Copolymer Fibers Research Articles

Development of a locally anesthetizing wound dressing based on eudragit RS ultrathin fibers

It was demonstrated that a locally anesthesizing dressing material based on the amine-containing copolymer Eudragit RS could be prepared by electrospinning. The dependences of the electrical conductivity and dynamic viscosity of binary solutions of Eudragit RS and lidocaine in EtOH on concentration were established. The kinetics of lidocaine release from Eudragit RS fibers into an aqueous medium were determined. The influence of copolymer fiber diameter and content of local anesthetic lidocaine in it on the duration of the release was found. It was shown that the obtained locally anesthesizing dressing material based on Eudragit RS provided timed-release of the drug.

Wetting behaviour and direct observation of thermally responsive polystyrene-block -poly(N -isopropylacrylamide)-block -polystyrene electrospun fibres in aqueous environment

Electrospun fibres of thermally responsive triblock copolymer polystyrene-block-poly(N-isopropylacrylamide)-block-polystyrene were prepared. Fibre morphology and swelling were studied below and above the lower critical solution temperature of poly(N-isopropylacrylamide) (PNIPAM) using cryo-electron microscopy. Cryo-transmission electron microscopy showed that the fibre diameter increased up to 150% after immersion in water at 20 °C. In contrast, at 45 °C the fibre diameter increased considerably less. The sessile drop technique was used to characterize temperature-dependent wetting of fibre mats. Contact angle (θCA) measurements revealed that a block copolymer fibre mat changed from hydrophobic (θCA > 90°) to hydrophilic (θCA < 90°) state within seconds after applying a water droplet on it at 20 °C. At 40 °C the initial contact angle was measured to be higher (135°) and it decreased much less than at 20 °C during the first minute of measurement. We observed using scanning electron microscopy that the electrospun fibres of the block copolymer having 77 wt% of PNIPAM lost their cylindrical shape and changed from fibres to thin sheets at both 20 and 40 °C within seconds after applying water on the fibres. Fibres having 55 wt% of PNIPAM were observed to be stable in water at both 20 and 40 °C, which resulted, surprisingly, in fibre mats with the strongest effects on thermally sensitive wetting. We discuss the surprising results and the implications that the evolution of fibre surface roughness has on the long-term wetting behaviour, demonstrating a self-adaptable hydrophilicity/hydrophobicity nature of the fibre mats. © 2013 Society of Chemical Industry

Enhanced emission efficiency in electrospun polyfluorene copolymer fibers

We report on the unique emission features of light-emitting fibers made of a prototype conjugated polymer, namely, poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1′-3}-thiadiazole)] (F8BT), realized by electrospinning with diameters in the range of 500-1000 nm. The fibers display emission polarized along their axis, evidencing a favoured alignment of the polymer molecules. Emission efficiency and time resolved measurements reveal an enhancement of both the quantum efficiency and the radiative rate (up to 22.5%) of the fibers compared to spin-coated films, shedding more light on their potential as miniaturized photon sources in optoelectronic devices requiring high recombination rates.

Tendon healing and anti-adhesion properties of electrospun fibrous membranes containing bFGF loaded nanoparticles

The ideal scaffolds should contain growth factors and thus can regulate cellular behaviors and tissue assembly. Electrospun fibrous membranes are widely-used scaffolds but growth factors are highly susceptible to losing their bioactivity during the electrospinning process. In this study, pre-formulated dextran glassy nanoparticles (DGNs) loaded with basic fibroblast growth factor (bFGF) were electrospun into a poly-l-lactic acid (PLLA) copolymer fiber to secure the bioactivity of bFGF in a sustained manner and then bioactivity retention was certificated by promoting cell proliferation and tendon healing. Meanwhile, the barrier effect of electrospun membrane was evaluated for clinic concern. In the in vitro release study, the protein encapsulation efficiency of the bFGF/DGNs-PLLA membrane reached 48.71 ± 13.53%, with a release kinetic of nearly 30 days. The enhanced cell proliferation and intrinsic tendon healing show that the bFGF/DGNs-loaded PLLA fibrous membrane can release bFGF sustainably and secure the bioactivity of bFGF better than the emulsion electrospun bFGF-loaded PLLA and PLLA fibrous membranes. Meanwhile, the anti-adhesion effect of electrospun membrane as barrier was fortunately combined as clinic concern.

In situ polymerization and characterization of graphene oxide‐co‐poly(phenylene benzobisoxazole) copolymer fibers derived from composite inner salts

AbstractA facile and efficient strategy for preparing well dispersed graphene oxide (GO)‐co‐Poly(phenylene benzobisoxazole) (PBO) copolymer fibers was carried out by direct in situ polycondensation of composite inner salts. The composite inner salts were achieved to improve the dispersivity, solubility, reactivity, and interfacial adhesion of GO in PBO polymer matrix. The structure and morphology of GO‐co‐PBO copolymer fibers have been characterized. It was demonstrated that GO were covalently incorporated with PBO molecular chains and dispersed considerably well in PBO fiber even the GO reach to 3 wt %. Meanwhile, the tensile modulus, tensile strength and thermal stability of GO‐co‐PBO copolymer fibers increased considerably with GO. The mechanism and theoretical calculation of GO enhanced PBO fiber were also discussed. The main reasons for the improvement on performance of PBO fiber should be attributed to good dispersion GO in PBO matrix and covalent bonding networks at the interface between GO and PBO molecular chains. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

The demonstration of a dense and stable circumferential layer in the subsurface of polyacrylonitrile fibers for carbon fibers

The radial structure of polyacrylonitrile (PAN) copolymer fibers was investigated quantitatively by etching layer by layer in an improved permanganic etchant; meanwhile the effect of the etchant on the fiber surface was taken into consideration. The aggregated structure (crystal size, crystallinity, orientation and density) and thermal stability of each circumferential layer of PAN fibers were determined in detail according to a model proposed in the study. A denser layer with a thickness of about 1 µm was observed in the subsurface (2 µm from the PAN fiber surface), possessing a greater crystal size and crystallinity as well as a relatively higher thermal stability than other layers. This layer was considered to be a barrier for the diffusion of oxygen into PAN fibers during the stabilization and accelerated the formation of a core-shell structure in the resulting carbon fibers.

Catalytic Oxidation of Toluene over Metal Oxides Supported on Fiber Material

Toluene is one of the major pollutants of indoor air pollution. Acrylonitrile-vinylidene chloride (AN-VDC) copolymer fibers containing activated carbon were wet-spun; and loaded with Cu-Mn oxide complex. The morphology and performance of the fiber was characterized using scanning electronic microscope (SEM), X-ray diffraction (XRD). The results show that, Cu-Mn oxide complex is loaded on the surface of the fiber. Cu-Mn oxide complex loaded fibers have a higher removal rate to toluene at room temperature. When the molar ratio of copper manganese reaches 1:5, the removal rate of the fiber is the highest among all, which is up to 81.77% The new material for toluene in indoor air purification has a good theoretical and practical value.

Influence of speciation in the release profiles and antimicrobial performance of electrospun ethylene vinyl alcohol copolymer (EVOH) fibers containing ionic silver ions and silver nanoparticles

In the present study, tailor-made ethylene vinyl alcohol copolymer (EVOH) fibers containing different amounts of antimicrobial silver ions and nanoparticles were developed by electrospinning and subsequent thermal annealing. The morphology of the fibers was examined by scanning and transmission electron microscopy and thermal properties were characterized by differential scanning calorimetry. Speciation and controlled release of silver from the fibers was monitored by anodic stripping voltammetry and energy dispersive X-ray spectroscopy. Before aging, 100 % of the silver recovered from the electrospun structures was in ionic form to be instantly released in contact with moisture with varying temperature-dependent kinetics. Thermal annealing of the fibers at 100 °C for 1, 2, and 4 days prompted the gradual transformation of 70, 93–94, and 98–99 % of the total silver into nanoparticles homogeneously distributed along the fibers, which were mostly retained within them, producing a substantial decrease in their release capacity. Speciation and release profiles from the fibers were correlated with their antibacterial performance against Listeria monocytogenes and Salmonella enteric. This study is a step forward in the understanding of silver-based electrospun antimicrobial polymers and puts forth the suitability of EVOH for the development of targeted delivery systems in a number of applications.

Micro X-ray diffraction mapping of a fluorene copolymer fibre

Using raster-scanning wide-angle X-ray scattering, we investigate oriented fibres of the low bandgap conjugated polymer, poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (F8TBT), that was developed in particular for polymer solar cells. For the first time, structural data are provided for F8TBT. Our results demonstrate that the nano-scale structure of this polymer is closely related to the externally observable features of the fibre, and thus emphasise the importance of having full control over the local molecular conformation. Liquid-crystalline phases are observed at elevated temperatures, and the molecular alignment in the drawn fibres yields scattering patterns that are dominated by broad peaks of equatorial diffuse scattering. The significant degree of preferred orientation facilitates the analysis, leading to estimates of (average) nearest-neighbour packing distances and coherence length of this macromolecule. In particular, we observe a pronounced broad signal assigned to packing of the conjugated backbone with an approximate spacing of 4.00–4.39 Å that is coherent over 5-6 polymer segments.

Effect of hydration on the structures and properties of poly(p-phenylene benzobisoxazole)/poly(pyridobisimidazole) block copolymer fibers

A rigid-rod copolymer, poly( p-phenylene benzobisoxazole)-block-poly(pyridobisimidazole) (PBO-b-PIPD), was synthesized, and the effect of hydration on the structures and performance of the block copolymer fibers was evaluated. PBO and PBO-b-PIPD as-spun fibers (AS-fibers) were prepared by dry-jet wet spinning, and subsequent thermal treatment in a nitrogen atmosphere was performed. Fourier transform infrared and wide-angle X-ray diffraction were used to characterize the structures of the thermally treated fibers. Mechanical properties of both the AS-fibers and thermally treated fibers were tested, and scanning electronic microscopy was used to observe the fracture surfaces of the fibers from tensile testing. It has been revealed that heat treatment is an effective method to remove the absorbed water to improve the orderly arrangement of chains along the fiber direction, which resulted in enhancement of the tensile modulus of the block copolymer fibers.

Synthesis and Characterization of Poly(p-phenylene benzobisoxazole)/Poly(pyridobisimidazole) Block Copolymers

Poly(p-phenylene benzobisoxazole)/poly(pyridobisimidazole) block copolymers (PBO-b-PIPD) were prepared by introducing poly(pyridobisimidazole) (PIPD) moieties into the main chains of poly(p-phenylene benzobisoxazole) (PBO) in order to enhance its photostability. PBO and copolymer fibers were directly prepared from the polymerization solutions by dry-jet wet-spinning. Chemical structures and molecular chains arrangement of the block copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, solid-state 13C-NMR and wide angle X-ray diffraction (WAXD). Thermal stability of the copolymers was investigated by thermogravimetric analysis (TGA) in nitrogen. Thin films of PBO and copolymers were cast from methanesulfonic acid (MSA) solutions. Both the films and fibers were exposed to UV light to determine their photostability. Changes in the chemical structures and surface morphologies of the films were characterized by FTIR spectra and scanning electronic microscopy (SEM), respectively. After UV light exposure, the retention of strength for copolymer fibers is improved compared to PBO fibers. The results revealed that copolymers suffered less photodegradation in comparison with homopolymer. The mechanism for the improved photostability of the copolymers was discussed.

Analysis of environmental impact on mechanical properties of aramid filaments

Aramid and aramid copolymer fibres are used in a wide variety of military and civilian applications; however, the effects of environmental exposure on mechanical properties are still not well understood. This paper analyzes the changes of Aramid 1414’s mechanical properties after its exposure to high temperatures, chemical solvents and sunlight, and then compares them with the properties of poly ( p-phenylene benzobisoxazole) as-spun and polysulfonamide fibres. The experimental results suggest that the overall environmental resistant performance of aramid filaments is better than poly ( p-phenylene benzobisoxazole) as-spun and polysulfonamide materials, some conclusions are put forward for the applications of aramid filaments.

One-pot preparation and continuous spinning of carbon nanotube/poly(p-phenylene benzobisoxazole) copolymer fibers

Poly(p-phenylene benzobisoxazole) (PBO) fibers are some of the strongest organic polymer fibers, however, even stronger fibers can be made using carbon nanotubes (CNTs). In the present study, the copolymerization of functionalized CNTs with PBO was successfully carried out by one-pot in situ polycondensation in polyphosphoric acid. Pristine CNTs were first oxidized to CNT–COOH and then modified by 4,6-diaminoresorcinol (DAR) or PBO trimer (DAR–TA–DAR) to improve the reactivity, solubility, dispersivity, and interfacial adhesion of CNTs in polymer matrix. Functionalized CNTs were further covalently incorporated with PBO through in situ polymerization. The chemical structure and morphology of functionalized CNTs and CNT–PBO copolymers were well characterized for confirming the formation of covalent bond between CNTs and PBO. Moreover, continuous CNT–PBO copolymer fibers have been fabricated using a dry-jet wet-spinning technique. The structure and morphology of CNT–PBO copolymer fibers have been characterized and their mechanical and thermal properties have been investigated. The tensile modulus, tensile strength, and thermal stability of CNT–PBO copolymer fibers have been improved. The improvement in PBO molecular chain packing order, the good dispersion and high alignment of CNTs in the PBO matrix, and the covalent bonding at the CNT–PBO interface have been suggested as the main reasons for the performance improvement of PBO.

Preparation Bi 2S 3–TiO 2 heterojunction/polymer fiber composites and its photocatalytic degradation of methylene blue under Xe lamp irradiation

This paper presented the preparation of Bi 2S 3–TiO 2 heterojunction/polymer fiber composites and their performance of the degradation of methylene blue using Xe lamp irradiation. The polysulphone (PSU)/styrene-maleic anhydride copolymer (SMA) fibers were prepared by electrospinning. Bismuth ions were introduced onto the surface of polymer fiber by the coordinating of carboxyl of SMA, sulfide ions were incorporated to react with bismuth ions under hydrothermal condition. TiO 2 was deposited on the surface of the Bi 2S 3 by the reaction of titanium ions with urea also under hydrothermal condition. Scanning electron microscopy (SEM) and high resolution transmission electron microscope (HRTEM) images revealed that Bi 2S 3–TiO 2 heterojunction was uniformly distributed on the surface of PSU/SMA fibers. The ultraviolet–visible absorption spectra (UV/VIS) showed that the Bi 2S 3–TiO 2 heterojunction/polymer fiber composites possess good visible-light response ability. The degradation rate of methylene blue in Bi 2S 3–TiO 2 heterojunction/polymer fiber composites system was considerably higher than that of Degussa P25 or Bi 2S 3–TiO 2 heterojunction system under Xe lamp irradiation.

Kinetics Modeling and Mechanism of Organic Matter Absorption in Functional Fiber Based on Butyl Methacrylate-Hydroxyethyl Methacrylate Copolymer and Low Density Polyethylene

Functional fiber based on butyl methacrylate-hydroxyethyl methacrylate copolymer and low density polyethylene was prepared via the method of gelation-spinning, and then the kinetics model and mechanism of organic matter absorption into the functional fiber were investigated. The results show that a lot of microvoids are constructed within the cross section of the functional fiber, but the microvoids do not make a significant contribution to the absorption of organic matter. The functional fiber can absorb toluene at a quick rate, while it can absorb trichloroethylene and chloroform at a relatively slower rate. The swelling capability of the blend fiber in selected organic matter is weaker than the one of butyl methacrylate-hydroxyethyl methacrylate copolymer fiber, and the swelling behavior is controlled by stress relaxation in the amorphous portion of the polymer blend network. Furthermore, second-order kinetics model is more suitable for describing the process of organic matter absorption than first-order kinetics model.

Preparation, characterization, and properties of fullerene-vinylpyrrolidone copolymers

Water-soluble fullerene (C(60))-N-vinylpyrrolidone copolymers were prepared by the radical polymerization method. The structures of the copolymers were characterized by Fourier transform infrared, UV-Vis, (1)H NMR, (13)C NMR, gel permeation chromatography, thermogravimetric analyses, and scanning electron microscopy (SEM). The results presented show that C(60) and vinylpyrrolidone (VP) can be copolymerized under different conditions. With a constant benzoyl peroxide amount, C(60) contents in the copolymers increase with increasing initial C(60):VP reactant ratio. The assembly behavior of water-soluble C(60)-N-vinylpyrrolidone copolymers was investigated by SEM. The results show that the copolymers create morphology that is sphere-like. Fullerene-containing micro-/nano-sized copolymer fibers were prepared, for the first time, by electrospinning. The cytotoxicity to cancer cell lines of the copolymers was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and confocal laser scanning microscope. The results show that copolymers exhibit better cytotoxicity against HeLa cells and mouse osteogenic sarcoma cells (cytotoxicity of copolymers is better than that of fullerene complex). The mechanism of fullerene-VP copolymerization was investigated for the first time.

Stretching-induced deformation of polyacrylonitrile chains both in quasicrystals and in amorphous regions during the in situ thermal modification of fibers prior to oxidative stabilization

In situ thermal stretching to modify the conformation of polyacrylonitrile (PAN) chains in quasicrystals and amorphous regions is carried out on PAN copolymer fibers prior to oxidative stabilization. Meanwhile, a model to evaluate the deformation of PAN quasicrystals and amorphous regions is proposed, in which deformation behavior (orientation or extension) and type (elastic or plastic) in the two regions are analyzed. PAN chains exhibit various deformations as a consequence of combined thermal treatment and mechanical stretching. The orientation of PAN chains occurs prior to their extension when the stretching ratio is under 1.06, however, no significant orientation but extension is observed when the deformation ratio ranges from 1.08 to 1.16. As the stretching ratio increases, elastic-dominated orientation of PAN chains is stronger in quasicrystals before 1.03 and is prominent in amorphous regions between 1.04 and 1.08. The mechanical properties of the resulting carbon fibers strongly depend on the orientation degree of PAN chains in amorphous regions.

Influence of Benzoic Acid End-Capping on Properties of Poly( &lt;i&gt;Ester-Imide-Ether&lt;/i&gt;) Block Copolymer and its Fiber

A type of benzoic acid end-capped ploy(ester-imide-ether) (PEIE) block copolymers was synthesized by melt polycondensation from polytetrahydrofuran diol (PTMG), 1,4-butanediol (BD), benzoic acid (BA) and a diacid monomer which was synthesized of trimellitic anhydride (TMA) with para aminobenzoic acid (PABA). The structures and properties of the copolymers were investigated by FT-IR spectroscopy and Ubbelohde viscometer, DSC and TGA. Some properties of the copolymer fibers such as breaking strength, breaking elongation and elasticity were also measured. The result demonstrated that the adding of BA can effectively reduce the inherent viscosities of PEIE. Especially the breaking strength, elastic recovery and heat stability of the fibers are improved obviously when adding 1 % (of the multiblock copolymer weight percentage) BA end capping agent.

Electrospinning and cutting of ultrafine bioerodible poly(lactide‐co‐ethylene oxide) tri‐ and multiblock copolymer fibers for inhalation applications

AbstractTriblock copolymers made up of poly(ethylene oxide) (PEO) and polylactide (PLA) were synthesized and converted to fibers by the electrospinning process. A two‐step in situ‐synthesis in bulk was applied to extend PLA‐PEO‐PLA triblock copolymers with relatively short block length and low molecular weight in order to obtain electrospinnable materials. DL‐lactide was polymerized to the hydroxyl chain ends of PEO via the stannous octoate route. Hexamethylene diisocyanate (HDI) was added as chain extender in the second step, leading to poly(ether‐ester‐urethane) multiblock copolymers. The materials were electrospun from solutions in chloroform. Different concentrations and voltages were analyzed. The ether and ester blocks were varied in their block length and their effects on the fiber morphology was studied. Variations in the electrical conductivity of the chloroform solutions were investigated by adding triethyl benzyl ammonium chloride (TEBAC) in different amounts. Finally, with high quality electrospun PLA‐PEO‐PEO triblock copolymer fibers mechanical cutting was possible. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Swelling Parameters and Mechanical Properties of Functional Fibers Based on Butyl Methacrylate-Hydroxyethyl Methacrylate Copolymer

Butyl methacrylate-hydroxyethyl methacrylate (BMA-HEMA) copolymers were synthesized by the method of suspension polymerization. The copolymer fibers were prepared for absorbing liquid organic matter by gelation-spinning in a twin screw extrusion machine. The swelling parameters and mechanical properties were investigated, and the morphology was observed by scanning electron microscope (SEM). The results show that the degree of equilibrium swelling for the fibers increased with increasing the mass fraction of HEMA in the monomer feed when toluene, trichloroethylene, or chloroform were selected as organic absorbates. All of the interaction parameters, χ 1, for the fibers and organic liquids were less than 0.5, with the order of the interaction parameters χ 1 being as follows: toluene > trichloroethylene > chloroform. Average molecular weights between crosslink points, M c, and effective crosslink density, V e, were dependent on the selected organic liquids; for the different organic liquids, M c and V e were different. The breaking tenacity, initial modulus, and yield stress of the fibers increased with an increase in the mass fraction of HEMA. However, elongation at break and elongation at yield decreased with increasing the mass fraction of HEMA; in particular, for the mass fraction of HEMA equal to 15 wt%, the fiber did not yield, and underwent a brittle fracture.