Yong Liu

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Organization: Institute of Chemistry
Department: 1 College of Mechanical and Electric Engineering
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Co-reporter:Haoqin Ma, Guangkai Chen, Jingnan Zhang, Yong Liu, Jun Nie, Guiping Ma
Polymer 2017 Volume 110(Volume 110) pp:
Publication Date(Web):10 February 2017
DOI:10.1016/j.polymer.2016.12.062
•HA/CS core-shell nanofibers are prepared via electrospinning.•Electric field induces phase separation, and leads CS and HA migrate.•The nanofibers showed more controlled and sustained release.The core-shell polyelectrolyte complexes chitosan (CS)/hyaluronic acid (HA) nanofibers could be produced from electric field inducing phase separation during the progress of electrospinning. The morphology of core-shell nanofibers was supported using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of CS on the shell of the nanofibers was also verified by X-ray photoelectron spectroscopy (XPS) analysis as further evidence of core-shell formation. In the electrospinning process, the protonated CS molecules migrated in the direction of the electric field, whereas the ionized HA molecules migrated in the opposite direction. Methylthiazolydiphenyl-tetrazolium bromide (MTT) assay was employed to investigate the toxic and cytocompatibility with the possible application for tissue engineering scaffolds. The drug release from core–shell nanofiber in vitro was investigated by UV spectrophotometry. The release profiles for core–shell nanofibers showed more controlled and sustained release. while fibroblasts cells could still adhere to and proliferate on the drug-loaded core–shell nanofiber membranes. The results implied that core-shell polyelectrolyte complexes CS/HA nanofibers encapsulating drugs have great potential in tissue engineering scaffolds.Download high-res image (159KB)Download full-size image
Co-reporter:Gai Xie, Yan Wang, Xiaotian Han, Yan Gong, Jiping Wang, Jianming Zhang, Depeng Deng, and Yong Liu
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 26) pp:7116-7123
Publication Date(Web):June 14, 2016
DOI:10.1021/acs.iecr.6b00958
In order to overcome the difficulty of reducing fiber diameters during melt electrospinning, a pulsed electric field is applied. The effect of the frequency and duty cycle of the pulsed electric field on the fiber diameter, crystallinity, and molecular orientation was studied. Results revealed that the diameter of the poly-l-(lactic acid) (PLLA) melt electrospun fiber was reduced by this pulsed electric field, especially at higher frequencies, and the finest fiber was obtained at a duty cycle of 29.8% and a frequency of 1 kHz. Both constant and pulsed electric fields can lead to a high molecular orientation in electrospun fibers, particularly in the crystalline regions. In addition, the molecular orientation and crystallinity of the fibers can also be improved by increasing the frequency and duty cycle of the pulsed power. Of note, fibers with multiple necking structures were interestingly observed at field frequencies of 8 and 10 kHz at the microfiber scale.
Co-reporter:Tian Song;Zhiyuan Chen;Hong He;Yuexing Liu;Seeram Ramakrishna
Journal of Applied Polymer Science 2015 Volume 132( Issue 14) pp:
Publication Date(Web):
DOI:10.1002/app.41755

ABSTRACT

In this study, Nafion® NR 40 beads with polyethylene oxide (PEO) are fabricated into a nanofiber membrane using electrospinning. In particular, Nafion® beads in non-toxic mixed solvent (EtOH and H2O) were blended with the carrier polymer PEO, which is the minor component in the solution responsible for the solution spinnability. The highest content of Nafion® in the nanofiber is 98.04%. To investigate the factors influencing the nanofiber diameter during electrospinning, an orthogonal design method was adopted. These factors include the carrier polymer content, distance between the syringe needle and roller collector, flow rate of the electrospinning solution, and the roller rotation speed. After obtaining the significant factors and optimal test level, an additional optimization experiment is conducted under the best conditions. The resulting nanofibers have a diameter of ∼150 nm. Moreover, the obtained Nafion® nanofiber membrane has strong potential for applications in polymer electrolyte membrane fuel cells (PEMFC), the chlor-alkali industry, catalysts, and metal ion removal. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41755.

Co-reporter:Gai Xie;Zhiyuan Chen;Seeram Ramakrishna
Journal of Applied Polymer Science 2015 Volume 132( Issue 38) pp:
Publication Date(Web):
DOI:10.1002/app.42574

ABSTRACT

Through orthogonal experimental methods, the melt electrospinning of pure phenolic fibers has been achieved. The preparation is based on an orthogonal experimental method, which was designed to investigate the optimal conditions for production through integrated effects of spinning temperature, gap between spinneret and collector, as well as applied voltage. We found that optimal spinning conditions at 160°C, a spinneret-to-collector gap of 8 cm, and applied voltage at 40 kV produce an average electrospun fiber diameter reaching 4.44 ± 0.76 μm, with narrow variance distribution. The fibers were cured in a solution with 18.5% formaldehyde and 12% hydrochloric acid, heated from room temperature to 80°C and maintained 1h. In this report, the morphology, structural changes, and heat resistance of the fibers are characterized. Obtained results reveal that curing the fiber reduces crystallization and improves heat resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42574.

Co-reporter:Yong Liu;Xiuhong Li;Seeram Ramakrishna
Journal of Polymer Science Part B: Polymer Physics 2014 Volume 52( Issue 14) pp:946-952
Publication Date(Web):
DOI:10.1002/polb.23511

ABSTRACT

Electrospinning is an efficient and direct method of fabricating nanofibers. Fibers are frequently unstable in the electrospinning process, and the uneven distribution of the electric field is an important factor leading to instability. Experimental and finite element simulation studies are conducted on the process of melt electrospinning in a parallel electric field. Two parallel metal disks are used to successfully generate a uniform electric field. Electric field intensity on the edges of the metal disk is always stronger than the field at the center of the disk or at the spinneret bottom. The diameters, distances, and relative areas of these disks significantly affect the distribution of the electric field. Thus, the parallel electric field effectively reduces jet buckling in melt electrospinning. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 946–952

Co-reporter:Fengwen Zhao;Huilin Yuan;Weimin Yang
Journal of Applied Polymer Science 2012 Volume 125( Issue 4) pp:2652-2658
Publication Date(Web):
DOI:10.1002/app.36426

Abstract

Melt electrospinning is a much simpler and safer method in the production of ultra-fine fibers compared with solution electrospinning. However, high-spinning temperature usually leads to serious degradation of polymer materials. In determining factors that affect the relative molecular mass of polylactic acid (PLA) fibers during melt electrospinning, an orthogonal design method was used to examine the influence of melting temperature, spinning distance, and species and content of antioxidants. Results showed that antioxidant content at the present three levels (i.e., 0.1%, 0.3%, and 0.5%) has the most considerable effect on the relative molecular mass of PLA fibers. Error analysis showed that changes in temperature, distance, and antioxidant content influence the experiment's results significantly. All interaction effects were larger than those of the single factor in the experimental results. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Co-reporter:Yong Liu;Xin Wang;Hua Yan;Changfeng Guan;Weimin Yang
Journal of Materials Science 2011 Volume 46( Issue 24) pp:
Publication Date(Web):2011 December
DOI:10.1007/s10853-011-5769-0
A number of theoretical problems, such as dynamic movement of molecular chains, present themselves in melt electrospinning, yet these important issues have not been thoroughly studied. In this article, a mesoscale simulation method called dissipative particle dynamics was used to study tentatively the dynamic movement of molecular chains, seeing as the diameter of spun fibers is of nanoscale dimensions, belonging to the mesoscale domain in physics. Results show that the downward traces of melting fibers are close to those obtained experimentally, the drop velocity is closely related to electrical force, the structures of the fibers differ with changes of temperature, and chain length varies at distinct descending periods.
Co-reporter:Yong Liu;Rongjian Deng;Mingfeng Hao;Hua Yan ;Weimin Yang
Polymer Engineering & Science 2010 Volume 50( Issue 10) pp:2074-2078
Publication Date(Web):
DOI:10.1002/pen.21753

Abstract

Melt electrospinning is a much more simple and safe method to produce ultra fine fibers than solution electrospinning. The diameters of melt electrospinning fibers are thicker. To find the factors that affect the fibers diameter in melt electrospinning, orthogonal design was used to examine melt temperature, spinning voltage, spinning distance, and melt flow rate (MFR) of polymer. Results showed that MFR at present three levels has the most important impact both on the average diameters and standard deviations of fiber diameters. The scanning electron microscopy pictures show that all the fibers have smooth surface, which means the melt electrospinning fibers have good mechanical properties. POLYM. ENG. SCI., 50:2074–2078, 2010. © 2010 Society of Plastics Engineers

Co-reporter:Yong Liu;Ying An;Hua Yan;Changfeng Guan ;Weimin Yang
Journal of Polymer Science Part B: Polymer Physics 2010 Volume 48( Issue 23) pp:2484-2489
Publication Date(Web):
DOI:10.1002/polb.22149

Abstract

The impacts of Rouse spring, Fraenkel spring, and one kind of finitely extensible nonlinear elastic spring (FENE-PM spring) on the surface tension-induced retraction of a polymer ellipsoid in a matrix were compared using dissipative particle dynamics. Using the same spring constant, obvious differences among the three kinds of springs were found. A fast retraction process was observed from the hard Fraenkel spring, a slow process from the soft Rouse spring, and an intermediate process from the FENE-PM spring. The effects of varying the spring constant and the chain length were also investigated. The results indicate that the influence of increasing spring hardness for a given spring type was significant; whereas, the influence of chain length was minor after five bonds were reached. The effects of varying the FENE-PM rm parameter were also studied to provide a reliable value for this study. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010

sikkimenoid D
sikkimenoid C
sikkimenoid B
sikkimenoid A
Chloro(2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl)(2'-amino-1,1'-biphenyl-2-yl)palladium(II)
5,12-epi-14-oxo-lagaspholone B
2,3-seco-5,12-epi-2,14-dioxo-3(6)-lactonic lagaspholone B