静电纺丝法制备聚乙烯醇-纤维素纳米纤维膜

以废旧涤棉混纺面料为原料,采用化学法对含棉成分进行溶解回收,将得到的纤维素粉末与聚乙烯醇(PVA)、Na Cl配成纺丝液,通过静电纺丝法制备出PVA-纤维素纳米纤维膜。对所纺纤维进行电镜观察,分析静电压、纤维素与PVA质量比、纺丝液中溶质质量分数对纺丝效果的影响。结果表明:随着电压增大,纤维直径先下降后上升;随着纤维素含量的增加,纤维直径逐渐变小;随着溶液浓度的升高,纤维直径逐渐变大。     

Poly(vinyl alcohol) foams reinforced with carbon nanotubes for stapedial annular ligament applications

This study aims to develop carbon nanotubes (CNTs) reinforced poly(vinyl alcohol) (PVA) foams as a possible material for stapedial annular ligament (SAL) application. As-grown (AG) and purified CNTs are used as reinforcing fillers for PVA foams. Uniaxial and cyclic compression tests reveal that specific modulus and energy dissipation behavior improve after reinforcing foam with CNTs. A relatively higher improvement in specific modulus is recorded for purified CNTs as they tend to produce stiffer cell walls. Thermogravimetric analysis shows thermal stability improves after addition of CNTs in PVA foams. The 50 wt % degradation temperature is higher for PVA_AG foam in comparison to neat PVA foam. Under dynamic loading storage, modulus is found to be higher for CNT doped foams with higher relative improvement with purified CNTs than AG CNTs. It is shown that reinforcing PVA foams with purified CNTs is a feasible strategy to improve their average mechanical properties and microstructure for SAL application. While the specific elastic modulus of neat PVA foam found to be in range of 0.05–0.06 MPa gcc⁻¹ with almost zero porosity. The addition of CNTs provides a wide range of specific elastic modulus 0.1–1.3 MPa gcc⁻¹ with an average pores size of about 300 μm. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48736.     

On the viscoelastic properties of poly(vinyl alcohol) and chemically crosslinked poly(vinyl alcohol)

Poly(vinyl alcohol)(PVA) films chemically crosslinked with glutaraldehyde(GA) in the presence of HCl were prepared by casting from aqueous solutions. The PVA and PVA gels were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA); their swelling characteristics and tensile strength were also determined. The DSC results for the gels displayed depressions of the melting and crystallization temperatures, as well as a decrease of the heat of fusion, when compared to those of PVA free of crosslinker. The DMA analysis revealed that: (1) The glass transition temperature of the wet PVA was lower than that of the dry one, indicating that the water had a plasticizing effect. (2) The gels had a lower glass transition temperature than PVA. (3) The glass transition temperature of the wet gels increased with increasing crosslink density. Possible explanations are provided for these observations. Whereas the thermogravimetric curves of PVA exhibited a single degradation peak, two degradation peaks were detected for the crosslinked PVA. The wet PVA and PVA gels displayed lower tensile strengths and higher elongations than the dried ones. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1816–1823, 2001     

Preparation of ketoprofen‐loaded high‐molecular‐weight poly(vinyl alcohol) gels

High‐molecular‐weight atactic poly(vinyl alcohol) (a‐PVA) gels loaded with (R,S)‐2‐(3‐benzoylphenyl)propionic acid (ketoprofen) were prepared from 5, 6, 7, and 8 g/dL solutions of a‐PVA with a number‐average degree of polymerization of 4000 in an ethylene glycol/water mixture with an aging method to identify the effect of the initial polymer concentration on the swelling behavior, morphology, and thermal properties of a‐PVA gels. Then, the release behavior of ketoprofen from a‐PVA gels was investigated. As the polymer concentration decreased, the ability for network formation decreased, and the degree of swelling of the a‐PVA gels increased. In addition, the enthalpy increased with an increase in the a‐PVA concentration, but the melting temperatures of the gels prepared at different initial polymer concentrations were the same; this indicated that tighter gel networks would be formed by a higher polymer chain density. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Crystallinity,reversibility, and injectability of physically crosslinked poly(vinyl alcohol) and poly(ethylene glycol) hydrogels

Crystallite regions within a hydrogel network contribute to its mechanical strength, which is crucial for use in load-bearing applications. However, high amounts of crystallinity can negatively impact the ability for hydrogels to be injected, an attractive property that could replace the need for highly invasive surgical procedures. The reversibility of crystallinity and its lasting impact on the injectability of poly(vinyl alcohol) and poly(ethylene glycol) hydrogels was evaluated in this paper. The relative percent crystallinity in hydrogels was evaluated after storage and autoclaving in syringes in weekly intervals using X-ray diffraction. Results indicate that crystallinity increased over time and significantly decreased after autoclaving for all samples, where postautoclaved samples contained comparable crystallinity percentages to freshly made gels (p > 0.05). Injectability was evaluated using calculated viscosity. Aged samples were able to be injected after autoclaving, yet there was no determination established between viscosity and storage times based on the data. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48706.     

Expanded Core/Shell Poly(vinyl acetate)/Poly(vinyl alcohol) Particles for Embolization

An improvement to a previously published suspension polymerization process for the production of spherical core/shell PVAc/PVA particles is described. To increase the settling time of the beads in the suspension, an expansion stage was introduced. The core/shell structure was obtained through the partial hydrolysis of the PVAc. The particle density was manipulated through addition of a solvent during the suspension polymerization stage and posterior expansion of the polymer beads obtained at the end of the process. This technique allows for effective reduction of the density of the final polymer beads. The expansion stage exerts also a beneficial effect on particle drying, avoiding particle aggregation during post‐polymerization processing of the polymer beads.

     

On physical and antibacterial properties and drug release behavior of poly(vinyl alcohol) hydrogels: effect of drug loaded chitosan nanoparticles

This paper deals with influence of chitosan nanoparticles (CNPs) loaded by tetracycline, as a drug, on the physico-mechanical and antibacterial properties as well as drug release behavior of poly(vinyl alcohol), PVA, hydrogels prepared by electron beam irradiation. The formation of spherical chitosan particles in nanoscale size prepared by an ionic gelation method was confirmed by FTIR and UV spectroscopy, and scanning electron microscopy analyses. The drug release kinetic studies from drug loaded chitosan nanoparticles (DLCNPs) at pH = 7.4 revealed a linear and steady release behavior over long period of time. The theoretical analysis of the swelling kinetic data, using Peppas’s model showed that the swelling kinetic is governed by Fickian diffusion for all the prepared hydrogels, however, the water diffusion coefficient, and therefore, the swelling content were lower for the hydrogels loaded with DLCNPs as compared to the ones with the neat drug. In agreement with these results, the hydrogels containing DLCNPs exhibited a more controlled drug release behavior with significantly stronger antibacterial activity. The tensile mechanical properties of the hydrogels not affected by the DLCNPs were found to be suitable for wound dressing applications.     

聚乙烯醇醇解度测定的定量核磁共振技术研究

建立了新的测定聚乙烯醇醇解度的定量核磁共振技术(QNMR)。结果表明:在实验温度303 K、脉冲等待时间2 s时,定量核磁共振方法得到的结果与滴定法十分吻合,而且精密度、重复性、稳定性均能达到要求。该方法具有快速准确、操作简便,不需对样品进行分离,可直接分析等特点。     

Polymer Nanocomposites based on Modified ZrO2 NPs and Poly(vinyl alcohol)/Poly(vinyl pyrrolidone) Blend: Optical,Morphological, and Thermal Properties

Nanocomposite films were prepared successfully by simple solution casting method from the blend of poly(vinyl alcohol) and poly(vinyl pyrrolidone) as the polymer matrix and functionalized ZrO₂ nanoparticles as nanofiller. To prevent aggregation and improve the dispersion of nanoparticles into the matrix, ZrO₂ nanoparticles were functionalized with citric acid and ascorbic acid. Then, nanocomposites were fabricated by adding different contents of modified nanoparticles into the poly(vinyl alcohol)–poly(vinyl pyrrolidone) matrix. Thermal stability of the obtained nanocomposite films was improved in comparison to the pure blend. Furthermore, optical property of nanocomposites makes them a potential candidate for ultraviolet shielding material.     

Microstructure and characterization of electrospun poly(vinyl alcohol) nanofiber scaffolds filled with graphene nanosheets

Graphene nanosheets (GNSs) have attracted significant scientific attention because of their remarkable features, including exceptional electron transport, excellent mechanical properties, high surface area, and antibacterial functions. Poly(vinyl alcohol) (PVA) solutions filled with GNSs were prepared for electrospinning, and their spinnability was correlated with their solution properties. The effects of GNS addition on solution rheology and conductivity were investigated. The as‐spun fibers were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC). The results revealed the effects of GNS on the microstructure, morphology, and crystallization properties of PVA/GNS composite nanofibers. The addition of GNSs in PVA solution increased the viscosity and conductivity of the solution. The electrospun fiber diameter of the PVA/GNS composite nanofiber was smaller than that of neat PVA nanofiber. GNSs were not only embedded at the fibers but also formed protrusions on the fibers. In addition, the crystallinity of PVA/GNS fiber decreased with higher GNS content. The possible application of PVA/GNS fibers in tissue engineering was also evaluated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41891.     

Poly(vinyl alcohol) nanocomposites with sepiolite and heat‐treated sepiolites

Poly(vinyl alcohol) (PVA) nanocomposites with pristine sepiolite and heat‐treated (HT) sepiolites were prepared by the method of solution dispersion. The measurements of XRD, FTIR, TEM, and AFM were used for the characterization of the nanocomposites. Furthermore, thermal and optical properties were investigated by TG/DTG/DTA and UV‐visible transmission spectra, respectively. Both the effects of sepiolite/polymer ratio and the structural changes in sepiolite on heating were examined in terms of changes in the properties of the nanocomposites. The addition of sepiolite/HT sepiolites into the PVA matrix resulted in a decrease in the thermal decomposition temperatures of the nanocomposites because of the fact that sepiolite and HT sepiolites facilitated the elimination of the water and acetate groups from the PVA in the second step based on the TG/DTG studies. The HT sepiolites‐PVA nanocomposites had lower thermal stability and more influenced optical clarity than those of the sepiolite PVA, at the same filler levels. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Study of cryostructuration of polymer systems. XVII. Poly(vinyl alcohol) cryogels: Dynamics of the cryotropic gel formation

Freeze‐thaw treatment of concentrated (>5 g/dL) aqueous solutions of poly(vinyl alcohol) (PVA) (MW 115,000; DD ≈100%) resulted in the formation of opaque gels. The extent of such a cryostructuration process was exhibited in the rheological properties of similar PVA cryogels. The gels' strength depended on the initial polymer concentration in the solution to be frozen and on the conditions of a cryogenic influence. The key factor was the defrostation dynamics: the slower the thawing rate, the stronger the cryogel sample formed, provided other parameters of the process were identical. The observation for the kinetics of the freeze‐thaw–induced gel formation revealed the extreme character of the temperature dependence of the efficacy of PVA cryotropic gelation, the maximum point being in the vicinity of −2°C. It was shown that the effect of the strengthening of PVA cryogels prepared by means of a single‐cycle cryogenic treatment could be reached either with use of as slow as possible thawing regimes, or by the prolonged frozen storage of the samples at “high” subzero temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2017–2023, 2000     

ZnO microparticle-loaded chitosan/poly(vinyl alcohol)/acacia gum nanosphere-based nanocomposite thin film wound dressings for accelerated wound healing

The present study deals with the development of novel ZnO microparticle-loaded chitosan/poly(vinyl alcohol)/acacia gum nanosphere-based nanocomposite thin films through electrospraying and evaluation of their potential use in wound healing applications for skin. ZnO microparticles were synthesized and used as bioactive agents. Morphology, size distribution, structure, and dispersion of the synthesized ZnO microparticles were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy (TEM). ZnO microparticles were incorporated into the ternary nanocomposite films by electrospraying technique. Thermogravimetric analyses reveal that incorporation of ZnO microparticles into the nanocomposite structure improves the thermal stability. Mechanical analyses show that tensile strength reaches to the maximum value of 12.75 MPa with 0.6 wt % ZnO content. SEM and TEM micrographs demonstrate that the nanocomposite films consist of nanospheres with nanocapsular structures whose sizes are mostly between 250 and 550 nm. Viability tests established prevailing cellular performance of the fibroblasts on 0.6 wt % ZnO microparticle-loaded nanocomposite films with a viability percentage of 160% compared to the control group. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48445.     

Evaluation of two chemical crosslinking methods of poly(vinyl alcohol) hydrogels for injectable nucleus pulposus replacement

Low back pain caused by intervertebral disc degeneration is one of the most common spinal disorders among patients seeking medical treatment. The most common surgical treatments are spinal fusion and total disc arthroplasty, both of which are very invasive surgical procedures. Nucleus pulposus replacement is an earlier stage intervention for disc degeneration. One of the material classes being studied for this application is hydrogels: a three‐dimensional hydrated network of polymer(s), which mimics the mechanical and physiological properties of the nucleus. Poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), and poly(ethylene glycol) (PEG) hydrogels have previously been shown to be great candidate materials for injectable nucleus pulposus replacement, but have experienced issues with swelling and mass retention. The addition of chemical crosslinking to the PVA/PVP/PEG hydrogel system will allow tailoring of the swelling, mechanical, injectability, and mass loss properties of the hydrogel network. Two chemical crosslinking methods were evaluated for the PVA/PVP/PEG hydrogel system by characterizing the hydrogels with compression, swelling, and spectroscopy experiments. The results of these experiments led to the selection of the difunctional crosslinking strategy using PEG functionalized with terminal epoxide group (PEG diglycidyl ether) as the preferred crosslinking method. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40843.     

Electrostatic immobilization of cetylpyridinium chloride to poly(vinyl alcohol) hydrogels for the simple fabrication of wound dressings with the suppressed release of antibacterial agents

Polymeric systems for antibacterial wound dressings require chemical reactions or syntheses for attaching or incorporating antibacterial moieties into polymer backbones. However, these materials often fail to satisfy the basic requirements, such as easy and inexpensive synthesis. We speculated that a positively charged organic antibacterial agent would be attracted to the polar groups of poly(vinyl alcohol) (PVA) hydrogels and would show suppressed release. PVA hydrogels containing cetylpyridinium chloride (CPC) were prepared by γ irradiation. CPC was barely released from the hydrogels, probably because of electrostatic interactions, and was stable upon γ irradiation. The suppressed release of CPC conferred antibacterial activity against Escherichia coli to the surface of the hydrogels, whereas no inhibition zone was observed around the hydrogels. The CPC‐containing PVA hydrogels were easy to prepare and contained known and safe materials. The simplicity and safety of this procedure for achieving the suppressed release of antibacterial agents were advantages of these CPC‐containing PVA hydrogels. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40456.     

Thermal,Mechanical and Chemical Properties of Hydrophilic Poly(vinyl alcohol) Film Improved by Hydrophobic Poly(propylene glycol)

A series of poly(vinyl alcohol)/poly(propylene glycol) (PVA/PPG) blend films with different PPG contents were prepared by casting the polymer blend solutions. Structure and morphologies of the PVA/PPG blend films were studied by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PVA/PPG blend films were investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), tensile strength tests, and other physical methods. It was revealed that the introduction of PPG could exert marked effects on the morphology and the properties of PVA film.     

Development and characterization of a poly (vinyl alcohol) and sodium alginate blend foam for wound dressing loaded with propolis and all-trans retinoic acid

Propolis is a complex mixture of phytochemicals, with antibacterial, anti-inflammatory, and healing properties. All-trans retinoic acid is implicated in wound healing by stimulating angiogenesis, cell recruitment, extracellular matrix deposition, and reepithelization. The incorporation of both agents to a polymeric wound dressing composed of poly (vinyl alcohol) and sodium alginate may result in improved healing allied to controlled release, fluid uptake, and wound protection. In the present work, we have physically characterized this wound dressing and analyzed its release kinetics. The anti-inflammatory capacity was assayed. SEM images showed a highly porous structure with a diverse morphology. FTIR spectra displayed a highly cross-linked structure with both polymers connected by hydrogen bonds and acetal bridges. The wound dressings were able to retain great volumes of PBS. Propolis and vitamin A releasing behavior were maintained for 6 h. The concentrations of the biologically active substances were capable of promoting anti-inflammatory action in an erythrocyte membrane stabilization model. The wound dressings obtained here showed adequate physical properties. The fabrication process did not affect the anti-inflammatory capacity. Further tests are needed to ensure the biocompatibility and to assess other biological activities of the therapeutic agents.     

Measurement of the nonlinear mechanical properties of a poly(vinyl alcohol) sponge under longitudinal and circumferential loading

Poly(vinyl alcohol) sponges (P‐sponges) have been used as a potential implant material for the replacement and repair of soft tissues, including cartilage, liver, and kidney. However, the application of P‐sponges as tissue replacement materials is almost entirely bounded because of a lack of sufficient mechanical properties. In this study, we characterized the mechanical properties of a fabricated poly(vinyl alcohol) sponge (P‐sponge) under a series of longitudinal and circumferential uniaxial loadings. The nonlinear mechanical behavior of the P‐sponge was also computationally investigated with hyperelastic strain energy density functions, that is, the Ogden, Yeoh, Mooney–Rivlin, and Neo‐Hookean models. A hyperelastic constitutive model was selected to best fit the axial behavior of the sponge. The results reveal that the Young's modulus and maximum stress of the P‐sponge in the longitudinal direction were 16 and 17% greater than that in the circumferential direction, respectively. The Yeoh model, in addition, was selected to represent the nonlinear behavior of the poly(vinyl alcohol) material and could be used in future biomechanical simulations of the soft tissues. These results can be used to understand the mechanical properties of spongy materials in different loading directions. In addition, they have implications for ophthalmic and plastic surgeries and wound healing and tissue engineering purposes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40257.     

Poly(vinyl alcohol)‐g‐lactic acid copolymers and films with silver nanoparticles

Poly(vinyl alcohol) (PVA), a well‐known synthetic biodegradable, biocompatible, and hydrophilic polymer is susceptible to several structural modifications, due to the presence of hydroxyl groups in its backbone. PVA was grafted with L (+)‐lactic acid (LA) in molar ratios VA/LA (1/1, 1.5/1, and 2.2/1), manganese acetate as catalyst, by solution polycondensation procedure, resulting the poly(vinyl alcohol)‐g‐lactic acid copolymers. Aqueous solutions of copolymers with glycerol as plasticizer, silver nanoparticles (Ag^o), and sodium tetraborate as crosslinking agent were used for films casting. The copolymers were characterized by FTIR and ¹H RMN spectroscopy, gel permeation chromatography, thermal analyses (DTG and DSC), silver particles size, while films were characterized by mechanical properties and mechanodynamic analyses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011