The Experts below are selected from a list of 18114 Experts worldwide ranked by ideXlab platform
Jean M. J. Fréchet - One of the best experts on this subject based on the ideXlab platform.
-
high field scanning probe lithography in hexadecane transitioning from field induced oxidation to solvent decomposition through Surface modification
Advanced Materials, 2007Co-Authors: Itai Suez, Marco Rolandi, Andreas Scholl, Scott A Backer, Andrew Doran, David Okawa, Alex Zettl, Jean M. J. FréchetAbstract:High field scanning probe lithography in hexadecane leads to two different chemical reactions depending on Surface Hydrophilicity. On a hydrophilic Surface, oxidation of the sample occurs; a hydrophobic Surface, results in solvent decomposition and nanoscale deposition of etch resistant material. The features are characterized with photoelectron emission microscopy and are carbonaceous in nature with a highly cross-linked bonding network. Tone reversal in a fluorinated etch is achieved.
-
hydrophilic Surface modification of cyclic olefin copolymer microfluidic chips using sequential photografting
IEEE Journal of Solid-state Circuits, 2007Co-Authors: Timothy B. Stachowiak, Tyler G. Holden, Dieudonne A. Mair, Frantisek Svec, Jean M. J. Fréchet, James L LeeAbstract:The plastic material known as cyclic olefin copolymer (COC) is a useful substrate material for fabricating microfluidic devices due to its low cost, ease of fabrication, excellent optical properties, and resistance to many solvents. However, the hydrophobicity of native COC limits its use in bioanalytical applications. To increase Surface Hydrophilicity and reduce protein adsorption, COC Surfaces were photografted with poly(ethylene glycol) methacrylate (PEGMA) using a two-step sequential approach: covalently-bound Surface initiators were formed in the first step and graft polymerization of PEGMA was then carried out from these sites in the second step. Contact angle measurements were used to monitor and quantify the changes in Surface Hydrophilicity as a function of grafting conditions. As water droplet contact angles decreased from 88° for native COC to 45° for PEGMA-grafted Surfaces, protein adsorption was also reduced by 78% for the PEGMA-modified COC microchannels as determined by a fluorescence assay. This photografting technique should enable the use of COC microdevices in a variety of bioanalytical applications that require minimal nonspecific adsorption of biomolecules.
-
Hydrophilic Surface modification of cyclic olefin copolymer microfluidic chips using sequential photografting
Journal of Separation Science, 2007Co-Authors: Timothy B. Stachowiak, Tyler G. Holden, Dieudonne A. Mair, Frantisek Svec, L. James Lee, Jean M. J. FréchetAbstract:The plastic material known as cyclic olefin copolymer (COC) is a useful substrate material for fabricating microfluidic devices due to its low cost, ease of fabrication, excellent optical properties, and resistance to many solvents. However, the hydrophobicity of native COC limits its use in bioanalytical applications. To increase Surface Hydrophilicity and reduce protein adsorption, COC Surfaces were photografted with poly(ethylene glycol) methacrylate (PEGMA) using a two-step sequential approach: covalently-bound Surface initiators were formed in the first step and graft polymerization of PEGMA was then carried out from these sites in the second step. Contact angle measurements were used to monitor and quantify the changes in Surface Hydrophilicity as a function of grafting conditions. As water droplet contact angles decreased from 88 degrees for native COC to 45 degrees for PEGMA-grafted Surfaces, protein adsorption was also reduced by 78% for the PEGMA-modified COC microchannels as determined by a fluorescence assay. This photografting technique should enable the use of COC microdevices in a variety of bioanalytical applications that require minimal nonspecific adsorption of biomolecules.
Tony Mcnally - One of the best experts on this subject based on the ideXlab platform.
-
graphene oxide enhanced ionic liquid plasticisation of chitosan alginate bionanocomposites
Carbohydrate Polymers, 2021Co-Authors: Pei Chen, Fengwei Xie, Fengzai Tang, Tony McnallyAbstract:Abstract The effect of graphene oxide (GO) or reduced GO (rGO) on the structure and properties of polyelectrolyte-complexed chitosan/alginate bionanocomposites is highly dependent on plasticiser type (glycerol or 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc])) due to the competing interactions between the components. For the glycerol-plasticised chitosan/alginate matrix, inclusion of GO/rGO enhanced the chitosan crystallinity and increased matrix ductility. While the chitosan/alginate matrix plasticised by [C2mim][OAc] showed dramatically weakened interactions between the two biopolymers, GO was highly effective at counteracting the effect of [C2mim][OAc] by interacting with the biopolymers and the ionic liquid ions, resulting in enhanced mechanical properties and decreased Surface Hydrophilicity. Compared with GO, rGO was much less effective at promoting chitosan–alginate interactions and even resulted in higher Surface Hydrophilicity. However, irrespective of the plasticiser type, inclusion of rGO resulted in reduced crystallinity by restricting the interactions between [C2mim][OAc] and the biopolymers, and higher ionic conductivity.
-
glycerol plasticisation of chitosan carboxymethyl cellulose composites role of interactions in determining structure and properties
International Journal of Biological Macromolecules, 2020Co-Authors: Pei Chen, Fengwei Xie, Fengzai Tang, Tony McnallyAbstract:Abstract Biopolymers such as chitosan and cellulose continue to attract much interest as they have many appealing characteristics such as biodegradability, biocompatibility, chemical versatility and natural functionality; however, many of their properties usually require further tailoring for specific purposes. This study shows that glycerol plasticisation and the addition of graphene oxide (GO) or reduced graphene oxide (rGO) altered the properties of chitosan and a chitosan/carboxymethyl cellulose (CMC) blend. For the chitosan/CMC matrix, GO or rGO was likely to disrupt polyelectrolyte complexation (PEC) between the two biopolymers, leading to weakened mechanical properties and increased Surface Hydrophilicity. Conversely, glycerol assisted PEC by increasing the biopolymer chain mobility, leading to reduced Surface Hydrophilicity. Moreover, some synergistic effects from a combination of glycerol and GO/rGO were evident. Specifically, GO/rGO notably increased the toughness of the chitosan film on inclusion of 40 wt% glycerol. Both GO and rGO reduced the relaxation temperatures of the chitosan/CMC film with 20 wt% glycerol added, resulting in increased biopolymer chain mobility. Moreover, the bionanocomposites showed high relative permittivity (54–387). Thus, this work describes how complex interactions in multiphasic biopolymer composite systems influence structure and properties.
Fengwei Xie - One of the best experts on this subject based on the ideXlab platform.
-
graphene oxide enhanced ionic liquid plasticisation of chitosan alginate bionanocomposites
Carbohydrate Polymers, 2021Co-Authors: Pei Chen, Fengwei Xie, Fengzai Tang, Tony McnallyAbstract:Abstract The effect of graphene oxide (GO) or reduced GO (rGO) on the structure and properties of polyelectrolyte-complexed chitosan/alginate bionanocomposites is highly dependent on plasticiser type (glycerol or 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc])) due to the competing interactions between the components. For the glycerol-plasticised chitosan/alginate matrix, inclusion of GO/rGO enhanced the chitosan crystallinity and increased matrix ductility. While the chitosan/alginate matrix plasticised by [C2mim][OAc] showed dramatically weakened interactions between the two biopolymers, GO was highly effective at counteracting the effect of [C2mim][OAc] by interacting with the biopolymers and the ionic liquid ions, resulting in enhanced mechanical properties and decreased Surface Hydrophilicity. Compared with GO, rGO was much less effective at promoting chitosan–alginate interactions and even resulted in higher Surface Hydrophilicity. However, irrespective of the plasticiser type, inclusion of rGO resulted in reduced crystallinity by restricting the interactions between [C2mim][OAc] and the biopolymers, and higher ionic conductivity.
-
glycerol plasticisation of chitosan carboxymethyl cellulose composites role of interactions in determining structure and properties
International Journal of Biological Macromolecules, 2020Co-Authors: Pei Chen, Fengwei Xie, Fengzai Tang, Tony McnallyAbstract:Abstract Biopolymers such as chitosan and cellulose continue to attract much interest as they have many appealing characteristics such as biodegradability, biocompatibility, chemical versatility and natural functionality; however, many of their properties usually require further tailoring for specific purposes. This study shows that glycerol plasticisation and the addition of graphene oxide (GO) or reduced graphene oxide (rGO) altered the properties of chitosan and a chitosan/carboxymethyl cellulose (CMC) blend. For the chitosan/CMC matrix, GO or rGO was likely to disrupt polyelectrolyte complexation (PEC) between the two biopolymers, leading to weakened mechanical properties and increased Surface Hydrophilicity. Conversely, glycerol assisted PEC by increasing the biopolymer chain mobility, leading to reduced Surface Hydrophilicity. Moreover, some synergistic effects from a combination of glycerol and GO/rGO were evident. Specifically, GO/rGO notably increased the toughness of the chitosan film on inclusion of 40 wt% glycerol. Both GO and rGO reduced the relaxation temperatures of the chitosan/CMC film with 20 wt% glycerol added, resulting in increased biopolymer chain mobility. Moreover, the bionanocomposites showed high relative permittivity (54–387). Thus, this work describes how complex interactions in multiphasic biopolymer composite systems influence structure and properties.
Pei Chen - One of the best experts on this subject based on the ideXlab platform.
-
graphene oxide enhanced ionic liquid plasticisation of chitosan alginate bionanocomposites
Carbohydrate Polymers, 2021Co-Authors: Pei Chen, Fengwei Xie, Fengzai Tang, Tony McnallyAbstract:Abstract The effect of graphene oxide (GO) or reduced GO (rGO) on the structure and properties of polyelectrolyte-complexed chitosan/alginate bionanocomposites is highly dependent on plasticiser type (glycerol or 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc])) due to the competing interactions between the components. For the glycerol-plasticised chitosan/alginate matrix, inclusion of GO/rGO enhanced the chitosan crystallinity and increased matrix ductility. While the chitosan/alginate matrix plasticised by [C2mim][OAc] showed dramatically weakened interactions between the two biopolymers, GO was highly effective at counteracting the effect of [C2mim][OAc] by interacting with the biopolymers and the ionic liquid ions, resulting in enhanced mechanical properties and decreased Surface Hydrophilicity. Compared with GO, rGO was much less effective at promoting chitosan–alginate interactions and even resulted in higher Surface Hydrophilicity. However, irrespective of the plasticiser type, inclusion of rGO resulted in reduced crystallinity by restricting the interactions between [C2mim][OAc] and the biopolymers, and higher ionic conductivity.
-
glycerol plasticisation of chitosan carboxymethyl cellulose composites role of interactions in determining structure and properties
International Journal of Biological Macromolecules, 2020Co-Authors: Pei Chen, Fengwei Xie, Fengzai Tang, Tony McnallyAbstract:Abstract Biopolymers such as chitosan and cellulose continue to attract much interest as they have many appealing characteristics such as biodegradability, biocompatibility, chemical versatility and natural functionality; however, many of their properties usually require further tailoring for specific purposes. This study shows that glycerol plasticisation and the addition of graphene oxide (GO) or reduced graphene oxide (rGO) altered the properties of chitosan and a chitosan/carboxymethyl cellulose (CMC) blend. For the chitosan/CMC matrix, GO or rGO was likely to disrupt polyelectrolyte complexation (PEC) between the two biopolymers, leading to weakened mechanical properties and increased Surface Hydrophilicity. Conversely, glycerol assisted PEC by increasing the biopolymer chain mobility, leading to reduced Surface Hydrophilicity. Moreover, some synergistic effects from a combination of glycerol and GO/rGO were evident. Specifically, GO/rGO notably increased the toughness of the chitosan film on inclusion of 40 wt% glycerol. Both GO and rGO reduced the relaxation temperatures of the chitosan/CMC film with 20 wt% glycerol added, resulting in increased biopolymer chain mobility. Moreover, the bionanocomposites showed high relative permittivity (54–387). Thus, this work describes how complex interactions in multiphasic biopolymer composite systems influence structure and properties.
Fengzai Tang - One of the best experts on this subject based on the ideXlab platform.
-
graphene oxide enhanced ionic liquid plasticisation of chitosan alginate bionanocomposites
Carbohydrate Polymers, 2021Co-Authors: Pei Chen, Fengwei Xie, Fengzai Tang, Tony McnallyAbstract:Abstract The effect of graphene oxide (GO) or reduced GO (rGO) on the structure and properties of polyelectrolyte-complexed chitosan/alginate bionanocomposites is highly dependent on plasticiser type (glycerol or 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc])) due to the competing interactions between the components. For the glycerol-plasticised chitosan/alginate matrix, inclusion of GO/rGO enhanced the chitosan crystallinity and increased matrix ductility. While the chitosan/alginate matrix plasticised by [C2mim][OAc] showed dramatically weakened interactions between the two biopolymers, GO was highly effective at counteracting the effect of [C2mim][OAc] by interacting with the biopolymers and the ionic liquid ions, resulting in enhanced mechanical properties and decreased Surface Hydrophilicity. Compared with GO, rGO was much less effective at promoting chitosan–alginate interactions and even resulted in higher Surface Hydrophilicity. However, irrespective of the plasticiser type, inclusion of rGO resulted in reduced crystallinity by restricting the interactions between [C2mim][OAc] and the biopolymers, and higher ionic conductivity.
-
glycerol plasticisation of chitosan carboxymethyl cellulose composites role of interactions in determining structure and properties
International Journal of Biological Macromolecules, 2020Co-Authors: Pei Chen, Fengwei Xie, Fengzai Tang, Tony McnallyAbstract:Abstract Biopolymers such as chitosan and cellulose continue to attract much interest as they have many appealing characteristics such as biodegradability, biocompatibility, chemical versatility and natural functionality; however, many of their properties usually require further tailoring for specific purposes. This study shows that glycerol plasticisation and the addition of graphene oxide (GO) or reduced graphene oxide (rGO) altered the properties of chitosan and a chitosan/carboxymethyl cellulose (CMC) blend. For the chitosan/CMC matrix, GO or rGO was likely to disrupt polyelectrolyte complexation (PEC) between the two biopolymers, leading to weakened mechanical properties and increased Surface Hydrophilicity. Conversely, glycerol assisted PEC by increasing the biopolymer chain mobility, leading to reduced Surface Hydrophilicity. Moreover, some synergistic effects from a combination of glycerol and GO/rGO were evident. Specifically, GO/rGO notably increased the toughness of the chitosan film on inclusion of 40 wt% glycerol. Both GO and rGO reduced the relaxation temperatures of the chitosan/CMC film with 20 wt% glycerol added, resulting in increased biopolymer chain mobility. Moreover, the bionanocomposites showed high relative permittivity (54–387). Thus, this work describes how complex interactions in multiphasic biopolymer composite systems influence structure and properties.
