Using an additive to control the electrospinning of fibres of poly(ε‐caprolactone)

Electrospinning is a route to polymer fibres with diameters considerably smaller than available from most fibre‐producing techniques. We explore the use of a low molecular weight compound as an effective control additive during the electrospinning of poly(ε‐caprolactone). This approach extends the control variables for the electrospinning of nanoscale fibres from the more usual ones such as the polymer molecular weight, solvent and concentration. We show that through the use of dual solvent systems, we can alter the impact of the additive on the electrospinning process so that finer as well as thicker fibres can be prepared under otherwise identical conditions. As well as the size of the fibres and the number of beads, the use of the additive allows us to alter the level of crystallinity as well as the level of preferred orientation of the poly(ε‐caprolactone) crystals. This approach, involving the use of a dual solvent and a low molar mass compound, offers considerable potential for application to other polymer systems. Copyright © 2010 Society of Chemical Industry     

Preparation and characterization of a Bacterial cellulose/Chitosan composite for potential biomedical application

Bacterial cellulose (BC)/Chitosan (Ch) composite has been successfully prepared by immersing wet BC pellicle in Ch solution followed by freeze-drying process. The morphology of BC/Ch composite was examined by scanning electron microscope (SEM) and compared with pristine BC. SEM images show that Ch molecules can penetrate into BC forming three-dimensional multilayered scaffold. The scaffold has very well interconnected porous network structure and large aspect surface. The composite was also characterized by Fourier transform infrared spectrum, X-ray diffraction, thermogravimetric analysis and tensile test. By incorporation of Ch into BC, crystallinity tends to decrease from 82% to 61%, and the thermal stability increases from 263 °C to 296 °C. At the same time, the mechanical properties of BC/Ch composite are maintained at certain levels between BC and Ch. The biocompatibility of composite was preliminarily evaluated by cell adhesion studies. The cells incubated with BC/Ch scaffolds for 48 h were capable of forming cell adhesion and proliferation. It showed much better biocompatibility than pure BC. Since the prepared BC/Ch scaffolds are bioactive and suitable for cell adhesion, these scaffolds can be used for wound dressing or tissue-engineering scaffolds.     

苎麻纤维增强聚碳酸亚丙酯复合材料的工艺与性能研究

采用苎麻纤维和聚碳酸亚丙酯制备了可降解复合材料,讨论了苎麻长度、含量对苎麻/聚碳酸亚丙酯复合材料机械性能的影响,并借助扫描电子显微镜对复合材料的冲击断口形貌进行了观察.结果表明:苎麻经碱液处理后,苎麻/聚碳酸亚丙酯复合材料的拉伸性能和冲击性能有了明显提高.     

Surface‐active amphiphilic poly[(2‐acrylamido‐2‐methylpropanesulfonic acid)‐co‐(N‐isopropylacrylamide)] nanoparticles as stabilizer in aqueous emulsion polymerization

This work reports the effect of nanogel solid particles on the surface and interfacial tension of water/air and water/styrene interfaces. Moreover, the work aimed to use nanogels as a stabilizer for miniemulsion aqueous polymerization. A series of amphiphilic crosslinked N‐isopropylacrylamide (NIPAm) and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) copolymer nanogels were synthesized based on an aqueous copolymerization batch method. Divinylbenzene and N,N‐methylene bisacrylamide were used as crosslinkers. The morphologies of the prepared nanogels were investigated using transmission and scanning electron microscopies. The lower critical transition temperatures were determined using differential scanning calorimetry. The surface tension of colloidal NIPAm/AMPS dispersions was measured as functions of surface age, temperature and the morphology of the NIPAm/AMPS nanogels. The NIPAm/AMPS nanogels reduced the surface tension of water to about 30.1 mN m^?1 at 298 K with a small increase at 313 K. Surface activities of these nanogels in water were determined by surface tension measurements. The NIPAm/AMPS dispersions had high surface activity and were used as a stabilizer to prepare a crosslinked poly(styrene‐co‐AMPS) microgel based on emulsion crosslinking polymerization. © 2013 Society of Chemical Industry     

Preparation of thermoresponsive poly(N-vinylcaprolactam-co-2-methoxyethyl acrylate) nanogels via inverse miniemulsion polymerization

Stimuli-responsive polymeric nanogels hold great potential in biological applications. In this work, thermoresponsive polymeric nanogels were conveniently prepared through inverse miniemulsion polymerization of two monomers with a good biocompatibility, N-vinylcaprolactam and 2-methoxyethyl acrylate. A macromolecular crosslinker, poly(ethylene glycol) dimethacrylate (PEGDMA), was used to achieve a better thermoresponsiveness, compared with low-molecular-weight crosslinkers. The prepared poly(N-vinylcaprolactam-co-2-methoxyethyl acrylate) (poly(NVCL-co-MEA)) nanogels could be well redispersed in aqueous systems, displaying a reversible thermoresponsive transition behavior. The influences of the synthesis parameters including the emulsifier content, PEGDMA content, and monomer composition on the particle properties of poly(NVCL-co-MEA) nanogels both in inverse emulsions and in aqueous dispersions were systematically investigated. Furthermore, the impacts of the monomer composition and PEGDMA content on the thermoresponsiveness of poly(NVCL-co-MEA) nanogels were also studied. Promisingly, the introduction of MEA monomeric units to the copolymer chains only slightly reduced the thermoresponsiveness of poly(NVCL-co-MEA) nanogels. This feature allows to improve the biocompatibility of polymeric nanogels by using MEA as the comonomer without need to compromise the thermoresponsiveness of nanogels. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48237.     

基于静电纺丝技术的PLGA载药纳米纤维膜的制备工艺

同轴静电纺丝法制备的聚乳酸-乙醇酸(PLGA)纳米纤维具有良好的生物相容性和生物可降解性, 加之其高孔隙率和高透氧率, 使其能成为优良的药物载体。本文初步摸索了PLGA的同轴静电纺丝的工艺条件, 并通过同轴静电纺丝法制备了PLGA载氟比洛芬酯(FA)的纳米纤维膜, 应用扫描电子显微镜、红外光谱分析观察纤维的表观形貌并确定其微观结构。重点探究了不同溶剂配比的混合溶剂对载药纤维膜药物释放性能影响。研究结果表明在U⁺为+15.00kV, U^-为-2.50kV, 接受距离为15cm, 壳层推进速度为0.4mm/min, 芯层推进速度为0.1mm/min进行静电纺丝时, 所制备的PLGA(壳)/PVP+FA(核)复合载药纤维膜壳核结构良好, 且成功载了约0.5%的FA。当改变壳层混合溶剂(DCM和DMF)和芯层混合溶剂(无水乙醇和DMF)体积比时, 纤维直径会随着DMF的减少而增大。     

Use of modified poly(ϵ‐caprolactone) in the compatibilization of poly(ϵ‐caprolactone)/maize starch blends

In this work, the compatibilization of a poly(?‐caprolactone) with a number‐average molecular weight of 120,000 g/mol (PCL¹²⁰) and maize starch was investigated by the addition of a chemically modified poly(?‐caprolactone). Two types of blends were prepared by melt extrusion. In type A blends, low‐molecular‐weight compatibilizers were used: (1) a poly(?‐caprolactone) with a number‐average molecular weight of 10,000 g/mol that was reacted with maleic anhydride to obtain chains terminating in carboxylic groups and (2) low‐molecular‐weight poly(?‐caprolactone)s (number‐average molecular weights of 600 and 2000 g/mol) with one pendant carboxylic group within the chains. With these groups of blends, tensile testing and scanning electron microscopy demonstrated that the compatibilizers were generally effective in inducing a better dispersion for a 60/40 poly(?‐caprolactone)/maize starch blend with a compatibilizer, improving the mechanical properties in comparison with uncompatibilized blends. The blends with 30% starch were not improved by the addition of compatibilizer, and this may be related to the rheology of the blends during preparation. In type B blends, high‐molecular‐weight compatibilizers were prepared through the grafting of variable amounts of acrylic acid or maleic anhydride to PCL¹²⁰ chains. The best compatibilizer action was obtained with 0.7 wt % maleic anhydride grafted to PCL¹²⁰ because both the dispersion and mechanical properties were further improved in comparison with uncompatibilized blends and type A blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of alkali treatment on properties of unidirectional isora fibre reinforced epoxy composites

Abstract

Unidirectional isora fibre reinforced epoxy composites were prepared by compression moulding. Isora is a natural bast fibre separated from Helicteres isora plant by retting process. The effect of alkali treatment on the properties of the fibre was studied by scanning electron microscopy (SEM), IR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Mechanical properties such as tensile strength, Young's modulus, flexural strength, flexural modulus and impact strength of the composites containing untreated and alkali treated fibres have been studied as a function of fibre loading. The optimum fibre loading for tensile properties of the untreated fibre composite was found to be 49% by volume and for flexural properties the loading was optimised at ～45%. Impact strength of the composite increased with increase in fibre loading and remained constant at a fibre loading of 54·5%. Alkali treated fibre composite showed improved thermal and mechanical properties compared to untreated fibre composite. From dynamic mechanical analysis (DMA) studies it was observed that the alkali treated fibre composites have higher E' and low tan δ maximum values compared to untreated fibre composites. From swelling studies in methyl ethyl ketone it was observed that the mole percentage of uptake of the solvent by the treated fibre composites is less than that by the untreated fibre composites. From these results it can be concluded that in composites containing alkalised fibres there is enhanced interfacial adhesion between the fibre and the matrix leading to better properties, compared to untreated fibre composites.     

Biodegradable hollow microfibres to produce bioactive scaffolds

Biodegradable hollow microfibres containing particles loaded with specific active agents can be potentially employed to produce a special kind of substrate for tissue engineering, able to function as a scaffold and at the same time to act as a drug‐releasing system. Biodegradable hollow microfibres based on poly(lactic acid) were produced by a dry–wet spinning procedure. Drug‐loaded microparticles were prepared by a simple oil‐in‐water emulsion and entrapped inside the fibres. The morphology of both fibres and particles was investigated by scanning electron microscopy. The mechanical and thermal properties of the fibres were investigated by tensile tests and differential scanning calorimetry. In vitro tests were performed to evaluate the release of the drug from the fibres loaded with the particles Copyright © 2004 Society of Chemical Industry     

Properties and phase segregation of crosslinked PCL‐based polyurethanes

Polyurethane (PU) films were prepared from different types of poly(ε‐caprolactone) glycols and hexamethylene diisocyanate without using any other ingredients such as solvent, catalyst, or chain extender. Polymers were stabilized by crosslinking formed as allophanate and/or biuret linkages during the curing process. The effects of different components on the product properties such as chemical structure, microphase segregation, mechanical strength, thermo‐mechanical, thermal properties, and surface hydrophilicities were investigated by FTIR‐ATR, atomic force microscope, mechanical tester, dynamic mechanical analyses, thermogravimetric analyzer, differential scanning calorimetry, and contact angle measurements. Phase separation of hard and soft segments significantly varied depending on the type and molecular weight of diol and triol. Films containing urethane‐urea bonds displayed the maximum phase separation and the highest mechanical strength. Polyols having higher molecular weight increased hydrophilicity while urea bonds caused a reverse effect resulted by bidentate hydrogen bonds. Results showed PUs with various properties can be synthesized via environmentally friendly process without using any solvent or catalyst. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39758.     

Preparation of poly(ε‐caprolactone)/poly(ε‐caprolactone‐co‐lactide) (PCL/PLCL) blend filament by melt spinning

Poly(ε‐caprolactone)/poly(ε‐caprolactone‐co‐lactide) (PCL/PLCL) blend filaments with various ratios of PCL and PLCL were prepared by melt spinning. The effect of PLCL content on the physical properties of the blended filament was investigated. The melt spinning of the blend was carried out and the as spun filament was subsequently subjected to drawing and heat setting process. The addition of PLCL caused significant changes in the mechanical properties of the filaments. Crystallinity of blend decreased with the addition of PLCL as observed by X‐ray diffraction (XRD) and differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) revealed that the fracture surface becomes rougher at higher PLCL content. It may be proposed that PCL and PLCL show limited interaction within the blend matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Biodegradable hollow fibres containing drug‐loaded nanoparticles as controlled release systems

A ‘multiple’ delivery system was studied, consisting of hollow microfibres containing drug‐loaded nanoparticles. Both fibres and nanoparticles are made of biodegradable polymers, so that the system does not need any surgical operation to be removed. The main advantage of the system is that it allows the contemporaneous release of different kinds of drugs. Copolymers of poly(lactic acid) and ?‐caprolactone were used for the preparation of the fibres through both wet and dry–wet spinning procedures. Two types of nanoparticles, gelatin and poly(DL ‐lactide‐co‐glycolide) nanoparticles, were prepared by simple water‐in‐oil and oil‐in‐water emulsions, respectively. Drugs such as dexamethasone and methotrexate were used to load the particles. The technique employed for the preparation of the nanoparticles filled fibres was described and the drug release characteristics of this system were investigated and compared with those of the free nanoparticles. © 2002 Society of Chemical Industry     

Effect of noncovalent chemical modification on the electrical conductivity and tensile properties of poly(methyl methacrylate)/carbon nanotube composites

Noncovalent chemical modification by initiated chemical vapor deposition technique is applied to carbon nanotubes (CNTs) to reduce average agglomerate size of the nanoparticles in the polymer matrix and to improve surface interaction between the composite constituents. CNT surfaces are coated conformally with thin poly(glycidyl methacrylate) (PGMA) polymer film and coated nanoparticles are incorporated in poly(methyl methacrylate) (PMMA) polymer matrix using solvent casting technique. Conformal PGMA coatings around individual nanotubes were identified by scanning electron microscopy analysis. Transmission electron microscopy and optical microscopy analyses show homogeneous composite morphology for composites prepared by using PGMA coated nanotubes. Fourier Transform Infrared and X‐ray photoelectron spectroscopy analyses show the successful deposition of polymer with high retention of epoxide functionality. PGMA coating of CNTs exhibits improvement in electrical conductivity and tensile properties of PGMA‐CNT/PMMA systems when compared with uncoated nanoparticles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Improved properties of molecular composite of nitrile rubber and poly (p-phenylene terephthalamide) by blending with poly (vinyl chloride)

Summary Nitrile rubber (NBR) was reinforced by poly(p-phenylene terephthalamide) (PPTA) with a coprecipitation method from a common solvent of them. PPTA was converted to N-sodium PPTA with sodium hydride in DMSO, forming homogeneous solution. DMF dissolves NBR. Both solutions were blended to form an isotropic solution. The precipitant was NBR reinforced by PPTA which was regenerated from N-sodium PPTA at coagulation as reported previously. The molecular composite thus obtained was mill-blended with poly(vinyl chloride) (PVC) in order to enhance solvent resistant property. The vulcanized composite of NBR/PVC reinforced by PPTA showed higher modulus, higher strength and more improved solvent resistance than the gum stock and the black stock of NBR/PVC. The properties of the molecular composite containing 5phr PPTA found approximately comparable to those of the black stock of NBR/PVC with 30–40phr ISAF carbon black.On Leave from Japan synthetic Rubber Co., Ltd., Higashi-yurigaoka, Assao-ku, Kawasaki 215, Japan     

Preparation and characterization of poly (vinyl chloride)-blend-poly (carbonate) heterogeneous cation exchange membrane: Investigation of solvent type and ratio effects

In this research polyvinylchloride/polycarbonate blend heterogeneous cation exchange membranes were prepared by solution casting technique using cation exchange resin powder as functional groups agent. Tetrahydrofuran (THF) and dimethylformamide (DMF) were utilized as solvents. The effect of solvent type and ratio (THF/DMF mixture) on properties of prepared membranes was studied. SEM and SOM images showed relatively uniform particle distribution and also uniform surface for the membranes. Images showed that at high DMF ratio decrease of polymer conformation with particles surface reduces the compatibility of polymer-particle. The membrane ion exchange capacity and permeability were enhanced initially by increase of DMF ratio up to 5% (v/v) in casting solution and then they began to decrease with more DMF ratio. Results showed that membrane potential, transport number, selectivity and thermal stability all were decreased by DMF ratio increasing. Conversely, membrane water content, specific surface area and roughness showed opposite trends. Membrane electrical resistance initially declined by increase in DMF content up to 15% (v/v) and then it began to increase. The increase of electrolyte concentration also led to decrease in membrane transport number and selectivity. Membrane with (95:5) (v/v) solvent ratio (THF:DMF) exhibited more appropriate performance compared to others.     

Influence of the coagulation‐bath temperature on the phase‐separation process of poly(vinylidene fluoride)‐graft‐poly(N‐isopropylacrylamide) solutions and membrane structures

A poly(vinylidene fluoride)‐graft‐poly(N‐isopropylacrylamide) (PVDF‐g‐PNIPAAm) copolymer was synthesized, and flat‐sheet membranes were prepared via the phase‐inversion method with N,N‐dimethylformamide (DMF) as the solvent and water as the coagulation bath. The effects of the coagulation‐bath temperature on poly(vinylidene fluoride) (PVDF)/DMF/water and PVDF‐g‐PNIPAAm/DMF/water ternary systems were studied with phase diagrams. The results showed that the phase‐separation process could be due to the hydrophilicity/hydrophobicity of poly(N‐isopropylacrylamide) at low temperatures, and the phase‐separation process was attributed to crystallization at high temperatures. The structures and properties of the membranes prepared at different coagulation‐bath temperatures were researched with scanning electron microscopy, porosity measurements, and flux measurements of pure water. The PVDF‐g‐PNIPAAm membranes, prepared at different temperatures, formed fingerlike pores and showed higher water flux and porosity than PVDF membranes. In particular, a membrane prepared at 30°C had the largest fingerlike pores and greatest porosity. The water flux of a membrane prepared in a 25°C coagulation bath showed a sharp increase with the temperature increasing to about 30°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterization of nano-structured poly(ε-caprolactone) nonwoven mats via electrospinning

Nano-structured poly(ε-caprolactone) (PCL) nonwoven mats were prepared by electrospinning process. In this study, three types of solution were used. One dissolved in only methylene chloride (MC), the second dissolved in mixture of MC and N,N-dimethylformamide (DMF), the third dissolved in mixture of MC and toluene. MC, toluene and DMF are a good, poor, and nonsolvent for PCL, respectively. For the MC only, electrospun fibers had very regular diameter of about 5500 nm, but electrospinng is not facilitated. For the mixture of MC and DMF, electrospinning is certainly enhanced as well as fiber diameter decreased dramatically as increasing DMF volume fraction. It was due to high electric properties of solution such as dielectric constant and conductivity. Whereas, as increasing toluene volume fraction, electrospinning is strictly restricted due to very high viscosity and low conductivity. As the results, it has regarded that solution properties is one of the important parameter in electrospinning. Properties such as conductivity, surface tension, viscosity and dielectric constant of the PCL solutions prepared from three types of solvent system were studied. The morphology, crystallinity and mechanical properties of electrospun PCL nonwoven mats were characterized by scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and universal testing method (UTM), respectively.     

Poly[N-(2-hydroxypropyl)methacrylamide-block-n-butyl acrylate] micelles in water/DMF mixed solvents

Three diblock copolymers of poly[N-(2-hydroxypropyl)methacrylamide] (poly(HPMA)) and poly(n-butyl acrylate) (poly(BA)) with varying lengths of blocks were prepared by atom transfer radical polymerization. All copolymers were found to be soluble in dimethylformamide (DMF) and poorly soluble or insoluble in water. In water and mixed DMF/H₂O solvents, the copolymers were dispersed in micellar form by controlled addition of water to DMF solutions of copolymers under continuous intensive stirring. The micellar solutions in water were prepared by dialysis of solutions in DMF/H₂O (95 vol% of H₂O) against water. Solution properties of diblock copolymers of poly(HPMA) and poly(BA) were studied using static and dynamic laser light scattering to characterize the behavior of the copolymers at the supramolecular level. The effects of preparation mode, organic solvent (DMF) and copolymer chemical composition on the formation of micelles were studied. While a slower mixing procedure was optimal for copolymers with short poly(HPMA) blocks, a faster mixing was more suitable for copolymers having longer poly(HPMA) blocks. Finally, the dimensions of micelles in water were evaluated. The most compact micelles were prepared from copolymers having short hydrophilic poly(HPMA) blocks. On the other hand, the copolymer with the longest poly(HPMA) block formed micelles with the smallest size and the lowest density.     

聚乙烯-乙烯醇/TiO2共混非织造布的制备及其表征

通过高压静电纺丝技术,以异丙醇/水为混合溶剂,通过TiO2共混改性,制备了不同二氧化钛含量的聚乙烯-乙烯醇(EVOH)/二氧化钛(TiO2)非织造布,通过扫描电子显微镜、X-射线衍射(XRD)对其微观形貌、结晶性能进行了研究,并分析了相对面电阻和吸碱率与TiO2共混量的关系。结果表明:经TiO2共混改性后,纤维中有白色团状突起出现,有实心纤维和空心纤维两种形貌;XRD分析表明,随着TiO2含量的增加,EVOH/TiO2非织造布的结晶度越来越低;非织造隔膜的吸碱率最大可达到950%。     

Influence of casting conditions on the properties of sulfonated poly(ether ether ketone ketone)/phosphotungstic acid composite proton exchange membranes

The sulfonated poly(ether ether ketone ketone)/phosphotungstic acid (SPEEKK/PWA) composite membranes were researched for proton exchange membranes. The effect of casting condition on the properties of membranes was studied in detail. The study showed that the casting condition has great influence on the membrane properties because of the hydrogen bond between the SPEEK and PWA and the interaction between the SPEEKK and dimethylformamide (DMF). The PWA particles are well crystallized on the surface when the velocity of the solvent volatilization is very slow under the SEM. The study will favor further research on excellent composite membranes for proton exchange membrane fuel cells. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4020–4026, 2007