Soft Matter, 2011, Advance Article DOI:10.1039/C1SM05360D (Paper) PDF Version. Covalent functiona... more Soft Matter, 2011, Advance Article DOI:10.1039/C1SM05360D (Paper) PDF Version. Covalent functionalization of carbon nanotubes for ultimate interfacial adhesion to liquid crystalline polymer. Nanda Gopal Sahoo, Henry Kuo ...
The effects of graphene oxide (GO) and ammonia functionalized graphene oxide (AGO) on microstruct... more The effects of graphene oxide (GO) and ammonia functionalized graphene oxide (AGO) on microstructure, thermoreversible and critical gelation properties of j-carrageenan in aqueous solution were studied by micro-differential scanning calorimetry (micro-DSC), field emission scanning electron microscopy (FESEM) and rheology. The presence of GO or AGO was able to decrease the gel formation and melting temperatures and reduce gel strength. The effect of AGO was more evident than that of GO. It was observed by FESEM that j-carrageenan gel was induced by the formation of a fibrillar network, and fibrillar size and density decreased with increasing GO or AGO content. The viscoelastic properties at the gel point were examined using the Winter-Chambon criterion to obtain the critical relaxation exponent n and the critical gel strength S g. n increased but S g decreased with increasing GO or AGO content. The more obvious increase in n and decrease in S g were observed in the AGO/j-carrageenan solution, which further demonstrated the stronger weakening effect of AGO. A schematic diagram has been proposed to explain the effect of AGO on the gelation of j-carrageenan, where AGO sheets attracted a number of j-carrageenan chains through hydrogen bonding and electrostatic interaction between sulfate groups of j-carrageenan and amine groups of AGO. As a result, the number of free j-carrageenan chains in solution decreased and the coil-helix transition and aggregation of helices of j-carrageenan were affected negatively.
The effects of two poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO)... more The effects of two poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) triblock copolymers, Pluronics-R 10R5 (PPO 8-PEO 22-PPO 8) and 25R4 (PPO 19-PEO 33-PPO 19), on the thermal and rheological properties as well as the phase transitions of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer (Pluronic F127, PEO 100-PPO 65-PEO 100) in aqueous solution have been systematically studied. Both 10R5 and 25R4 could shift the critical micellization temperature of F127 to lower temperatures, showing a "salt-out like" effect. When F127 itself is unable to form a gel at low concentrations, 25R4 could assist micelles of F127 to be connected into a gel network. However, 10R5 is too short to be able to assist F127 to form a gel. At low contents of 10R5 or 25R4, F127 dominates its gelation but 25R4 could affect the hard gel-soft gel transition while10R5 showed a weaker effect on the hard gel-soft gel transition than 25R4. The rheological scaling law in the vicinity of the gel point was examined to obtain the critical relaxation exponent n and the critical gel strength S g. n decreases and S g increases with increasing 25R4 at low concentrations of F127. However, 10R5 and 25R4 affected n and S g differently at high concentrations of F127.
A comb-like dual hydrophilic graft chitosan copolymer, chitosan-graft-poly(N-isopropylacrylamide)... more A comb-like dual hydrophilic graft chitosan copolymer, chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAM), was synthesized by means of atom transfer radical polymerization (ATRP) and click chemistry. The thermo-responsive association behavior of the copolymer in dilute aqueous solutions has been investigated by laser light scattering (LLS), zeta potential, and transmission electron microscopy (TEM). The core-shell structured micelles with the hydrophobic PNIAPM as a core and the hydrophilic CS as a shell were formed at low pH (<4) and high temperature (>32 degrees C), whereas the obtained micelles became large aggregates and precipitated in alkaline solutions (pH > 7). Additionally, the low critical solution temperature (LCST) phase transitions of dense copolymer solutions in the presence of salts (NaCl and NaI) and a cationic surfactant (dodecyltrimethylammonium bromide, DTAB) respectively were studied by micro differential scanning calorimetry (DSC) and UV turbidimetry. It was found that both salts (NaCl and NaI) and DATB could shift the LCST to lower or higher temperatures from a pure copolymer solution, depending on the beneath mechanisms.
ABSTRACT A novel thermoreversible gelling system consisting of tamarind seed xyloglucan (TSX) and... more ABSTRACT A novel thermoreversible gelling system consisting of tamarind seed xyloglucan (TSX) and gallic acid (GA) was prepared and investigated. The thermal transition temperatures obtained from both micro-DSC and viscoelastic methods were consistent. The hysteresis was observed for the GA–TSX gelling system. The hydrogen bonding interactions between GA and TSX were detected using 13C nuclear magnetic resonance analyses. The carboxylic acid and the hydroxyl group at the para position of GA are the principal groups that interact with TSX. A low temperature induced intermolecular aggregation of TSX via hydrogen bonds between GA and TSX, leading to the formation of a gel network. The thermal stability of the GA–TSX gel increased with increasing the GA concentration. The viscoelastic behavior of the GA–TSX mixtures depended on the concentration of GA. For the mixture of GA and 1% (w/v) TSX, the critical gel concentration of GA was 0.69% (w/v) at physiological temperature (37 °C) and the sol–gel transition was well described by the scaling law. Moreover, the dried GA–TSX gels exhibited various morphologies that reflected the dependence of the arrangement of the TSX chains on the GA concentration.
Nowadays, the concept of drug transmission is an important topic in the field of drug delivery re... more Nowadays, the concept of drug transmission is an important topic in the field of drug delivery research. Drug delivery is the method or process of administering a pharmaceutical compound to achieve a therapeutic effect in humans or animals. In this study, we report the development of a novel platform for the loading and release of doxorubicin (DOX). It is based on porous reduced graphene oxide (prGO) nanosheets and chitosan (CS) biocompatible polymer, where prGO can be dispersed in chitosan through amide linkages. The loading and release of DOX on the CS-prGO nanocomposite were investigated by voltammetry, FE-SEM, and FTIR and UV-Vis spectroscopy methods. We showed that chitosan-modified prGO (CS-prGO) was an extremely efficient matrix. An efficient loading of DOX (86% at pH 7.00, time 3 h and initial concentration of 0.5 mg mL À1) was observed on CS-prGO as compared to the case of prGO due to the presence of the-OH and-NH 2 groups of chitosan. At the normal physiological pH of 7.00, approximately 10% of DOX could be released from CS-prGO in a time span of 1 h; however, when exposed to pH 4.00, 25% of DOX was released in 1 h. After 20 h, 18% and 62% of DOX was released at pH 7.00 and 4.00, respectively. This illustrates the major benefits of the developed approach for biomedical applications.
Carbon nanotube-based nanocomposites of chitosan were successfully prepared by a simple solution-... more Carbon nanotube-based nanocomposites of chitosan were successfully prepared by a simple solution-evaporation method. Multiwalled carbon nanotubes (MWCNTs) were treated by poly(3,4ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT-PSS) in water before mixed with a chitosan solution to improve the dispersion of MWCNTs and interfacial compatibility between MWCNTs and chitosan. The morphological and mechanical properties of the prepared PEDOT-PSS/MWCNT/chitosan nanocomposites have been characterized with field emission scanning electron microscopy (FESEM) and tensile tests. MWCNTs were observed to be homogeneously dispersed throughout the chitosan matrix. As compared with the neat chitosan, the tensile strength and modulus of the nanocomposite were greatly improved by about 61% and 34%, respectively, with incorporation of only 0.5 wt.% of MWCNTs into the chitosan matrix. The comparison of mechanical properties for PEDOT-PSS/MWCNT/chitosan and pristine MWCNT/chitosan nanocomposites has been made. The hardness of the nanocomposites was also evaluated by nanoindentation.
Methylcellulose (MC), chitosan (CS), and κ-carrageenan (KC) are chosen as typical representatives... more Methylcellulose (MC), chitosan (CS), and κ-carrageenan (KC) are chosen as typical representatives of neutral and positively, and negatively charged polysaccharides, respectively. Sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) are chosen as anionic and cationic surfactants, respectively. From these polymers and surfactants, six combinations of polymer−surfactant are made: MC−SDS, MC−CTAB, CS−SDS, CS−CTAB, KC−SDS, and KC−CTAB. The polymer−surfactant interactions for the six pairs are systematically investigated by isothermal titration calorimetry (ITC). It was observed that MC−SDS exhibited strong hydrophobic interaction, as evidenced by the endothermic peak, followed by a weak ion−dipole interaction. KC−SDS did not show any ionic interaction, as expected, but exhibited weaker hydrophobic interaction than MC−SDS. Strong ionic interaction was found for CS−SDS, followed by hydrophobic interaction between some hydrophobic moieties of CS and SDS tails. Titration of CTAB with MC resulted ...
Multiwalled carbon nanotubes (MWCNTs) were functionalized on their sidewalls with p-nitrophenyl (... more Multiwalled carbon nanotubes (MWCNTs) were functionalized on their sidewalls with p-nitrophenyl (C6H4NO2) to make MWCNTs compatible with liquid crystalline polymer (LCP) through a specific interaction with LCP. This study examined the rheological, morphological, mechanical, dynamic mechanical, and thermal properties of LCP in detail with a variation of the nitrophenyl-functionalized MWCNTs in the LCP matrix. A higher complex viscosity, storage, and
The nanoparticles of chitosan (CS) were prepared using pentasodium triphosphate (TPP) as a crossl... more The nanoparticles of chitosan (CS) were prepared using pentasodium triphosphate (TPP) as a crosslinking agent and the influences of cetyltrimethylammonium bromide (CTAB) on the physicochemical properties of the CS-TPP nanoparticles were first studied by laser light scattering, zeta potential, and transmission electron microscopy (TEM). The concentration played a significant role in controlling the particle size of CS and the overlap concentration c * was testified to be about 1.0 mg/mL. The combination of static light scattering (SLS) and dynamic light scattering (DLS) allowed us to obtain more information about the CS-TPP nanoparticles in the presence of surfactant molecules. The addition of CTAB could reduce the hydrodynamic diameter of nanoparticles effectively in the salt solutions and simultaneously increase the zeta potential of the nanoparticles. The effect of CTAB concentration on the size of CS-TPP nanoparticle was also examined. The critical micelle concentration (CMC) of CTAB was used to interpret the complicated complex formed by the polyelectrolyte and the surfactant. Finally, TEM was used to observe the CS-TPP nanoparticles, which were affected by CTAB, to verify the results obtained by light scattering.
Materials and methods 1) Materials The MWCNTs were purchased from Iljin Nano Tech, Korea. Their d... more Materials and methods 1) Materials The MWCNTs were purchased from Iljin Nano Tech, Korea. Their diameter and length were about 10-20 nm and 20 μm, respectively. These nanotubes (purity of 95%) were produced by chemical vapor deposition. Graphite with an average particle size of 100 μm was obtained from Sigma-Aldrich. CPT was purchased from Guanyu Bio Inc from China. Poly (vinyl alcohol) (PVA) (M w ~61,000) was obtained from Fluka. (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) (MTT) and other mentioned reagents were purchased from Aldrich and used as received. 2) Preparation of MWCNT-PVA The MWCNTs were functionalized with PVA in a carbodiimide-activated esterification reaction. In a typical procedure, 55 mg purified CNT-COOH was dissolved in 10 mL dimethyl sulfoxide (DMSO) and sonicated for 30 min to obtain a homogeneous black-colored solution. The catalysts, N,N'-dicyclohexylcarbodiimide (DCC) (600mg, 2.91 mmol) and 4dimethylaminopyridine (DMAP) (99 mg, 0.81 mmol) were gradually charged into the flask and stirred for 10 min. Then, a solution of PVA in DMSO (100 mg/mL, 5 mL) was added, and the mixture was sonicated to react at 50 °C for 24 h. After it was terminated, the dark suspension was filtered over a 0.2 μm PTFE microporous membrane, and the obtained solid was washed
The excellent water solubility of graphene oxide (GO) imparts it feasibility as a new filler for ... more The excellent water solubility of graphene oxide (GO) imparts it feasibility as a new filler for reinforcing hydrophilic biopolymers. In this work, we present a simple and green approach to fabrication of GO/chitosan nanocomposite films. Mechanical properties of the nanocomposite have been significantly enhanced without sacrificing the optical transparency. GO sheets are unidirectionally aligned in the chitosan matrix and parallel to the surface of nanaocomposite film, which has been manifested by the morphological observation and explained by the theoretical prediction of tensile modulus. With incorporation of 1wt% GO, the fracture strength and tensile modulus of the nanocomopsites are significantly enhanced by 93% and 51%, respectively. The simultaneous improvement of strength and toughness could be attributed to the homogeneous dispersion and alignment of GO sheets in the chitosan matrix, the strong interfacial adhesion between GO and chitosan, as well as the high specific surface area and the two-dimensional geometry of GO.
Water-soluble chitosan-grafted reduced graphene oxide (CS-rGO) sheets are successfully synthesize... more Water-soluble chitosan-grafted reduced graphene oxide (CS-rGO) sheets are successfully synthesized via amidation reaction and chemical reduction. CS-rGO possesses not only remarkable graphitic property but also favorable water solubility, which is found to be able to effectively disperse multiwalled carbon nanotubes (MWCNTs) in acidic solutions via noncovalent interaction. The efficiency of CS-rGO in dispersing MWCNTs is tested to be higher than that of plain graphene oxide (GO) and a commercial surfactant, sodium dodecyl sulfate (SDS). With incorporation of 1 wt % CS-rGO dispersed MWCNTs (CS-rGO-MWCNTs), the tensile modulus, strength and toughness of the chitosan (CS) nanocomposites can be increased by 49, 114, and 193%, respectively. The reinforcing and toughening effects of CS-rGO-MWCNTs are much more prominent than those of single-component fillers, such as MWCNTs, GO, and CS-rGO. Noncovalent π−π interactions between graphene sheets and nanotubes and hydrogen bonds between grafted CS and the CS matrix are responsible for generating effective load transfer between CS-rGO-MWCNTs and the CS matrix, causing the simultaneously increased strength and toughness of the nanocomposites.
Poly (vinyl alcohol) is used as raw material in this study. With adding graphene oxide, the PVA/G... more Poly (vinyl alcohol) is used as raw material in this study. With adding graphene oxide, the PVA/GO membrane was prepared with solution casting method. To evaluate the effect of different casting method on the conductivity of PVA/GO membrane, knife casting method with different casting surface were conducted in this study. Ionic conductivity for PVA/GO prepared by solution casting method is about 0.0526 S/ cm; whereas the ionic conductivity is sharply improved to 0.1439 S/cm for PVA/GO prepared by casting membrane on the glass with vacuum..
Covalently functionalized graphene sheets are prepared by grafting a welldefi ned thermo-responsi... more Covalently functionalized graphene sheets are prepared by grafting a welldefi ned thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) via click chemistry. The PNIPAM-grafted graphene sheets (PNIPAM-GS) consist of about 50% polymer, which endows the sheets with a good solubility and stability in physiological solutions. The PNIPAM-GS exhibits a hydrophilic to hydrophobic phase transition at 33 ° C, which is relatively lower than that of a PNIPAM homopolymer because of the interaction between graphene sheets and grafted PNIPAM. Moreover, through π-π stacking and hydrophobic interaction between PNIPAM-GS and an aromatic drug, the PNIPAM-GS is able to load a water-insoluble anticancer drug, camptothecin (CPT), with a superior loading capacity of 15.6 wt-% (0.185 g CPT per g PNIPAM-GS). The in vitro drug release behavior of the PNIPAM-GS-CPT complex is examined both in water and PBS at 37 ° C. More importantly, the PNIPAM-GS does not exhibit a practical toxicity and the PNIPAM-GS-CPT complex shows a high potency of killing cancer cells in vitro. The PNIPAM-GS is demonstrated to be an effective vehicle for anticancer drug delivery.
The nanoparticles of chitosan (CS) were prepared using pentasodium triphosphate (TPP) as a crossl... more The nanoparticles of chitosan (CS) were prepared using pentasodium triphosphate (TPP) as a crosslinking agent and the influences of cetyltrimethylammonium bromide (CTAB) on the physicochemical properties of the CS-TPP nanoparticles were first studied by laser light scattering, zeta potential, and transmission electron microscopy (TEM). The concentration played a significant role in controlling the particle size of CS and the overlap concentration c * was testified to be about 1.0 mg/mL. The combination of static light scattering (SLS) and dynamic light scattering (DLS) allowed us to obtain more information about the CS-TPP nanoparticles in the presence of surfactant molecules. The addition of CTAB could reduce the hydrodynamic diameter of nanoparticles effectively in the salt solutions and simultaneously increase the zeta potential of the nanoparticles. The effect of CTAB concentration on the size of CS-TPP nanoparticle was also examined. The critical micelle concentration (CMC) of CTAB was used to interpret the complicated complex formed by the polyelectrolyte and the surfactant. Finally, TEM was used to observe the CS-TPP nanoparticles, which were affected by CTAB, to verify the results obtained by light scattering.
Soft Matter, 2011, Advance Article DOI:10.1039/C1SM05360D (Paper) PDF Version. Covalent functiona... more Soft Matter, 2011, Advance Article DOI:10.1039/C1SM05360D (Paper) PDF Version. Covalent functionalization of carbon nanotubes for ultimate interfacial adhesion to liquid crystalline polymer. Nanda Gopal Sahoo, Henry Kuo ...
The effects of graphene oxide (GO) and ammonia functionalized graphene oxide (AGO) on microstruct... more The effects of graphene oxide (GO) and ammonia functionalized graphene oxide (AGO) on microstructure, thermoreversible and critical gelation properties of j-carrageenan in aqueous solution were studied by micro-differential scanning calorimetry (micro-DSC), field emission scanning electron microscopy (FESEM) and rheology. The presence of GO or AGO was able to decrease the gel formation and melting temperatures and reduce gel strength. The effect of AGO was more evident than that of GO. It was observed by FESEM that j-carrageenan gel was induced by the formation of a fibrillar network, and fibrillar size and density decreased with increasing GO or AGO content. The viscoelastic properties at the gel point were examined using the Winter-Chambon criterion to obtain the critical relaxation exponent n and the critical gel strength S g. n increased but S g decreased with increasing GO or AGO content. The more obvious increase in n and decrease in S g were observed in the AGO/j-carrageenan solution, which further demonstrated the stronger weakening effect of AGO. A schematic diagram has been proposed to explain the effect of AGO on the gelation of j-carrageenan, where AGO sheets attracted a number of j-carrageenan chains through hydrogen bonding and electrostatic interaction between sulfate groups of j-carrageenan and amine groups of AGO. As a result, the number of free j-carrageenan chains in solution decreased and the coil-helix transition and aggregation of helices of j-carrageenan were affected negatively.
The effects of two poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO)... more The effects of two poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) triblock copolymers, Pluronics-R 10R5 (PPO 8-PEO 22-PPO 8) and 25R4 (PPO 19-PEO 33-PPO 19), on the thermal and rheological properties as well as the phase transitions of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer (Pluronic F127, PEO 100-PPO 65-PEO 100) in aqueous solution have been systematically studied. Both 10R5 and 25R4 could shift the critical micellization temperature of F127 to lower temperatures, showing a "salt-out like" effect. When F127 itself is unable to form a gel at low concentrations, 25R4 could assist micelles of F127 to be connected into a gel network. However, 10R5 is too short to be able to assist F127 to form a gel. At low contents of 10R5 or 25R4, F127 dominates its gelation but 25R4 could affect the hard gel-soft gel transition while10R5 showed a weaker effect on the hard gel-soft gel transition than 25R4. The rheological scaling law in the vicinity of the gel point was examined to obtain the critical relaxation exponent n and the critical gel strength S g. n decreases and S g increases with increasing 25R4 at low concentrations of F127. However, 10R5 and 25R4 affected n and S g differently at high concentrations of F127.
A comb-like dual hydrophilic graft chitosan copolymer, chitosan-graft-poly(N-isopropylacrylamide)... more A comb-like dual hydrophilic graft chitosan copolymer, chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAM), was synthesized by means of atom transfer radical polymerization (ATRP) and click chemistry. The thermo-responsive association behavior of the copolymer in dilute aqueous solutions has been investigated by laser light scattering (LLS), zeta potential, and transmission electron microscopy (TEM). The core-shell structured micelles with the hydrophobic PNIAPM as a core and the hydrophilic CS as a shell were formed at low pH (<4) and high temperature (>32 degrees C), whereas the obtained micelles became large aggregates and precipitated in alkaline solutions (pH > 7). Additionally, the low critical solution temperature (LCST) phase transitions of dense copolymer solutions in the presence of salts (NaCl and NaI) and a cationic surfactant (dodecyltrimethylammonium bromide, DTAB) respectively were studied by micro differential scanning calorimetry (DSC) and UV turbidimetry. It was found that both salts (NaCl and NaI) and DATB could shift the LCST to lower or higher temperatures from a pure copolymer solution, depending on the beneath mechanisms.
ABSTRACT A novel thermoreversible gelling system consisting of tamarind seed xyloglucan (TSX) and... more ABSTRACT A novel thermoreversible gelling system consisting of tamarind seed xyloglucan (TSX) and gallic acid (GA) was prepared and investigated. The thermal transition temperatures obtained from both micro-DSC and viscoelastic methods were consistent. The hysteresis was observed for the GA–TSX gelling system. The hydrogen bonding interactions between GA and TSX were detected using 13C nuclear magnetic resonance analyses. The carboxylic acid and the hydroxyl group at the para position of GA are the principal groups that interact with TSX. A low temperature induced intermolecular aggregation of TSX via hydrogen bonds between GA and TSX, leading to the formation of a gel network. The thermal stability of the GA–TSX gel increased with increasing the GA concentration. The viscoelastic behavior of the GA–TSX mixtures depended on the concentration of GA. For the mixture of GA and 1% (w/v) TSX, the critical gel concentration of GA was 0.69% (w/v) at physiological temperature (37 °C) and the sol–gel transition was well described by the scaling law. Moreover, the dried GA–TSX gels exhibited various morphologies that reflected the dependence of the arrangement of the TSX chains on the GA concentration.
Nowadays, the concept of drug transmission is an important topic in the field of drug delivery re... more Nowadays, the concept of drug transmission is an important topic in the field of drug delivery research. Drug delivery is the method or process of administering a pharmaceutical compound to achieve a therapeutic effect in humans or animals. In this study, we report the development of a novel platform for the loading and release of doxorubicin (DOX). It is based on porous reduced graphene oxide (prGO) nanosheets and chitosan (CS) biocompatible polymer, where prGO can be dispersed in chitosan through amide linkages. The loading and release of DOX on the CS-prGO nanocomposite were investigated by voltammetry, FE-SEM, and FTIR and UV-Vis spectroscopy methods. We showed that chitosan-modified prGO (CS-prGO) was an extremely efficient matrix. An efficient loading of DOX (86% at pH 7.00, time 3 h and initial concentration of 0.5 mg mL À1) was observed on CS-prGO as compared to the case of prGO due to the presence of the-OH and-NH 2 groups of chitosan. At the normal physiological pH of 7.00, approximately 10% of DOX could be released from CS-prGO in a time span of 1 h; however, when exposed to pH 4.00, 25% of DOX was released in 1 h. After 20 h, 18% and 62% of DOX was released at pH 7.00 and 4.00, respectively. This illustrates the major benefits of the developed approach for biomedical applications.
Carbon nanotube-based nanocomposites of chitosan were successfully prepared by a simple solution-... more Carbon nanotube-based nanocomposites of chitosan were successfully prepared by a simple solution-evaporation method. Multiwalled carbon nanotubes (MWCNTs) were treated by poly(3,4ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT-PSS) in water before mixed with a chitosan solution to improve the dispersion of MWCNTs and interfacial compatibility between MWCNTs and chitosan. The morphological and mechanical properties of the prepared PEDOT-PSS/MWCNT/chitosan nanocomposites have been characterized with field emission scanning electron microscopy (FESEM) and tensile tests. MWCNTs were observed to be homogeneously dispersed throughout the chitosan matrix. As compared with the neat chitosan, the tensile strength and modulus of the nanocomposite were greatly improved by about 61% and 34%, respectively, with incorporation of only 0.5 wt.% of MWCNTs into the chitosan matrix. The comparison of mechanical properties for PEDOT-PSS/MWCNT/chitosan and pristine MWCNT/chitosan nanocomposites has been made. The hardness of the nanocomposites was also evaluated by nanoindentation.
Methylcellulose (MC), chitosan (CS), and κ-carrageenan (KC) are chosen as typical representatives... more Methylcellulose (MC), chitosan (CS), and κ-carrageenan (KC) are chosen as typical representatives of neutral and positively, and negatively charged polysaccharides, respectively. Sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) are chosen as anionic and cationic surfactants, respectively. From these polymers and surfactants, six combinations of polymer−surfactant are made: MC−SDS, MC−CTAB, CS−SDS, CS−CTAB, KC−SDS, and KC−CTAB. The polymer−surfactant interactions for the six pairs are systematically investigated by isothermal titration calorimetry (ITC). It was observed that MC−SDS exhibited strong hydrophobic interaction, as evidenced by the endothermic peak, followed by a weak ion−dipole interaction. KC−SDS did not show any ionic interaction, as expected, but exhibited weaker hydrophobic interaction than MC−SDS. Strong ionic interaction was found for CS−SDS, followed by hydrophobic interaction between some hydrophobic moieties of CS and SDS tails. Titration of CTAB with MC resulted ...
Multiwalled carbon nanotubes (MWCNTs) were functionalized on their sidewalls with p-nitrophenyl (... more Multiwalled carbon nanotubes (MWCNTs) were functionalized on their sidewalls with p-nitrophenyl (C6H4NO2) to make MWCNTs compatible with liquid crystalline polymer (LCP) through a specific interaction with LCP. This study examined the rheological, morphological, mechanical, dynamic mechanical, and thermal properties of LCP in detail with a variation of the nitrophenyl-functionalized MWCNTs in the LCP matrix. A higher complex viscosity, storage, and
The nanoparticles of chitosan (CS) were prepared using pentasodium triphosphate (TPP) as a crossl... more The nanoparticles of chitosan (CS) were prepared using pentasodium triphosphate (TPP) as a crosslinking agent and the influences of cetyltrimethylammonium bromide (CTAB) on the physicochemical properties of the CS-TPP nanoparticles were first studied by laser light scattering, zeta potential, and transmission electron microscopy (TEM). The concentration played a significant role in controlling the particle size of CS and the overlap concentration c * was testified to be about 1.0 mg/mL. The combination of static light scattering (SLS) and dynamic light scattering (DLS) allowed us to obtain more information about the CS-TPP nanoparticles in the presence of surfactant molecules. The addition of CTAB could reduce the hydrodynamic diameter of nanoparticles effectively in the salt solutions and simultaneously increase the zeta potential of the nanoparticles. The effect of CTAB concentration on the size of CS-TPP nanoparticle was also examined. The critical micelle concentration (CMC) of CTAB was used to interpret the complicated complex formed by the polyelectrolyte and the surfactant. Finally, TEM was used to observe the CS-TPP nanoparticles, which were affected by CTAB, to verify the results obtained by light scattering.
Materials and methods 1) Materials The MWCNTs were purchased from Iljin Nano Tech, Korea. Their d... more Materials and methods 1) Materials The MWCNTs were purchased from Iljin Nano Tech, Korea. Their diameter and length were about 10-20 nm and 20 μm, respectively. These nanotubes (purity of 95%) were produced by chemical vapor deposition. Graphite with an average particle size of 100 μm was obtained from Sigma-Aldrich. CPT was purchased from Guanyu Bio Inc from China. Poly (vinyl alcohol) (PVA) (M w ~61,000) was obtained from Fluka. (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) (MTT) and other mentioned reagents were purchased from Aldrich and used as received. 2) Preparation of MWCNT-PVA The MWCNTs were functionalized with PVA in a carbodiimide-activated esterification reaction. In a typical procedure, 55 mg purified CNT-COOH was dissolved in 10 mL dimethyl sulfoxide (DMSO) and sonicated for 30 min to obtain a homogeneous black-colored solution. The catalysts, N,N'-dicyclohexylcarbodiimide (DCC) (600mg, 2.91 mmol) and 4dimethylaminopyridine (DMAP) (99 mg, 0.81 mmol) were gradually charged into the flask and stirred for 10 min. Then, a solution of PVA in DMSO (100 mg/mL, 5 mL) was added, and the mixture was sonicated to react at 50 °C for 24 h. After it was terminated, the dark suspension was filtered over a 0.2 μm PTFE microporous membrane, and the obtained solid was washed
The excellent water solubility of graphene oxide (GO) imparts it feasibility as a new filler for ... more The excellent water solubility of graphene oxide (GO) imparts it feasibility as a new filler for reinforcing hydrophilic biopolymers. In this work, we present a simple and green approach to fabrication of GO/chitosan nanocomposite films. Mechanical properties of the nanocomposite have been significantly enhanced without sacrificing the optical transparency. GO sheets are unidirectionally aligned in the chitosan matrix and parallel to the surface of nanaocomposite film, which has been manifested by the morphological observation and explained by the theoretical prediction of tensile modulus. With incorporation of 1wt% GO, the fracture strength and tensile modulus of the nanocomopsites are significantly enhanced by 93% and 51%, respectively. The simultaneous improvement of strength and toughness could be attributed to the homogeneous dispersion and alignment of GO sheets in the chitosan matrix, the strong interfacial adhesion between GO and chitosan, as well as the high specific surface area and the two-dimensional geometry of GO.
Water-soluble chitosan-grafted reduced graphene oxide (CS-rGO) sheets are successfully synthesize... more Water-soluble chitosan-grafted reduced graphene oxide (CS-rGO) sheets are successfully synthesized via amidation reaction and chemical reduction. CS-rGO possesses not only remarkable graphitic property but also favorable water solubility, which is found to be able to effectively disperse multiwalled carbon nanotubes (MWCNTs) in acidic solutions via noncovalent interaction. The efficiency of CS-rGO in dispersing MWCNTs is tested to be higher than that of plain graphene oxide (GO) and a commercial surfactant, sodium dodecyl sulfate (SDS). With incorporation of 1 wt % CS-rGO dispersed MWCNTs (CS-rGO-MWCNTs), the tensile modulus, strength and toughness of the chitosan (CS) nanocomposites can be increased by 49, 114, and 193%, respectively. The reinforcing and toughening effects of CS-rGO-MWCNTs are much more prominent than those of single-component fillers, such as MWCNTs, GO, and CS-rGO. Noncovalent π−π interactions between graphene sheets and nanotubes and hydrogen bonds between grafted CS and the CS matrix are responsible for generating effective load transfer between CS-rGO-MWCNTs and the CS matrix, causing the simultaneously increased strength and toughness of the nanocomposites.
Poly (vinyl alcohol) is used as raw material in this study. With adding graphene oxide, the PVA/G... more Poly (vinyl alcohol) is used as raw material in this study. With adding graphene oxide, the PVA/GO membrane was prepared with solution casting method. To evaluate the effect of different casting method on the conductivity of PVA/GO membrane, knife casting method with different casting surface were conducted in this study. Ionic conductivity for PVA/GO prepared by solution casting method is about 0.0526 S/ cm; whereas the ionic conductivity is sharply improved to 0.1439 S/cm for PVA/GO prepared by casting membrane on the glass with vacuum..
Covalently functionalized graphene sheets are prepared by grafting a welldefi ned thermo-responsi... more Covalently functionalized graphene sheets are prepared by grafting a welldefi ned thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) via click chemistry. The PNIPAM-grafted graphene sheets (PNIPAM-GS) consist of about 50% polymer, which endows the sheets with a good solubility and stability in physiological solutions. The PNIPAM-GS exhibits a hydrophilic to hydrophobic phase transition at 33 ° C, which is relatively lower than that of a PNIPAM homopolymer because of the interaction between graphene sheets and grafted PNIPAM. Moreover, through π-π stacking and hydrophobic interaction between PNIPAM-GS and an aromatic drug, the PNIPAM-GS is able to load a water-insoluble anticancer drug, camptothecin (CPT), with a superior loading capacity of 15.6 wt-% (0.185 g CPT per g PNIPAM-GS). The in vitro drug release behavior of the PNIPAM-GS-CPT complex is examined both in water and PBS at 37 ° C. More importantly, the PNIPAM-GS does not exhibit a practical toxicity and the PNIPAM-GS-CPT complex shows a high potency of killing cancer cells in vitro. The PNIPAM-GS is demonstrated to be an effective vehicle for anticancer drug delivery.
The nanoparticles of chitosan (CS) were prepared using pentasodium triphosphate (TPP) as a crossl... more The nanoparticles of chitosan (CS) were prepared using pentasodium triphosphate (TPP) as a crosslinking agent and the influences of cetyltrimethylammonium bromide (CTAB) on the physicochemical properties of the CS-TPP nanoparticles were first studied by laser light scattering, zeta potential, and transmission electron microscopy (TEM). The concentration played a significant role in controlling the particle size of CS and the overlap concentration c * was testified to be about 1.0 mg/mL. The combination of static light scattering (SLS) and dynamic light scattering (DLS) allowed us to obtain more information about the CS-TPP nanoparticles in the presence of surfactant molecules. The addition of CTAB could reduce the hydrodynamic diameter of nanoparticles effectively in the salt solutions and simultaneously increase the zeta potential of the nanoparticles. The effect of CTAB concentration on the size of CS-TPP nanoparticle was also examined. The critical micelle concentration (CMC) of CTAB was used to interpret the complicated complex formed by the polyelectrolyte and the surfactant. Finally, TEM was used to observe the CS-TPP nanoparticles, which were affected by CTAB, to verify the results obtained by light scattering.
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