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Clinical utility of small-diameter vascular grafts is still challenging in blood vessel regeneration owing to thrombosis and intimal hyperplasia. To cope with the issues, modulation of gene expression via microRNAs (miRNAs) could be a feasible approach by rational regulating physiological activities of both vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). Our previous studies demonstrated that individually loaded miRNA-126 (miR-126) or miRNA-145 (miR-145) in the electrospun membranes showed the tendency to promote vascular regeneration. In this work, the bilayered electrospun graft in 1.5-mm diameter was developed by emulsion electrospinning to dual-load miR-126 and miR-145 for target regulation of both VECs and VSMCs, respectively. Accelerated release of miR-126 was achieved by introducing poly(ethylene glycol) in the inner electrospun poly(ethylene glycol)-b-poly(l-lactide-co-caprolactone) ultrafine fibrous membrane, reaching 61.3 ± 1.2% of the cumulative release in the initial 10 days, whereas the outer electrospun poly(l-lactide-co-glycolide) membrane composed of microfibers fulfilled prolonged release of miR-145 for about 56 days. In vivo tests suggested that dual-loading with miR-126 and miR-145 in the bilayered electrospun membranes could modulate both VECs and VSMCs for rapid endothelialization and hyperplasia inhibition as well. It is reasonably expected that dual target-delivery of miR-126 and miR-145 in the electrospun vascular grafts has effective potential for small-diameter vascular regeneration. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 371-382, 2019.

Growing black carbon (BC) emission has become one of the major urgent environmental issues facing human beings. Usually, BC or BC-containing carbon nanoparticles (CNPs) were recognized as non-directly toxic components of atmospheric particulate matter. However, epidemiology studies have provided much evidence of the associations of exposure of particulate-containing carbon particles with cardiovascular diseases. There are still no related studies to support the epidemiological conclusions. Hence, in this article we exposed adult zebrafish to CNPs for 60 days, and then explored the heart location and potential adverse effects on cardiac tissues of these nanosized carbon particles. Our results first showed direct visualization of cardiac endothelial uptake and heart deposition of CNPs in zebrafish. In addition, CNPs caused significant ultrastructural alterations in myocardial tissue and induced the expression of inflammatory cytokines in a dose-dependent manner, resulting in sub-endocardial inflammation and cell apoptosis. Moreover, our data demonstrated the perturbations caused by CNPs on DNA methylation, suggesting that DNA methylome remodeling might play a critical role in CNP-induced cardiotoxicity in zebrafish heart. Therefore, this study not only proved a laboratory link between CNP exposure and cardiotoxicity in vivo, but also indicated a possible toxicity mechanism involved.

Polymers with low surface energy such as silicone and fluoropolymers are widely applied in preparing anti-icing coatings, but they may have some limitations. To improve the anti-icing properties of the coatings, composite coatings were developed by introducing phase-change microcapsules (PCMs). Room temperature vulcanized silicone rubber and a fluorosilicone methacrylate copolymer were examined. Tests involving infrared thermal imaging, icing delay time, and ice shear strength were performed to determine the anti-icing properties of the coatings. It was found that during cooling the composite coatings containing PCMs could release the latent heat of phase change to delay the icing process of water droplets on its surface. The introduction of PCMs increased the surface roughness, and the ice shear strengths of the composite coatings could remain at a low level and ice on the coatings could be easily removed, indicating that PCMs could be practicably applied in anti-icing coatings. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

A method of ultra high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry was developed for the simultaneous quantification of 11 sesquiterpene lactones in 11 Jerusalem artichoke leaf samples harvested in a number of areas at different periods. The optimal chromatographic conditions were achieved on a ZORBAX Eclipse Plus C18 column (3.0 × 150 mm, 1.8 μm) with linear gradient elution of methanol and water in 8 min. Quantitative analysis was carried out under selective ion monitoring mode. All of the sesquiterpene lactones showed good linearity (R2 ≥ 0.9949), repeatability (relative standard deviations < 4.66%), and intra- and interday precisions (relative standard deviations < 4.52%) with an accuracy of 95.24-104.84%. The recoveries measured at three concentration levels varied from 95.07 to 104.87% with relative standard deviations less than 4.9%. The limit of detection and limit of quantitation for this method were 0.89-5.05 and 1.12-44.33 ng/mL, respectively. The results showed that the contents of sesquiterpene lactones varied significantly in the Jerusalem artichoke leaf samples from different areas. Among them, the content of sesquiterpene lactones in the sample collected from Dalian, Liaoning province was the highest and the early flowering period was considered to be the optimal harvest time.

Well-defined magnetic polyelectrolytes with tetrachlorideferrate (FeCl4−) as counter ion are prepared. In this approach, norbornene-based monomer containing ammonium chloride group (TAENDI-Cl) is designed and synthesized. Well-defined magnetic polymers (Poly(TAENDI-FeCl4)) are obtained by ring-opening metathesis polymerization of TAENDI-Cl in the presence of Grubbs third generation catalyst followed by complexing with FeCl3. Magnetic block copolymers are thus prepared. Both the monomer and polymers are paramagnetic as measured by superconducting quantum interference device method. Studies show that the magnetic susceptibility increases with increasing degree of polymerization (DP) and reaches maximum at DP of 100, and then decreases with increasing DP. Block copolymer with lower FeCl4− content shows higher magnetic susceptibility. And, by introducing FeCl4−, the polymers show obviously magnetic responsive in solution, powder, and film which have potential applications in magnetic switching, transport, and separation.

A new compound was synthesized by chemical combination of (3-mercapto)propyl-heptaisobutyl polyhedral oligomeric silsesquioxane (POSS-SH) and 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS) via epichlorohydrin while hydroxyl groups were still retained in the product POSS-DMDBS. The prepared POSS-DMDBS was introduced into isotactic polypropylene (iPP) to improve crystallization behaviors of iPP and obtain nanocomposites with suitable mechanical properties. Crystallization and mechanical properties of iPP/POSS-DMDBS were systematically investigated by wide-angle X-ray diffraction, polarization microscopy, atomic force microscopy, differential scanning calorimetry, and tensile tests. The spherulite size of the modified iPP was obviously decreased with the addition of POSS-DMDBS, while the crystallization temperature was increased by 5°C to 9°C depending on the content of POSS-DMDBS incorporated. POSS-DMDBS exhibited relatively higher nucleating efficiency on iPP which is similar to that of DMDBS, confirmed by the increased crystallization temperature. It was also found that the tensile modulus of iPP after adding POSS-DMDBS increased significantly with respect to pristine iPP, but the elongation values decreased. Introduction of POSS-DMDBS in content less than 1 wt% could bring about effective influence on the crystallization behaviors of iPP, demonstrating its potential applications. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

Airborne fine particulate matter (PM2.5 ) is an "invisible killer" to human health. There is increasing evidence revealing the adverse effects of PM2.5 on the early embryonic development and pregnancy outcome, but the molecular mechanism underlying PM2.5 -induced embryotoxicity is largely unknown. Previous studies have documented that exposure to PM triggers ROS generation, leads to subsequent activation of MAPKs signaling, and results in corresponding cell biological changes including enhanced apoptosis and altered cell cycle in the cardiopulmonary system. Here, we investigated whether ROS-MAPKs-apoptosis/cell cycle arrest pathways play an important role in PM2.5 -induced embryotoxicity using the rat whole embryo culture system. The results showed that PM2.5 treatment led to embryonic growth retardation at concentrations of 50 μg/ml and above, as evidenced by the reduced yolk sac diameter, crown-rump length, head length and somite number. PM2.5 -induced embryonic growth retardation was accompanied by cell apoptosis and G0/G1 phase arrest. Furthermore, ROS generation and subsequent activation of JNK and ERK might be involved in PM2.5 -induced apoptosis and G0/G1 phase arrest by downregulating Bcl-2/Bax protein ratio and upregulating p15INK4B , p16INK4A , and p21WAF1/CIP1 transcription level. In conclusion, our results indicate that ROS-JNK/ERK-apoptosis and G0/G1 arrest pathways are involved in PM2.5 -induced embryotoxicity, which not only provides insights into the molecular mechanism of PM2.5 -induced embryotoxicity, but also may help to identify specific interventions to improve adverse pregnancy outcomes of PM2.5 . © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 2028-2044, 2016.

Low density polyethylene (LDPE)/barium sulfate (BaSO4) composites with different contents of BaSO4 nanoparticles after modification by stearic acid (SA) were prepared. Characterizations of morphology, thermal, and mechanical properties of the LDPE/SA-BaSO4 composites were systematically performed by scanning electron microscope, thermal gravimetric analysis, tensile and flexural tests. Specially, the X-ray radiographic and developable properties were examined by the X-ray fluoroscopy test and the ageing resistant properties were analyzed by the simplified protocol of accelerated aging. It was found that the Young's modulus and tensile strength of the composites were increased by 24.6 and 11.0% while flexural modulus and flexural strength were increased by 10.8 and 14.0%, respectively, together with the elongation at break of 455.1% ± 26.3% which was 74.4% of LDPE when the SA-BaSO4 content reached 25 wt%. By contrast, when accelerated ageing for 5 years, the retention ratios of Young's modulus, tensile strength and elongation remained at 89.3, 69.5, and 69.6%, respectively. In addition, X-ray radiographic and developable properties of the composites were also improved by the addition of SA-BaSO4, making it possible to achieve some applications in medical devices such as intrauterine devices and body brackets which could be easily implanted into human bodies and enable accurate external monitoring using an X-ray medical diagnostic machine. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers

Repair of cartilage-bone interface tissue remains challenging, because it combines different cell types and gradients of composition and properties. To enable simultaneous regeneration of bone, cartilage, and especially their interface, a conically graded scaffold of chitosan-gelatin hydrogel/poly(l-lactide-co-glycolide) (PLGA) was facilely prepared in the study. The chitosan-gelatin hydrogel containing transforming growth factor β1 (TGF-β1) was used for chondrogenesis, while the PLGA scaffold loading bone morphogenetic protein-2 (BMP-2) for osteogenesis. The conically graded transition from the hydrogel to PLGA scaffold and graded variation in amount of growth factors from TGF-β1 to BMP-2 benefited the cartilage-bone interface reconstruction. The graded scaffold exhibited spatio-temporal delivery of TGF-β1 and BMP-2. Preliminary results of in vitro cell culture demonstrated that the hydrogel and PLGA phases could promote bone marrow mesenchymal stem cells toward chondrogenic and osteogenic differentiation, respectively. From the result of the pilot in vivo experiment, it showed that the regenerated hyaline-like cartilage surface and subchondral bone excellently integrated with the native tissues were found by using the TGF-β1 and BMP-2 double-loaded hydrogel/PLGA graded scaffold via H&E and immunohistochemical stainings of collagen I, collagen II, and osteocalcin at 2 months. The obtained preliminary experiment results showed that the hydrogel/PLGA graded scaffold combining multiphasic composition and spatial dual growth-factor delivery would be useful for cartilage-bone interface tissue defect repair.

Poly(l-lactide-co-glycolide) (PLGA) microspheres with diverse internal structures and different release behaviors were prepared via a modified double-emulsion method by introduction of heparin or carboxymethyl chitosan in the inner aqueous phase and calcium chloride in the outer aqueous phase, respectively. The main factors affecting the microsphere morphology were systematically studied, including compositions in the inner aqueous phase, the oily phase, and the outer aqueous phase. The transmission electron microscope images demonstrated that the microspheres are featured with single core, hollow, and multicore structures when their sizes were less than 200 nm, in the range of 200–700 nm, and greater than 700 nm, respectively. In comparison with hollow PLGA microspheres, the PLGA microspheres with heparin and carboxymethyl chitosan in the inner aqueous phase also showed multicore and single core structures, respectively, and exhibited higher loading efficiencies and slower release rates by using bovine serum albumin as a model for bioactive substances. It was concluded that this study provided a facile method to prepare microspheres with single core, multicore, or hollow feature, and the tunability of the different internal structures and related release profiles enables these systems cater to specific requirements for potential applications in controlled biomolecule delivery for tissue regeneration. POLYM. ENG. SCI., 55:896–906, 2015. © 2014 Society of Plastics Engineers

Composite ultrafine fibers of hydrogel/polylactide copolymer were successfully electrospun from water-in-oil suspensions. Effects of the suspension composition on the morphology and microstructure of the obtained fibers were investigated, including both aqueous phase and oily phase, that is, hydrogel (chitosan or gelatin), polylactide copolymers [poly(ethylene glycol)-b-poly (L-lactide-co-caprolactone) (PELCL) or poly(L-lactide-co-glycolide) (PLGA)], organic solvents and surfactants. Scanning electron micrographs showed that mixed solvents of chloroform and N,N-dimethyl formamide or 2,2,2-trifluoroethanol were preferred to form beads-free ultrafine fibers with diameter in the range of 230–470 nm. With ethyl acetate as organic solvent, compared with chitosan hydrogel/PELCL composite fibers, chitosan hydrogel/PLGA fibers showed narrower distribution of diameter in 230–590 nm. Different hydrogel and surfactants used in this experiment had slight effects on the morphology of the obtained fibers, whereas transmission electron micrographs exhibited chitosan and gelatin hydrogel could be in situ encapsulated in the fibers discontinuously. This method may promise a new aqueous reservoir for encapsulation and controlled release of bioactive agents. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Effect of benzyl triethylammonium chloride (BTEAC) on the microstructure of electrospun bicomponent fibers, i.e., polyvinylidene fluoride (PVDF)/polycarbonate (PC), polyacrylonitrile (PAN)/polyethylene glycol (PEG), and PAN/PVDF, was investigated in this article. The evolution of morphology and microstructure of the above bicomponent fibers were examined by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results showed that distinct core/shell structured fibers were successfully prepared from PVDF/PC and PAN/PVDF via introducing a small amount of BTEAC, whereas only cocontinuous structure was detected in the electrospun PAN/PEG fibers. This study could be an example of electrospun multipolymer dispersions influencing by an organic salt, and it could be extended to control the structure of carbon nanofibers via electrospinning. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Because of the great effect of mechanical loads on degradation of biodegradable biomaterials, investigation on degradation of electrospun membranes under dynamic loading is of importance. In this article, degradation of electrospun poly(L-lactide) (PLLA) membranes was carried out in a Tris-HCl buffer solution containing proteinase K under a cyclic stretch loading (dynamic condition) in comparison with that in shaking water bath (static condition). The evolutions of mass loss, morphology, thermal properties, and relative molecular weight of PLLA were monitored during degradation. The results showed that after degradation for 10 h, the mass of the electrospun PLLA membranes dropped by 38.7% and 31.3%, respectively, under dynamic and static conditions. And the electrospun PLLA membranes showed higher value of crystallinity during degradation under both cyclic loading and static condition. In addition, benzyl triethyl ammonium chloride (BTEAC) was introduced during electrospinning, and the effects of electrospun membranes characteristic and crystallinity on degradation were also investigated. The degradation study results are expected to be a basic study in mimicking actually mechanical environments. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci 124:258–266, 2012

Poly(vinylidene fluoride) (PVDF)/polycarbonate (PC) dispersed solutions were electrospun into ultrafine core/shell fibers and modified by hot-press. Morphology, tensile properties, porosity, and liquid absorption of the electrospun membranes as well as the crystallinity of PVDF were examined before and after hot-press. Results showed that the tensile strength and tensile modulus of the electrospun membranes increased after hot-press, especially when poly(methyl methacrylate) (PMMA) or benzyl triethylammonium chloride (BTEAC) was introduced for the formation of distinct core/shell fiber structure. The elongation of the hot-pressed electrospun PVDF/PC membrane with addition of BTEAC was also significantly enhanced by reason of the clearest core/shell structure. The crystallinity of PVDF did not change too much before and after hot-press, however the porosity and liquid absorption of the hot-pressed electrospun membranes decreased to about 58% and around 75–90%, respectively, with no significant differences between PVDF/PC, PVDF/PC/PMMA, and PVDF/PC with BTEAC membranes. This study could be an example of electrospun membranes in multi-polymer components and it could be extended to other systems of electrospinning for applications in filtration and so on. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Microcapsules containing phase change materials (microPCMs) have been widely applied in smart temperature-controlling materials. Interface stability plays a key role in these microPCMs/matrix composites. The aim of this study was to investigate the interface stability behaviors of methanol-melamine-formaldehyde (MMF) shell microPCMs containing paraffin/epoxy matrix composites. MMF prepolymer can be applied to fabricated microcapsules with smooth shells. The average diameter of the microPCMs could be controlled in the range of 5–45 μm by stirring speed of 500–6,000 r min−1. From the SEM morphologies of the interphase between the microPCMs and the epoxy-matrix, it is concluded that the interaction may be enhanced by MMF graft structure due to the increasing of molecular interaction in the interface. During a repeated heat-transmission process, not only the repeated-times of thermal absorbing-releasing process will damage the interface bonding, but also higher thermal conductive speed will make the interface bearing more debonding stress. Large microPCMs in matrix may supply better interface stability. Moreover, the numerical and experimental results are consistent to obtain a clear insight into the rule of interface debonding for microPCMs/matrix composites that the interface perfection can be enhanced by increasing the thickness of interphase. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

A nanocomposite of silver nanoparticles (AgNPs) embedded in chitosan (Cts) matrix was successfully synthesized by crosslinking technology. Colloidal AgNPs formed in situ by chemical reduction of silver ions in presence of Cts showed a good stability. Transmission electron micrographs, X-ray diffraction patterns, and UV-visible spectra of Ag-Cts composite particles confirmed the formation of silver nanocrystals. Fourier transform infrared spectroscopy verified the presence of Cts as a stabilizing agent surrounded AgNPs. Thermogravimetric-differential scanning calorimeter analysis revealed Ag-Cts nanocomposite had a higher thermal stability than Cts. X-ray photoelectron spectroscopy suggested that the Ag-O bond in the nanocomposite coule lead to the tight combination between silver and Cts. Microbial experiments showed the nanocomposite had excellent and wide spectrum antibacterial properties, and were more efficient than either AgNPs or Cts alone for inactivating bacteria. Therefore, the resultant nanocomposite could be used as antimicrobial materials for medical and biological applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

Localized dual-drug delivery from biodegradable scaffolds is an important strategy in tissue engineering. In this study, porous poly(L-lactide-co-glycolide) (PLGA)/β-tricalcium phosphate scaffolds containing both dexamethasone (Dex) and bovine serum albumin (BSA) were prepared by incorporating Dex-loaded and BSA-loaded microspheres into the scaffolds. PLGA microspheres containing Dex or BSA were prepared by spray-drying and double emulsion/solvent evaporation, respectively. In vitro release studies indicated that microspheres prepared from PLGA in 3:1 molar ratio of L-lactide/glycolide and 89.5 kDa relative molecular mass showed prolonged release profiles compared with those prepared from PLGA in 1:1 L-lactide/glycolide molar ratio and 30.5 kDa relative molecular mass. Additionally, introduction of poly(ethylene glycol) in the PLGA chain could improve the encapsulation efficiency and reduce the release rate. Based on the above results, controllable dual-release of Dex and BSA with relatively higher or lower release rate was achieved by incorporating Dex-loaded and BSA-loaded microspheres with different release profiles into the PLGA/β-tricalcium phosphate scaffolds. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.

Fibrous gelatin scaffolds fabricated via electrospinning followed by crosslinking were used as substrates for apatite mineralization. Gelatin macromolecules were confined by their fibers and further restricted by the crosslinked structure while proper flexibility could be attained upon hydration. After 4 or 5 days of mineralization, partially carbonated hydroxyapatite was proved to deposit uniformly on the surface of the fibers. The property of the substrate, such as stiffness of the scaffolds and flexibility of macromolecules chain, was changed by different crosslinking ways. The influences of these properties on the formation of apatite were also investigated. Results showed that a relatively less rigid interface and more flexible chain acquired by glutaraldehyde solution crosslinking seemed to favor the nucleation of minerals and to reduce the size of the inorganic products. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

We report a new method for generating both continuous and discrete density gradients in microparticles of biodegradable polymers via an electrospray technique. The gradients were generated by spatially varying the deposition time of electrosprayed microparticles. The substrate coated with a density gradient of microparticles has varying surface roughness, offering a unique system for studying the effect of physical cues on neurite outgrowth from dorsal root ganglia. We obtained an optimal surface roughness for promoting neuron adhesion and neurite extension in vitro. Furthermore, this capability of approach was extended to generate a gradient of fluorescein isothiocyanate-labeled bovine serum albumin by encapsulating it in the polymer microparticles in situ during electrospray. Taken together, this new class of substrates with gradients of microparticle density can potentially be used in various biomedical applications such as neural tissue engineering.

To promote the heat-sealing properties of soy protein isolate (SPI) films applied in the packaging field, we mixed a synthetic polymer of poly(vinyl alcohol) (PVA) with SPI to fabricate blend films by a solution-casting method in this study. To clarify the relationship between the heat-sealing properties and the heat-sealing temperature, strength, melting process, crystalline structure, and microstructure, variations of the heat-sealing parts of the films were evaluated by means of differential scanning calorimetry, tensile testing, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy, respectively. The test results showed that both the PVA and glycerol contents greatly affected the melting behavior and heat of fusion of the SPI/PVA blends; these blend films had a higher melting temperature than the pure SPI films. The peel strength and tensile strength tests indicated that the long molecular chain of PVA had a main function of enhancing the mechanical properties above the melting temperature. With increasing heat-sealing temperature, all of the mechanical properties were affected by the microstructure of the interface between the laminated films including the chain entanglement, crystallization, and recrystallization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

It has been found that composites of chitosan (CS) and Ag nanoparticles can exhibit excellent antibacterial activities. However, the weak mechanical performances of these composite materials limit their wide application. Grafting of vinyl monomers onto CS is one of the most effective methods to improve the performances of CS without sacrificing its properties. A nanocomposite of chitosan-graft-(methyl methacrylate) (CS-g-MMA) containing Ag nanoparticles was prepared by in situ chemical reduction of Ag ions in an aqueous acetic acid solution of CS and graft copolymerization of MMA onto CS. Transmission electron micrographs, X-ray diffraction patterns and UV-visible spectra of the nanocomposite confirmed the formation of Ag nanocrystals. X-ray photoelectron spectroscopy proved that AgO bonds exist in the composite. Thermogravimetric analysis/differential scanning calorimetry showed that the decomposition temperature of CS was 319.8 °C while that of the CS-g-MMA/Ag composite shifted to a higher temperature of 422.1 °C. Antimicrobial experiments showed that the antimicrobial rates of the CS-g-MMA/Ag composite to E. coli, B. subtilis, S. aureus and P. aeruginosa were 93–98%. CS molecules can act as stabilizing agents to prevent the aggregation of Ag nanoparticles in the process of synthesizing CS-g-MMA/Ag nanocomposites. The antimicrobial activity of the as-prepared nanocomposites is higher than that of CS alone. Copyright © 2009 Society of Chemical Industry

Dispersed solutions of poly(vinylidene fluoride) (PVDF)/polycarbonate (PC) in the mixed solvent of N,N-dimethylformamide (DMF)/tetrahydrofuran (THF) were used to electrospin in order to discuss the relationship between the properties of the polymer dispersions and the morphology of the obtained ultrafine fibers. With the changes of the mass ratio of PVDF/PC, the relative molecular mass of PVDF, and the volume ratio of DMF/THF, the morphology and the microstructure of the prepared PVDF/PC ultrafine fibers altered in accord with the viscosity, surface tension, and conductivity of the PVDF/PC dispersions. When the PVDF/PC mass ratio varied from 9/1 to 5/5, the ability of the polymer chain entanglement in PVDF/PC dispersion decreased as to the lower relative molecular mass of PC and higher chain rigidity, which lead to the formation of the beaded fibers together with the distinct core/shell structure. Similar phenomenon was also found when the lower molecular mass of PVDF was used instead of a higher one. Though the change of DMF/THF volume ratio did not specifically contribute to the properties of PVDF/PC dispersions, the accelerated evaporation and solubility of the mixed solvent by the THF amount increasing was feasible to generate the uniform fibrous morphology and the distinct core/shell structure. © 2009 Wiley Periodicals, Inc.J Polym Sci Part B: Polym Phys 48: 372–380, 2010

By the use of a high-speed collection drum, poly(vinylidene fluoride) (PVDF) was electrospun into aligned ultrafine fibrous membranes from its solutions in a mixture of N,N-dimethylformamide and acetone (9:1, v/v), and a continuous hot-press post-treatment was performed on the membranes to improve their mechanical properties. Anisotropic tensile results and rupture behaviors of the hot-pressed PVDF membranes with higher fiber alignments in both revolving direction (RD) and cross direction were obtained. It was found that, due to the true fracture of electrospun fibers and improvement of the interfiber compaction by hot-press, the tensile strength and modulus of the hot-pressed membranes in RD reached the highest values at 58.12 ± 4.46 MPa and 519.9 ± 34.1 MPa, respectively when the collection speed was 10.42 m/s. The decrease of porosity and liquid absorption also represented the compaction improvement of the electrospun fibrous membranes. The combination of fiber alignments and hot-press could provide a novel method to fabricate high strength of electrospun membranes which have highly potential applications in filtration or battery separators. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

For the modification of an electrospun poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP) membrane for its potential use as an electrolyte or separator in lithium batteries, poly(ethylene glycol) dimethacrylate (PEGDMA) was introduced into a polymer solution for electrospinning. A post heat treatment of the as-electrospun membrane at an elevated temperature was performed for PEGDMA polymerization, and this was verified by Fourier transform infrared spectroscopy. The results showed that no significant variations in the membrane morphology were detected when a small amount of PEGDMA (PVDF–HFP/PEGDMA mass ratio = 4/1) was incorporated. This electrospun membrane after heat treatment at 130°C for 2 h exhibited a significantly higher tensile strength (6.26 ± 0.22 MPa) than that of an electrospun PVDF–HFP membrane (3.28 ± 0.35 MPa) without PEGDMA. The porosity and liquid absorption of the electrospun PVDF–HFP/PEGDMA (4/1) membrane were 70.0 ± 1.6% and 267 ± 11%, respectively, lower than those of the electrospun PVDF–HFP membrane (76.5 ± 0.3% and 352 ± 15%) because of the introduction of PEGDMA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Blend films from nature soy protein isolates (SPI) and synthetical poly(vinyl alcohol) (PVA) compatibi- lized by glycerol were successfully fabricated by a solu- tion-casting method in this study. Properties of compatibility, mechanical properties, and thermal stability of SPI/PVA films were investigated based on the effect of the PVA concentration. XRD tests confirm that the SPI/ PVA films were partially crystalline materials with peaks of 2y ¼ 20 � . And, the addition of glycerol will insert the crystalline structure and destroy the blend microstructure of SPI/PVA. Differential scanning calorimetry (DSC) tests show that SPI/PVA blend polymers have a single glass transition temperature (Tg) between 80 and 115.0 � C, which indicate that SPI and PVA have good compatibility. The tension tests show that SPI/PVA films exhibit both higher tensile strength (rb) and percentage elongation at break point (P.E.B.). Thermogravimetric analysis (TGA) and water solubility tests show that SPI/PVA blend polymer has more stable stability than pure SPI. All the results reflect that SPI/PVA/glycerol blend film provides a con- venient and promising way to prepare soy protein plastics for practical application. V C 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3706-3716, 2008

A novel method for the fabrication of porous poly(L-lactide-co-glycolide) (PLGA) scaffolds by combining thermally induced phase separation and porogen leaching is presented in this article. Big pores with about 75–400 μm diameters in the obtained scaffolds were generated by the porogen, sucrose particles, while small pores with diameters less than 20 μm induced via phase separation. Extraction of the solvent, chloroform by ethanol at cool temperatures could reduce the scaffold toxicity. Effects of PLGA concentration, freezing temperature, volume fraction of porogen, and introduction of β-tricalcium phosphate (β-TCP) on morphology, porosity, and compressive properties of the scaffolds were systematically discussed. Results showed that the size of small pores decreased by decreasing the polymer concentration and reducing the freezing temperature, whereas the interconnectivity of the scaffolds was improved by increasing the porogen fraction. The compressive modulus and strength were significantly lowered by increasing the scaffold porosity, that is, by increasing porogen fraction, or decreasing the polymer concentration, or reducing the freezing temperature. Addition of β-TCP into the scaffolds did not influence the compressive modulus significantly but tended to decrease the compressive strength. The obtained scaffolds with diverse pore sizes would be potentially used in bone tissue engineering. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Poly(vinylidene fluoride) (PVDF) was electrospun into ultrafine fibrous membranes from its solutions in a mixture of N,N-dimethylformamide and acetone (9:1, v/v). The electrospun membranes were subsequently treated by continuous hot-press at elevated temperatures up to 155°C. Changes of morphology, crystallinity, porosity, liquid absorption, and mechanical properties of the membranes after hot-press were investigated. Results of scanning electron microscopy showed that there were no significant changes in fibrous membrane morphology when the hot-press temperature varied from room temperature to 130°C, but larger pores were formed because of fibers melting and bonding under higher temperatures. Analyses of X-ray diffraction and differential scanning calorimeter exhibited that the crystalline form of PVDF could transfer from β-type to α-type during hot-press at temperatures higher than 65°C. Tensile tests suggested that the mechanical properties of the electrospun PVDF membranes were remarkably enhanced from 25 to 130°C, whereas the porosity and the liquid absorption decreased. The hot-press at 130°C was optimal for the electrospun PVDF membranes. The continuous hot-press post-treatment could be a feasible method to produce electrospun membranes, not limited to PVDF, with suitable mechanical properties as well as good porosity and liquid absorption for their applications in high-quality filtrations or battery separators. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

This study investigated the process feasibility and stability of core/shell structured bicomponent ultrafine fibers of poly(vinyl pyrrolidone) (PVP) and poly(D,L-lactide) (PLA) by coaxial electrospinning. The morphological structure of the core/shell ultrafine fibers was studied by means of scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Results suggested that PVP/PLA core/shell ultrafine fibers with drawbacks could be produced from 6 or 8% PVP solutions (inner) in the mixture of N,N-dimethlformamide (DMF) and ethanol and a 22% PLA solution (outer) in DMF and acetone when the flow rates of inner and outer fluids were 0.05 and 0.1 mL/h, respectively. The tensile modulus and tensile strength of the core/shell PVP/PLA membrane were dramatically lower than those of the electrospun PLA membrane, and its water uptake was twice more than that of the PLA membrane. Membranes made from the biodegradable core/shell ultrafine fibers could be potentially used in loading bioactive molecules for tissue regeneration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 39–45, 2006

Poly(vinylidene fluoride) (PVDF) was electrospun into fibrous membranes from its solutions in a mixture of N,N-dimethylformamide (DMF) and acetone. The electrospun PVDF membranes were viewed under a scanning electron microscope. Effects of acetone amount, polymer concentration, and capillary-collector distance on the morphology of the membranes were studied. It was suggested that uniform fibrous membranes with fiber diameters ranging mainly from 50 nm to 300 nm were formed from a 15% (wt/v) PVDF solutions in 8 : 2 (v/v) DMF/acetone at 5-kV voltage, 0.3-mL/h flow rate, and 10 ∼ 20-cm capillary-collector distance. After about 10 h of electrospinning, fibrous PVDF membranes with thickness of approximate 46 μm were obtained. The tensile moduli and the tensile strengths of the electrospun PVDF membranes were 100 ∼ 170 MPa and 4 ∼ 5 MPa, respectively, from the 13% PVDF solution. Analysis of differential scanning calorimeter and wide angle X-ray diffraction showed that the crystallization of PVDF in the electrospun membranes was weakened compared to the casting film and the raw material. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 466–474, 2005

Ultrafine fibers of bisphenol-A polysulfone (PSF) were prepared by electrospinning of PSF solutions in mixtures of N,N-dimethylacetamide (DMAC) and acetone at high voltages. The morphology of the electrospun PSF fibers was investigated by scanning electron microscopy. Results showed that the concentration of polymer solutions and the acetone amount in the mixed solvents influenced the morphology and the diameter of the electrospun fibers. The processing parameters, including the applied voltage, the flow rate, and the distance between capillary and collection screen, were also important for control of the morphology of electrospun PSF fibers. It was suggested that uniform ultrafine PSF fibers with diameter of 300–400 nm could be obtained by electrospinning of a 20 % (wt/v) PSF/DMAC/acetone (DMAC:acetone = 9:1) solution at 10–20 kV voltages when the flow rate was 0.66 ml h−1 and capillary–screen distance was 10 cm. Copyright © 2004 Society of Chemical Industry

Polyblend fibrous scaffolds in mass ratios of 100/0, 90/10, 80/20, and 70/30 from poly(L-lactide) (PLLA) and poly(ϵ-caprolactone) (PCL) for cartilage tissue engineering were prepared in three steps: gelation, solvent exchanging, and freeze-drying. Effects of the blend ratio, the exchange medium, and the operating temperature on the morphology of scaffolds were investigated by SEM. PLLA/PCL scaffolds presented an ultrafine fibrous network with the addition of a “small block” structure. Smooth and regular fibrous networks were formed when ethanol was used as the exchange medium. Properties of the scaffolds, such as thermal and mechanical properties, were also studied. The results suggested that the compressive modulus declined as PCL amount increased. The incorporation of PCL effectively contributed to reduce the rigidity of PLLA. Bovine chondrocytes were seeded onto PLLA/PCL scaffold. Cells attached onto the fibrous network and their morphology was satisfactory. This polyblend fibrous scaffold will be a potential scaffold for cartilage tissue engineering. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1676–1684, 2004

In vitro degradation of poly(L-lactic acid) (PLLA) fibers was studied by incubating the fibers in phosphate buffered saline (pH 7.4) at 37°C for 35–45 weeks. Three kinds of PLLA fibers with different diameters and different initial viscosity-average molecular weights were tested. The viscosity-average molecular weight, crystallinity, morphology, and tensile properties of the PLLA fibers were monitored along the degradation period. The results showed that the viscosity-average molecular weight of the PLLA fibers dropped gradually during the in vitro degradation period, and it decreased by 40–60% at the end of the experimental period. The crystallinity of the PLLA fibers measured by differential scanning calorimetry was noted to increase slightly. The tensile moduli, ultimate strengths, and elongations of the fibers did not exhibit significant changes in 35 weeks of degradation but PLLA fibers with a smaller diameter of 113 μm showed significant decreases in their ultimate strengths with respect to the initial value after 35–45 weeks of degradation. Microcracks appeared on part of the fiber surfaces, which might ultimately lead to the decrease of the mechanical strength of the PLLA fibers. The spotty defects reported in this study apparently did not affect the mechanical properties of the fibers. The results suggested that the tensile properties of the PLLA fibers were mechanically stable in 35 weeks of in vitro degradation, although their molecular weights decreased remarkably and obvious spotty defects appeared on their surfaces. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 936–943, 2002

upramolecular hydrogels composed of poly(ethylene glycol) (PEG) containing polymer and α-cyclodextrins (α-CDs) show great potential in drug delivery. Herein, PEGylated magnetic nanoparticles (MNPs) and gold nanoparticles (AuNPs) of ≈10 nm are synthesized in the presence of poly(poly(ethylene glycol) methyl ether acrylate) (PPEGMA) grafted poly(acrylic acid) copolymers (PPEGMA-co-PAA, P1) and PPEGMA grafted poly(2-(dimethylamino)ethyl methacrylate) copolymers (PPEGMA-co-PDMAEMA, P2), respectively. The produced PEGylated NPs are hybridized into supramolecular hydrogels by mixing them with α-CDs through inclusion complexation between PEG branches and α-CDs. As a result, supramolecular hydrogels hybridized with inorganic MNPs and AuNPs are prepared and characterized by rheological measurements, X-ray diffraction, and scanning electron microscopy. Both MNP and AuNP hybrid hydrogels show reversible sol–gel transition, which is stimulated by changes in temperature and pH. The nanoparticles hybridized in the hydrogels can be released gradually in the process of hydrogel disruption. These hydrogels may have potential applications in biomaterials and drug delivery.

The relative polarizability effect of alkyl substituent can be conveniently obtained by calculating the so-called Polarizability Effect Index (PEI) value, proposed firstly in our laboratories, PEI = Σ (a i /N i 2 ), where a i is the polarizability of primary units CH3, CH 2 -, CH C-, and the N i is the carbon atom number from reaction site to the primary unit. By using the PEl and atomic charge in a molecule, the ionization potential of alkyl halide, the enthalpy of reaction for the gas-phase addition of a proton to an alcohol or ether (proton affinity), the gas-phase basicity of alcohols or ethers (proton affinity), and gas-phase acidity of alcohols can be quantitatively modeled by the two-parameter expression equation.

Biodegradable poly(L-lactic acid) (PLLA) fibers were processed by a two-step melt-spinning method (melt extrusion and hot draw) from PLLA with three different viscosity-average molecular weights (494,600, 304,700, and 262,800). Before spinning, the polymer flakes were first milled into powders and dried under vacuum. Viscosity-average molecular weight of PLLA following the fabrication process was monitored. Tensile properties of as-spun and hot-drawn fibers were investigated. Morphology of the PLLA fibers was viewed under a scanning electron microscope. Crystallinity of these fibers was assessed by thermogram analysis of differential scanning calorimetry. Results showed that the extent of decrease in the viscosity-average molecular weight of PLLA dropped sharply by 13.1–19.5% during pulverization and by 39.0–69.0% during melt-extrusion. The hot-draw process in this study had a little effect on the viscosity-average molecular weight of PLLA. Smoother fibers could be obtained for the die temperature at least 230°C for raw materials with higher crystallinity (more than 75%) and at least 220°C for raw materials with lower crystallinity (about 60%). The as-spun fibers showed crystallinity of 16.5–22.8% and the value increased to 50.3–63.7% after hot draw. Tensile moduli of the as-spun fibers were in the range of 1.2–2.4 GPa, which were raised to 3.6–5.4 GPa after hot draw. The final PLLA fibers with 110–160 μm diameters showed tensile strengths of 300–600 MPa. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 251–260, 2001

Bone-like apatite coating on poly(L-lactic acid) (PLLA) fibers was formed by immersing the fibers in a modified simulated body fluid (SBF) at 37°C and pH 7.3 after hydrolysis of the fibers in water. The ion concentrations in SBF were nearly 1.5 times of those in the human blood plasma. The apatite was characterized by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thin-film X-ray diffraction, and Fourier transform infrared spectroscopy. After 15 days of incubation in SBF, an apatite layer with about 5–6 μm thickness was formed on the surface of the fibers. This apatite had a Ca/P ratio similar to that of natural bone. The mass of apatite coated PLLA fibers increased with extending the incubation time. After 20 days incubation, the fibers increased their mass by 25.8 ± 2.1%. The apatite coating had no significant effect on the tensile properties of PLLA fibers. In this article, the bone-like apatite coating on three-dimensional PLLA braids was also studied. The motivation for this apatite coating was that it might demonstrate enhanced osteoconductivity in the future studies when they serve as biodegradable scaffolds in tissue engineering. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res 57: 140–150, 2001

Pressed films of binary blends (polyamide with low-density polyethylene or Surlyn) and ternary (polyamide with low-density polyethylene and Surlyn or a graft-copolymer of acrylic acid onto low-density polyethylene) were examined by dynamic mechanical analysis, thermally stimulated current, and small-angle X-ray scattering. The variation of the glass transition temperature for two phases in the blends was studied by dynamic mechanical analysis and thermally stimulated current. X-ray scattering from the relation of the phases was analyzed using Porod's law and led to values of the interface layer in the blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 488–494, 2000

Surface modification of membranes of an acrylonitrile copolymer (PAN) containing 5.5% methyl methacrylate (MMA) and 4.0% sodium methylpropylenesulfonate by grafting acrylamide (AAm) with cetric ammonium nitrate as initiator in the aqueous medium has been studied. Results showed that the extent of grafting was varied with some parameters, such as dimethyl formamide and Tween-20 amount in the reaction solution, concentration of AAm, and reaction time. The grafted copolymer was verified by infrared spectra and X-ray photoelectron spectroscopy. Both of these methods also showed that the ester group of MMA unit on the surface of PAN membranes may be partially hydrolyzed into carboxyl group in the copolymerization condition. Surface and pore structures of PAN membranes after grafting were viewed under a scanning electron microscope (SEM). From SEM photos we know that AAm homopolymer branches were grafted onto the surface of the membrane and the morphology of membrane did not change. Results of contact angle of isooctane on the membrane under water showed that the wettability of the modified membrane was improved.

The kinetics and mechanism of grafting of acrylamide onto acrylonitrile copolymer membranes with Fe2+/H2O2 as the initiator in an aqueous medium were studied. The experimental results were found to be in good agreement with the proposed kinetic scheme. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1917–1921, 1998