Highly thermally resistant, hydrophobic poly(vinyl alcohol)–silica hybrid nanofibers (original) (raw)
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Macromolecules, 2007
Polyhedral oligosilsesquioxane (POSS)-containing amphiphilic poly(vinyl alcohol) (PVA) hybrids (PVA-POSS hybrids) were synthesized by urethane linkage between the hydroxyl groups of PVA and the monoisocyanate group of POSS macromers. The hydrophobicity of the amphiphilic PVA-POSS hybrids was varied by changing the incorporated amounts of the hydrophobic POSS macromers, resulting in control over water resistance. The synthesized amphiphilic PVA-POSS hybrids were characterized by 1 H NMR, FT-IR, DSC, and TGA and revealed modified thermal stability and solubility depending on the incorporated amounts of POSS macromers. That is, modification in both solid form and solution is observed, which is attributed to the bulkiness and hydrophobicity of POSS moieties. As a result, the amphiphilic PVA-POSS hybrids with the molar ratio of POSS macromer to-OH mole of PVA ranging from 1.0 to 15.0 could be obtained. Amphiphilic PVA-POSS hybrids showed microstructural features characteristic structure of two separate crystalline components, that is, the dual system of PVA and POSS crystalline phases. In addition, the electrospun nanofibers of PVA-POSS hybrids suggest a new method to enhance/control the water resistance of PVA nanofibers without cross-linking.
Journal of Achievements in Materials and Manufacturing Engineering, 2016
Purpose: The aim of this study was to produce poly(vinylpyrrolidone) (PVP) containingsilica nanofibers using electrospinning method from 10% PVP/EtOH solutions with differentmass concentration 0 and 30% of tetraethoxysilane. Sol-gel technique was used to obtainnanofiber membranes with high amount of inorganic phase. In the case when metal alkoxide,such as tetraethyl orthosilicate (TEOS) is mixed with an organic polymer, hydrolysis andcondensation reaction of TEOS occur in-situ with polymer matrix, which allows to fabricateorganic-inorganic hybrid structures with uniform dispersion.Design/methodology/approach: The examination of the morphology of the obtainedPVP/silicon dioxide nanofibers using scanning electron microscope (SEM) has been made.The chemical structure of produced nanostructures was investigated by Fourier - TransformInfrared spectroscopy (FTIR) and Energy Dispersive Spectrometry (EDX) to analyze theregular dispersion by examining types of bonds occurring between polymer...
Water-Resistant Poly(vinyl alcohol)-Silica Hybrids through Sol-Gel Processing
Chemical Engineering & Technology, 2014
Poly(vinyl alcohol) (PVA)-silica hybrids with exceptionally reduced solubility in water were synthesized. The hybrid xerogels were fabricated through sol-gel processing of a mixture of PVA and the acid-catalyzed silica precursor tetraethoxysilane. The effects of varying ratios of PVA and silica precursor on the surface structure, thermal properties, crystallinity, and solubility of the hybrids were investigated. Unlike the highly water-soluble nature of PVA, all the hybrids displayed considerably reduced solubility in water. This anomalous behavior of PVA in the hybrids can be attributed to the unavailability of its pendant-OH groups. Water-resistant PVA-silica hybrids can find applications in various technologies requiring biocompatible systems that are stable in aqueous environments.
Journal of Applied Polymer Science, 2012
Organic-inorganic nanocomposites consisting of co-poly(vinyl chloride-vinyl acetate-vinyl alcohol) and silica were prepared via sol-gel process. Two types of hybrids were prepared, one in which interactions between hydroxyl group present in the copolymer chain and silanol groups of silica network were developed. In the second set, extensive chemical bonding between the phases was achieved through the reaction of hydroxyl groups on the copolymer chains with 3-isocyanatopropyltriethoxysilane (ICTS). Hydrolysis and condensation of tetraethoxysilane and pendant ethoxy groups on the chain yielded inorganic network structure. Mechanical and thermal behaviors of the hybrid films were studied. Increase in Young's modulus, tensile strength, and toughness was observed up to 2.5 wt % silica content relative to the neat copolymer. The system in which ICTS was employed as binding agent, the tensile strength and toughness of hybrid films increased significantly as compared to the pure copolymer. Thermogravimetric analysis showed that these nanocomposite materials were stable up to 250 C. The glass transition temperature increases up to 2.5 wt % addition of silica in both the systems. Field emission scanning electron microscope results revealed uniform distribution of silica in the copolymer matrix. V C 2012 Wiley Periodicals, Inc. J Appl Polym
European Polymer Journal, 2007
Nanocomposites of poly(vinyl alcohol)/silica nanoparticles (PVA-SNs) were prepared by in-situ radical copolymerization of vinyl silica nanoparticles functionalized by vinyltriethoxysilane (VTEOS) and vinyl acetate with benzoyl peroxide (BPO, i.e., initiator), subsequently saponified via direct-hydrolysis with NaOH solution. The resulting vinyl silica nanoparticles, PVA-SNs were characterized by means of fourier transformation spectroscopy (FTIR), transmission electron microscopy (TEM) and elemental analysis method. Effects of silica nanoparticles on viscosity and alcoholysis of PVA-SNs were studied by an ubbelohode capillary viscometer and back titration method. The morphological structure of PVA-SNs film was investigated by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile test were used to determine the thermal and mechanical properties of PVA-SNs films. The results indicated that the content of vinyl group on the surface of the vinyl silica nanoparticles was up to 3.02 mmol/g and vinyl silica nanoparticles had been successfully copolymerized with vinyl acetate. Furthermore, compared to pure PVA, silica nanoparticles bonded with polymer matrix in low concentration affected the viscosity and alcoholysis of the PVA-SNs materials. At the same time, it resulted in the improvement of the thermal and mechanical properties of the PVA-SNs materials due to strong interaction between silica nanoparticles and polymer matrix via covalent bond. Also, it could be found that optical clarity of membrane was changed through UV-Vis absorption spectrum because of introduction of silica nanoparticles.
Crosslinked Sulfonated Poly(vinyl alcohol)/Graphene Oxide Electrospun Nanofibers as Polyelectrolytes
Nanomaterials, 2019
Taking advantage of the high functionalization capacity of poly(vinyl alcohol) (PVA), bead-free homogeneous nanofibrous mats were produced. The addition of functional groups by means of grafting strategies such as the sulfonation and the addition of nanoparticles such as graphene oxide (GO) were considered to bring new features to PVA. Two series of sulfonated and nonsulfonated composite nanofibers, with different compositions of GO, were prepared by electrospinning. The use of sulfosuccinic acid (SSA) allowed crosslinked and functionalized mats with controlled size and morphology to be obtained. The functionalization of the main chain of the PVA and the determination of the optimum composition of GO were analyzed in terms of the nanofibrous morphology, the chemical structure, the thermal properties, and conductivity. The crosslinking and the sulfonation treatment decreased the average fiber diameter of the nanofibers, which were electrical insulators regardless of the composition. ...
Fabrication and investigation of silica nanofibers via electrospinning
Electrospinning is a versatile and cost-effective method for fabricating nanofibers of different materials suitable for various applications. In this work, silica nanofibers have produced using the electrospinning method followed by the heat treatment. To fabricate silica nanofibers, polyvinylpyrrolidone (PVP), tetraethyl orthosilicate (TEOS) and Butanol were used to prepare the dope solutions. The optimized concentration for polymer in the dope solutions was then measured at 0.1 g/ml. The electrospinning process was conducted under the optimum circumstances of voltage, injection flow, tip to collector distance, ambient temperature (25°C) and the humidity of 47%. Having conducted the thermal analysis (TG/DTA), electrospun fibers were exposed to thermal analysis in three different temperatures of 500, 700, and 1000°C for 5 h. Following this, the morphology and the diameter of the fibers, as well as the chemical composition and the crystallinity of each sample were analyzed using scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), and x-ray diffractometry (XRD), respectively. The noteworthy conditions of 700°C and 5 h of heat treatment (i.e., calcination) have provided satisfactory results in terms of silica nanofibers morphology and fibers; diameter, i.e., 110 and 600 nm. For cytotoxicity assay, murine fibroblast cells L929 were cultured on a mat of as-spun silica nanofibers. After 24 h and 48 h cultivation time, samples showed no evidence of cytotoxicity effect, which will be a promising result.
Journal of Applied Polymer Science, 2009
Poly(vinyl alcohol) (PVOH) was obtained from the alkaline hydrolysis of poly(vinyl acetate) (PVAc). Nonwoven membranes (mats) of PVOH nanofibers were produced by electrospinning of solutions of PVOH in water with and without aluminum chloride. The concentration of the PVOH/water solution was 12.4% w/v. The morphology of the mats was analyzed by scanning electron microscopy (SEM). The thermal properties and the degree of crystallinity of the nanofibers were measured by differential scanning calorimetry (DSC); the crystal structure of the mats was evaluated by wide-angle X-ray diffraction. The best nanofibers were obtained by electrospinning the PVOH/water solution with aluminum chloride (45% w/v) in which an electrical field of 3.0 kV/cm was applied. It was observed that the addition of the aluminum chloride and the increase in the applied electrical field decreased the number-average nanofibers diameters. The mats without aluminum chloride had higher melting temperatures and higher degrees of crystallinity than the mats with the salt. The crystal structure of the mats was found to be monoclinic; however, the mats were neither highly oriented nor have a high degree of crystallinity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Bicomponent aligned nanofibers of N-carboxyethylchitosan and poly(vinyl alcohol)
European Polymer Journal, 2007
Bicomponent nanofibers of N-carboxyethylchitosan (CECh) and poly(vinyl alcohol) (PVA) were obtained by electrospinning of mixed aqueous solutions. The electrospinning of CECh-containing nanofibers was enabled by the ability of PVA to form an elastically deformable entanglement network based on hydrogen bonds. The average diameters of the bicomponent fibers were in the range 100-420 nm. Water-resistant nanofibrous mats were obtained by thermal crosslinking at 100°C for 10 h. Nanofibrous materials with 1D-, 1D-transversery or 3D fiber alignment were obtained depending on the type of the collector used.
Hybrid Carbon Silica Nanofibers through Sol–Gel Electrospinning
Langmuir, 2014
A controlled sol−gel synthesis incorporated with electrospinning is employed to produce polyacrylonitrile−silica (PAN−silica) fibers. Hybrid fibers are obtained with varying amounts of silica precursor (TEOS in DMF catalyzed by HCl) and PAN. Solution viscosity, conductivity, and surface tension are found to relate strongly to the electrospinnability of PAN−silica solutions. TGA and DSC analyses of the hybrids indicate strong intermolecular interactions, possibly between the −OH group of silica and −CN of PAN. Thermal stabilization of the hybrids at 280°C followed by carbonization at 800°C transforms fibers to carbon−silica hybrid nanofibers with smooth morphology and diameter ranging from 400 to 700 nm. FTIR analysis of the fibers confirms the presence of silica in the as-spun as well as the carbonized material, where the extent of carbonization is also estimated by confirming the presence of −CC and −CO peaks in the carbonized hybrids. The graphitic character of the carbon−silica fibers is confirmed through Raman studies, and the role of silica in the disorder of the carbon structure is discussed.