A series of multi-block copolymers, poly(L-lactide)-b-poly (?-caprolactone) (PLLA-b-PCL) were synthesized. The first step of the synthesis consisted of the transesterification between the PLLA and 1,4-Butanediol, followed by the copolymerization of PLLA-diols and PCL, using isophorone diisocyanate (IPDI) as a coupling agent. The synthesized polymers were characterized by Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). PLLA/PCL block copolymers were electrospun into ultrafine fibers. The morphology of the electrospun fibrous scaffolds were investigated by Scanning Electron Microscopy (SEM). Results showed that the morphology and diameter of the fibers were affected by the electrospinning solution concentrationan and different weight ratio of PLLA/PCL. These electrospun PLLA-b-PCL fibrous membranes exhibited good flexibility and deformability. In comparison with the electrospun PLLA membrane, the electrospun fibrous membranes of PLLA-b-PCL demonstrated an enhanced elongation with still high tensile strength and Young's modulus to be beneficial for tissue engineering scaffolds. 相似文献
Composite nanofibrous membranes were prepared by the electrospinning and the thermal treatment from poly(vinylidene fluoride) (PVDF)-tetramethyl orthosilicate (TMOS) blend solutions. The average diameter of nanofibers was reduced with increasing the concentration of TMOS in the solution due to the decrease of the solution viscosity. The EDX spectra confirmed the presence of TMOS on the external surface of the composite nanofibrous membrane. The porosity of membranes was effectively enhanced by the introduction of electrospinning technique. However, the mechanical properties, thermal stability and hydrophobicity were not markedly amplified. Thus the thermal treatment of the composite membranes was carried out, leading to the enormous enhancement of the mechanical properties and hydrophobicity. In addition, XRD results revealed that the crystal structure of PVDF in the composite membranes transformed from α-phase to β-phase due to the formation of silica particles by the thermal treatment. 相似文献
Novel bio-based and biodegradable block copolymers were synthesized by "click" reaction between poly(L-lactide)(PLLA) and polyamide 4(PA4). Upon tuning the molar mass of PLLA block, the properties of copolymers and electrospun ultrafine fibers were investigated and compared with those of PLLA and PA4 blends. PLLA and PA4 were found incompatible and formed individual crystalline regions, along with reciprocal inhibition in crystallization. Electrospun fibers were highly hydrophobic, even if hydrophilic PA4 was the rich component. The crystallinity of either PLLA or PA4 decreased after electrospinning and PLLA-rich as-spun fibers were almost amorphous. Immersion tests proved that fibers of block copolymers were relatively homogeneous with micro-phase separation between PLLA and PA4. The fibrous structures of copolymers were different from those of the fibers electrospun from blends, for which sheath-core structure induced by macro-phase separation between homopolymers of PLLA and PA4 was confirmed by TEM, EDS, and XPS. 相似文献
Polymorphism control of PVDF has been realized through electrospinning. PVDF fibrous membranes with fiber diameter in the range of 100 nm to several micrometers were produced by electrospinning and the crystal phase of electrospun PVDF fibers can be adjusted at the same time. Through the control of electrospinning parameters such as the solvent, electrospinning temperature, feeding rate, and tip‐to‐collector distance, PVDF fibrous membranes containing mainly α‐ or β‐ or γ‐phase could be fabricated successfully.
Three well-defined diblock copolymers of poly(methyl methacrylate-b-methacrylic acid)(P(MMA-b-MAA))were synthesized using atom transfer radical polymerization method and varying poly(methacrylic acid)(PMAA)chain lengths. These copolymers were blended with PVC to fabricate porous membranes via phase inversion process.Membrane morphologies were observed by scanning electron microscopy(SEM),and chemical composition changes of the membrane surfaces were measured by X-ray photoelectron spectroscopy(XPS).Static and dynamic protein adsorption experiments were used to evaluate antifouling properties of the blend membranes.It was found that,the blend membranes containing longer PMAA arm length showed lower static protein adsorption,higher water permeation flux and better protein solution flux recovery. 相似文献
AbstractHydrophilicity-controlled poly(arylene ether sulfone) copolymers with phenolphthalein-based carboxylic acid groups (PES-COOH-X) were synthesized via direct copolymerization by adjusting the feed molar ratio. The chemical structures of the obtained copolymers were confirmed by 1H nuclear magnetic resonance (NMR) spectroscopy. The copolymers showed good solubility in common aprotic solvents and exhibited excellent mechanical properties. The water contact angles of the obtained copolymers could be reduced by approximately 52% from 92.1° to 44.2° with increasing content of phenolphthalein-derived monomer, 2-[bis(4-hydroxyphenyl)methyl] benzoic acid (PPH-COOH), in the feed molar ratio. A series of PES-COOH-X membranes was prepared via a conventional immersion precipitation phase inversion method. The effects of the monomer feed molar ratio on the morphology, hydrophilicity, pure water flux, and water uptake of the prepared membranes were investigated. The results showed that the pure water flux of the PES-COOH-X membranes was significantly enhanced by almost a factor of two as compared to the pristine PES membrane. From the water contact angle data, it was identified that the hydrophilicity of the membranes was increased rapidly with increasing PPH-COOH content in the membranes. These hydrophilicity-controlled poly(arylene ether sulfone) copolymers may be considered as good candidates for separation membrane materials. 相似文献
Summary: In the present study, electrospinning of hyaluronic acid (HA) and hyaluronic acid/gelatin (HA‐GE) blends in N,N‐dimethylformamide (DMF)/water‐mixed solvents have been investigated. When the volume ratio of DMF to water was in the range of 1.5–0.5, HA solutions could be electrospun into fibrous membranes successfully. The average diameter of HA fibers was about 200 nm. The HA‐GE composite nanofibrous membranes with varied HA/GE weight ratio in the range of 100/20–100/100 have also been successfully fabricated. The average diameter of HA‐GE fibers was in the range of 190–500 nm. The decrease in surface tension could promote fiber formation. Thus, an introduction of DMF that could decrease the surface tension distinctively, without significant change or increase in viscosity of the solution, could bypass the use of blowing‐assisted electrospinning. Our postulated picture is that the lower surface tension could help the ejection of stream with relatively high viscosity and reduce or prevent the droplet formation during the spinning process.
HA/GE (100/80) nanofibrous membrane produced by electrospinning. 相似文献
Aligned poly(L-lactide) (PLLA)/poly(?-caprolactone) (PCL)/hydroxyapaite (HA) composite fibrous membranes were fabricated by electrospinning. Their morphology, thermal stability, mechanical properties, hydrophilic properties and biocompatibility were investigated. The electrospun fibers are highly aligned and the HA are oriented along the fiber axis. When HA are incorporated, the PLLA/PCL/HA composite fibers become thinner due to the increased conductivity. In addition, the aligned HA reinforce the electrospun fibrous membranes. The larger porosity and higher hydrophilic properties induced by HA in the electrospun fibers have improved the degradation of the PLLA/PCL/HA fibrous membranes which have no toxic effect on proliferation of adipose-derived stem cells. 相似文献
Aligned poly(L-lactide) (PLLA)/poly(?-caprolactone) (PCL)/poly(ethylene glycol)(PEG) fibrous membranes were fabricated by electrospinning. Their morphology, thermal stability, mechanical properties, hydrophilic properties and in vitro degradation behaviors were investigated. With increasing the content of PEG, the PLLA/PCL/PEG blend fibers become thinner due to the increment in solution conductivity and decrease in solution viscosity. The thermal stability, hydrophilic properties, the tensile strength and elongation-at-break of PLLA/PCL/PEG blend fibrous membranes were improved, but porosity were decreased with the content of PEG changing from 10 wt% to 30 wt%. Furthermore, the incorporation of PEG enhanced the degradation of the PLLA/PCL/PEG fibrous membranes due to the better hydrophilic properties. In addition, the PLLA/PCL/PEG fibrous membranes have no toxic effect on proliferation of adipose-derived stem cells. 相似文献