The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
K.l. Tan - One of the best experts on this subject based on the ideXlab platform.
-
Chemical modification of polyaniline powders by surface Graft Copolymerization
Polymer, 2000Co-Authors: Yongjun Chen, En-tang Kang, Koon Gee Neoh, K.l. TanAbstract:Abstract Chemical modification of emeraldine (EM) based powders via thermally induced surface Graft Copolymerization with acrylic acid (AAc), 4-styrenesulfonic acid (SSAc) and amphoteric N,N′-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS) was carried out in aqueous media. The effects of temperature on Graft Copolymerization and Mohr's salt on homopolymerization were also studied. The chemical composition and structure of the Graft-copolymerized powders were studied by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. In all cases, the Graft yield increased with the monomer concentration and the temperature used for Graft Copolymerization. Certain Mohr's salts effectively inhibited the production of the homopolymers. Graft Copolymerization with AAc and SSAc readily gave rise to self-protonated and semi-conductive EM powders, with the conductivity increasing with the extent of Grafting. However, steric hindrance and spatial configuration of the Grafted chains had substantially limited the extent of protonation of the EM substrate by the protonic acid functional groups of these chains.
-
surface modification of poly tetrafluoroethylene films by Graft Copolymerization for adhesion improvement with evaporated copper
Macromolecules, 1999Co-Authors: E T Kang, K G Neoh, H S Han, K.l. TanAbstract:Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film via UV light-induced Graft Copolymerization with 1-vinylimidazole (VIDz) and glycidyl methacrylate (GMA) were carried out to improve the adhesion with evaporated copper. The surface compositions of the Graft-copolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The Graft yield increases with the monomer concentration. The adhesion strength of the Graft-copolymerized PTFE film and the evaporated copper is affected by the type of monomer used for Graft Copolymerization, the Graft concentration, the plasma posttreatment time after Graft Copolymerization, and the extent of heat posttreatment after evaporation of copper. A double Graft Copolymerization process, which involved first the Graft Copolymerization with VIDz, followed by Graft Copolymerization with GMA, was also employed to enhance the adhesion of evaporated Cu to PTFE. The T-type peel strength of the PTFE/Cu interface so obtained is about 1...
-
Surface Modification of Poly(tetrafluoroethylene) Film by Consecutive Graft Copolymerization with 4-Vinylaniline and Aniline
Macromolecules, 1999Co-Authors: En-tang Kang, Koon Gee Neoh, K.l. TanAbstract:Surface modification of argon plasma-pretreated poly(tetrafluoroethylene) (PTFE) film by UV-induced Graft Copolymerization with 4-vinylaniline (4-VAn), followed by oxidative Copolymerization of the aniline moiety of the Grafted 4-VAn polymer with aniline, was carried out to render the PTFE surface conductive. The surface compositions of the Graft-modified PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The yield of the initially Grafted 4-VAn polymer increased with increasing monomer concentration and UV Graft Copolymerization time. The efficiency of the subsequent surface oxidative Copolymerization with aniline (and thus the resulting surface conductivity) was enhanced by the high concentration of the 4-VAn polymer from the initial Graft Copolymerization. The surface resistivity of the PTFE films was reduced to the order of 106 Ω/□ by the two consecutive surface Graft Copolymerization processes. The doping−undoping (protonation−deprotonation) behavior of the surface Graft copolymerized...
-
Surface Modification of Poly(Tetrafluoroethylene) Films by Graft Copolymerization for Adhesion Improvement with Sputtered In-Sn Oxides
The Journal of Adhesion, 1999Co-Authors: En-tang Kang, Koon Gee Neoh, K.l. Tan, C.q. Cui, Thiam Beng LimAbstract:Abstract Surface modification of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) films was carried out via UV-induced Graft Copolymerization with glycidyl methacrylate (GMA), acrylamide (AAm) and hydroxylethylacrylate (HEA) to improve the adhesion strength with sputtered indium-tin-oxide (ITO). The surface compositions of the Graftcopolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The Graft yield increases with increasing monomer concentration and Ar plasma pre-treatment time of the PTFE films. The T-peel adhesion strength was affected by the type of monomer used for Graft Copolymerization, the Graft concentration, and the thermal post-treatment after ITO deposition. A double Graft-Copolymerization process, which involved initially the Graft copolymeri/ation with AAm or HEA, followed by Graft Copolymerization with GMA. was also employed to enhance the adhesion of sputtered ITO to PTFE. T-peel adhesion strengths in excess of 8 N cm were achieved in the ITO Graft-modified...
-
Modification of substrate surface for BGA overmold adhesion enhancement by Graft Copolymerization
Materials Research Bulletin, 1996Co-Authors: Tie Wang, Koon Gee Neoh, K.l. Tan, E.t. Rang, C.q. Cui, K.k. Chakravorty, Thiam Beng LimAbstract:To improve the adhesion between epoxy molding compound (EMC) and ball grid array (BGA) substrate in the packaging of microelectronics systems, the surface of the epoxy-based BGA substrate was modified first by ozone pretreatment, followed by near-UV-light induced Graft Copolymerization with glycidyl methacrylate (GMA). The surface structure and composition of the substrate, before and after modification, were characterized by angle-resolved X-ray photoelectron spectroscopy (XPS). The angular-dependent XPS results suggest that the Grafted GMA polymer has penetrated substantially below the substrate surface. The amount of Grafted GMA polymer increased with increasing temperature and time of near-UV-light illumination during Graft Copolymerization. The surface of the BGA substrate became completely covered with GMA polymer after 2 h of near-UV-light induced surface Graft Copolymerization. The changes in surface morphology after Graft Copolymerization were clearly revealed by the atomic force microscopic (AFM) images. Test coupons with surface modified BGA substrate exhibited a minimum of three-fold increase in adhesion strength to the epoxy overmold. The adhesion enhancement has been attributed to the formation of covalent bonds between the epoxide groups of the Grafted GMA polymer and the curing agent in the overmold.
En-tang Kang - One of the best experts on this subject based on the ideXlab platform.
-
Surface Functionalization of Glass and Polymeric Substrates via Graft Copolymerization of Viologen in an Aqueous Medium
Langmuir, 2002Co-Authors: Xin Liu, Koon Gee Neoh, Luping Zhao, En-tang KangAbstract:Surface functionalization of low-density polyethylene (LDPE), silanized glass, and free-standing polyaniline (PANI) films via UV-induced Graft Copolymerization with 1,1‘-bis(4-vinyl-benzyl)-4,4‘-bipyridinium dichloride (VBV) was carried out. The vinyl group containing viologen was synthesized by the double Anderson reaction using 4,4‘-bipyridine and vinyl benzyl chloride and characterized by elemental analysis, FTIR spectrum, and X-ray photoelectron spectroscopy. The Graft Copolymerization of VBV was carried out by placing the plasma-pretreated substrate in contact with an aqueous solution of VBV under UV irradiation. The effects of the plasma-pretreatment time of the substrate, UV-induced Graft Copolymerization time, and monomer concentration on the VBV-Graft copolymer concentration were investigated. The responses of the VBV-Graft-copolymerized LDPE films and silanized glass slides to photoirradiation were monitored. In both cases, intensely blue viologen radical cations were formed after 10 min of UV i...
-
Lamination of conductive polypyrrole films to poly(tetrafluoroethylene) films via interfacial Graft Copolymerization
Journal of Applied Polymer Science, 2001Co-Authors: V.w.l. Lim, En-tang Kang, Koon Gee Neoh, Kian-ming TanAbstract:A simple technique for the lamination of a conductive polymer film to an inert dielectric polymer film was demonstrated. The electrochemically synthesized and p-toluenesulfonic acid-doped polypyrrole (PPY) film was laminated simultaneously to the argon plasma-pretreated PTFE film during the thermally induced Graft Copolymerization of the PTFE surface with a functional monomer. The Graft Copolymerization was carried out using glycidyl methacrylate (GMA) monomer containing 20% v/v hexamethyldiamine (HMDA) and in the absence of any polymerization initiator. Thermally induced Graft Copolymerization of the GMA monomer on the PPY surface was minimal. The lap shear and T-peel adhesion strengths of the laminates were found to be dependent on the GMA Graft concentration on the PTFE surface, which, in turn, was affected by the plasma pretreatment time of the film. To increase the GMA Graft concentration for the enhancement of adhesion strength, the plasma-pretreated PTFE surfaces were premodified via UV-induced Graft Copolymerization with GMA prior to the simultaneous thermal Graft Copolymerization and lamination process. The modified surfaces and interfaces were characterized by X-ray photoelectron spectroscopy (XPS). Through XPS measurements of the delaminated surfaces, it was found that the PPY/PTFE laminates failed predominantly by cohesive failure inside the PTFE substrate.
-
Chemical modification of polyaniline powders by surface Graft Copolymerization
Polymer, 2000Co-Authors: Yongjun Chen, En-tang Kang, Koon Gee Neoh, K.l. TanAbstract:Abstract Chemical modification of emeraldine (EM) based powders via thermally induced surface Graft Copolymerization with acrylic acid (AAc), 4-styrenesulfonic acid (SSAc) and amphoteric N,N′-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS) was carried out in aqueous media. The effects of temperature on Graft Copolymerization and Mohr's salt on homopolymerization were also studied. The chemical composition and structure of the Graft-copolymerized powders were studied by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. In all cases, the Graft yield increased with the monomer concentration and the temperature used for Graft Copolymerization. Certain Mohr's salts effectively inhibited the production of the homopolymers. Graft Copolymerization with AAc and SSAc readily gave rise to self-protonated and semi-conductive EM powders, with the conductivity increasing with the extent of Grafting. However, steric hindrance and spatial configuration of the Grafted chains had substantially limited the extent of protonation of the EM substrate by the protonic acid functional groups of these chains.
-
Modification of poly(tetrafluoroethylene) and gold surfaces by thermal Graft Copolymerization for adhesion improvement
Journal of Adhesion Science and Technology, 2000Co-Authors: Junfeng Zhang, En-tang Kang, C.q. Cui, Thiam Beng Lim, Koon Gee NeohAbstract:The adhesion between a poly(tetrafluoroethylene) (PTFE) film and a gold substrate was achieved by surface Graft Copolymerization of glycidyl methacrylate (GMA) on an argon plasma-pretreated PTFE film at elevated temperature with simultaneous lamination to a surface-modified gold substrate. The plasma pretreatment introduces peroxides which are thermally degraded into radicals to initiate the Graft Copolymerization of GMA on the PTFE surface. The gold surface, on the other hand, was first pretreated with 3-mercaptopropionic acid (MPA), 3-mercaptopropionic acid-2-ethylhexyl ester (MPAEE), or (3-mercaptopropyl)trimethoxysilane (MPTMS) to form self-assembled monolayers (SAMs) and then subjected to Ar plasma treatment. The simultaneous Graft Copolymerization and lamination of the PTFE film to the gold surface was carried out in the presence of GMA and an amine hardener at an elevated temperature under atmospheric conditions. The modified surfaces and interfaces were characterized by X-ray photoelectron spectro...
-
Surface Modification of Poly(tetrafluoroethylene) Film by Consecutive Graft Copolymerization with 4-Vinylaniline and Aniline
Macromolecules, 1999Co-Authors: En-tang Kang, Koon Gee Neoh, K.l. TanAbstract:Surface modification of argon plasma-pretreated poly(tetrafluoroethylene) (PTFE) film by UV-induced Graft Copolymerization with 4-vinylaniline (4-VAn), followed by oxidative Copolymerization of the aniline moiety of the Grafted 4-VAn polymer with aniline, was carried out to render the PTFE surface conductive. The surface compositions of the Graft-modified PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The yield of the initially Grafted 4-VAn polymer increased with increasing monomer concentration and UV Graft Copolymerization time. The efficiency of the subsequent surface oxidative Copolymerization with aniline (and thus the resulting surface conductivity) was enhanced by the high concentration of the 4-VAn polymer from the initial Graft Copolymerization. The surface resistivity of the PTFE films was reduced to the order of 106 Ω/□ by the two consecutive surface Graft Copolymerization processes. The doping−undoping (protonation−deprotonation) behavior of the surface Graft copolymerized...
Koon Gee Neoh - One of the best experts on this subject based on the ideXlab platform.
-
Surface Functionalization of Glass and Polymeric Substrates via Graft Copolymerization of Viologen in an Aqueous Medium
Langmuir, 2002Co-Authors: Xin Liu, Koon Gee Neoh, Luping Zhao, En-tang KangAbstract:Surface functionalization of low-density polyethylene (LDPE), silanized glass, and free-standing polyaniline (PANI) films via UV-induced Graft Copolymerization with 1,1‘-bis(4-vinyl-benzyl)-4,4‘-bipyridinium dichloride (VBV) was carried out. The vinyl group containing viologen was synthesized by the double Anderson reaction using 4,4‘-bipyridine and vinyl benzyl chloride and characterized by elemental analysis, FTIR spectrum, and X-ray photoelectron spectroscopy. The Graft Copolymerization of VBV was carried out by placing the plasma-pretreated substrate in contact with an aqueous solution of VBV under UV irradiation. The effects of the plasma-pretreatment time of the substrate, UV-induced Graft Copolymerization time, and monomer concentration on the VBV-Graft copolymer concentration were investigated. The responses of the VBV-Graft-copolymerized LDPE films and silanized glass slides to photoirradiation were monitored. In both cases, intensely blue viologen radical cations were formed after 10 min of UV i...
-
Lamination of conductive polypyrrole films to poly(tetrafluoroethylene) films via interfacial Graft Copolymerization
Journal of Applied Polymer Science, 2001Co-Authors: V.w.l. Lim, En-tang Kang, Koon Gee Neoh, Kian-ming TanAbstract:A simple technique for the lamination of a conductive polymer film to an inert dielectric polymer film was demonstrated. The electrochemically synthesized and p-toluenesulfonic acid-doped polypyrrole (PPY) film was laminated simultaneously to the argon plasma-pretreated PTFE film during the thermally induced Graft Copolymerization of the PTFE surface with a functional monomer. The Graft Copolymerization was carried out using glycidyl methacrylate (GMA) monomer containing 20% v/v hexamethyldiamine (HMDA) and in the absence of any polymerization initiator. Thermally induced Graft Copolymerization of the GMA monomer on the PPY surface was minimal. The lap shear and T-peel adhesion strengths of the laminates were found to be dependent on the GMA Graft concentration on the PTFE surface, which, in turn, was affected by the plasma pretreatment time of the film. To increase the GMA Graft concentration for the enhancement of adhesion strength, the plasma-pretreated PTFE surfaces were premodified via UV-induced Graft Copolymerization with GMA prior to the simultaneous thermal Graft Copolymerization and lamination process. The modified surfaces and interfaces were characterized by X-ray photoelectron spectroscopy (XPS). Through XPS measurements of the delaminated surfaces, it was found that the PPY/PTFE laminates failed predominantly by cohesive failure inside the PTFE substrate.
-
Chemical modification of polyaniline powders by surface Graft Copolymerization
Polymer, 2000Co-Authors: Yongjun Chen, En-tang Kang, Koon Gee Neoh, K.l. TanAbstract:Abstract Chemical modification of emeraldine (EM) based powders via thermally induced surface Graft Copolymerization with acrylic acid (AAc), 4-styrenesulfonic acid (SSAc) and amphoteric N,N′-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS) was carried out in aqueous media. The effects of temperature on Graft Copolymerization and Mohr's salt on homopolymerization were also studied. The chemical composition and structure of the Graft-copolymerized powders were studied by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. In all cases, the Graft yield increased with the monomer concentration and the temperature used for Graft Copolymerization. Certain Mohr's salts effectively inhibited the production of the homopolymers. Graft Copolymerization with AAc and SSAc readily gave rise to self-protonated and semi-conductive EM powders, with the conductivity increasing with the extent of Grafting. However, steric hindrance and spatial configuration of the Grafted chains had substantially limited the extent of protonation of the EM substrate by the protonic acid functional groups of these chains.
-
Modification of poly(tetrafluoroethylene) and gold surfaces by thermal Graft Copolymerization for adhesion improvement
Journal of Adhesion Science and Technology, 2000Co-Authors: Junfeng Zhang, En-tang Kang, C.q. Cui, Thiam Beng Lim, Koon Gee NeohAbstract:The adhesion between a poly(tetrafluoroethylene) (PTFE) film and a gold substrate was achieved by surface Graft Copolymerization of glycidyl methacrylate (GMA) on an argon plasma-pretreated PTFE film at elevated temperature with simultaneous lamination to a surface-modified gold substrate. The plasma pretreatment introduces peroxides which are thermally degraded into radicals to initiate the Graft Copolymerization of GMA on the PTFE surface. The gold surface, on the other hand, was first pretreated with 3-mercaptopropionic acid (MPA), 3-mercaptopropionic acid-2-ethylhexyl ester (MPAEE), or (3-mercaptopropyl)trimethoxysilane (MPTMS) to form self-assembled monolayers (SAMs) and then subjected to Ar plasma treatment. The simultaneous Graft Copolymerization and lamination of the PTFE film to the gold surface was carried out in the presence of GMA and an amine hardener at an elevated temperature under atmospheric conditions. The modified surfaces and interfaces were characterized by X-ray photoelectron spectro...
-
Surface Modification of Poly(tetrafluoroethylene) Film by Consecutive Graft Copolymerization with 4-Vinylaniline and Aniline
Macromolecules, 1999Co-Authors: En-tang Kang, Koon Gee Neoh, K.l. TanAbstract:Surface modification of argon plasma-pretreated poly(tetrafluoroethylene) (PTFE) film by UV-induced Graft Copolymerization with 4-vinylaniline (4-VAn), followed by oxidative Copolymerization of the aniline moiety of the Grafted 4-VAn polymer with aniline, was carried out to render the PTFE surface conductive. The surface compositions of the Graft-modified PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The yield of the initially Grafted 4-VAn polymer increased with increasing monomer concentration and UV Graft Copolymerization time. The efficiency of the subsequent surface oxidative Copolymerization with aniline (and thus the resulting surface conductivity) was enhanced by the high concentration of the 4-VAn polymer from the initial Graft Copolymerization. The surface resistivity of the PTFE films was reduced to the order of 106 Ω/□ by the two consecutive surface Graft Copolymerization processes. The doping−undoping (protonation−deprotonation) behavior of the surface Graft copolymerized...
K G Neoh - One of the best experts on this subject based on the ideXlab platform.
-
surface modification of poly tetrafluoroethylene films by Graft Copolymerization for adhesion improvement with evaporated copper
Macromolecules, 1999Co-Authors: E T Kang, K G Neoh, H S Han, K.l. TanAbstract:Surface modifications of Ar plasma-pretreated poly(tetrafluoroethylene) (PTFE) film via UV light-induced Graft Copolymerization with 1-vinylimidazole (VIDz) and glycidyl methacrylate (GMA) were carried out to improve the adhesion with evaporated copper. The surface compositions of the Graft-copolymerized PTFE films were studied by X-ray photoelectron spectroscopy (XPS). The Graft yield increases with the monomer concentration. The adhesion strength of the Graft-copolymerized PTFE film and the evaporated copper is affected by the type of monomer used for Graft Copolymerization, the Graft concentration, the plasma posttreatment time after Graft Copolymerization, and the extent of heat posttreatment after evaporation of copper. A double Graft Copolymerization process, which involved first the Graft Copolymerization with VIDz, followed by Graft Copolymerization with GMA, was also employed to enhance the adhesion of evaporated Cu to PTFE. The T-type peel strength of the PTFE/Cu interface so obtained is about 1...
-
surface modification of plasma pretreated poly tetrafluoroethylene films by Graft Copolymerization
Macromolecules, 1993Co-Authors: K.l. Tan, E T Kang, L L Woon, H K Wong, K G NeohAbstract:Surface modification of poly(tetrafluoroethylene) (PTFE) films by radio frequency argon plasma treatment as well as by Graft Copolymerization of the plasma-pretreated films with acrylamide (AAm) has been carried out. XPS results show that mild plasma treatment is sufficient to cause substantial surface defluorination end oxidation. The oxygen functionalities incorporated greatly facilitate subsequent Graft Copolymerization in the presence of near-UV radiation. Strong plasma treatment, on the contrary, results in considerable cross-linking of polymers on the surface and thus has an adverse effect on the Graft copolymerizetion
Hoikuan Lao - One of the best experts on this subject based on the ideXlab platform.
-
modification of poly 3 hydroxybutyrate co 3 hydroxyvalerate film by chemical Graft Copolymerization
Biomacromolecules, 2007Co-Authors: Hoikuan Lao, Estelle Renard, Isabelle Linossier, Valerie Langlois, Karine ValleerehelAbstract:The Graft Copolymerization of 2-hydroxyethylmethacrylate (HEMA) onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) films has been investigated. The Graft Copolymerization was conducted in aq...
-
Modification of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) film by chemical Graft Copolymerization.
Biomacromolecules, 2007Co-Authors: Hoikuan Lao, Estelle Renard, Isabelle Linossier, Valerie Langlois, Karine Vallée-réhelAbstract:The Graft Copolymerization of 2-hydroxyethylmethacrylate (HEMA) onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) films has been investigated. The Graft Copolymerization was conducted in aqueous media using benzoyl peroxide (BPO) as chemical initiator. PHBHV films were prepared by solvent casting. Different parameters affecting the Graft yield were studied such as monomer concentration, initiator concentration, and reaction time. The extent of Grafting has been modulated by the preparation conditions, in particular the concentration of HEMA. However, it is interesting to note that the initiator concentration had only a slight influence on the Graft yield. Characterization of the Grafted PHBHV films assumed that the Graft Copolymerization not only occurred on the film surface but also took place into the film bulk. Differential scanning calorimetry showed that crystallinity dramatically decreased with increasing Graft yield, indicating that Graft Copolymerization hindered the crystallization process. Wettability has been obviously improved by Grafting a hydrophilic monomer such as HEMA for high Graft yield (>130%).
