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2014 Volume 32 Issue 8
2014, 32(8): 969-974
doi: 10.1007/s10118-014-1489-7
Abstract:
In this study, a novel approach by combining base-catalyzed epoxide ring-opening and thiol-ene click chemistry is presented for the side-chain modification of dextran. The vinyl-modified dextran is prepared by a basic epoxide ring opening reaction of allyl glycidyl ether in 0.1 mol/L NaOH, followed by thiol-addition click reaction of three model sulfhydryl compounds using water-soluble Irgacure 2959 as the photoinitiator, leading to side-chain functionalized dextran modified with carboxyl, bidentate dicarboxyl or amino groups. This is the first example of combining epoxide ring-opening and thiol-ene click chemistry for side-chain modification of dextran in aqueous media. Importantly, it may also be extended as a convenient and efficient method for the side-chain modification of other polysaccharides.
In this study, a novel approach by combining base-catalyzed epoxide ring-opening and thiol-ene click chemistry is presented for the side-chain modification of dextran. The vinyl-modified dextran is prepared by a basic epoxide ring opening reaction of allyl glycidyl ether in 0.1 mol/L NaOH, followed by thiol-addition click reaction of three model sulfhydryl compounds using water-soluble Irgacure 2959 as the photoinitiator, leading to side-chain functionalized dextran modified with carboxyl, bidentate dicarboxyl or amino groups. This is the first example of combining epoxide ring-opening and thiol-ene click chemistry for side-chain modification of dextran in aqueous media. Importantly, it may also be extended as a convenient and efficient method for the side-chain modification of other polysaccharides.
2014, 32(8): 975-985
doi: 10.1007/s10118-014-1488-8
Abstract:
Simultaneous functionalization and reduction of graphene oxide (GO) is realized by refluxing of GO suspension with polyetheramine (D2000) followed by thermal treatment at 120℃. Compared to GO, the D2000-treated GO (GO-D2000) becomes hydrophobic, thermally stable and highly conductive with an electrical conductivity of 11 S/m, which is almost 8 orders of magnitude higher than that of GO. Due to the high conductivity and improved dispersion of GO-D2000, its epoxy nanocomposites exhibit a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.71 vol%. With 3.6 wt% GO-D2000, the glass transition temperature of the epoxy nanocomposite is 27 K higher than that of neat epoxy.
Simultaneous functionalization and reduction of graphene oxide (GO) is realized by refluxing of GO suspension with polyetheramine (D2000) followed by thermal treatment at 120℃. Compared to GO, the D2000-treated GO (GO-D2000) becomes hydrophobic, thermally stable and highly conductive with an electrical conductivity of 11 S/m, which is almost 8 orders of magnitude higher than that of GO. Due to the high conductivity and improved dispersion of GO-D2000, its epoxy nanocomposites exhibit a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.71 vol%. With 3.6 wt% GO-D2000, the glass transition temperature of the epoxy nanocomposite is 27 K higher than that of neat epoxy.
2014, 32(8): 986-995
doi: 10.1007/s10118-014-1469-y
Abstract:
In this paper, the effects of temperature from 60℃ to 80℃ and the molar ratios in monomer feed on the copolymerization of a-methylstyrene (AMS) and styrene (St) were studied. The resulting copolymers, designated as PAS, were characterized by FTIR, GPC, NMR and TGA. When the reaction temperature was below 75℃, the molecular weights increased almost linearly as the evolution of the copolymerization. The phenomenon revealed that AMS could mediate the conventional free radical polymerization having some features of a controlled system. As the AMS/St=50/50 (molar) in feed, the overall fraction of the AMS unit incorporated into the copolymer was as high as 42 mol%, the monomer conversion could be more than 90 wt% and the molecular weights could reach as high as 4400. However, since the styrene is more reactive than AMS, the AMS fraction in copolymer increased with the overall monomer conversion. The 13C-NMR revealed the products were random copolymers which had triads, such as -AMS-AMS-AMS-, -St-AMS-AMS- (-AMS-AMS-St-) and -St-AMS-St-. TGA curves demonstrated that the degradation temperature of the resulting copolymers went down from about 356.9℃ (0 mol% AMS) to 250.2℃ (42 mol% AMS). This behavior demonstrated that there exist weak bonds in the AMS-containing sequences which could be used as potential free radical generators.
In this paper, the effects of temperature from 60℃ to 80℃ and the molar ratios in monomer feed on the copolymerization of a-methylstyrene (AMS) and styrene (St) were studied. The resulting copolymers, designated as PAS, were characterized by FTIR, GPC, NMR and TGA. When the reaction temperature was below 75℃, the molecular weights increased almost linearly as the evolution of the copolymerization. The phenomenon revealed that AMS could mediate the conventional free radical polymerization having some features of a controlled system. As the AMS/St=50/50 (molar) in feed, the overall fraction of the AMS unit incorporated into the copolymer was as high as 42 mol%, the monomer conversion could be more than 90 wt% and the molecular weights could reach as high as 4400. However, since the styrene is more reactive than AMS, the AMS fraction in copolymer increased with the overall monomer conversion. The 13C-NMR revealed the products were random copolymers which had triads, such as -AMS-AMS-AMS-, -St-AMS-AMS- (-AMS-AMS-St-) and -St-AMS-St-. TGA curves demonstrated that the degradation temperature of the resulting copolymers went down from about 356.9℃ (0 mol% AMS) to 250.2℃ (42 mol% AMS). This behavior demonstrated that there exist weak bonds in the AMS-containing sequences which could be used as potential free radical generators.
2014, 32(8): 996-1002
doi: 10.1007/s10118-014-1459-0
Abstract:
Poly(bis(phenoxy)phosphazene) (SPBPP)/phosphotungstic acid (PWA)/silica composite membranes for fuel cells were prepared. The composite membranes were characterized by using FTIR, TGA and SEM techniquies. Incorporation of PWA particles and silica particles into the SPBPP polymer matrix and a specific interaction between them were confirmed by FTIR spectra. TGA results showed that the composite membranes had high thermal stability. Homogeneous distribution of PWA and silica particles within the SPBPP matrix was verified by SEM micrographs. The doped membranes showed increased water uptake and proton conductivity.
Poly(bis(phenoxy)phosphazene) (SPBPP)/phosphotungstic acid (PWA)/silica composite membranes for fuel cells were prepared. The composite membranes were characterized by using FTIR, TGA and SEM techniquies. Incorporation of PWA particles and silica particles into the SPBPP polymer matrix and a specific interaction between them were confirmed by FTIR spectra. TGA results showed that the composite membranes had high thermal stability. Homogeneous distribution of PWA and silica particles within the SPBPP matrix was verified by SEM micrographs. The doped membranes showed increased water uptake and proton conductivity.
2014, 32(8): 1003-1009
doi: 10.1007/s10118-014-1477-y
Abstract:
A facile one-pot synthesis of a-cyclodextrin-based polyrotaxane (PR) in aqueous solution is reported, where the peptide glutathione was used as the end-capping agent and the thiol-ene Michael addition was used as the end-capping reaction. Both polyrotaxanes with low threading ratio and high threading ratio were successfully obtained. In contrast to the conventionally used multiple-step synthesis methods and hydrophobic end cappers, this one-pot aqueous synthesis as well as the biocompatibility of the end-capping agent could result in a much more biocompatible PR to be used as biomaterials.
A facile one-pot synthesis of a-cyclodextrin-based polyrotaxane (PR) in aqueous solution is reported, where the peptide glutathione was used as the end-capping agent and the thiol-ene Michael addition was used as the end-capping reaction. Both polyrotaxanes with low threading ratio and high threading ratio were successfully obtained. In contrast to the conventionally used multiple-step synthesis methods and hydrophobic end cappers, this one-pot aqueous synthesis as well as the biocompatibility of the end-capping agent could result in a much more biocompatible PR to be used as biomaterials.
2014, 32(8): 1010-1018
doi: 10.1007/s10118-014-1481-2
Abstract:
Atom transfer radical polymerization of styrene (St) and methyl methacrylate (MMA) in bulk and in different solvents using activators generated by electron transfer (AGET ATRP) were investigated in the presence of a limited amount of air using FeCl36H2O as the catalyst, ascorbic acid sodium salt (AsAc-Na) as the reducing agent, and a cheap and commercially available tetrabutylammonium bromide (TBABr) as the ligand. It was found that polymerization in THF resulted in shorter induction period than that in bulk and in toluene for AGET ATRP of St, while referring to AGET ATRP of MMA, polymerization in THF showed three advantages compared with that in bulk and toluene: 1) shortening the induction period, 2) enhancing the polymerization rate and 3) having better controllability. The living features of the obtained polymers were verified by chain end analysis and chain-extension experiments.
Atom transfer radical polymerization of styrene (St) and methyl methacrylate (MMA) in bulk and in different solvents using activators generated by electron transfer (AGET ATRP) were investigated in the presence of a limited amount of air using FeCl36H2O as the catalyst, ascorbic acid sodium salt (AsAc-Na) as the reducing agent, and a cheap and commercially available tetrabutylammonium bromide (TBABr) as the ligand. It was found that polymerization in THF resulted in shorter induction period than that in bulk and in toluene for AGET ATRP of St, while referring to AGET ATRP of MMA, polymerization in THF showed three advantages compared with that in bulk and toluene: 1) shortening the induction period, 2) enhancing the polymerization rate and 3) having better controllability. The living features of the obtained polymers were verified by chain end analysis and chain-extension experiments.
2014, 32(8): 1019-1031
doi: 10.1007/s10118-014-1484-z
Abstract:
A novel graphene oxide doped poly(hydroxymethylated-3,4-ethylenedioxythiophene) (PEDOT-MeOH/GO) composite film was synthesized and utilized as an efficient electrode material for simultaneous detection of rutin and ascorbic acid (AA). PEDOT-MeOH/GO films were synthesized on glassy carbon electrode (GCE) by a facile one-step electrochemical approach and were characterized by scanning electron microscopy, UV-Vis spectroscopy, FTIR spectra and electrochemical methods. Then the PEDOT-MeOH/GO/GCE was applied successfully in the simultaneous detection of rutin and AA. The results showed that the oxidation peak currents of rutin and AA obtained at the PEDOT-MeOH/GO/GCE were much higher than those at the traditional conducting polymer PEDOT/GO/GCE, PEDOT-MeOH/GCE, PEDOT/GCE and bare GCE. Under optimized conditions, the linear ranges for rutin and AA are 20 nmol/L-10 mol/L and 8 mol/L-1 mmol/L, respectively. The detection limit is 6 nmol/L for rutin and 2 mol/L for AA (S/N=3), which are lower than those of the reported electrochemical sensors.
A novel graphene oxide doped poly(hydroxymethylated-3,4-ethylenedioxythiophene) (PEDOT-MeOH/GO) composite film was synthesized and utilized as an efficient electrode material for simultaneous detection of rutin and ascorbic acid (AA). PEDOT-MeOH/GO films were synthesized on glassy carbon electrode (GCE) by a facile one-step electrochemical approach and were characterized by scanning electron microscopy, UV-Vis spectroscopy, FTIR spectra and electrochemical methods. Then the PEDOT-MeOH/GO/GCE was applied successfully in the simultaneous detection of rutin and AA. The results showed that the oxidation peak currents of rutin and AA obtained at the PEDOT-MeOH/GO/GCE were much higher than those at the traditional conducting polymer PEDOT/GO/GCE, PEDOT-MeOH/GCE, PEDOT/GCE and bare GCE. Under optimized conditions, the linear ranges for rutin and AA are 20 nmol/L-10 mol/L and 8 mol/L-1 mmol/L, respectively. The detection limit is 6 nmol/L for rutin and 2 mol/L for AA (S/N=3), which are lower than those of the reported electrochemical sensors.
2014, 32(8): 1032-1039
doi: 10.1007/s10118-014-1485-y
Abstract:
Five fluorine-containing vinyl ether monomers were prepared by the reaction between 2-vinyloxy ethanol, a fluorinated alcohol and hexafluorobenzene in the presence of sodium hydride in dimethylformamide. Two representative properties of these monomers, UV-curing behavior initiated by a cationic photo-initiator PAG 201 and surface free energy of coating films, were investigated. Photo-polymerization proceeded both rapidly and completely with a high double-bond conversion ( 90%) and a fast curing rate (maximum curing time 21 s) for three monomers. The surface energies of the monomers and the resulting polymer films were then investigated. The minimum surface free energy of the UV-cured homopolymer films reaches 7.1 mJ/m2. X-ray photoelectron spectroscopy data show that the low surface tension is influenced by fluorine content in the soft segments and fluorinated chains' migration to the surface. The five monomers exhibit low viscosity, low surface energy, good thermal stability and good photo-polymerization properties, which make them great candidates for UV coating and photoresist applications.
Five fluorine-containing vinyl ether monomers were prepared by the reaction between 2-vinyloxy ethanol, a fluorinated alcohol and hexafluorobenzene in the presence of sodium hydride in dimethylformamide. Two representative properties of these monomers, UV-curing behavior initiated by a cationic photo-initiator PAG 201 and surface free energy of coating films, were investigated. Photo-polymerization proceeded both rapidly and completely with a high double-bond conversion ( 90%) and a fast curing rate (maximum curing time 21 s) for three monomers. The surface energies of the monomers and the resulting polymer films were then investigated. The minimum surface free energy of the UV-cured homopolymer films reaches 7.1 mJ/m2. X-ray photoelectron spectroscopy data show that the low surface tension is influenced by fluorine content in the soft segments and fluorinated chains' migration to the surface. The five monomers exhibit low viscosity, low surface energy, good thermal stability and good photo-polymerization properties, which make them great candidates for UV coating and photoresist applications.
2014, 32(8): 1040-1051
doi: 10.1007/s10118-014-1483-0
Abstract:
Electroactive conducting copolymers of aniline (ANI) and diphenylamine (DPA) are prepared on indium tin oxide (ITO) surface from 1 mol/L H2SO4 aqueous solution with different feed ratios of ANI to DPA by using a potentiostatic method. FTIR spectra and SEM measurements are used to confirm the formation of copolymers. Due to the combination of the N,N-diphenyl benzidine and aniline units in the molecular chain, the copolymer films exhibit improved electrochemical and electrochromic properties, compared to PANI and PDPA. The copolymer [marked as P(ANI9-co-DPA1)] film prepared at a ratio of 9:1 (ANI/DPA) exhibits novel transmittance modulation both in visible and near-infrared (NIR) region between -0.8 V and 0.8 V (52% and 67% respectively) and fast response time (3.6 s for coloration and 2.3 s for bleaching at 600 nm). An electrochromic device (ECD) based on P(ANI9-co-DPA1) and PEDOT:PSS is also fabricated and shows a multicolor electrochromic performance, with a good optical contrast (29% in visible region and 40% in NIR region), acceptable response time (8.3 s for coloration and 7.5 s for bleaching at 600 nm) and long-term stability. Clear color changes from transparent (-0.8 V), bright green (0 V), seagreen (0.4 V) to dark slate gray (0.8 V) are demonstrated.
Electroactive conducting copolymers of aniline (ANI) and diphenylamine (DPA) are prepared on indium tin oxide (ITO) surface from 1 mol/L H2SO4 aqueous solution with different feed ratios of ANI to DPA by using a potentiostatic method. FTIR spectra and SEM measurements are used to confirm the formation of copolymers. Due to the combination of the N,N-diphenyl benzidine and aniline units in the molecular chain, the copolymer films exhibit improved electrochemical and electrochromic properties, compared to PANI and PDPA. The copolymer [marked as P(ANI9-co-DPA1)] film prepared at a ratio of 9:1 (ANI/DPA) exhibits novel transmittance modulation both in visible and near-infrared (NIR) region between -0.8 V and 0.8 V (52% and 67% respectively) and fast response time (3.6 s for coloration and 2.3 s for bleaching at 600 nm). An electrochromic device (ECD) based on P(ANI9-co-DPA1) and PEDOT:PSS is also fabricated and shows a multicolor electrochromic performance, with a good optical contrast (29% in visible region and 40% in NIR region), acceptable response time (8.3 s for coloration and 7.5 s for bleaching at 600 nm) and long-term stability. Clear color changes from transparent (-0.8 V), bright green (0 V), seagreen (0.4 V) to dark slate gray (0.8 V) are demonstrated.
2014, 32(8): 1052-1059
doi: 10.1007/s10118-014-1480-3
Abstract:
A green approach to the synthesis and morphological control of high performance polyimides and their nanohybrid shish-kebabs in glycerol through reaction-induced crystallization of nylon-salt-type monomers was reported. Crystalline polyimide nanoplates can be observed by direct polycondensation of pyromellitic acid with various kinds of aliphatic or aromatic diamines. With the existence of carbon nanotubes, the polyimides can be successfully decorated on the surface of CNTs through a reaction-induced hetero-epitaxial crystallization process, and resulted in novel polyimide/CNT nanohybrid shish-kebabs (NHSKs) structures. The morphologies of the NHSKs can be fine-tuned through changing the concentration of monomers or the reaction temperature, especially through the introduction of dynamic imine chemistry, the formation process of NHSKs can be attributed to a soft epitaxy mechanism. Thus a green approach for the synthesis of high performance polyimides and their CNT based nanohybrid structures was explored, which should be of great value for their applications in high performance reinforced nanocomposites.
A green approach to the synthesis and morphological control of high performance polyimides and their nanohybrid shish-kebabs in glycerol through reaction-induced crystallization of nylon-salt-type monomers was reported. Crystalline polyimide nanoplates can be observed by direct polycondensation of pyromellitic acid with various kinds of aliphatic or aromatic diamines. With the existence of carbon nanotubes, the polyimides can be successfully decorated on the surface of CNTs through a reaction-induced hetero-epitaxial crystallization process, and resulted in novel polyimide/CNT nanohybrid shish-kebabs (NHSKs) structures. The morphologies of the NHSKs can be fine-tuned through changing the concentration of monomers or the reaction temperature, especially through the introduction of dynamic imine chemistry, the formation process of NHSKs can be attributed to a soft epitaxy mechanism. Thus a green approach for the synthesis of high performance polyimides and their CNT based nanohybrid structures was explored, which should be of great value for their applications in high performance reinforced nanocomposites.
2014, 32(8): 1060-1067
doi: 10.1007/s10118-014-1490-1
Abstract:
Doped polyaniline films were prepared with electrochemistry method. A small conjugated molecule, anthracenecarboxylic acid (2-ACA), was used as the dopant, considering its electrical activeness due to the conjugated -* structure. Film morphology of doped and undoped polyaniline samples was investigated. The corresponding changes in optical and electrical properties after ACA doping were discussed. By measuring and calculating their energy level distribution, a promising application of polyaniline thin films as buffer layer in optic-electric devices is expectable.
Doped polyaniline films were prepared with electrochemistry method. A small conjugated molecule, anthracenecarboxylic acid (2-ACA), was used as the dopant, considering its electrical activeness due to the conjugated -* structure. Film morphology of doped and undoped polyaniline samples was investigated. The corresponding changes in optical and electrical properties after ACA doping were discussed. By measuring and calculating their energy level distribution, a promising application of polyaniline thin films as buffer layer in optic-electric devices is expectable.
2014, 32(8): 1068-1076
doi: 10.1007/s10118-014-1467-0
Abstract:
A series of trans-1,4-butadiene/isoprene copolymers were prepared using the catalyst system TiCl4/MgCl2-Al(i-Bu)3 with bulk precipitation technology at different temperatures. Monomers reactivity ratios were calculated based on the Kelen-Tds (K-T) method and the Mao-Huglin (M-H) method. The influence of temperature on copolymer composition and polymerization rate was discussed in detail. The increase of reaction temperature brought the decrease of butadiene reactivity ratio rBd and supplied an effective adjustment on copolymers￠ composition distribution.
A series of trans-1,4-butadiene/isoprene copolymers were prepared using the catalyst system TiCl4/MgCl2-Al(i-Bu)3 with bulk precipitation technology at different temperatures. Monomers reactivity ratios were calculated based on the Kelen-Tds (K-T) method and the Mao-Huglin (M-H) method. The influence of temperature on copolymer composition and polymerization rate was discussed in detail. The increase of reaction temperature brought the decrease of butadiene reactivity ratio rBd and supplied an effective adjustment on copolymers￠ composition distribution.
2014, 32(8): 1077-1085
doi: 10.1007/s10118-014-1486-x
Abstract:
A novel TU derivative, N-phenyl-N-(g-triethoxysilane)-propyl thiourea (STU), is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time of NR compounds with STU is the shortest, indicating a more nucleophilic reaction occurs. The Py-GC/MS results present that the phenyl iso-thiocyanate fragment still remains in the NR/STU compounds with or without extracting treatment, but no silane segment can be found in the vulcanizate with extracting treatment. Vibrations of C=S, NH and aromatic ring in FTIR experiments and a new methyne carbon peak, as well as the peaks of phenyl group of STU, in the solid state 13C-NMR experiments are found in the NR/STU vulcanizate with extracting treatment. Moreover, the crosslinking density of vulcanizates with STU evolves to lower level, indicating the sulfur atom of STU does not contribute to the sulfur crosslinking. Therefore, a new vulcanization kinetic mechanism of STU is propounded that the thiourea groups can graft to the rubber main chains as pendant groups by chemical bonds during the vulcanization process, which is in accordance with the experimental observations quite well.
A novel TU derivative, N-phenyl-N-(g-triethoxysilane)-propyl thiourea (STU), is prepared and its binary accelerator system is investigated in detail. Compared to the control references, the optimum curing time of NR compounds with STU is the shortest, indicating a more nucleophilic reaction occurs. The Py-GC/MS results present that the phenyl iso-thiocyanate fragment still remains in the NR/STU compounds with or without extracting treatment, but no silane segment can be found in the vulcanizate with extracting treatment. Vibrations of C=S, NH and aromatic ring in FTIR experiments and a new methyne carbon peak, as well as the peaks of phenyl group of STU, in the solid state 13C-NMR experiments are found in the NR/STU vulcanizate with extracting treatment. Moreover, the crosslinking density of vulcanizates with STU evolves to lower level, indicating the sulfur atom of STU does not contribute to the sulfur crosslinking. Therefore, a new vulcanization kinetic mechanism of STU is propounded that the thiourea groups can graft to the rubber main chains as pendant groups by chemical bonds during the vulcanization process, which is in accordance with the experimental observations quite well.
2014, 32(8): 1086-1098
doi: 10.1007/s10118-014-1479-9
Abstract:
Cyclophosphazene nanotube (PZT) incorporated poly(benzoxazine-co--caprolactam) (P(BZ-co-CPL)) nano-composites were developed for improving flame retardant properties. The effects of PZT on the flammability properties of P(BZ-co-CPL) matrix were evaluated through UL-94 flammability test and limiting oxygen index (LOI). The UL-94 results of P(BZ-co-CPL)/PZT hybrid nanocomposites showed V-1 rating, whereas neat P(BZ-co-CPL) showed burning rating. The LOI values are increased from 25.4 to 31.4 for 1.5 wt% PZT incorporated P(BZ-co-CPL) nanocomposite systems. SEM was used to study the char morphology of P(BZ-co-CPL)/PZT after being exposed to UL-94 flammability test. Data from thermal studies indicate that the PZT incorporated P(BZ-co-CPL) systems possess better Tg and thermal degradation behavior when compared to the neat P(BZ-co-CPL). The values of dielectric constant are decreased with increasing temperature. From the values, it is ascertained that the P(BZ-co-CPL)/PZT systems exhibit stable dielectric behavior with regard to variation in temperature. The TEM images ascertain the uniform dispersion of PZT in the P(BZ-co-CPL) matrix.
Cyclophosphazene nanotube (PZT) incorporated poly(benzoxazine-co--caprolactam) (P(BZ-co-CPL)) nano-composites were developed for improving flame retardant properties. The effects of PZT on the flammability properties of P(BZ-co-CPL) matrix were evaluated through UL-94 flammability test and limiting oxygen index (LOI). The UL-94 results of P(BZ-co-CPL)/PZT hybrid nanocomposites showed V-1 rating, whereas neat P(BZ-co-CPL) showed burning rating. The LOI values are increased from 25.4 to 31.4 for 1.5 wt% PZT incorporated P(BZ-co-CPL) nanocomposite systems. SEM was used to study the char morphology of P(BZ-co-CPL)/PZT after being exposed to UL-94 flammability test. Data from thermal studies indicate that the PZT incorporated P(BZ-co-CPL) systems possess better Tg and thermal degradation behavior when compared to the neat P(BZ-co-CPL). The values of dielectric constant are decreased with increasing temperature. From the values, it is ascertained that the P(BZ-co-CPL)/PZT systems exhibit stable dielectric behavior with regard to variation in temperature. The TEM images ascertain the uniform dispersion of PZT in the P(BZ-co-CPL) matrix.
2014, 32(8): 1099-1110
doi: 10.1007/s10118-014-1487-9
Abstract:
Polylactide (PLA) was successfully toughened by blending with bio-based poly(ester)urethane (TPU) elastomers which contained bio-based polyester soft segments synthesized from biomass diols and diacids. The miscibility, mechanical properties, phase morphology and toughening mechanism of the blend were investigated. Both DSC and DMTA results manifested that the addition of TPU elastomer not only accelerated the crystallization rate, but also increased the final degree of crystallinity, which proved that TPU has limited miscibility with PLA and has functioned as a plasticizer. All the blend samples showed distinct phase separation phenomenon with sea-island structure under SEM observation and the rubber particle size in the PLA matrix increased with the increased contents of TPU. The mechanical property variation of PLA/TPU blends could be quantitatively explained by Wu's model. With the variation of TPU, a brittle-ductile transition has been observed for the TPU/PLA blends. When these blends were under tensile stress conditions, the TPU particles could be debonded from the PLA matrix and the blends showed a high ability to induce large area plastic deformation before break, which was important for the dissipation of the breaking energy. Such mechanism was demonstrated by tensile tests and scanning electron microcopy (SEM) observations.
Polylactide (PLA) was successfully toughened by blending with bio-based poly(ester)urethane (TPU) elastomers which contained bio-based polyester soft segments synthesized from biomass diols and diacids. The miscibility, mechanical properties, phase morphology and toughening mechanism of the blend were investigated. Both DSC and DMTA results manifested that the addition of TPU elastomer not only accelerated the crystallization rate, but also increased the final degree of crystallinity, which proved that TPU has limited miscibility with PLA and has functioned as a plasticizer. All the blend samples showed distinct phase separation phenomenon with sea-island structure under SEM observation and the rubber particle size in the PLA matrix increased with the increased contents of TPU. The mechanical property variation of PLA/TPU blends could be quantitatively explained by Wu's model. With the variation of TPU, a brittle-ductile transition has been observed for the TPU/PLA blends. When these blends were under tensile stress conditions, the TPU particles could be debonded from the PLA matrix and the blends showed a high ability to induce large area plastic deformation before break, which was important for the dissipation of the breaking energy. Such mechanism was demonstrated by tensile tests and scanning electron microcopy (SEM) observations.
2014, 32(8): 1111-1118
doi: 10.1007/s10118-014-1491-0
Abstract:
In this study a cisplatin-loaded, multilayered polylactide (PLA) electrospun nanofibers, with the structure of two layers of drug-loaded mat being sandwiched by three layers of blank mat, were designed for prolonged cisplatin release at surgical margin to prevent local cancer recurrence following surgical resection in a murine model. In vivo drug release and biodistribution study suggested that the multilayered fibrous mat displayed a slower cisplatin release behavior and a more stable drug rentention in the local tissue within 24 h than that of single-layered fibrous mat. By covering the surgical site with the multilayered fibrous mat following resection of subcutaneous liver cancer in mice, retarded tumor recurrence, prolonged survival time and less systemic toxicity were observed compared with other treatment groups.
In this study a cisplatin-loaded, multilayered polylactide (PLA) electrospun nanofibers, with the structure of two layers of drug-loaded mat being sandwiched by three layers of blank mat, were designed for prolonged cisplatin release at surgical margin to prevent local cancer recurrence following surgical resection in a murine model. In vivo drug release and biodistribution study suggested that the multilayered fibrous mat displayed a slower cisplatin release behavior and a more stable drug rentention in the local tissue within 24 h than that of single-layered fibrous mat. By covering the surgical site with the multilayered fibrous mat following resection of subcutaneous liver cancer in mice, retarded tumor recurrence, prolonged survival time and less systemic toxicity were observed compared with other treatment groups.
