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2008 Volume 26 Issue 3
2008, 26(3): 249-254
Abstract:
The carrier transport properties of the blends of the hole transport material poly(N-vinylcarbazole) (PVK) and the electron transport material tris (8-hydroxyquinolinolato) aluminum III (Alq3) are investigated at room temperature using steady-state and time-resolved transient photocurrent measurements as a function of doping concentration of Alq3. Due to lower LUMO and higher HOMO energy level of Alq3 than those of PVK, Alq3 molecules may act as carrier trap states in PVK films at low concentration. However, at high concentration of Alq3, phase separation reduces trap states to some extent, which leads to the rise of photocurrent. It is concluded that strong excitation transfer from PVK to Alq3 does harm to photocurrent, because strong fluorescence effect of Alq3 inhibits photogeneration of charge carriers. In time-resolved transient photocurrent measurements, it is found that the decay time is obviously shortened because the recombination rate increases and the electron mobility of Alq3 is higher than the hole mobility of PVK.
The carrier transport properties of the blends of the hole transport material poly(N-vinylcarbazole) (PVK) and the electron transport material tris (8-hydroxyquinolinolato) aluminum III (Alq3) are investigated at room temperature using steady-state and time-resolved transient photocurrent measurements as a function of doping concentration of Alq3. Due to lower LUMO and higher HOMO energy level of Alq3 than those of PVK, Alq3 molecules may act as carrier trap states in PVK films at low concentration. However, at high concentration of Alq3, phase separation reduces trap states to some extent, which leads to the rise of photocurrent. It is concluded that strong excitation transfer from PVK to Alq3 does harm to photocurrent, because strong fluorescence effect of Alq3 inhibits photogeneration of charge carriers. In time-resolved transient photocurrent measurements, it is found that the decay time is obviously shortened because the recombination rate increases and the electron mobility of Alq3 is higher than the hole mobility of PVK.
2008, 26(3): 255-262
Abstract:
Tremolite, a kind of inorganic filler, was modified with a silane coupling agent γ-methacryloxypropyl trimethoxy silane (MPS) in ethanol/ammonia solution. The graft of MPS on tremolite was confirmed by X-ray photoelectron spectroscopy (XPS), IR and thermogramitric analysis (TGA) measurements. In addition, contact angle analysis showed that particle surface property was changed from hydrophilicity to hydrophobicity after the modification. Modified tremolite and pure tremolite were blended respectively with PA1010 (polydecamethylene esbacamide) and the mechanical properties of the composites were studied. Results revealed that MPS had a remarkable influence on the mechanical properties of the composites due to the improvement of interfacial adhesion between filler and matrix. Tensile strength and notched Izod impact strength of MPS-modified tremolite composites were improved simultaneously compared to those with pure tremolite. Composites with MPS modified tremolite exhibited a much higher thermal stability than the samples with pure tremolite confirmed by TGA. The morphologies of the composites were also investigated using scanning electron microscopy (SEM). Results showed that better dispersion of MPS modified tremolite in matrix was obtained.
Tremolite, a kind of inorganic filler, was modified with a silane coupling agent γ-methacryloxypropyl trimethoxy silane (MPS) in ethanol/ammonia solution. The graft of MPS on tremolite was confirmed by X-ray photoelectron spectroscopy (XPS), IR and thermogramitric analysis (TGA) measurements. In addition, contact angle analysis showed that particle surface property was changed from hydrophilicity to hydrophobicity after the modification. Modified tremolite and pure tremolite were blended respectively with PA1010 (polydecamethylene esbacamide) and the mechanical properties of the composites were studied. Results revealed that MPS had a remarkable influence on the mechanical properties of the composites due to the improvement of interfacial adhesion between filler and matrix. Tensile strength and notched Izod impact strength of MPS-modified tremolite composites were improved simultaneously compared to those with pure tremolite. Composites with MPS modified tremolite exhibited a much higher thermal stability than the samples with pure tremolite confirmed by TGA. The morphologies of the composites were also investigated using scanning electron microscopy (SEM). Results showed that better dispersion of MPS modified tremolite in matrix was obtained.
2008, 26(3): 263-273
Abstract:
Membranes for gas separation have developed significantly in the last twenty years, however, there is still a need for high temperature and chemically resistant membranes that exhibit good selectivity and gas permeability. Our study examines the fundamental properties of polyetherketone (PEK, a thermally stable and chemically resistant polymer) membranes prepared using concentrated sulphuric acid (98% H2SO4) as the solvent. Non-solvents used in the work included acetic acid, ethanol, methanol, glycerol, and water. The concentration of the polymer solutions was chosen to be 20%. The membrane structures were examined using SEM, and the gas separation properties were measured using a lab-scale test rig. The results show that formation and control of membrane structures are complicated, and many preparation parameters affect membrane morphology and performance. Using appropriate conditions skinned sponge-like structured hollow fiber membranes could be made from PEK by using acetic acid as the internal coagulant. PEK hollow fibers spun from 20%PEK/H2SO4 solutions with 50% aqueous acetic acid as internal coagulant had selectivity for hydrogen/methane of around 40, implying a solution diffusion separation mechanism for gas separation without the need for fiber coating or after post-treatments.
Membranes for gas separation have developed significantly in the last twenty years, however, there is still a need for high temperature and chemically resistant membranes that exhibit good selectivity and gas permeability. Our study examines the fundamental properties of polyetherketone (PEK, a thermally stable and chemically resistant polymer) membranes prepared using concentrated sulphuric acid (98% H2SO4) as the solvent. Non-solvents used in the work included acetic acid, ethanol, methanol, glycerol, and water. The concentration of the polymer solutions was chosen to be 20%. The membrane structures were examined using SEM, and the gas separation properties were measured using a lab-scale test rig. The results show that formation and control of membrane structures are complicated, and many preparation parameters affect membrane morphology and performance. Using appropriate conditions skinned sponge-like structured hollow fiber membranes could be made from PEK by using acetic acid as the internal coagulant. PEK hollow fibers spun from 20%PEK/H2SO4 solutions with 50% aqueous acetic acid as internal coagulant had selectivity for hydrogen/methane of around 40, implying a solution diffusion separation mechanism for gas separation without the need for fiber coating or after post-treatments.
2008, 26(3): 275-283
Abstract:
The scanning force microscopy (SFM)/chemical force microscopy (CFM) were used to study the growth of grafted polyacrylamide (PAM) chains onto polyethylene (PE)-film with varying grafting time. Results from the CFM reveal reduced interaction between the probe and areas with grafted-PAM on the surface. The topography and the friction trace-minus-retrace (TMR) images are complementary to one another resulting from the reduced interaction of the probe that has specificity to chemical domains.
The scanning force microscopy (SFM)/chemical force microscopy (CFM) were used to study the growth of grafted polyacrylamide (PAM) chains onto polyethylene (PE)-film with varying grafting time. Results from the CFM reveal reduced interaction between the probe and areas with grafted-PAM on the surface. The topography and the friction trace-minus-retrace (TMR) images are complementary to one another resulting from the reduced interaction of the probe that has specificity to chemical domains.
2008, 26(3): 285-290
Abstract:
The main subject of this work is about the effect of T-ZnOw on the toughness and stiffness of polystyrene (PS). In order to avoid the rupture of T-ZnOw during the melt processing, T-ZnOw/PS composites were obtained via the combination of solution blending and injection moulding methods. Although the tensile strength of the composites decreases slightly, the impact strength and tensile modulus increase with the increase of the T-ZnOw content in the matrix. The stiffness and toughness of the composites are enhanced simultaneously. SEM results of the impact-fractured surface show more polymer avulsions, ridges and micro-cracks formed in the T-ZnOw/PS composites, companied with pullout of T-ZnOw from PS matrix and local yielding of PS matrix around T-ZnOw during the impact processing. The possible reasons for the toughness increment of T-ZnOw/PS composites are attributed to the interfacial debonding, pullout of T-ZnOw from PS matrix, anchoring effect of T-ZnOws special three dimensional structure, local yielding of PS matrix and the formation and propagation of micro-cracks.
The main subject of this work is about the effect of T-ZnOw on the toughness and stiffness of polystyrene (PS). In order to avoid the rupture of T-ZnOw during the melt processing, T-ZnOw/PS composites were obtained via the combination of solution blending and injection moulding methods. Although the tensile strength of the composites decreases slightly, the impact strength and tensile modulus increase with the increase of the T-ZnOw content in the matrix. The stiffness and toughness of the composites are enhanced simultaneously. SEM results of the impact-fractured surface show more polymer avulsions, ridges and micro-cracks formed in the T-ZnOw/PS composites, companied with pullout of T-ZnOw from PS matrix and local yielding of PS matrix around T-ZnOw during the impact processing. The possible reasons for the toughness increment of T-ZnOw/PS composites are attributed to the interfacial debonding, pullout of T-ZnOw from PS matrix, anchoring effect of T-ZnOws special three dimensional structure, local yielding of PS matrix and the formation and propagation of micro-cracks.
2008, 26(3): 291-298
Abstract:
The phase diagram of a ternary system of PVDF, dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) was determined in terms of a pseudo binary system with the same polymer concentration and different DBP content in diluent mixture. The experimental results showed that as the DBP content increased in diluent mixture, the phase separation changed from liquid-liquid phase separation to solid-liquid phase separation, and both the cloudy point for L-L phase separation and crystallization temperature shifted to lower temperature. Molar excess free energy of mixing △GE implying the estimated interaction between PVDF and diluent mixture was characterized to explain the features in the phase diagram. The effects of DBP content in diluent mixture on crystallization behavior and phase separated structure were investigated. The crystallization of PVDF in system with L-L phase separation was perfect, but the crystallinity was lower relative to the system with only S-L phase separation. The phase separated structures can be controlled successfully by varying the DBP content in diluent mixture as the cooling conditions kept constant.
The phase diagram of a ternary system of PVDF, dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) was determined in terms of a pseudo binary system with the same polymer concentration and different DBP content in diluent mixture. The experimental results showed that as the DBP content increased in diluent mixture, the phase separation changed from liquid-liquid phase separation to solid-liquid phase separation, and both the cloudy point for L-L phase separation and crystallization temperature shifted to lower temperature. Molar excess free energy of mixing △GE implying the estimated interaction between PVDF and diluent mixture was characterized to explain the features in the phase diagram. The effects of DBP content in diluent mixture on crystallization behavior and phase separated structure were investigated. The crystallization of PVDF in system with L-L phase separation was perfect, but the crystallinity was lower relative to the system with only S-L phase separation. The phase separated structures can be controlled successfully by varying the DBP content in diluent mixture as the cooling conditions kept constant.
2008, 26(3): 299-309
Abstract:
A novel charring agent, bis(1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane) phenylphosphine sulfide (BCPPS), has been synthesized, and it is combined with ammonium polyphosphate (APP) and melamine phosphate (MP) to impart flame retardance and dripping resistance for polypropylene (PP). The fire performance of the treated PP is investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter, and the thermal stability and thermal oxidative stability of the composites are studied using thermogravimetric analysis (TG). It has been found that the treated PP with the optimal flame retardant formulation of APP:MP:BCPPS = 12:6:12 (weight ratio, formulation 10) gives an LOI of 31.3 and UL-94 V-0 rating. The results from cone calorimeter indicate that both the heat release rate (HRR) and the total heat evolved (THE) of IFR-PP (formulation 10) decrease significantly compared with those of neat PP. The TG result shows that the IFR-PP (formulation 10) has a high yield of residual char at high temperature. FTIR is used to investigate the residue of the treated PP that degrades at 400°C for different time. The compact outer surface and the shaggy inner surface can be observed from the SEM graph of the residual chars after LOI test, which form a much better barrier for the transfer of heat and fuel during combustion and show good flame retardancy. Moreover, the treated PP and its residue are investigated by XPS analysis.
A novel charring agent, bis(1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane) phenylphosphine sulfide (BCPPS), has been synthesized, and it is combined with ammonium polyphosphate (APP) and melamine phosphate (MP) to impart flame retardance and dripping resistance for polypropylene (PP). The fire performance of the treated PP is investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter, and the thermal stability and thermal oxidative stability of the composites are studied using thermogravimetric analysis (TG). It has been found that the treated PP with the optimal flame retardant formulation of APP:MP:BCPPS = 12:6:12 (weight ratio, formulation 10) gives an LOI of 31.3 and UL-94 V-0 rating. The results from cone calorimeter indicate that both the heat release rate (HRR) and the total heat evolved (THE) of IFR-PP (formulation 10) decrease significantly compared with those of neat PP. The TG result shows that the IFR-PP (formulation 10) has a high yield of residual char at high temperature. FTIR is used to investigate the residue of the treated PP that degrades at 400°C for different time. The compact outer surface and the shaggy inner surface can be observed from the SEM graph of the residual chars after LOI test, which form a much better barrier for the transfer of heat and fuel during combustion and show good flame retardancy. Moreover, the treated PP and its residue are investigated by XPS analysis.
2008, 26(3): 311-319
Abstract:
The effects of three organic colorants on photo-initiated crosslinking and photo-oxidation degradation of polyethylene (PE) samples irradiated by microwave excited (MWE) UV lamp in the melt and the related mechanism have been studied by gel content and thermal extension rate determinations, X-ray photoelectron spectroscopy (XPS), mechanical property tests, UV spectroscopy, and light microscope. The data from the gel content and thermal extension rate determinations of photo-crosslinked polyethylene (XLPE) samples show that the three colorants can decrease the efficiency of photo-initiated crosslinking of polyethylene to some different degree, in which the effect of red colorant is the largest among the three colorants. The colorized samples of 1 mm thickness are easily to be crosslinked to a satisfactory gel content of about 70% by the MWE lamp and optimized reaction conditions, such as the concentration of colorant, irradiation time, and so on. The XPS results give the evidence that the colorants can accelerate the surface photo-oxidation during the photo-crosslinking of polyethylene. The photo-oxidation products such as ―CH2―O― and ―C(C＝O)― groups on the surface of XLPE samples with the colorants apparently increase with increasing the irradiation time. The data from the mechanical tests show that the colorants reduce the tensile strength and improve the elongation at break of XLPE samples. All the above results show that the effects of the three colorants on photo-initiated crosslinking and photo-oxidative degradation decrease with the order of red blue green colorants. The light microscope photos show that the colorant can disperse well in PE resin. The mechanism of the colorant effects can be elucidated by comparison of the UV absorption spectra of photo-initiator and colorants. This is because the colorants absorb the same UV wavelength regions as photo-initiator, and thus decrease the photo-crosslinking efficiency of photo-initiator and accelerate the surface photo-oxidation of XLPE materials.
The effects of three organic colorants on photo-initiated crosslinking and photo-oxidation degradation of polyethylene (PE) samples irradiated by microwave excited (MWE) UV lamp in the melt and the related mechanism have been studied by gel content and thermal extension rate determinations, X-ray photoelectron spectroscopy (XPS), mechanical property tests, UV spectroscopy, and light microscope. The data from the gel content and thermal extension rate determinations of photo-crosslinked polyethylene (XLPE) samples show that the three colorants can decrease the efficiency of photo-initiated crosslinking of polyethylene to some different degree, in which the effect of red colorant is the largest among the three colorants. The colorized samples of 1 mm thickness are easily to be crosslinked to a satisfactory gel content of about 70% by the MWE lamp and optimized reaction conditions, such as the concentration of colorant, irradiation time, and so on. The XPS results give the evidence that the colorants can accelerate the surface photo-oxidation during the photo-crosslinking of polyethylene. The photo-oxidation products such as ―CH2―O― and ―C(C＝O)― groups on the surface of XLPE samples with the colorants apparently increase with increasing the irradiation time. The data from the mechanical tests show that the colorants reduce the tensile strength and improve the elongation at break of XLPE samples. All the above results show that the effects of the three colorants on photo-initiated crosslinking and photo-oxidative degradation decrease with the order of red blue green colorants. The light microscope photos show that the colorant can disperse well in PE resin. The mechanism of the colorant effects can be elucidated by comparison of the UV absorption spectra of photo-initiator and colorants. This is because the colorants absorb the same UV wavelength regions as photo-initiator, and thus decrease the photo-crosslinking efficiency of photo-initiator and accelerate the surface photo-oxidation of XLPE materials.
2008, 26(3): 321-329
Abstract:
Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent. In the first step, free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent, pentaerythritol tetrakis(3-mercaptopropinate). At appropriate monomer conversions, two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were obtained. In the second step, free radical polymerization of styrene was carried out using PMMAs obtained above as macro-chain transfer agent. When styrene conversion was lower than 30%, heteroarm star-shaped polymers, (PMMA)2(PS)2 and (PMMA)3(PS), were obtained successfully.
Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent. In the first step, free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent, pentaerythritol tetrakis(3-mercaptopropinate). At appropriate monomer conversions, two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were obtained. In the second step, free radical polymerization of styrene was carried out using PMMAs obtained above as macro-chain transfer agent. When styrene conversion was lower than 30%, heteroarm star-shaped polymers, (PMMA)2(PS)2 and (PMMA)3(PS), were obtained successfully.
2008, 26(3): 331-339
Abstract:
Thermal and flammability properties of acrylonitrile-butadiene-styrene copolymer (ABS) with the addition of multi-walled carbon nanotubes (MWNTs) were studied. ABS/MWNTs composites were prepared via melt blending with the MWNTs content varied from 0.2% to 4.0% by mass. Thermogravimetry results showed that the addition of MWNTs accelerated the degradation of ABS during the whole process under air atmosphere, and both onset and maximum degradation temperature were lower than those of pure ABS. The destabilization effect of MWNTs on the thermal stability of the composites became unobvious under nitrogen, and the addition of MWNTs could improve the maximum degradation temperature. The heat release rate and time of ignition (tign) for the composites reduced greatly with the addition of MWNTs especially when the concentration of nanotubes was higher than 1.0%. The accumulation of carbon nanotubes with a network structure was observed and the char layer became thicker with increasing nanotubes concentration. Results from Raman spectra showed a higher degree of graphitization for the residues of ABS/MWNTs composites.
Thermal and flammability properties of acrylonitrile-butadiene-styrene copolymer (ABS) with the addition of multi-walled carbon nanotubes (MWNTs) were studied. ABS/MWNTs composites were prepared via melt blending with the MWNTs content varied from 0.2% to 4.0% by mass. Thermogravimetry results showed that the addition of MWNTs accelerated the degradation of ABS during the whole process under air atmosphere, and both onset and maximum degradation temperature were lower than those of pure ABS. The destabilization effect of MWNTs on the thermal stability of the composites became unobvious under nitrogen, and the addition of MWNTs could improve the maximum degradation temperature. The heat release rate and time of ignition (tign) for the composites reduced greatly with the addition of MWNTs especially when the concentration of nanotubes was higher than 1.0%. The accumulation of carbon nanotubes with a network structure was observed and the char layer became thicker with increasing nanotubes concentration. Results from Raman spectra showed a higher degree of graphitization for the residues of ABS/MWNTs composites.
2008, 26(3): 341-352
Abstract:
Amphiphilic block copolymers, poly(ethylene oxide)-b-poly(N-acryloxysuccinimide) (PEO-b-PNAS) with various molecular weights have been successfully synthesized by atom transfer radical polymerization (ATRP) of NAS using functionalized PEO (PEO-Br) as ATRP macroinitiator. The self-assembling of the block copolymers in water, which is a good solvent for PEO and a non-solvent for PNAS, yielded spherical core-shell micelles with PNAS as core and PEO as shell. The cross-linked reaction of oxysuccinimide in PNAS chains with ethylenediamine occurred in the core of micelles, and the core cross-linked micelles were formed. The flower-like and dendritic aggregates were formed by self-assembling of the core cross-linked micelles on the glass slides or silicon wafers. Longer PNAS block in the block copolymers and higher evaporation temperature formed bigger spherical particles. The optical microscope was used to follow the formation and growth of the flower-like aggregates from the colloidal solution and the main driving forces for the self-assembling are solution fluid and interactions between PEO chains.
Amphiphilic block copolymers, poly(ethylene oxide)-b-poly(N-acryloxysuccinimide) (PEO-b-PNAS) with various molecular weights have been successfully synthesized by atom transfer radical polymerization (ATRP) of NAS using functionalized PEO (PEO-Br) as ATRP macroinitiator. The self-assembling of the block copolymers in water, which is a good solvent for PEO and a non-solvent for PNAS, yielded spherical core-shell micelles with PNAS as core and PEO as shell. The cross-linked reaction of oxysuccinimide in PNAS chains with ethylenediamine occurred in the core of micelles, and the core cross-linked micelles were formed. The flower-like and dendritic aggregates were formed by self-assembling of the core cross-linked micelles on the glass slides or silicon wafers. Longer PNAS block in the block copolymers and higher evaporation temperature formed bigger spherical particles. The optical microscope was used to follow the formation and growth of the flower-like aggregates from the colloidal solution and the main driving forces for the self-assembling are solution fluid and interactions between PEO chains.
2008, 26(3): 353-362
Abstract:
2,2,3,3,4,4,5,5-Octafluoropentyl acrylate was grafted onto silk fiber in a two-step heterogeneous system through the vinyl bonds of acryloyloxyethyl isocyanate modified on the silk. The grafted copolymer was analyzed by FTIR and WAXD, and the results revealed that the fluoroacrylate was successfully grafted onto silk fiber and the crystalline structure of silk fibroin with β-sheet structure was not changed after graft copolymerization. The FT-IR corrected method was used to simulate the grafting yield onto silk compared with the weight increasing method. The results obtained from these two methods were roughly consistent.The influence of the initiator concentration, monomer concentration, react time and temperature on the graft yield was also investigated. The experimental data of thermogravimetry (TG) and differential thermal analysis (DTA) showed that the thermal stability of the modified silk fibers was improved due to the introduction of fluoroacrylate. In comparison with the untreated silk fibers, the water repellence of the modified silk fibers was also improved.
2,2,3,3,4,4,5,5-Octafluoropentyl acrylate was grafted onto silk fiber in a two-step heterogeneous system through the vinyl bonds of acryloyloxyethyl isocyanate modified on the silk. The grafted copolymer was analyzed by FTIR and WAXD, and the results revealed that the fluoroacrylate was successfully grafted onto silk fiber and the crystalline structure of silk fibroin with β-sheet structure was not changed after graft copolymerization. The FT-IR corrected method was used to simulate the grafting yield onto silk compared with the weight increasing method. The results obtained from these two methods were roughly consistent.The influence of the initiator concentration, monomer concentration, react time and temperature on the graft yield was also investigated. The experimental data of thermogravimetry (TG) and differential thermal analysis (DTA) showed that the thermal stability of the modified silk fibers was improved due to the introduction of fluoroacrylate. In comparison with the untreated silk fibers, the water repellence of the modified silk fibers was also improved.
2008, 26(3): 363-367
Abstract:
A glycopolymer bearing glucose residues was tethered onto the surface of polypropylene microporous membrane by UV-induced graft polymerization of α-allyl glucoside. Concanavalin A (Con A), a glucose recognizing lectin, could be specifically adsorbed to the membrane surface. On the other hand, the membrane surface showed no recognition ability to another lectin peanut agglutinin. Moreover, the recognition complex between the glycosylated membrane surface and Con A could be inhibited by glucose and mannose solution. This surface glycosylated membrane could be used as affinity membrane for protein separation and purification.
A glycopolymer bearing glucose residues was tethered onto the surface of polypropylene microporous membrane by UV-induced graft polymerization of α-allyl glucoside. Concanavalin A (Con A), a glucose recognizing lectin, could be specifically adsorbed to the membrane surface. On the other hand, the membrane surface showed no recognition ability to another lectin peanut agglutinin. Moreover, the recognition complex between the glycosylated membrane surface and Con A could be inhibited by glucose and mannose solution. This surface glycosylated membrane could be used as affinity membrane for protein separation and purification.
2008, 26(3): 369-374
Abstract:
Abstract A novel pH-sensitive nanoparticle drug delivery system (DDS) derived from natural polysaccharide pullulan for doxorubicin (DOX) release was prepared. Pullulan was functionalized by successive carboxymethylization and amidation to introduce hydrazide groups. DOX was then grafted onto pullulan backbone through the pH-sensitive hydrazone bond to form a pullulan/DOX conjugate. This conjugate self-assembled to form nano-sized particles in aqueous solution as a result of the hydrophobic interaction of the DOX. Transmission electron microscope (TEM) and dynamic light scattering (DLS) characterization showed that the nanoparticles were spherical and their size was less than 100 nm. The DOX released from the nanoparticles in a pH-sensitive manner. In vitro cytotoxicity assay indicated the pullulan/DOX nanoparticles showed comparable cytotoxicity effect with free DOX on the 4T1 mouse breast cancer cells.
Abstract A novel pH-sensitive nanoparticle drug delivery system (DDS) derived from natural polysaccharide pullulan for doxorubicin (DOX) release was prepared. Pullulan was functionalized by successive carboxymethylization and amidation to introduce hydrazide groups. DOX was then grafted onto pullulan backbone through the pH-sensitive hydrazone bond to form a pullulan/DOX conjugate. This conjugate self-assembled to form nano-sized particles in aqueous solution as a result of the hydrophobic interaction of the DOX. Transmission electron microscope (TEM) and dynamic light scattering (DLS) characterization showed that the nanoparticles were spherical and their size was less than 100 nm. The DOX released from the nanoparticles in a pH-sensitive manner. In vitro cytotoxicity assay indicated the pullulan/DOX nanoparticles showed comparable cytotoxicity effect with free DOX on the 4T1 mouse breast cancer cells.
