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2012 Volume 30 Issue 1
2012, 30(1): 1-15
doi: 10.1007/s10118-012-1098-2
Abstract:
The great achievements of click chemistry have encouraged polymer scientists to use this reaction in their field. This review assembles an update of the advances of using azide-alkyne click polymerization to prepare functional polytriazoles (PTAs) with linear and hyperbranched structures. The Cu(I)-mediated click polymerization furnishes 1,4-regioregular PTAs, whereas, the metal-free click polymerization of propiolates and azides produces PTAs with 1,4-regioisomer contents up to 90%. The PTAs display advanced functions, such as aggregation-induced emission, thermal stability, biocompatibility and optical nonlinearity.
The great achievements of click chemistry have encouraged polymer scientists to use this reaction in their field. This review assembles an update of the advances of using azide-alkyne click polymerization to prepare functional polytriazoles (PTAs) with linear and hyperbranched structures. The Cu(I)-mediated click polymerization furnishes 1,4-regioregular PTAs, whereas, the metal-free click polymerization of propiolates and azides produces PTAs with 1,4-regioisomer contents up to 90%. The PTAs display advanced functions, such as aggregation-induced emission, thermal stability, biocompatibility and optical nonlinearity.
2012, 30(1): 16-25
doi: 10.1007/s10118-012-1091-9
Abstract:
Electrorheological properties and creep-recovery behavior of polythiophene/polyoxymethylene-blend having PT(50%)/POM(50%) composition were investigated. Particle size, conductivity and dielectric values were measured to be 24.77 m, 3.85 10-5 Sm-1 and 26.75, respectively. Sedimentation ratio was measured to be 64% at the end of 16 days. The effects of dispersed particle volume fraction, external electric field strength, shear rate, frequency and temperature on ER properties and storage modulus of PT/POM-blend/silicone oil (SO) suspensions were examined. Enhancement were observed in the electric field viscosities of the suspensions and thus they were classified as a smart material. Shear thinning non-Newtonian viscoelastic behavior was determined for PT/POM-blend/SO system. Further, time-dependent deformation was examined by creep-recovery tests and recoverable viscoelastic deformation established.
Electrorheological properties and creep-recovery behavior of polythiophene/polyoxymethylene-blend having PT(50%)/POM(50%) composition were investigated. Particle size, conductivity and dielectric values were measured to be 24.77 m, 3.85 10-5 Sm-1 and 26.75, respectively. Sedimentation ratio was measured to be 64% at the end of 16 days. The effects of dispersed particle volume fraction, external electric field strength, shear rate, frequency and temperature on ER properties and storage modulus of PT/POM-blend/silicone oil (SO) suspensions were examined. Enhancement were observed in the electric field viscosities of the suspensions and thus they were classified as a smart material. Shear thinning non-Newtonian viscoelastic behavior was determined for PT/POM-blend/SO system. Further, time-dependent deformation was examined by creep-recovery tests and recoverable viscoelastic deformation established.
2012, 30(1): 26-35
doi: 10.1007/s10118-012-1099-1
Abstract:
Polystyrene coated silica (SiO2@PS) core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface of -methacryloxypropyltrimethoxysilane grafted SiO2 nanoparticles of 20-50 nm in diameter. Rheological behavior and dispersion stability of SiO2@PS suspension in 10 wt% PS solution were compared with suspensions of untreated SiO2 and silane modified SiO2 nanoparticles. Suspensions of the untreated and the silane modified SiO2 exhibited obvious shear thinning. The SiO2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO2 at low shear rates. Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions, implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.
Polystyrene coated silica (SiO2@PS) core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface of -methacryloxypropyltrimethoxysilane grafted SiO2 nanoparticles of 20-50 nm in diameter. Rheological behavior and dispersion stability of SiO2@PS suspension in 10 wt% PS solution were compared with suspensions of untreated SiO2 and silane modified SiO2 nanoparticles. Suspensions of the untreated and the silane modified SiO2 exhibited obvious shear thinning. The SiO2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO2 at low shear rates. Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions, implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.
2012, 30(1): 36-44
doi: 10.1007/s10118-012-1102-x
Abstract:
Thermally stable polymers containing 1,3,4-oxadiazole units have been synthesized through Huisgen reaction of the aromatic/aliphatic bis-tetrazole compounds with the aromatic/aliphatic bis-acid chlorides in pyridine as solvent. The obtained polymers are insoluble or slightly soluble even in polar aprotic solvents such as DMSO and DMF. Relatively high inherent viscosity values (0.61-1.33 dL/g, in 0.125% H2SO4 at 25C) were observed for these compounds. Thermal analyses of the polymers using DSC and TGA techniques showed that the polymers have improved thermal stabilities. The glass transition temperature has not been observed in the fully aromatic polymers, but the polymers obtained from 5-[6-(1H-tetrazol-5-yl)hexyl]-1H-tetrazole (IV) showed very clear Tg. A model reaction was also investigated and the resulting bis-1,3,4-oxadiazole compound was characterized by conventional spectroscopy methods.
Thermally stable polymers containing 1,3,4-oxadiazole units have been synthesized through Huisgen reaction of the aromatic/aliphatic bis-tetrazole compounds with the aromatic/aliphatic bis-acid chlorides in pyridine as solvent. The obtained polymers are insoluble or slightly soluble even in polar aprotic solvents such as DMSO and DMF. Relatively high inherent viscosity values (0.61-1.33 dL/g, in 0.125% H2SO4 at 25C) were observed for these compounds. Thermal analyses of the polymers using DSC and TGA techniques showed that the polymers have improved thermal stabilities. The glass transition temperature has not been observed in the fully aromatic polymers, but the polymers obtained from 5-[6-(1H-tetrazol-5-yl)hexyl]-1H-tetrazole (IV) showed very clear Tg. A model reaction was also investigated and the resulting bis-1,3,4-oxadiazole compound was characterized by conventional spectroscopy methods.
2012, 30(1): 45-55
doi: 10.1007/s10118-012-1101-y
Abstract:
The structural transition of a single polymer chain with chain length of 100, 200 and 300 beads was investigated by parallel tempering MD simulation. Our simulation results can capture the structural change from random coil to orientationally ordered structure with decreasing temperature. The clear transition was observed on the curves of radius of gyration and global orientational order parameter P as the function of temperature, which demonstrated structural formation of a single polymer chain. The linear relationships between three components of square radius of gyration Rgx2,Rgy2,Rgz2 and global orientational order P can be obtained under the structurally transformational process. The slope of the linear relationship between x (or y-axis) component Rgx2(or Rgy2) and P is negative, while that of Rgz2 as the function of P is positive. The absolute value of slope is proportional to the chain length. Once the single polymer chain takes the random coil or ordered configuration, the linear relationship is invalid. The conformational change was also analyzed on microscopic scale. The polymer chain can be treated as the construction of rigid stems connecting by flexible loops. The deviation from exponentially decreased behavior of stem length distribution becomes prominent, indicating a stiffening of the chain arises leading to more and more segments ending up in the trans state with decreasing temperature. The stem length Ntr is about 21 bonds indicating the polymer chain is ordered with the specific fold length. So, the simulation results, which show the prototype of a liquid-crystalline polymer chain, are helpful to understand the crystallization process of crystalline polymers.
The structural transition of a single polymer chain with chain length of 100, 200 and 300 beads was investigated by parallel tempering MD simulation. Our simulation results can capture the structural change from random coil to orientationally ordered structure with decreasing temperature. The clear transition was observed on the curves of radius of gyration and global orientational order parameter P as the function of temperature, which demonstrated structural formation of a single polymer chain. The linear relationships between three components of square radius of gyration Rgx2,Rgy2,Rgz2 and global orientational order P can be obtained under the structurally transformational process. The slope of the linear relationship between x (or y-axis) component Rgx2(or Rgy2) and P is negative, while that of Rgz2 as the function of P is positive. The absolute value of slope is proportional to the chain length. Once the single polymer chain takes the random coil or ordered configuration, the linear relationship is invalid. The conformational change was also analyzed on microscopic scale. The polymer chain can be treated as the construction of rigid stems connecting by flexible loops. The deviation from exponentially decreased behavior of stem length distribution becomes prominent, indicating a stiffening of the chain arises leading to more and more segments ending up in the trans state with decreasing temperature. The stem length Ntr is about 21 bonds indicating the polymer chain is ordered with the specific fold length. So, the simulation results, which show the prototype of a liquid-crystalline polymer chain, are helpful to understand the crystallization process of crystalline polymers.
2012, 30(1): 56-62
doi: 10.1007/s10118-012-1094-6
Abstract:
The cationic ring-opening polymerization of tetrahydrofuran using maghnite-H+ is reported. Maghnite-H+, is a non-toxic solid catalyst issued from proton exchanged montmorillonite clay. Polytetrahydrofuran, also called poly(butandiol) ether, with acetate and hydroxyl end groups was successfully synthesized. Effects of reaction temperature, weight ratio of initiator/monomer and reaction time on the conversion of monomer and on the molecular weight are investigated. A cationic mechanism of the reaction was proposed. This chemistry can be considered as a suitable route for preparing poly(THF) as a soft segment for thermoplastic elastomers.
The cationic ring-opening polymerization of tetrahydrofuran using maghnite-H+ is reported. Maghnite-H+, is a non-toxic solid catalyst issued from proton exchanged montmorillonite clay. Polytetrahydrofuran, also called poly(butandiol) ether, with acetate and hydroxyl end groups was successfully synthesized. Effects of reaction temperature, weight ratio of initiator/monomer and reaction time on the conversion of monomer and on the molecular weight are investigated. A cationic mechanism of the reaction was proposed. This chemistry can be considered as a suitable route for preparing poly(THF) as a soft segment for thermoplastic elastomers.
2012, 30(1): 63-71
doi: 10.1007/s10118-012-1104-8
Abstract:
A novel tripyridylporphyrin monomer, 5-[4-[2-(acryloyloxy)ethoxy]phenyl]-l0,l5,20-tris(4-pyridyl)porphyrin (TrPyP), was synthesized and polymerized with acrylamide (AM) to prepare the hydrophobically associating water-soluble polymer PAM-TrPyP. The aggregation behavior of porphyrin pendants was investigated by UV-Visible and fluorescence spectra. The polymer displays a strong tendency of hydrophobic association even in dilute solutions. With increasing the concentration, the maximum absorption wavelength of Soret band changes from 416 nm to 407 nm, and the fluorescence corrected for the inner filter effect exhibits moderate concentration quenching. All the results indicate that - interaction of porphyrin pendants plays a key role in association of PAM-TrPyP, and H-aggregates of porphyrins are mainly formed in the concentrated solution. On the other hand, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to follow the changes in size and structure of the macromolecular assemblies with the concentration increase. The polymer aggregation conformation changes from loose vesicle-like morphology to solid globule accordingly. When pH value of solution decreases to 4.3, pyridine moieties on porphyrin pendants could be protonated and the H-aggregates formed in macromolecular matrix are destroyed by electrostatic repulsion interactions.
A novel tripyridylporphyrin monomer, 5-[4-[2-(acryloyloxy)ethoxy]phenyl]-l0,l5,20-tris(4-pyridyl)porphyrin (TrPyP), was synthesized and polymerized with acrylamide (AM) to prepare the hydrophobically associating water-soluble polymer PAM-TrPyP. The aggregation behavior of porphyrin pendants was investigated by UV-Visible and fluorescence spectra. The polymer displays a strong tendency of hydrophobic association even in dilute solutions. With increasing the concentration, the maximum absorption wavelength of Soret band changes from 416 nm to 407 nm, and the fluorescence corrected for the inner filter effect exhibits moderate concentration quenching. All the results indicate that - interaction of porphyrin pendants plays a key role in association of PAM-TrPyP, and H-aggregates of porphyrins are mainly formed in the concentrated solution. On the other hand, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to follow the changes in size and structure of the macromolecular assemblies with the concentration increase. The polymer aggregation conformation changes from loose vesicle-like morphology to solid globule accordingly. When pH value of solution decreases to 4.3, pyridine moieties on porphyrin pendants could be protonated and the H-aggregates formed in macromolecular matrix are destroyed by electrostatic repulsion interactions.
2012, 30(1): 72-81
doi: 10.1007/s10118-012-1100-z
Abstract:
The synergistic effect of phosphorus oxynitride (PON) with a novolac-based char former modified by salification (NA-metal salt) on the flame retardance of polyamide 6 (PA6) was investigated. For this purpose, various flame-retardant PA6 systems were melt-compounded with PON, PON/NA, PON/NA-V2O5 and PON/NA-Fe2O3, and their flame retardance was evaluated by measuring the limiting oxygen index (LOI) values and UL-94 vertical burning ratings. The results showed that, compared with the PA6/PON/NA system, the combination of two char formers (NA-V2O5, NA-Fe2O3) with PON could obviously improve the char formation and flame retardance of PA6. The flame retardance and cone calorimetric analyses showed the stronger synergism as well as the better flame retardant performance of PON/NA-Fe2O3 flame retardant system. The effects of different char formers on the flame retardance and thermal stability of this system were also discussed.
The synergistic effect of phosphorus oxynitride (PON) with a novolac-based char former modified by salification (NA-metal salt) on the flame retardance of polyamide 6 (PA6) was investigated. For this purpose, various flame-retardant PA6 systems were melt-compounded with PON, PON/NA, PON/NA-V2O5 and PON/NA-Fe2O3, and their flame retardance was evaluated by measuring the limiting oxygen index (LOI) values and UL-94 vertical burning ratings. The results showed that, compared with the PA6/PON/NA system, the combination of two char formers (NA-V2O5, NA-Fe2O3) with PON could obviously improve the char formation and flame retardance of PA6. The flame retardance and cone calorimetric analyses showed the stronger synergism as well as the better flame retardant performance of PON/NA-Fe2O3 flame retardant system. The effects of different char formers on the flame retardance and thermal stability of this system were also discussed.
2012, 30(1): 82-92
doi: 10.1007/s10118-012-1105-7
Abstract:
New types of polyamides containing pendent triaryl pyridine groups were successfully synthesized by direct polycondensation of a symmetry diamine, (4-(4-(2,6-diphenylpyridin-4yl)phenoxy)phenyl)-3,5-diaminobezamide (DPDAB), and various aromatic and aliphatic dicarboxylic diacids in NMP using triphenyl phosphate (TPP) and pyridine as catalyst. The diamine and all the prepared polyamides were fully characterized by using FT-IR, 1H-NMR, UV-Vis spectroscopy, fluorimetry and elemental analysis. The inherent viscosity of polyamides ranged from 0.45 dL/g to 0.68 dL/g. All the polymers exhibited solubility in common polar aprotic solvents such as NMP, DMAc, DMF, DMSO, pyridine, HMPA, and even in less polar solvents such as THF and m-cresol at room temperature. Thermal properties of polyamides were evaluated by means of DSC, DMTA and TGA. These polymers showed glass transition temperatures (Tg) in the range of 138-210C. Their initial decomposition temperature (Ti) varied from 265C to 310C under N2. The dilute solution (0.2 g/dL) of polyamides in DMF exhibited fluorescence emission with max in the range of 470-550 nm.
New types of polyamides containing pendent triaryl pyridine groups were successfully synthesized by direct polycondensation of a symmetry diamine, (4-(4-(2,6-diphenylpyridin-4yl)phenoxy)phenyl)-3,5-diaminobezamide (DPDAB), and various aromatic and aliphatic dicarboxylic diacids in NMP using triphenyl phosphate (TPP) and pyridine as catalyst. The diamine and all the prepared polyamides were fully characterized by using FT-IR, 1H-NMR, UV-Vis spectroscopy, fluorimetry and elemental analysis. The inherent viscosity of polyamides ranged from 0.45 dL/g to 0.68 dL/g. All the polymers exhibited solubility in common polar aprotic solvents such as NMP, DMAc, DMF, DMSO, pyridine, HMPA, and even in less polar solvents such as THF and m-cresol at room temperature. Thermal properties of polyamides were evaluated by means of DSC, DMTA and TGA. These polymers showed glass transition temperatures (Tg) in the range of 138-210C. Their initial decomposition temperature (Ti) varied from 265C to 310C under N2. The dilute solution (0.2 g/dL) of polyamides in DMF exhibited fluorescence emission with max in the range of 470-550 nm.
2012, 30(1): 93-100
doi: 10.1007/s10118-012-1093-7
Abstract:
Electrical conductivity and optical properties of polypyrrole-chitosan (PPy-CHI) conducting polymer composites have been investigated to determine the optical transition characteristics and energy band gap of composite films. The two electrode method and I-V characteristic technique were used to measure the conductivity of the PPy-CHI thin films, and the optical band gap was obtained from their ultraviolet absorption edges. Depending upon experimental parameter, the optical band gap (Eg) was found within 1.302.32 eV as estimated from optical absorption data. The band gap of the composite films decreased as the CHI content increased. The room temperature electrical conductivity of PPy-CHI thin films was found in the range of 5.84 10-7-15.25 10-7 Scm-1 depending on the chitosan content. The thermogravimetry analysis (TGA) showed that the CHI can improve the thermal stability of PPy-CHI composite films.
Electrical conductivity and optical properties of polypyrrole-chitosan (PPy-CHI) conducting polymer composites have been investigated to determine the optical transition characteristics and energy band gap of composite films. The two electrode method and I-V characteristic technique were used to measure the conductivity of the PPy-CHI thin films, and the optical band gap was obtained from their ultraviolet absorption edges. Depending upon experimental parameter, the optical band gap (Eg) was found within 1.302.32 eV as estimated from optical absorption data. The band gap of the composite films decreased as the CHI content increased. The room temperature electrical conductivity of PPy-CHI thin films was found in the range of 5.84 10-7-15.25 10-7 Scm-1 depending on the chitosan content. The thermogravimetry analysis (TGA) showed that the CHI can improve the thermal stability of PPy-CHI composite films.
2012, 30(1): 101-111
doi: 10.1007/s10118-012-1095-5
Abstract:
A novel natural-synthetic hybrid block copolymer was synthesized by Aeromonas hydrophila 4AK4 in poly(ethylene glycol) (PEG, Mn = 200) modified fermentation. This hybrid biomaterial consists of the natural hydrophobic polymer poly(3-hydroxybutyrat-co-3-hydroxyhexanoate) (PHBHHx) end-capped with hydrophilic PEG, which has the increased flexibility as well as the improved thermal stability. Addition of diethylene glycol (DEG) and ethylene glycol could not result in the accumulation of hybrid block copolymer. DEG and ethylene glycol, together with PEG-200, could cause a reduction of molar mass of PHBHHx, resulting in a series of low molecular weight polymer and the reduction of the polymer yield as well as the cellular productivity. In vitro degradation of PHBHHx and PHBHHx-PEG with different molecular weight showed that the decrease of molecular weight accelerated the degradation of copolymers, but PEG modification has little effect on its degradation rate. The results in this study provided a convenient and direct method to produce a series of PHBHHx and PHBHHx-PEG materials with adjustable molecular weight and broad molecular weight distribution which will be very useful for the biomedical applications.
A novel natural-synthetic hybrid block copolymer was synthesized by Aeromonas hydrophila 4AK4 in poly(ethylene glycol) (PEG, Mn = 200) modified fermentation. This hybrid biomaterial consists of the natural hydrophobic polymer poly(3-hydroxybutyrat-co-3-hydroxyhexanoate) (PHBHHx) end-capped with hydrophilic PEG, which has the increased flexibility as well as the improved thermal stability. Addition of diethylene glycol (DEG) and ethylene glycol could not result in the accumulation of hybrid block copolymer. DEG and ethylene glycol, together with PEG-200, could cause a reduction of molar mass of PHBHHx, resulting in a series of low molecular weight polymer and the reduction of the polymer yield as well as the cellular productivity. In vitro degradation of PHBHHx and PHBHHx-PEG with different molecular weight showed that the decrease of molecular weight accelerated the degradation of copolymers, but PEG modification has little effect on its degradation rate. The results in this study provided a convenient and direct method to produce a series of PHBHHx and PHBHHx-PEG materials with adjustable molecular weight and broad molecular weight distribution which will be very useful for the biomedical applications.
2012, 30(1): 112-121
doi: 10.1007/s10118-012-1092-8
Abstract:
A novel aromatic diamine, 2-(5-(3,5-diaminophenyl)-1,3,4-oxadiazole-2-yl)pyridine (POBD), containing a pyridine ring and a 1,3,4-oxadiazole moiety, was synthesized. It was used in a polycondensation with various aromatic and aliphatic diacid chlorides to generate a series of new aromatic polyamides with pendant 1,3,4-oxadiazole groups. The prepared polyamides were characterized by IR, elemental analysis and through the synthesis of model compounds. Thermo-physical properties of the synthesized polyamides have been studied by DSC, TGA and inherent viscosity measurements. Relatively high inherent viscosity values (0.76-1.62 dL/g, in 0.125% H2SO4 at 25C) were observed for these compounds. Number average molecular weight (Mn) of the polymers was measured by vapor phase osmometry (VPO). The introduction of bulky side chains in the structure of aromatic polyamides led to increased solubility of these polymers in common polar and aprotic solvents, such as DMF, DMSO, NMP and DMAc, which allowed thin films to be cast from polymer solutions. The highest molecular weight (Mn = 51190) was observed for polymer (IX), which was prepared from pyridine-2,6-dichlorocarbonyl.
A novel aromatic diamine, 2-(5-(3,5-diaminophenyl)-1,3,4-oxadiazole-2-yl)pyridine (POBD), containing a pyridine ring and a 1,3,4-oxadiazole moiety, was synthesized. It was used in a polycondensation with various aromatic and aliphatic diacid chlorides to generate a series of new aromatic polyamides with pendant 1,3,4-oxadiazole groups. The prepared polyamides were characterized by IR, elemental analysis and through the synthesis of model compounds. Thermo-physical properties of the synthesized polyamides have been studied by DSC, TGA and inherent viscosity measurements. Relatively high inherent viscosity values (0.76-1.62 dL/g, in 0.125% H2SO4 at 25C) were observed for these compounds. Number average molecular weight (Mn) of the polymers was measured by vapor phase osmometry (VPO). The introduction of bulky side chains in the structure of aromatic polyamides led to increased solubility of these polymers in common polar and aprotic solvents, such as DMF, DMSO, NMP and DMAc, which allowed thin films to be cast from polymer solutions. The highest molecular weight (Mn = 51190) was observed for polymer (IX), which was prepared from pyridine-2,6-dichlorocarbonyl.
2012, 30(1): 122-129
doi: 10.1007/s10118-012-1097-3
Abstract:
The compositional heterogeneity of two impact polypropylene copolymers (IPCs) was studied by a combinatory investigation of temperature rising elution fractionation (TREF) and solvent fractionation. The chain structures and composition of fractions obtained from solvent fractionation were examined in detail. The TREF results shows that there are much more E-P segmented copolymer and more uniform distribution of ethylene sequence in IPC-1, which is responsible for its better comprehensive mechanical performance. The fractions from hexane and heptane are ethylene-propylene rubber phase and E-P block copolymers respectively. The result of solvent fractionation method also shows that custom hexane or heptane extractions can not extract the E-P copolymer completely.
The compositional heterogeneity of two impact polypropylene copolymers (IPCs) was studied by a combinatory investigation of temperature rising elution fractionation (TREF) and solvent fractionation. The chain structures and composition of fractions obtained from solvent fractionation were examined in detail. The TREF results shows that there are much more E-P segmented copolymer and more uniform distribution of ethylene sequence in IPC-1, which is responsible for its better comprehensive mechanical performance. The fractions from hexane and heptane are ethylene-propylene rubber phase and E-P block copolymers respectively. The result of solvent fractionation method also shows that custom hexane or heptane extractions can not extract the E-P copolymer completely.
2012, 30(1): 130-137
doi: 10.1007/s10118-012-1096-4
Abstract:
Electrospun material with bio-inspired ordered architectures and patterns is very interesting, yet remains a challenge. We report here that nanofibrous mats with bird's nest patterned structures can be directly electrospun from chlorinated polypropylene solutions doped with an ionic liquid. The solution viscosity and the ionic liquid content are two dominant factors to influence the topological morphology of the nanofibrous mats. The patterned structures can be further modulated by the collection time of electrospinning, the humidity of environment and the design of collector. We suggest the electrostatic repulsion between the residual charges of the mat surface and the upcoming nanofibers plays a key role in the formation of the bird's nest patterns.
Electrospun material with bio-inspired ordered architectures and patterns is very interesting, yet remains a challenge. We report here that nanofibrous mats with bird's nest patterned structures can be directly electrospun from chlorinated polypropylene solutions doped with an ionic liquid. The solution viscosity and the ionic liquid content are two dominant factors to influence the topological morphology of the nanofibrous mats. The patterned structures can be further modulated by the collection time of electrospinning, the humidity of environment and the design of collector. We suggest the electrostatic repulsion between the residual charges of the mat surface and the upcoming nanofibers plays a key role in the formation of the bird's nest patterns.
2012, 30(1): 138-142
doi: 10.1007/s10118-012-1103-9
Abstract:
Electrically conductive thermoplastic vulcanizates (TPVs) filled by multi-walled carbon nanotubes (MWCNTs) are prepared by a simple one-step melt mixing process, based on linear low density polyethylene (LLDPE) and ultrafine full-vulcanized rubber particles (UFRP). An ideal morphology with controlled localization of MWCNTs in continuous LLDPE matrix and appropriate size of finely-dispersed UFRP can be achieved at the same time. The controlled localization of MWCNTs in the continuous phase facilitates the formation of conductive pathway, and thus the volume resistivity of the as-prepared LLDPE/UFRP/MWCNTs thermoplastic vulcanizates is significantly decreased. The results show that both the blend ratio of LLDPE/UFRP and the loading of MWCNTs have remarkable effect on the volume resistivity. Significantly, the electrically conductive TPVs exhibit good mechanical properties duo to the fine dispersion of UFRP in LLDPE. The added MWCNTs are capable of imparting reinforcement effects to thermoplastic vulcanizates with just a slight loss of stretchability and elasticity.
Electrically conductive thermoplastic vulcanizates (TPVs) filled by multi-walled carbon nanotubes (MWCNTs) are prepared by a simple one-step melt mixing process, based on linear low density polyethylene (LLDPE) and ultrafine full-vulcanized rubber particles (UFRP). An ideal morphology with controlled localization of MWCNTs in continuous LLDPE matrix and appropriate size of finely-dispersed UFRP can be achieved at the same time. The controlled localization of MWCNTs in the continuous phase facilitates the formation of conductive pathway, and thus the volume resistivity of the as-prepared LLDPE/UFRP/MWCNTs thermoplastic vulcanizates is significantly decreased. The results show that both the blend ratio of LLDPE/UFRP and the loading of MWCNTs have remarkable effect on the volume resistivity. Significantly, the electrically conductive TPVs exhibit good mechanical properties duo to the fine dispersion of UFRP in LLDPE. The added MWCNTs are capable of imparting reinforcement effects to thermoplastic vulcanizates with just a slight loss of stretchability and elasticity.
