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Laura A. Smith Callahan - One of the best experts on this subject based on the ideXlab platform.

  • Mechanical stabilization of proteolytically degradable Polyethylene Glycol Dimethacrylate hydrogels through peptide interaction.
    Acta biomaterialia, 2018
    Co-Authors: Hyun Ju Lim, Zara Khan, T. Hiran Perera, Thomas S. Wilems, Krishna T. Ravivarapu, Laura A. Smith Callahan
    Abstract:

    Abstract Balancing enhancement of neurite extension against loss of matrix support in synthetic hydrogels containing proteolytically degradable and bioactive signaling peptides to optimize tissue formation is difficult. Using a systematic approach, Polyethylene Glycol hydrogels containing concurrent continuous concentration gradients of the laminin derived bioactive signaling peptide, Ile-Lys-Val-Ala-Val (IKVAV), and collagen derived matrix metalloprotease degradable peptide, GPQGIWGQ, were fabricated and characterized. During proteolytic degradation of the concentration gradient hydrogels, the IKVAV and IWGQ cleavage fragment from GPQGIWGQ were found to interact and stabilize the bulk Young’s Modulus of the hydrogel. Further testing of discrete samples containing GPQGIWGQ or its cleavage fragments, GPQG and IWGQ, indicates hydrophobic interactions between the peptides are not necessary for mechanical stabilization of the hydrogel, but changes in the concentration ratio between the peptides tethered in the hydrogel and salts and ions in the swelling solution can affect the stabilization. Encapsulation of human induced pluripotent stem cell derived neural stem cells did not reduce the mechanical properties of the hydrogel over a 14 day neural differentiation culture period, and IKVAV was found to maintain concentration dependent effects on neurite extension and mRNA gene expression of neural cytoskeletal markers, similar to previous studies. As a result, this work has significant implications for the analysis of biological studies in matrices, as the material and mechanical properties of the hydrogel may be unexpectedly temporally changing during culture due to interactions between peptide signaling elements, underscoring the need for greater matrix characterization during the degradation and cell culture. Statement of significance Greater emulation of the native extracellular matrix is necessary for tissue formation. To achieve this, matrices are becoming more complex, often including multiple bioactive signaling elements. However, peptide signaling in Polyethylene Glycol matrices and amino acids interactions between peptides can affect hydrogel material and mechanical properties, but are rarely studied. The current study identifies such an interaction between laminin derived peptide, IKVAV, and collagen derived matrix metalloprotease degradable peptide, GPQGIWGQ. Previous studies using these peptides did not identify their interactions’ ability to mechanically stabilize the hydrogel during degradation. This work underscores the need for greater matrix characterization and consideration of bioactive signaling element effects temporally on the matrix’s material and mechanical properties, as they can contribute to cellular response.

  • Effects of free radical initiators on Polyethylene Glycol Dimethacrylate hydrogel properties and biocompatibility.
    Journal of biomedical materials research. Part A, 2017
    Co-Authors: Thomas S. Wilems, Hyun Ju Lim, Yuki E. Kurosu, Zara Khan, Laura A. Smith Callahan
    Abstract:

    Many studies have utilized Irgacure 2959 photopolymerized poly(ethylene Glycol) (PEG) hydrogels for tissue engineering application development. Due to the limited penetration of ultraviolet light through tissue, Irgacure 2959 polymerized hydrogels are not suitable for use in tissues where material injection is desirable, such as the spinal cord. To address this, several free radical initiators (thermal initiator VA044, ammonium persulfate (APS)/TEMED reduction–oxidation reaction, and Fenton chemistry) are evaluated for their effects on the material and mechanical properties of PEG hydrogels compared with Irgacure 2959. To emulate the effects of endogenous thiols on in vivo polymerization, the effects of chain transfer agent (CTA) dithiothreitol on gelation rates, material properties, Young's and shear modulus, are examined. Mouse embryonic stem cells and human induced pluripotent stem cell derived neural stem cells were used to investigate the cytocompatibility of each polymerization. VA044 and Fenton chemistry polymerization of PEG hydrogels both had gelation rates and mechanical properties that were highly susceptible to changes in CTA concentration and showed poor cytocompatibility. APS/TEMED polymerized hydrogels maintained consistent gelation rates and mechanical properties at high CTA concentration and had a similar cytocompatibility as Irgacure 2959 when cells were encapsulated within the PEG hydrogels. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3059–3068, 2017.

  • Concentration dependent survival and neural differentiation of murine embryonic stem cells cultured on Polyethylene Glycol Dimethacrylate hydrogels possessing a continuous concentration gradient of n-cadherin derived peptide His-Ala-Val-Asp-Lle.
    Acta biomaterialia, 2016
    Co-Authors: Hyun Ju Lim, Matthew C. Mosley, Yuki E. Kurosu, Laura A. Smith Callahan
    Abstract:

    Abstract N-cadherin cell-cell signaling plays a key role in the structure and function of the nervous system. However, few studies have incorporated bioactive signaling from n-cadherin into tissue engineering matrices. The present study uses a continuous gradient approach in Polyethylene Glycol Dimethacrylate hydrogels to identify concentration dependent effects of n-cadherin peptide, His-Ala-Val-Asp-Lle (HAVDI), on murine embryonic stem cell survival and neural differentiation. The n-cadherin peptide was found to affect the expression of pluripotency marker, alkaline phosphatase, in murine embryonic stem cells cultured on n-cadherin peptide containing hydrogels in a concentration dependent manner. Increasing n-cadherin peptide concentrations in the hydrogels elicited a biphasic response in neurite extension length and mRNA expression of neural differentiation marker, neuron-specific class III β-tubulin, in murine embryonic stem cells cultured on the hydrogels. High concentrations of n-cadherin peptide in the hydrogels were found to increase the expression of apoptotic marker, caspase 3/7, in murine embryonic stem cells compared to that of murine embryonic stem cell cultures on hydrogels containing lower concentrations of n-cadherin peptide. Increasing the n-cadherin peptide concentration in the hydrogels facilitated greater survival of murine embryonic stem cells exposed to increasing oxidative stress caused by hydrogen peroxide exposure. The combinatorial approach presented in this work demonstrates concentration dependent effects of n-cadherin signaling on mouse embryonic stem cell behavior, underscoring the need for the greater use of systematic approaches in tissue engineering matrix design in order to understand and optimize bioactive signaling in the matrix for tissue formation. Statement of Significance Single cell encapsulation is common in tissue engineering matrices. This eliminates cellular access to cell-cell signaling. N-cadherin, a cell-cell signaling molecule, plays a vital role in the development of neural tissues, but has not been well studied as a bioactive signaling element in neural tissue engineering matrices. The present study uses a systematic continuous gradient approach to identify concentration dependent effects of n-cadherin derived peptide, HAVDI, on the survival and neural differentiation of murine embryonic stem cells. This work underscores the need for greater use to combinatorial strategies to understand the effect complex bioactive signaling, such as n-cadherin, and the need to optimize the concentration of such bioactive signaling within tissue engineering matrices for maximal cellular response.

  • Influence of discrete and continuous culture conditions on human mesenchymal stem cell lineage choice in RGD concentration gradient hydrogels.
    Biomacromolecules, 2013
    Co-Authors: Laura A. Smith Callahan, Gina M. Policastro, Sharon L. Bernard, Erin P. Childers, Ronna Boettcher, Matthew L. Becker
    Abstract:

    Stem cells have shown lineage-specific differentiation when cultured on substrates possessing signaling groups derived from the native tissue. A distinct determinant in this process is the concentration of the signaling motif. While several groups have been working actively to determine the specific factors, concentrations, and mechanisms governing the differentiation process, many have been turning to combinatorial and gradient approaches in attempts to optimize the multiple chemical and physical parameters needed for the next advance. However, there has not been a direct comparison between the cellular behavior and differentiation of human mesenchymal stem cells cultured in gradient and discrete substrates, which quantitates the effect of differences caused by cell-produced, soluble factors due to design differences between the culture systems. In this study, the differentiation of human mesenchymal stem cells in continuous and discrete Polyethylene Glycol Dimethacrylate (PEGDM) hydrogels containing an ...

  • Maximizing phenotype constraint and extracellular matrix production in primary human chondrocytes using arginine-glycine-aspartate concentration gradient hydrogels.
    Acta biomaterialia, 2013
    Co-Authors: Laura A. Smith Callahan, Sharon L. Bernard, Erin P. Childers, Scott D. Weiner, Matthew L. Becker
    Abstract:

    New systematic approaches are necessary to determine and optimize the chemical and mechanical scaffold properties for hyaline cartilage generation using the limited cell numbers obtained from primary human sources. Peptide functionalized hydrogels possessing continuous variations in physico-chemical properties are an efficient three-dimensional platform for studying several properties simultaneously. Herein, we describe a Polyethylene Glycol Dimethacrylate (PEGDM) hydrogel system possessing a gradient of arginine–glycine–aspartic acid peptide (RGD) concentrations from 0 mM to 10 mM. The system is used to correlate primary human osteoarthritic chondrocyte proliferation, phenotype maintenance and extracellular matrix (ECM) production to the gradient hydrogel properties. Cell number and chondrogenic phenotype (CD14:CD90 ratios) were found to decline in regions with higher RGD concentrations, while regions with lower RGD concentrations maintained cell number and phenotype. Over three weeks of culture, hydrogel regions containing lower RGD concentrations experience an increase in ECM content compared to regions with higher RGD concentrations. Variations in actin amounts and vinculin organization were observed within the RGD concentration gradients that contribute to the differences in chondrogenic phenotype maintenance and ECM expression.

Jun Nie - One of the best experts on this subject based on the ideXlab platform.

  • Design of photoinitiator-functionalized hydrophilic nanogels with uniform size and excellent biocompatibility
    Polymer Chemistry, 2019
    Co-Authors: Meng Wei, Jun Nie, Yanjing Gao, Shengling Jiang, Fang Sun
    Abstract:

    Three hydrophilic photoinitiator-functionalized nanogels with uniform size distribution were designed and synthesized through activator generated electron transfer atom transfer radical polymerization (AGET ATRP) in an inverse miniemulsion, based on oligo(ethylene Glycol) monomethyl ether methacrylate (OEOMA), Polyethylene Glycol Dimethacrylate (PEGDMA) and 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959). Compared to Irgacure 2959, the nanogels possess excellent water solubility which reaches up 50 wt%. The nanogels have an absorption centered at 273 nm in anhydrous acetonitrile and can effectively initiate the polymerization of acrylate monomers. The nanogels can not only improve the thermostability of the polymer, but can also exhibit an excellent toughening effect. Furthermore, the migration of photolysis fragments from a photocured film was alleviated significantly due to their high molecular weight. Importantly, the cytotoxicity of the nanogels and their photocured film was tested against HeLa cervical cancer cells using the MTT cell viability assay and their cell viability is 93%–94%, indicating that the nanogels have potential in biomaterials.

  • injectable hydrogels based on chitosan derivative Polyethylene Glycol Dimethacrylate n n dimethylacrylamide as bone tissue engineering matrix
    Carbohydrate Polymers, 2010
    Co-Authors: Dongzhi Yang, Kemin Wang, Binling Chen, John F. Kennedy, Jun Nie
    Abstract:

    Abstract Injectable hydrogels were prepared from chitosan derivative (EGAMA-CS) / Polyethylene Glycol Dimethacrylate (PEGDA)/ N , N -dimethylacrylamide (DMMA) by photopolymerization. The morphology of the hydrogels was observed by scanning electron microscope (SEM). The relationship of double bond conversion with photopolymerization time was revealed by Real-time FTIR. The thermal behaviour of the hydrogels was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The equilibrium swelling ratio was also evaluated. In addition, the potential use of the hydrogels as scaffolding materials for bone regeneration was evaluated in vitro with Human bone sarcoma cell (SW1353) as reference cell lines. Indirect cytotoxicity assessment of the hydrogels indicated that the EGAMA-CS / PEGDA / DMMA hydrogels was non-toxic to the SW1353 cell. Cell culture results showed that fibrous mats were good in promoting the cell attachment and proliferation. The photopolymerized hydrogels are promised for the applications in the biomaterials area as bone tissue engineering matrix.

  • Injectable hydrogels based on chitosan derivative/Polyethylene Glycol Dimethacrylate/N,N-dimethylacrylamide as bone tissue engineering matrix
    Carbohydrate Polymers, 2010
    Co-Authors: Dongzhi Yang, Kemin Wang, Binling Chen, John F. Kennedy, Jun Nie
    Abstract:

    Abstract Injectable hydrogels were prepared from chitosan derivative (EGAMA-CS) / Polyethylene Glycol Dimethacrylate (PEGDA)/ N , N -dimethylacrylamide (DMMA) by photopolymerization. The morphology of the hydrogels was observed by scanning electron microscope (SEM). The relationship of double bond conversion with photopolymerization time was revealed by Real-time FTIR. The thermal behaviour of the hydrogels was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The equilibrium swelling ratio was also evaluated. In addition, the potential use of the hydrogels as scaffolding materials for bone regeneration was evaluated in vitro with Human bone sarcoma cell (SW1353) as reference cell lines. Indirect cytotoxicity assessment of the hydrogels indicated that the EGAMA-CS / PEGDA / DMMA hydrogels was non-toxic to the SW1353 cell. Cell culture results showed that fibrous mats were good in promoting the cell attachment and proliferation. The photopolymerized hydrogels are promised for the applications in the biomaterials area as bone tissue engineering matrix.

Clement L. Higginbotham - One of the best experts on this subject based on the ideXlab platform.

  • synthesis and photopolymerisation of maleic polyvinyl alcohol based hydrogels for bone tissue engineering
    Journal of Polymer Research, 2014
    Co-Authors: John A. Killion, Declan M. Devine, Luke M. Geever, Laura Grehan, Martin O Cloonan, Cathal Waldron, Keith Quinn, John G Lyons, Clement L. Higginbotham
    Abstract:

    The novel synthesis of photopolymerisable polyvinyl alcohol (PVA) was achieved by reacting maleic anhydride with the hydroxyl groups of PVA. The incorporation of photopolymerisable double bonds onto the PVA polymeric chain was confirmed by both 1H NMR and 13C NMR spectroscopy. Hydrogel blends were prepared by mixing maleic PVA and Polyethylene Glycol Dimethacrylate (PEGDMA) precursors at different concentrations and molecular weights. It was observed that the increase in crosslinking with the introduction of maleic PVA crosslinks resulted in higher compressive properties and storage modulus values. These values fall below those reported for bone; however, if these scaffolds were used in conjunction with fixation devices and with the sustained release of dexamethasone it would allow for faster regeneration of bone defects. Drug release results showed that the release profile of the hydrogels was between 11 and 16 days. This was as a result of altering the swelling and pore sizes of the hydrogels by varying the precursor concentrations. Preliminary in vitro cytotoxicity evaluations were performed using the MTT assay as an end point, showing that these novel hydrogels are non-toxic to mouse embryonic fibroblast cell line.

  • Synthesis and Characterization of Polyethylene Glycol Dimethacrylate Hydrogels for Biomedical Application
    Applied Mechanics and Materials, 2014
    Co-Authors: Malgorzata A. Poplawska, Iska Schimpf, Damien B. Brady, Carmel Kealey, Anne Mulvihill, Clement L. Higginbotham
    Abstract:

    Photo-polymerized Polyethylene Glycol Dimethacrylate (PEGDMA) scaffolds were synthesized using two macromolecular monomers of 750 and 550 number average molecular weight. Variation in chain length of macromolecular monomers visibly influenced viscoelastic properties of the compositions, exhibiting an increase in shear storage and loss modulus in PEGDMA 750 hydrogels. Furthermore, water content in the pre-polymerization mixture was a main factor determining physical appearance of the samples, where increase in water content resulted in polymerization induced phase separation, demonstrated by opaqueness of preparations containing 60 and 75% (w/w) of H2O. In addition to this, swelling, gel fraction, compression and rheological measurements are found to be influenced by the amount of water incorporated in the hydrogels, resulting in the increased distance between polymer chains within the network. Furthermore this resulted in an apparent decrease in viscoelastic and mechanical properties of compositions, as well as in lowering their crosslinking density and compressive strength. Preliminary cytotoxicity results show no toxicity of the samples with approximately 80% cell viability after 24 h exposure of MC3T3-E1 Subclone 4 cells to the hydrogels, thus indicating that these materials could be potentially applied in the biomedical arena.

  • Modulating the mechanical properties of photopolymerised Polyethylene Glycol–polypropylene Glycol hydrogels for bone regeneration
    Journal of Materials Science, 2012
    Co-Authors: John A. Killion, Declan M. Devine, Luke M. Geever, Laura Grehan, James E. Kennedy, Clement L. Higginbotham
    Abstract:

    Hydrogels formulated from single polymers are often insufficient in terms of their mechanical properties for use as bone substitute materials. Hence, hydrogels synthesised from combinations of polymers have been investigated to optimise the performance of such materials. In the current study, polypropylene Glycol Dimethacrylate was added to Polyethylene Glycol Dimethacrylate of a variety of molecular weights and photopolymerised to form a series of hydrogels. Polyethylene Glycol and polypropylene Glycol have the same chemical structure with the exception of a methyl group on the later. Herein, the influence of the methyl group of polypropylene Glycol on the mechanical properties of hydrogels for bone regeneration applications is reported. For both unconfined and cyclic compression testing, results demonstrated that the incorporation of PEGDMA into the precursor improves the compression strength of the hydrogels. For example, in unconfined compression tests the Young’s modulus varied between 6.62 ± 0.31 MPa and 8.08 ± 0.81 MPa with the incorporation of PEGDMA 400.

  • Modulating the mechanical properties of photopolymerised Polyethylene Glycol-polypropylene Glycol hydrogels for bone regeneration
    Journal of Materials Science, 2012
    Co-Authors: John A. Killion, Declan M. Devine, Luke M. Geever, Laura Grehan, James E. Kennedy, Clement L. Higginbotham
    Abstract:

    Hydrogels formulated from single polymers are often insufficient in terms of their mechanical properties for use as bone substitute materials. Hence, hydrogels synthesised from combinations of polymers have been investigated to optimise the performance of such materials. In the current study, polypropylene Glycol Dimethacrylate was added to Polyethylene Glycol Dimethacrylate of a variety of molecular weights and photopolymerised to form a series of hydrogels. Polyethylene Glycol and polypropylene Glycol have the same chemical structure with the exception of a methyl group on the later. Herein, the influence of the methyl group of polypropylene Glycol on the mechanical properties of hydrogels for bone regeneration applications is reported. For both unconfined and cyclic compression testing, results demonstrated that the incorporation of PEGDMA into the precursor improves the compression strength of the hydrogels. For example, in unconfined compression tests the Young’s modulus varied between 6.62 ± 0.31 MPa and 8.08 ± 0.81 MPa with the incorporation of PEGDMA 400.

Fiore Pasquale Nicoletta - One of the best experts on this subject based on the ideXlab platform.

  • Combining antioxidant hydrogels with self-assembled microparticles for multifunctional wound dressings
    Journal of Materials Chemistry B, 2019
    Co-Authors: Mariagrazia Di Luca, Giuseppe Cirillo, Manuela Curcio, Emanuele Valli, Florida Voli, Maria Eugenia Butini, Annafranca Farfalla, Elvira Pantuso, Antonella Leggio, Fiore Pasquale Nicoletta
    Abstract:

    A multi-functional composite to be employed as a dressing material was prepared by combining hydrogel and microparticle systems. For the synthesis of the hydrogel counterpart, a free radical polymerization was carried out using a gelatin–curcumin conjugate, previously obtained through immobilized laccase catalysis, and Polyethylene Glycol Dimethacrylate as a functional element, plasticizer, and crosslinker. The hydrogel was found to possess high water affinity, biocompatibility, and the ability to reduce the H2O2-induced oxidative stress on MRC-5 cells by 30%. The spherical microparticle system (mean diameter of 1.75 μm) was prepared by self-assembly of a keratin-methacrylated Polyethylene Glycol-40 stearate derivative synthesized by a free radical reaction. The final composite, prepared by absorption of microparticles on the hydrogel system, was found to be effective as a support for enhanced cell growth (3.5 times). Furthermore, a reduction of methicillin-resistant Staphylococcus aureus proliferation by 1 log10 CFU was reached taking advantage of the sustained release of the antimicrobial quercetin.

  • Electro-responsive graphene oxide hydrogels for skin bandages: The outcome of gelatin and trypsin immobilization
    International journal of pharmaceutics, 2018
    Co-Authors: Mariagrazia Di Luca, Giuseppe Cirillo, Manuela Curcio, Fiore Pasquale Nicoletta, Orazio Vittorio, Silke Hampel, Florida Voli, Annafranca Farfalla, Magdalena Czuban, Francesca Iemma
    Abstract:

    A free radical polymerization method was adopted for the fabrication of hybrid hydrogel films based on acrylamide and Polyethylene Glycol Dimethacrylate as plasticizing and crosslinking agents, respectively, to be employed as smart skin bandages. Electro-sensitivity, biocompatibility and proteolytic properties were conferred to the final polymer networks by introducing graphene oxide (0.5% w/w), gelatin or trypsin (10% w/w) in the polymerization feed. The physical chemical and mechanical characterization of hybrid materials was performed by means of determination of protein content, Raman spectroscopy, thermogravimetric analysis and measurement of tensile strength. The evaluation of both water affinity and curcumin release profiles (analyzed by suitable mathematical modelling) upon application of an external electric stimulation in the 0-48 voltage range, confirmed the possibility to modulate the release kinetics. Proper proteolytic tests showed that the trypsin enzymatic activity was retained by 80% upon immobilization. Moreover, for all samples, we observed a viability higher than 94% in normal human fibroblast cells (MRC-5), while a reduction of methicillin-resistant Staphylococcus aureus CFU mL-1 (90%) was obtained with curcumin loaded samples.

  • Carbon nanotubes hybrid hydrogels for electrically tunable release of Curcumin
    European Polymer Journal, 2017
    Co-Authors: Giuseppe Cirillo, Umile Gianfranco Spizzirri, Manuela Curcio, Nevio Picci, Francesca Iemma, Orazio Vittorio, Paola Tucci, Silke Hampel, Fiore Pasquale Nicoletta
    Abstract:

    Abstract Electro-responsive hybrid hydrogels were synthesized by free radical polymerization using Gelatin-coated multi-walled carbon nanotubes as electro-conductive component, acrylamide and Polyethylene Glycol Dimethacrylate as plasticizing and crosslinking monomer, respectively. Dynamic light scattering, Raman spectroscopy, scanning electron microscopy, resistivity measurement, cell viability assay, and evaluation of swelling degree upon application of an external voltage at 0, 12, 24, 36, and 48 V were performed as characterization tools. Composite materials were found to be highly versatile in modulating the drug delivery of neutral drugs (e.g. Curcumin) as a function of both nanotube content and voltage magnitude, with drug partition between carrier and releasing media being dependent on the balance between electrostatic attractive and repulsive forces and hydrogel swelling degree. Finally, suitable mathematical modelling were employed for the kinetic characterization of the release mechanism. The results allowed hypothesizing the use of hybrid for different therapeutic needs in wound healing treatment.

  • Cotton gauze-hydrogel composites: Valuable tools for electrically modulated drug delivery
    International Journal of Polymeric Materials and Polymeric Biomaterials, 2016
    Co-Authors: Giuseppe Cirillo, Umile Gianfranco Spizzirri, Manuela Curcio, Tania Spataro, Nevio Picci, Fiore Pasquale Nicoletta, Francesca Iemma
    Abstract:

    ABSTRACTCotton gauze was inserted into a hydrogel network composed of acrylamide, sodium methacrylate, and Polyethylene Glycol Dimethacrylate to fabricate an electroresponsive delivery system for wound dressing. The composite was characterized by swelling measurements, showing that shrinking or swelling depend on the applied voltage. The release profile of incorporated diclofenac sodium salt shows the possibility to modulate the kinetics by changes in the amplitude and duration of applied electric pulses. Mathematical models allow a characterization of release profiles, which are slower when an external voltage of 6, 12, and 18 V is applied, and faster at 24 V.

C.l. Cheng - One of the best experts on this subject based on the ideXlab platform.

  • Thermal shutdown behavior of PVdF-HFP based polymer electrolytes comprising heat sensitive cross-linkable oligomers
    Elsevier, 2009
    Co-Authors: C.l. Cheng
    Abstract:

    [[abstract]]c2005 Elsevier - PVdF-HFP (polyvinylidenefluoride-hexafluoropropylene) polymer electrolytes comprising cross-linkable PEGDMA (Polyethylene Glycol Dimethacrylate) oligomers with thermal shutdown characteristic have been developed. In contrast to the melting mechanism of polyolefin, this new polymer electrolyte possesses a thermal shutdown characteristic by a rapid cross-linking reaction of PEGDMA. The cross-linked PEGDMA network inside the PVdF-HFP matrix can provide the mechanical strength for the electrolytes, while the un-cross-linked PEGDMA oligomers serve as plasticizers for PVdF-HFP to improve the mobility of lithium ions at normal operation temperatures. In addition, the un-cross-linked PEGDMA oligomers can initiate cross-linking upon a sudden rise of temperature and thus provide thermal shutdown protection at elevated temperatures.[[department]]化學工程學

  • Preparation of porous, chemically cross-linked, PVdF-based gel polymer electrolytes for rechargeable lithium batteries
    Elsevier, 2009
    Co-Authors: C.l. Cheng
    Abstract:

    [[abstract]]c2004 Elsevier - This study reports the development of a new system of porous, chemically cross-linked, gel polymer electrolytes based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF–HFP) copolymer as a polymer matrix, Polyethylene Glycol (PEG) as a plasticizer, and Polyethylene Glycol Dimethacrylate (PEGDMA) as a chemical cross-linking oligomer. The electrolytes are prepared by a combination of controlled evaporation and thermal polymerization of PEGDMA. PVdF–HFP/PEG/PEGDMA gel polymer electrolytes with a composition of 5/3/2 exhibit both high ambient ionic conductivity, viz., >1 mS cm−1, and a high tensile modulus of 52 MPa, because of their porous and network structures. All the blends of electrolytes are electrochemically stable up to 5 V versus Li/Li+ in the presence of 1 M LiPF6/ethylene carbonate–diethyl carbonate (EC–DEC). With these polymer electrolytes, rechargeable lithium batteries composed of carbon anode and LiCoO2 cathode have acceptable cycleability and a good rate capability.[[department]]化學工程學

  • Microporous PVDF-HFP based gel polymer electrolytes reinforced by PEGDMA network
    Elsevier, 2009
    Co-Authors: C.l. Cheng
    Abstract:

    [[abstract]]c2004 Elsevier - We have successfully developed a new process to prepare microporous poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) copolymer based gel electrolyte with Polyethylene Glycol Dimethacrylate (PEGDMA) network without the need for extraction process. Microporous structure in polymer matrix is achieved by solvent controlled evaporation from solution containing a copolymer in a mixture of volatile solvent and nonsolvent. The high tensile modulus and better flexibility of the membrane are improved by combination of PEGDMA network and PVdF-HFP copolymer chain which is plasticized by Polyethylene Glycol (PEG). The blend polymer membrane with composition of PVdF-HFP/PEG/PEGDMA (5/3/2) shows electrolyte uptake of 98.2% and ionic conductivity exceeding 1.0 × 10−3 S cm−1 at room temperature in the presence of 1 M LiPF6/EC-DEC. AC impedance studies also confirm that this blend gel electrolyte can form stable passivation layer on the lithium metal surface. In addition, the use of the blend gel electrolyte assures electrochemical stability up to 5.0 V vs. Li/Li+.[[department]]化學工程學

  • Thermal shutdown behavior of PVdF-HFP based polymer electrolytes comprising heat sensitive cross-linkable oligomers
    Journal of Power Sources, 2005
    Co-Authors: C.l. Cheng, C.c. Wan, Y.y. Wang
    Abstract:

    PVdF-HFP (polyvinylidenefluoride-hexafluoropropylene) polymer electrolytes comprising cross-linkable PEGDMA (Polyethylene Glycol Dimethacrylate) oligomers with thermal shutdown characteristic have been developed. In contrast to the melting mechanism of polyolefin, this new polymer electrolyte possesses a thermal shutdown characteristic by a rapid cross-linking reaction of PEGDMA. The cross-linked PEGDMA network inside the PVdF-HFP matrix can provide the mechanical strength for the electrolytes, while the un-cross-linked PEGDMA oligomers serve as plasticizers for PVdF-HFP to improve the mobility of lithium ions at normal operation temperatures. In addition, the un-cross-linked PEGDMA oligomers can initiate cross-linking upon a sudden rise of temperature and thus provide thermal shutdown protection at elevated temperatures.

  • Microporous PVdF-HFP based gel polymer electrolytes reinforced by PEGDMA network
    Elsevier, 2004
    Co-Authors: C.l. Cheng, C.c. Wan, Y.y. Wang
    Abstract:

    We have successfully developed a new process to prepare microporous poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) copolymer based gel electrolyte with Polyethylene Glycol Dimethacrylate (PEGDMA) network without the need for extraction process. Microporous structure in polymer matrix is achieved by solvent controlled evaporation from solution containing a copolymer in a mixture of volatile solvent and nonsolvent. The high tensile modulus and better flexibility of the membrane are improved by combination of PEGDMA network and PVdF-HFP copolymer chain which is plasticized by Polyethylene Glycol (PEG). The blend polymer membrane with composition of PVdF-HFP/PEG/PEGDMA (5/3/2) shows electrolyte uptake of 98.2% and ionic conductivity exceeding 1.0×10−3 Scm−1 at room temperature in the presence of 1 M LiPF6/EC-DEC. AC impedance studies also confirm that this blend gel electrolyte can form stable passivation layer on the lithium metal surface. In addition, the use of the blend gel electrolyte assures electrochemical stability up to 5.0 V vs. Li/Li+. Keywords: PVDF-HFP copolymer, Polyethylene Glycol Dimethacrylate, Polymer electrolytes, Controlled evaporation, Lithium batterie