedded calcium crosslinked polyvinyl alcohol thin film

The removal of phosphate from water is necessary to avoid eutrophication. In this work, a novel composite film of calcium silicate hydrate (CSH) immobilized within calcium cross-linked polyvinyl alcohol (CSH–PVA) was developed for efficient phosphate removal from water using a simple and environmentally friendly preparation method. The characterization showed that flake crystal-like CSH nanoparticles were immobilized on a PVA film (86–106 μm). Amorphous calcium phosphate and hydroxyapatite were observed after phosphate adsorption. The adsorption efficiency and capability of phosphate were examined under various conditions using batch experiments. The phosphate removal data fitted well to the pseudo-second-order kinetic model (R2 = 0.9903–0.9999) and the Langmuir isotherm model (R2 = 0.9958), which estimated a maximum removal capacity (99.01 mg g−1). Phosphate adsorption was found to be endothermic with spontaneous adsorption via chemisorption with strong affinity (ΔG° = −3.96 to −8.62 kJ mol−1, ΔH° = 65.4 kJ mol−1, and ΔS° = 232.94 J mol−1 K−1). Additionally, significant amounts of fluoride and carbonate ions affected phosphate adsorption at levels exceeding 5-fold and 20-fold that of phosphate, respectively. An excellent removal efficiency was achieved in the range of 72.06%–97.87% using phosphate-containing real samples. Therefore, the proposed CSH–PVA film showed great potential for effective phosphate removal from water, with potential for further use as a fertilizer.

Nickel oxide nanoparticles embedded in polymer-matrix nanocomposite prepared by nanosecond laser ablation method for optoelectronic applications

The polymeric PVA structure embedded with nickel oxide nanoparticles (NiO NPs) was synthesized using nanosecond pulsed laser ablation in liquid media technique for optoelectronic applications. A comprehensive investigation was conducted on the optical and electrical characteristics of the fabricated films to demonstrate the proficiency of the proposed nanocomposite film in that particular domain. Different weights of NiO nanoparticles were generated by embedding them in PVA film using different ablation durations. It was shown that as the concentration of NiO embedded in PVA increased in correlation with the ablation period, the absorption peak changed to a longer wavelength, and the absorption edge of PVA changed towards lower photon energy with a reduction in the band gap density. Followed by the increase in disorder degree through the addition of NiO NPs, while an average value of the dispersion energy is identical, and the nonlinear parameters (χ(3) and n2) increase. Also, the results emphsies that the dielectric characteristics were affected as the concentration of NiO NPs increased due to the rise in the density of states, which resulted in the generation of polarization. Due to the creation of the charge transfer complex, the optical conductivity of the produced nanocomposites rises as the concentration of NiO NPs increases. Therefore, the optical and electrical characteristics of PVA are significantly affected by the incorporation of NiO nanocomposites.

Effect of structural evolution and orientation behavior on optical properties of iodine-dyed PVA film during uniaxial stretching

In the process of preparing polarizing film, based on the research on the influence of the initial condensed structure of Poly (vinyl alcohol) (PVA) film on the dyeing and stretching process, the connection between the structure and performance of polarizing film is established, which is more conducive to understanding the post-processing process of solution casting molding of optical grade PVA film and the optimization of subsequent dyeing and stretching process. In this paper, PVA film with an appropriate swelling degree were selected for dyeing treatment, and the evolution of the condensed structure during stretching was studied in detail. The work also examined the formation and orientation of PVA-iodine complexes and the feedback effect of complex formation on the structural evolution of the film, with the goal of establishing the relationship between stretching ratio, structure, and performance of the polarizing film. The results show that the dyeing process inhibits the recrystallization of the PVA film during uniaxial stretching. However, the PVA-iodine complexes formed act as "anchors" to stabilize the oriented microfiber network, reducing the critical strains (εw and εs) required for the PVA film to enter the strain-hardening zone. Furthermore, as strain increases, the content of polyiodide ions and PVA-iodine complexes in the dyed PVA film also increases, especially making the formation of long iodide chains (I5−) and PVA-I5− complex more sensitive. Additionally, with increasing strain, both the transmittance and degree of polarization of the dyed PVA film improve, reaching optimal values in the strong strain-hardening zone (>εs). This indicates that εs is the minimum critical strain required to ensure optimal polarization performance of the film in the visible light region.

Intelligent luminescent microneedle and hydrogel patches for visual monitoring of lactic acid and dopamine

Dopamine (DA) and lactic acid (LA) are vital biochemical indicators of neurotransmitters and tissue oxidation monitoring, which can comprehensively assess the neurological and physical conditions. The combination of fluorescent sensor and artificial intelligence shows great potentials in monitoring and quantizing of human biochemicals. Herein, a Tb3+ functionalized hydrogen-bonded organic framework material (Tb@ME-TPA) is synthesized based on coordination post-synthesis modification, and its sensing mechanism for DA and LA is investigated by experiments and theoretical calculations. For visual detection of DA and LA in actual environment, Tb@ME-TPA is fabricated into PVA films and microneedle patches, which hold the advantages of high efficiency, sensitivity and anti-interference. In addition, microneedles-based probe for minimally invasive sensing of DA in the dermal interstitial fluid along with a portable smartphone platform are designed to monitor with high accuracy. Furthermore, an intelligent back-propagation neural network model based on fluorescence image recognition is constructed, which can combine optical sensing of LA with deep learning by computer, greatly improving the efficiency and accuracy. This work not only presents a novel idea for the integration of fluorescent materials, smartphones and deep learning, but also provides an effective method for the prediction of diseases as well as the real-time monitoring of overall well-being.

Green Synthesis of ZnO Nanoparticles via Ganoderma Lucidum Extract: Structural and Functional Analysis in Polymer Composites.

Metallic nanoparticles are of growing interest due to their broad applications. This study presents the green synthesis of zinc oxide (ZnO) nanoparticles (ZnNPs) using Ganoderma Lucidum mushroom extract, characterized by DLS, SEM, XRD, and FTIR spectroscopy analyses. The synthesis parameters, including extract/salt ratio and mixing time, significantly influenced nanoparticle yield, size, and polydispersity, with longer mixing times leading to larger, more varied particles. Specifically, the sizes of ZnNPs synthesized at a 1:1 extract/ZnCl2 ratio after 3 h and 24 h were 90.0 nm and 243.3 nm, with PDI values of 48.69% and 51.91%, respectively. At a 1:2 ratio, the sizes were 242.3 nm at 3 h (PDI: 43.19%) and a mixture of 1.5 nm, 117.4 nm, and 647.9 nm at 24 h (PDI: 2.72%, 10.97%, and 12.43%). Polymer films incorporating PVA, chitosan, and ZnNPs were analyzed for their morphological, spectroscopic, and mechanical properties. Chitosan reduced tensile strength and elongation due to its brittleness, while ZnNPs further increased film brittleness and structural degradation. A comparison of the tensile strength of films A and C revealed that the addition of chitosan to the PVA film resulted in an approximately 10.71% decrease in tensile strength. Similarly, the analysis of films B1 and B2 showed that the tensile strength of the B2 film decreased by 10.53%. Swelling tests showed that ZnNPs initially enhanced swelling, but excessive amounts led to reduced capacity due to aggregation. This pioneering study demonstrates the potential of Ganoderma Lucidum extract in nanoparticle synthesis and provides foundational insights for future research, especially in wound dressing applications.

Low temperature sensing using photoluminescence of carbon quantum dot-based PVA film

In recent years, non-contact temperature reading sensors based on carbon quantum dots (CQDs) have attracted a lot of attention, most researchers have studied them at room temperature and high temperature. In this paper, red-CQDs (R-CQDs) was synthesized by hydrothermal method using o-phenylenediamine and chemically characterized by transmission electron microscopy, Fourier transform spectroscopy and X-ray photoelectron spectroscopy. The bandgap energy of R-CQDs was calculated from the absorption spectra, and the photoluminescence (PL) spectra at different laser powers showed that the PL of the R-CQDs were single-photo absorbing process. For better application, R-CQDs/polyvinyl alcohol (PVA) films were prepared. The PL properties of the film were studied. Experiments show in temperature range of 190∼260 K, the PL intensity decreases linearly with increasing temperature. Relative sensitivities of temperature sensing were calculated to be about −0.62% K−1. This work demonstrates the feasibility of its application in low temperature sensing.

Preparation of Coir Cellulose Nanofibers by Peroxyformic Acid Method and Their Application in Reinforced PVA Composite Films.

To increase the value of waste coconut shells and further broaden their use by biorefining, a milder and greener method to prepare cellulose nanofibers (CCNFs) was developed. The CCNFs were separated from coir fibers by using peroxyformic acid and alkali treatment in combination with high-power ultrasonication. The basic properties of the CCNFs were comprehensively evaluated using scanning and transmission electron microscopy, spectroscopy, diffraction, and thermogravimetric techniques. The results revealed that the developed preparation method provided CCNFs with typical nanocellulose sizes, structures, and properties. Nanocellulose-reinforced poly(vinyl acetate) (PVA) composite films were prepared using the CCNFs, and their mechanical properties, transmittance, crystallinity, and thermal stability were investigated. The elongation at break of the film with 8% CCNFs was 612%. The tensile strength of the films with 4 and 12% CCNFs was 41.3 MPa, which was higher than that of a PVA film (36 MPa). The transmittance and thermal stability of the PVA composite films were not appreciably affected by the CCNFs. The CCNFs show promise as a nanofiller for PVA-based composite films with favorable mechanical properties, crystallinity, and high transparency.

Evaluating Optical Properties of Mixed-Phase 2D MoSe2/Poly(vinyl alcohol) Nanocomposite Film.

Highly solar light-absorbing poly(vinyl alcohol) (PVA) nanocomposite films have garnered wide attention in fields such as flexible optoelectronics, solar energy harvesting, and photothermal therapy. However, fabricating PVA nanocomposite films with a broad spectrum of solar absorption using cost-effective and non-toxic nanofillers remains challenging. Herein, nanocomposite films of PVA incorporating various concentrations of mixed-phase 2D MoSe2 nanosheets (i.e., a combination of the 2H and 1T phase) were prepared using a solution casting technique. Scanning electron microscopy (SEM) shows homogenous dispersion of MoSe2 nanosheets in the PVA matrix even at higher concentrations, while atomic force microscopy (AFM) reveals increasing surface roughness with increasing MoSe2 content, reaching a plateau after 20 wt%. With the increase in the concentration of MoSe2, the nanocomposite films exhibit interesting light absorption characteristics reaching their highest absorption (average 94.9%) at 40 wt% MoSe2. The incorporated mixed-phase MoSe2 nanosheets induce a significant change in the energy levels of the PVA matrix, which is reflected in the reduced optical band gap energy (2.63 eV) at 40 wt% MoSe2 against pure PVA (5.28 eV). The excellent light absorption of PVA nanocomposite films across the entire range from 250 nm to 2500 nm is attributed to the thin 2D structure of MoSe2 and the presence of its mixed phase.

Humidity‐adaptive, mechanically robust, and recyclable bioplastic films amplified by nanoconfined assembly

AbstractPoly(vinyl alcohol) (PVA) is biodegradable, recyclable, and has high tensile strength. Therefore, it is ideal for the development of environment‐friendly sustainable bioplastics. However, at elevated humidity, the mechanical properties of PVA bioplastic films undergo degradation owing to their intrinsic hydrophilic and hygroscopic nature, hindering their applications. This study proposes a nanoconfined assembly strategy to produce humidity‐adaptive, mechanically robust, and recyclable bioplastic film. The strong hydrogen bonds between PVA and cellulose nanofibrils inhibit the penetration of water molecules into the film to promote humidity resistance. Further, the robust coordination interactions between bentonite nanoplates, PVA, and cellulose nanofibrils restrict the slip of polymer chains during deformation, leading to enhanced mechanical properties. Benefiting from the nanoconfined assembly architecture in aggregated composites, the resulting reinforced PVA film simultaneously exhibits strength, stiffness, toughness, fracture energy, and tearing energy of 55.9 MPa, 1,275.6 MPa, 162.9 MJ m−3, 630.9 kJ m−2, and 465.0 kJ m−2, respectively. Moreover, the film maintains a strength of approximately 48.7 MPa even at 80% relative humidity for 180 days. This efficient design strategy applies to diverse scales and structured cellulose biomacromolecules. Moreover, it facilitates the application of recyclable high‐performance bioplastic films to settings that require high humidity tolerance.

Fabrication of multifunctional ZnO@tannic acid nanoparticles embedded in chitosan and polyvinyl alcohol blend packaging film

The current study explores biodegradable packaging materials that have high food quality assurance, as food deterioration is mostly caused by UV degradation and oxidation, which can result in bad flavor and nutrition shortages. Thus, new multifunctional zinc oxide nanoparticles/tannic acid (ZnO@TA) with antioxidant and antibacterial activities were incorporated into polyvinyl alcohol/chitosan (PVA/CH) composite films with different ratios (1%, 3%, and 5% based on the total dry weight of the film) via a solution blending method in a neutral aqueous solution. Additionally, ZnO nanoparticles have unique antibacterial mechanisms through the generation of excessive reactive oxygen species (ROS) that may lead to intensify pathogen resistance to conventional antibacterial agents. Thus, minimizing the negative effects caused by excessive levels of ROS may be possible by developing unique, multifunctional ZnO nanoparticles with antioxidant potential via coordination bond between tannic acid and ZnO nanoparticles (ZnO@TA). ZnO@TA nanoparticles were examined using Fourier-transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effect of the incorporation of ZnO@TA nanoparticles on the barrier, mechanical, thermal, antioxidant, antimicrobial, and UV blocking characteristics of chitosan/polyvinyl alcohol (ZnO@TA@CH/PVA) films was investigated. The lowest water vapor and oxygen permeability and the maximum antioxidant capacity% are 31.98 ± 1.68 g mm/m2 kPa day, 0.144 ± 5.03 × 10–2 c.c/m2.day, and 69.35 ± 1.6%, respectively, which are related to ZnO@TA(50)@CH/PVA. Furthermore, ZnO@TA(50)@CH/PVA film exhibits the maximum UV shielding capacity of UVB (99.994). ZnO@TA(50) @PVA/CH films displayed better tensile strength and Young`s modulus of 48.72 ± 0.23 MPa and 2163.46 ± 61.4 MPa, respectively, than the other film formulations. However, elongation % at break exhibited the most reduced value of 19.62 ± 2.3%. ZnO@TA@CH/PVA film exhibits the largest inhibition zones of 11 ± 1.0, 12.3 ± 0.57, and 13.6 ± 0.57 mm against Staphylococcus aureus, Aspergillus flavus, and Candida albicans, respectively. In accordance with these results, ZnO@TA@CH/PVA films could be utilized for food preservation for the long-term.

Photophysical properties of hybrid porphyrin-erythrosine B fluorophore in aqueous media and PVA films

Photophysical properties of hybrid porphyrin-erythrosine B fluorophore in aqueous media and PVA films

Influence of the odd‐even effect of dicarboxylic acids as crosslinker on the physicochemical properties of polyvinyl alcohol

AbstractPolyvinyl alcohol (PVA) was crosslinked with a homologous series of four different dicarboxylic acids, HOOC(CH2) n‐2COOH (n = 2 to 5) viz. oxalic acid (OA; C2), malonic acid (MA; C3), succinic acid (SA; C4) and glutaric acid (GA; C5) containing odd and even number of carbon atoms. The characterization and assessment of synthesized crosslinked films were done using ATR‐FTIR, XRD, SEM, AFM, DSC, rheology, percent swelling and sessile drop contact angle. The odd‐even effect of dicarboxylic acids was observed to significantly influence the physicochemical properties of PVA when employed as a crosslinker. PVA films crosslinked using dicarboxylic acids containing an even number of carbon atoms, displayed translucency, roughness, and an irregular matrix. In contrast, films incorporating an odd number of carbon atoms were transparent, homogenous, and densely packed. Furthermore, films containing even acids exhibited relatively lower crystallinity, lower melting temperature (Tm) and displayed an unexpected irregular trend in swelling as crosslinker concentration increased compared to films containing dicarboxylic acids with an odd number of carbon atoms which exhibits a consistent swelling with increasing crosslinker concentration. These results are attributed to the difference in the solubility and crystal structures of the odd‐even series of dicarboxylic acids.

PREPARATION, CHARACTERIZATION AND ANALYSIS OF NANOSCALE MORPHOLOGY OF POLY(VINYL ALCOHOL) FILMS ASSOCIATED WITH SILK FIBROIN FUNCTIONALIZED WITH COPAÍBA OLEORESIN

Biodegradable films based on poly(vinyl alcohol) (PVA) and bioactive substances have been receiving great attention in the food industry, as they offer an eco-friendly alternative to conventional packaging. In this context, we synthesized PVA (PVAF) films containing silk fibroin (SF) formulations functionalized with copaiba oleoresin (CO) for use as bioactive packaging. Four different formulations were prepared using the casting method, varying the SF-CO concentrations from 0 to 15% (v/v) in the PVA matrix. The samples were characterized regarding morphology, nanotexture, physicochemical, and barrier properties. SEM images revealed the uniform morphology of the films, and AFM data allowed the quantification of surface characteristics such as uniformity and homogeneity, confirming the uniform distribution of SF-OC in the PVA matrix. All films showed high water absorption power (more than twice their mass weight), and the incorporation of SF-CO did not change the water vapor permeability rate of PVAF. In contrast, the solubility of PVAF decreases with SF-CO content. FTIR and UV-vis spectra confirmed the presence of SF-CO in PVAF and indicated possible intermolecular interactions between PVA and SF-CO. Finally, our findings suggest that the incorporation of SF-CO into the PVA matrix is a viable alternative for producing eco-friendly packaging.