Mohammad Changez | Gwangju Institute of Science and Technology (original) (raw)
Papers by Mohammad Changez
Advanced materials (Deerfield Beach, Fla.), 2012
The reaction between atactic poly(2-vinylpyridine) and 1,4-dibromobutane leads to formation of lo... more The reaction between atactic poly(2-vinylpyridine) and 1,4-dibromobutane leads to formation of long-range 3D molecular ordering in polymer chains mainly because the side group (pyridine) of the polymer chain changes to a syndotactic configuration. This may enable the production of functional molecular devices that operate on a 3D atomic scale.
Nanoscale, 2013
A poly(2-vinylpyridine)-block-poly(2-(4-vinylphenyl)pyridine) (P2VP106-b-PVPPy95) coil-coil diblo... more A poly(2-vinylpyridine)-block-poly(2-(4-vinylphenyl)pyridine) (P2VP106-b-PVPPy95) coil-coil diblock copolymer forms hollow flower micelles in a mixed solvent of methanol and water (95/5, v/v) in a one step process. The geometry and composition of the micelles allow formation of a Pt-Au bimetallic dendritic nanocatalyst with a Pt leaf at room temperature.
Macromolecular rapid communications, 2011
A rare self-assembly behavior is observed in a hydrophilic monomer (4-vinylpyridine) (4VP) when p... more A rare self-assembly behavior is observed in a hydrophilic monomer (4-vinylpyridine) (4VP) when polymerized in water with a hydrophilic initiator that results in the production of monodisperse polymeric nanoparticles in a single step. This behavior mimics the behavior obtained with the more commonly reported amphiphilic block copolymers. The synthesis and self-assembly of homopolymer nanoparticle from 4VP without the use of any crosslinker, stabilizing agent, surfactant, or polymeric emulsifier are described along with fundamental aspects of the mechanism of this polymerization. This facile and robust procedure enabled the production of highly monodisperse P4VP nanoparticle with a tunable size ranging from 80 to 445 nm. For the first time, we have investigated the growth mechanism of these polymeric nanoparticles to clarify the mechanism of polymeric nanoparticle formation. This work also provides direct visible evidence through transmission electron microscopy (TEM) images at the nanometer scale, which helps in obtaining a better understanding of the mechanism of self-assembly. The effect of temperature on the size of the polymeric nanoparticles was also examined along with the effect of initiator, monomer, and solvent concentrations. We therefore report a versatile and scalable process for the production of monodisperse polymeric nanoparticles, which we call self-emulsion polymerization (SEP).
Small (Weinheim an der Bergstrasse, Germany), 2012
Amphiphilic homopolymer poly(2-(4-vinylphenyl)pyridine) (PVPPy) forms hollow micelles with uni-mo... more Amphiphilic homopolymer poly(2-(4-vinylphenyl)pyridine) (PVPPy) forms hollow micelles with uni-molecular thickness in a tetrahydrofuran/water (95/5 v/v) azeotropic solvent. Depending on the pH of the media, the micelles may be transformed to vesicles.
Drug Development and Industrial Pharmacy, 2000
The aerosol-OT (AOT)/water/isopropyl myristate microemulsion was investigated as a carrier in tra... more The aerosol-OT (AOT)/water/isopropyl myristate microemulsion was investigated as a carrier in transdermal drug delivery of tetracaine hydrochloride. The study included in vivo analgesic studies on rats and histopathological, irritation, and oxidative stress measurements on mice. The tetracaine hydrochloride encapsulated in AOT/water/isopropyl myristate showed an eightfold enhancement in the analgesic response of drug compared to the aqueous solution of the drug as measured by the tail-flick method. The analgesic response of tetracaine hydrochloride, however, highly depended on the concentration of AOT and water of the microemulsion. The preliminary histopathological, irritation, and oxidative stress studies showed that AOT/water/isopropyl myristate microemulsion system is a safe transdermal carrier of tetracaine hydrochloride with a concentration of AOT in isopropyl myristate up to 21:79 w/w.
Macromolecular Rapid Communications, 2009
An isopropyl myristate (IPM) biocompatible oil and an IPM solution of dodecanethiol-capped Ag nan... more An isopropyl myristate (IPM) biocompatible oil and an IPM solution of dodecanethiol-capped Ag nanoparticles (NPs, 4.5 nm) were used as hydrophobes to suppress the Ostwald ripening of monomer/hydrophobe miniemulsified droplets in a surfactant-stabilized water phase. The formation of non-IPM-encapsulated nanospheres (48 nm) and IPM-encapsulated nanocapsules (90 nm) were precisely controlled by using a water-soluble and an oil-soluble initiator, respectively, in the presence of a pure IPM as a hydrophobe in miniemulsion polymerization. Well-defined PS nanospheres, on which surfaces were coated with Ag NPs (Ag/PS nanospheres, 65 nm), and nanocapsules encapsulating both NPs and IPM liquid phase (Ag-IPM/PS nanocapsules, 115 nm) were made by replacing the hydrophobe from pure IPM with Ag/IPM solution. These nanostructures were characterized by transmission and scanning electron microscopes.
Macromolecular Rapid Communications, 2010
Reactive & Functional Polymers, 2009
This review highlights the precise synthesis and application of various well-defined rod-coil and... more This review highlights the precise synthesis and application of various well-defined rod-coil and coil-coil block copolymers composed of poly(2-(or 4-)vinylpyridine) (P2VP or P4VP) block(s) with pyridine moieties. These polymers were synthesized by means of living anionic polymerization. Poly(hexyl isocyanate) (PHIC) was used as the rod-like segment, because hexyl isocyanate undergoes living anionic polymerization under carefully selected conditions. This review describes the syntheses of the block copolymers, polystyrene-b-P2VP, polystyrene-b-P4VP, polyisoprene-b-P2VP, P2VP-b-poly(methyl methacrylate), P2VP-b-poly(ethylene oxide), P2VP-b-poly(2-(N-carbazolyl)ethyl methacrylate), P2VP-b-PHIC, P2VP-b-PHIC-b-P2VP, and PHIC-b-P2VP-b-PHIC. The formation of self-organized nanostructured materials and molecular assemblies by such block copolymers and their possible applications are also described. These assemblies include monolayers, microphase-separated periodic-ordered nanostructures, micelles, polymer-metal complexes, nanoparticles, inorganic and metal layers, and nanoporous films with nanoparticles.
Langmuir, 2010
The self-aggregation behavior of an amphiphilic rod-coil block copolymer of poly(n-hexyl isocyana... more The self-aggregation behavior of an amphiphilic rod-coil block copolymer of poly(n-hexyl isocyanate-block-2-vinylpyridine) (PHIC 189 -b-P2VP 228 ) (f P2VP = 0.78, M n = 24.5K) in a tetrahydrofuran (THF)/water system was examined using dynamic light scattering (DLS), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). The presence of a certain amount of water in the THF-based polymer solution induced a morphological transition from spherical solid micelles to open mouth platelike vesicles. The size of the aggregates increased with an increase in water content in the mixed solvent of THF/water. In the range of 30-40% water, the polymer formed vesicles with an interdigitated architecture of poly(n-hexyl isocyanate) (PHIC) at the center of the membrane and with the poly(2-vinylpyridine) (P2VP) block forming the outer layers and pointing toward the solvent. However, at higher water contents, the thickness of the bilayer increased due to the rearrangement of the vesicle membrane from a flip-flop to a lamellar architecture. After the degradation of the PHIC from the vesicles at basic pH, hollow spherical aggregates remained stable. After removing the THF from the mixed solvent using dialysis, large-sized compound vesicles were formed.
Macromolecules, 2007
ABSTRACT The amphiphilic monomer 2-(4-vinylphenyl)pyridine(VPPy) has been successfully polymerize... more ABSTRACT The amphiphilic monomer 2-(4-vinylphenyl)pyridine(VPPy) has been successfully polymerized using a complex of sec-butyllithium (s-BuLi) with lithium chloride (LiCl) and coordination of VPPy with LiCl at -45 degrees C for 72 h without side reactions such as cross-linking and branching. However, it takes 3 days to complete the polymerization with 100% yield, and the polydispersity index (M-w/M-n = 1.15) was relatively broad. In contrast, the anionic polymerization using diphenylmethyl potassium (DPM-K) as the weak initiator was more feasible. The yield of the polymer reached 100% within 150 min at -78 degrees C, which significantly reduced polymerization time with a narrow molecular weight distribution below 1.1. To investigate their living nature and reactivity, the block copolymerization of VPPy with styrene, isoprene, 2-vinylpyridine, and methyl methacrylate were carried out by sequential anionic polymerizations without additives such as LiCl and Et2Zn. The resulting block copolymers of PVPPy-b-PMMA in tetrahydrofuran showed the microphase separation, which was confirmed by transmission electron microscopy.
Polymer, 2011
We recently achieved quantitative synthesis of an amphiphilic coil-rod-coil triblock copolymer, p... more We recently achieved quantitative synthesis of an amphiphilic coil-rod-coil triblock copolymer, poly(2vinylpyridine)-b-poly(n-hexyl isocyanate)-b-poly(2-vinylpyridine), by coupling in situ living diblock copolymer poly(2-vinylpyridine)-b-poly(n-hexyl isocyanate) (P2VP-b-PHIC) using malonyl chloride in the presence of pyridine. This led to the introduction of an active methylene group that is a site for further functionalization in the rod block. The Michael addition reaction of the triblock copolymer with 7-(4-trifluoromethyl) coumarin acrylamide led to copolymer bearing a fluorescent pendent in the rod block. The fluorescent labeled copolymers were isolated in w94% yields. Similarly C 60 pendent was introduced to the rod block by the Bingel reaction. The yields of C 60 functionalized copolymers were w54%. The precursor and functionalized amphiphilic coil-rod-coil copolymer show diverse morphologies, such as micelles and vesicles by simply changing the solvent. For the C 60 functionalized block copolymer, structural constraints in micelles and vesicles prevented C 60 pendents to aggregate. Crown
Macromolecules, 2008
... An amphiphilic water-soluble stimuli-responsive rod−coil AB2 miktoarm star copolymers have be... more ... An amphiphilic water-soluble stimuli-responsive rod−coil AB2 miktoarm star copolymers have been prepared by atom transfer radical polymerization.(12) Synthesis of amphiphilic miktoarmstar polymer with a rod component is of considerable significance particularly because ...
Langmuir, 2009
Morphologies of the poly(n-hexyl isocyanate)-block-poly(2-vinylpyridine) (PHIC-b-P2VP, fP2VP=0.3)... more Morphologies of the poly(n-hexyl isocyanate)-block-poly(2-vinylpyridine) (PHIC-b-P2VP, fP2VP=0.3) amphiphilic rod-coil block copolymer were studied in rod-selective chloroform (CHCl3), both-block-soluble tetrahydrofuran (THF), and CHCl3/THF mixed solvent systems. Spherical, solid micelles with a P2VP core and PHIC shell were formed in CHCl3, whereas a microphase-separated liquid crystalline morphology was prominent in the presence of THF. In the CHCl3/THF mixed solvent system, a unique long-range intermicellar-chained network (v/v=7/3) and a more evolved cylindrical micellar network (v/v=3/7) were remarkably formed, respectively. PHIC-b-P2VP network nanostructures were used as a template for the in situ synthesis of Au nanoparticles (8 nm) selectively within the functional P2VP core domains.
Chemical Communications, 2009
The rod-like chains wrap tangentially to the curved interface of the spherical cores of the rod-c... more The rod-like chains wrap tangentially to the curved interface of the spherical cores of the rod-coil micelles and vesicles that are reversibly interchangeable by varying the polymer concentration.
Macromolecules, 2009
Anionic polymerization of n-alkoxycarbonylaminohexyl isocyanates was carried out using a sodium b... more Anionic polymerization of n-alkoxycarbonylaminohexyl isocyanates was carried out using a sodium benzanilide (Na-BA) as an initiator without additives in tetrahydrofuran (THF) at− 98° C under high vacuum (10− 6 Torr). The polymerization of methoxycarbonylaminohexyl ...
Colloids and Surfaces B-biointerfaces, 2006
In vivo transdermal permeation of tetracaine hydrochloride encapsulated in lecithin water-in-oil ... more In vivo transdermal permeation of tetracaine hydrochloride encapsulated in lecithin water-in-oil and oil-in-water microemulsion was studied. The effect of the composition of the lecithin microemulsion on analgesic response of tetracaine hydrochloride was evaluated on Wistar rats by tail flick method. To find out the toxicity of lecithin/n-propanol/isopropyl myristate/water/tetracaine hydrochloride microemulsion histopathological and irritation response were measured in Swiss mice. Time course studies were also conducted for the biochemical response of microemulsion by measuring catalase, glutathione and lipid peroxidation levels of the treated mice skin. The analgesic response was found to be dependent on the drug concentration and composition of the systems. The histopathological, irritation and biochemical findings reveal that lecithin/npropanol/isopropyl myristate/water/tetracaine hydrochloride microemulsion is a safe carrier for transdermal drug delivery systems. Confocal laser scanning microscopy observation indicated that sweat gland and hair follicle also provided the path for transdermal permeation of lecithin/npropanol/isopropyl myristate/water microemulsion.
Biomaterials, 2005
The safety and efficacy of gentamycin sulphate (GS)-or vancomycin hydrochloride (VCl)-loaded poly... more The safety and efficacy of gentamycin sulphate (GS)-or vancomycin hydrochloride (VCl)-loaded polymer devices based on poly(acrylic acid) and gelatin crosslinked selectively using 0.3 mol % N,N 0 -methylene bisacrylamide and 1 wt% glutaraldehyde were evaluated by varying the drug concentration onto the devices. The placebo and drug-loaded device of AxGx (acrylic acid:gelatin: 1:1 w/w) were employed for the treatment of experimental osteomyelitis in rabbit. Rabbits were categorized into four groups. Twelve rabbits in each group were treated with 1271mg of AxGx-1a (22% w/w GS), 1271mg of AxGx-1b (44% w/w GS), 1671mg of AxGx-1b (44% w/w GS) and 16 7 1 mg of AxGx-1c (44% w/w VCl). The drug concentration was measured following implantation in the adjacent tissue of femoral cavity, and serum. In femoral cavity maximum drug concentration was found on the 7th day with all the four types of devices. No drug was found after 21 days, at the local site with devices AxGx-1a and AxGx-1b (12 7 1 mg), whereas it was detected after 6 weeks with 1671 mg device (44% w/w GS or VCl). Macroscopic evaluation after treatment revealed that swelling, redness, local warmth and drainage decreased depending upon the drug loading of the implants. Sequential radiographs, histology, microbiologic assay and scanning electron micrography demonstrated devices AxGx-1b and AxGx-1c (16 7 1mg of 44% w/w drug loading) to be the most suitable device, which heals the infection after 6 weeks of treatment. No significant difference (p>0.05) in the rate of healing was observed between GS-and VCl-loaded devices. None of the implant showed toxic level of drug in serum at any given time.
Colloids and Surfaces B-biointerfaces, 2006
Effect of composition of lecithin water-in-oil and oil-in-water microemulsion on in vitro transde... more Effect of composition of lecithin water-in-oil and oil-in-water microemulsion on in vitro transdermal permeation of tetracaine hydrochloride was studied on mice model. The results were compared with an aqueous solution of tetracaine hydrochloride (2.7 mg/ml). In vitro skin flux and permeability coefficients were obtained using the Franz diffusion cell. Differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) were used to study the mechanism of action of the microemulsion. Micrographs of TEM and CLSM studies were analyzed by using Image Pro Plus image software. Skin flux of tetracaine hydrochloride was found to be dependent on the composition of lecithin/n-propanol/isopropyl myristate/water microemulsions. At lower K m ratio (i.e. 0.5:1 and 0.8:1) of microemulsion, the rate of permeation of tetracaine hydrochloride was higher when compared to the microemulsion of higher K m ratio (1:1 and 1.5:1). Image analysis of TEM micrograph, 6 h after application of lecithin microemulsion, showed 3.5 ± 0.75-fold (p < 0.001) increase in the intercellular space in the epidermis and 3.8 ± 0.4-fold (p < 0.001) enhancement in upper dermis. CLMS results show that sweat gland and hair follicles also provided path for permeation of the drug through the skin.
Advanced materials (Deerfield Beach, Fla.), 2012
The reaction between atactic poly(2-vinylpyridine) and 1,4-dibromobutane leads to formation of lo... more The reaction between atactic poly(2-vinylpyridine) and 1,4-dibromobutane leads to formation of long-range 3D molecular ordering in polymer chains mainly because the side group (pyridine) of the polymer chain changes to a syndotactic configuration. This may enable the production of functional molecular devices that operate on a 3D atomic scale.
Nanoscale, 2013
A poly(2-vinylpyridine)-block-poly(2-(4-vinylphenyl)pyridine) (P2VP106-b-PVPPy95) coil-coil diblo... more A poly(2-vinylpyridine)-block-poly(2-(4-vinylphenyl)pyridine) (P2VP106-b-PVPPy95) coil-coil diblock copolymer forms hollow flower micelles in a mixed solvent of methanol and water (95/5, v/v) in a one step process. The geometry and composition of the micelles allow formation of a Pt-Au bimetallic dendritic nanocatalyst with a Pt leaf at room temperature.
Macromolecular rapid communications, 2011
A rare self-assembly behavior is observed in a hydrophilic monomer (4-vinylpyridine) (4VP) when p... more A rare self-assembly behavior is observed in a hydrophilic monomer (4-vinylpyridine) (4VP) when polymerized in water with a hydrophilic initiator that results in the production of monodisperse polymeric nanoparticles in a single step. This behavior mimics the behavior obtained with the more commonly reported amphiphilic block copolymers. The synthesis and self-assembly of homopolymer nanoparticle from 4VP without the use of any crosslinker, stabilizing agent, surfactant, or polymeric emulsifier are described along with fundamental aspects of the mechanism of this polymerization. This facile and robust procedure enabled the production of highly monodisperse P4VP nanoparticle with a tunable size ranging from 80 to 445 nm. For the first time, we have investigated the growth mechanism of these polymeric nanoparticles to clarify the mechanism of polymeric nanoparticle formation. This work also provides direct visible evidence through transmission electron microscopy (TEM) images at the nanometer scale, which helps in obtaining a better understanding of the mechanism of self-assembly. The effect of temperature on the size of the polymeric nanoparticles was also examined along with the effect of initiator, monomer, and solvent concentrations. We therefore report a versatile and scalable process for the production of monodisperse polymeric nanoparticles, which we call self-emulsion polymerization (SEP).
Small (Weinheim an der Bergstrasse, Germany), 2012
Amphiphilic homopolymer poly(2-(4-vinylphenyl)pyridine) (PVPPy) forms hollow micelles with uni-mo... more Amphiphilic homopolymer poly(2-(4-vinylphenyl)pyridine) (PVPPy) forms hollow micelles with uni-molecular thickness in a tetrahydrofuran/water (95/5 v/v) azeotropic solvent. Depending on the pH of the media, the micelles may be transformed to vesicles.
Drug Development and Industrial Pharmacy, 2000
The aerosol-OT (AOT)/water/isopropyl myristate microemulsion was investigated as a carrier in tra... more The aerosol-OT (AOT)/water/isopropyl myristate microemulsion was investigated as a carrier in transdermal drug delivery of tetracaine hydrochloride. The study included in vivo analgesic studies on rats and histopathological, irritation, and oxidative stress measurements on mice. The tetracaine hydrochloride encapsulated in AOT/water/isopropyl myristate showed an eightfold enhancement in the analgesic response of drug compared to the aqueous solution of the drug as measured by the tail-flick method. The analgesic response of tetracaine hydrochloride, however, highly depended on the concentration of AOT and water of the microemulsion. The preliminary histopathological, irritation, and oxidative stress studies showed that AOT/water/isopropyl myristate microemulsion system is a safe transdermal carrier of tetracaine hydrochloride with a concentration of AOT in isopropyl myristate up to 21:79 w/w.
Macromolecular Rapid Communications, 2009
An isopropyl myristate (IPM) biocompatible oil and an IPM solution of dodecanethiol-capped Ag nan... more An isopropyl myristate (IPM) biocompatible oil and an IPM solution of dodecanethiol-capped Ag nanoparticles (NPs, 4.5 nm) were used as hydrophobes to suppress the Ostwald ripening of monomer/hydrophobe miniemulsified droplets in a surfactant-stabilized water phase. The formation of non-IPM-encapsulated nanospheres (48 nm) and IPM-encapsulated nanocapsules (90 nm) were precisely controlled by using a water-soluble and an oil-soluble initiator, respectively, in the presence of a pure IPM as a hydrophobe in miniemulsion polymerization. Well-defined PS nanospheres, on which surfaces were coated with Ag NPs (Ag/PS nanospheres, 65 nm), and nanocapsules encapsulating both NPs and IPM liquid phase (Ag-IPM/PS nanocapsules, 115 nm) were made by replacing the hydrophobe from pure IPM with Ag/IPM solution. These nanostructures were characterized by transmission and scanning electron microscopes.
Macromolecular Rapid Communications, 2010
Reactive & Functional Polymers, 2009
This review highlights the precise synthesis and application of various well-defined rod-coil and... more This review highlights the precise synthesis and application of various well-defined rod-coil and coil-coil block copolymers composed of poly(2-(or 4-)vinylpyridine) (P2VP or P4VP) block(s) with pyridine moieties. These polymers were synthesized by means of living anionic polymerization. Poly(hexyl isocyanate) (PHIC) was used as the rod-like segment, because hexyl isocyanate undergoes living anionic polymerization under carefully selected conditions. This review describes the syntheses of the block copolymers, polystyrene-b-P2VP, polystyrene-b-P4VP, polyisoprene-b-P2VP, P2VP-b-poly(methyl methacrylate), P2VP-b-poly(ethylene oxide), P2VP-b-poly(2-(N-carbazolyl)ethyl methacrylate), P2VP-b-PHIC, P2VP-b-PHIC-b-P2VP, and PHIC-b-P2VP-b-PHIC. The formation of self-organized nanostructured materials and molecular assemblies by such block copolymers and their possible applications are also described. These assemblies include monolayers, microphase-separated periodic-ordered nanostructures, micelles, polymer-metal complexes, nanoparticles, inorganic and metal layers, and nanoporous films with nanoparticles.
Langmuir, 2010
The self-aggregation behavior of an amphiphilic rod-coil block copolymer of poly(n-hexyl isocyana... more The self-aggregation behavior of an amphiphilic rod-coil block copolymer of poly(n-hexyl isocyanate-block-2-vinylpyridine) (PHIC 189 -b-P2VP 228 ) (f P2VP = 0.78, M n = 24.5K) in a tetrahydrofuran (THF)/water system was examined using dynamic light scattering (DLS), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). The presence of a certain amount of water in the THF-based polymer solution induced a morphological transition from spherical solid micelles to open mouth platelike vesicles. The size of the aggregates increased with an increase in water content in the mixed solvent of THF/water. In the range of 30-40% water, the polymer formed vesicles with an interdigitated architecture of poly(n-hexyl isocyanate) (PHIC) at the center of the membrane and with the poly(2-vinylpyridine) (P2VP) block forming the outer layers and pointing toward the solvent. However, at higher water contents, the thickness of the bilayer increased due to the rearrangement of the vesicle membrane from a flip-flop to a lamellar architecture. After the degradation of the PHIC from the vesicles at basic pH, hollow spherical aggregates remained stable. After removing the THF from the mixed solvent using dialysis, large-sized compound vesicles were formed.
Macromolecules, 2007
ABSTRACT The amphiphilic monomer 2-(4-vinylphenyl)pyridine(VPPy) has been successfully polymerize... more ABSTRACT The amphiphilic monomer 2-(4-vinylphenyl)pyridine(VPPy) has been successfully polymerized using a complex of sec-butyllithium (s-BuLi) with lithium chloride (LiCl) and coordination of VPPy with LiCl at -45 degrees C for 72 h without side reactions such as cross-linking and branching. However, it takes 3 days to complete the polymerization with 100% yield, and the polydispersity index (M-w/M-n = 1.15) was relatively broad. In contrast, the anionic polymerization using diphenylmethyl potassium (DPM-K) as the weak initiator was more feasible. The yield of the polymer reached 100% within 150 min at -78 degrees C, which significantly reduced polymerization time with a narrow molecular weight distribution below 1.1. To investigate their living nature and reactivity, the block copolymerization of VPPy with styrene, isoprene, 2-vinylpyridine, and methyl methacrylate were carried out by sequential anionic polymerizations without additives such as LiCl and Et2Zn. The resulting block copolymers of PVPPy-b-PMMA in tetrahydrofuran showed the microphase separation, which was confirmed by transmission electron microscopy.
Polymer, 2011
We recently achieved quantitative synthesis of an amphiphilic coil-rod-coil triblock copolymer, p... more We recently achieved quantitative synthesis of an amphiphilic coil-rod-coil triblock copolymer, poly(2vinylpyridine)-b-poly(n-hexyl isocyanate)-b-poly(2-vinylpyridine), by coupling in situ living diblock copolymer poly(2-vinylpyridine)-b-poly(n-hexyl isocyanate) (P2VP-b-PHIC) using malonyl chloride in the presence of pyridine. This led to the introduction of an active methylene group that is a site for further functionalization in the rod block. The Michael addition reaction of the triblock copolymer with 7-(4-trifluoromethyl) coumarin acrylamide led to copolymer bearing a fluorescent pendent in the rod block. The fluorescent labeled copolymers were isolated in w94% yields. Similarly C 60 pendent was introduced to the rod block by the Bingel reaction. The yields of C 60 functionalized copolymers were w54%. The precursor and functionalized amphiphilic coil-rod-coil copolymer show diverse morphologies, such as micelles and vesicles by simply changing the solvent. For the C 60 functionalized block copolymer, structural constraints in micelles and vesicles prevented C 60 pendents to aggregate. Crown
Macromolecules, 2008
... An amphiphilic water-soluble stimuli-responsive rod−coil AB2 miktoarm star copolymers have be... more ... An amphiphilic water-soluble stimuli-responsive rod−coil AB2 miktoarm star copolymers have been prepared by atom transfer radical polymerization.(12) Synthesis of amphiphilic miktoarmstar polymer with a rod component is of considerable significance particularly because ...
Langmuir, 2009
Morphologies of the poly(n-hexyl isocyanate)-block-poly(2-vinylpyridine) (PHIC-b-P2VP, fP2VP=0.3)... more Morphologies of the poly(n-hexyl isocyanate)-block-poly(2-vinylpyridine) (PHIC-b-P2VP, fP2VP=0.3) amphiphilic rod-coil block copolymer were studied in rod-selective chloroform (CHCl3), both-block-soluble tetrahydrofuran (THF), and CHCl3/THF mixed solvent systems. Spherical, solid micelles with a P2VP core and PHIC shell were formed in CHCl3, whereas a microphase-separated liquid crystalline morphology was prominent in the presence of THF. In the CHCl3/THF mixed solvent system, a unique long-range intermicellar-chained network (v/v=7/3) and a more evolved cylindrical micellar network (v/v=3/7) were remarkably formed, respectively. PHIC-b-P2VP network nanostructures were used as a template for the in situ synthesis of Au nanoparticles (8 nm) selectively within the functional P2VP core domains.
Chemical Communications, 2009
The rod-like chains wrap tangentially to the curved interface of the spherical cores of the rod-c... more The rod-like chains wrap tangentially to the curved interface of the spherical cores of the rod-coil micelles and vesicles that are reversibly interchangeable by varying the polymer concentration.
Macromolecules, 2009
Anionic polymerization of n-alkoxycarbonylaminohexyl isocyanates was carried out using a sodium b... more Anionic polymerization of n-alkoxycarbonylaminohexyl isocyanates was carried out using a sodium benzanilide (Na-BA) as an initiator without additives in tetrahydrofuran (THF) at− 98° C under high vacuum (10− 6 Torr). The polymerization of methoxycarbonylaminohexyl ...
Colloids and Surfaces B-biointerfaces, 2006
In vivo transdermal permeation of tetracaine hydrochloride encapsulated in lecithin water-in-oil ... more In vivo transdermal permeation of tetracaine hydrochloride encapsulated in lecithin water-in-oil and oil-in-water microemulsion was studied. The effect of the composition of the lecithin microemulsion on analgesic response of tetracaine hydrochloride was evaluated on Wistar rats by tail flick method. To find out the toxicity of lecithin/n-propanol/isopropyl myristate/water/tetracaine hydrochloride microemulsion histopathological and irritation response were measured in Swiss mice. Time course studies were also conducted for the biochemical response of microemulsion by measuring catalase, glutathione and lipid peroxidation levels of the treated mice skin. The analgesic response was found to be dependent on the drug concentration and composition of the systems. The histopathological, irritation and biochemical findings reveal that lecithin/npropanol/isopropyl myristate/water/tetracaine hydrochloride microemulsion is a safe carrier for transdermal drug delivery systems. Confocal laser scanning microscopy observation indicated that sweat gland and hair follicle also provided the path for transdermal permeation of lecithin/npropanol/isopropyl myristate/water microemulsion.
Biomaterials, 2005
The safety and efficacy of gentamycin sulphate (GS)-or vancomycin hydrochloride (VCl)-loaded poly... more The safety and efficacy of gentamycin sulphate (GS)-or vancomycin hydrochloride (VCl)-loaded polymer devices based on poly(acrylic acid) and gelatin crosslinked selectively using 0.3 mol % N,N 0 -methylene bisacrylamide and 1 wt% glutaraldehyde were evaluated by varying the drug concentration onto the devices. The placebo and drug-loaded device of AxGx (acrylic acid:gelatin: 1:1 w/w) were employed for the treatment of experimental osteomyelitis in rabbit. Rabbits were categorized into four groups. Twelve rabbits in each group were treated with 1271mg of AxGx-1a (22% w/w GS), 1271mg of AxGx-1b (44% w/w GS), 1671mg of AxGx-1b (44% w/w GS) and 16 7 1 mg of AxGx-1c (44% w/w VCl). The drug concentration was measured following implantation in the adjacent tissue of femoral cavity, and serum. In femoral cavity maximum drug concentration was found on the 7th day with all the four types of devices. No drug was found after 21 days, at the local site with devices AxGx-1a and AxGx-1b (12 7 1 mg), whereas it was detected after 6 weeks with 1671 mg device (44% w/w GS or VCl). Macroscopic evaluation after treatment revealed that swelling, redness, local warmth and drainage decreased depending upon the drug loading of the implants. Sequential radiographs, histology, microbiologic assay and scanning electron micrography demonstrated devices AxGx-1b and AxGx-1c (16 7 1mg of 44% w/w drug loading) to be the most suitable device, which heals the infection after 6 weeks of treatment. No significant difference (p>0.05) in the rate of healing was observed between GS-and VCl-loaded devices. None of the implant showed toxic level of drug in serum at any given time.
Colloids and Surfaces B-biointerfaces, 2006
Effect of composition of lecithin water-in-oil and oil-in-water microemulsion on in vitro transde... more Effect of composition of lecithin water-in-oil and oil-in-water microemulsion on in vitro transdermal permeation of tetracaine hydrochloride was studied on mice model. The results were compared with an aqueous solution of tetracaine hydrochloride (2.7 mg/ml). In vitro skin flux and permeability coefficients were obtained using the Franz diffusion cell. Differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) were used to study the mechanism of action of the microemulsion. Micrographs of TEM and CLSM studies were analyzed by using Image Pro Plus image software. Skin flux of tetracaine hydrochloride was found to be dependent on the composition of lecithin/n-propanol/isopropyl myristate/water microemulsions. At lower K m ratio (i.e. 0.5:1 and 0.8:1) of microemulsion, the rate of permeation of tetracaine hydrochloride was higher when compared to the microemulsion of higher K m ratio (1:1 and 1.5:1). Image analysis of TEM micrograph, 6 h after application of lecithin microemulsion, showed 3.5 ± 0.75-fold (p < 0.001) increase in the intercellular space in the epidermis and 3.8 ± 0.4-fold (p < 0.001) enhancement in upper dermis. CLMS results show that sweat gland and hair follicles also provided path for permeation of the drug through the skin.