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2016 Volume 34 Issue 7
2016, 34(7): 797-804
doi: 10.1007/s10118-016-1797-1
Abstract:
Trans-1,4-polyisoprene (TPI) nanofibers have been fabricated successfully through electrospinning technology. Through the control of electrospinning parameters, highly crystallized TPI fresh fibers composed mainly of b phase were produced. Morphology and diameter of TPI nanofibers can be controlled by adjusting the electrospinning conditions. The in situ observations of FTIR spectra revealed that the crystallinity of the TPI fibers decreased with aging. While for TPI nanofibers aging at 45 ℃ for 24 h, a decrease in crystallinity as well as b to a transformation was observed with aging and these changings happened in the first 50 h during aging. The mechanism for b-TPI formation during electrospinning process and the reduced crystallinity with aging were proposed.
Trans-1,4-polyisoprene (TPI) nanofibers have been fabricated successfully through electrospinning technology. Through the control of electrospinning parameters, highly crystallized TPI fresh fibers composed mainly of b phase were produced. Morphology and diameter of TPI nanofibers can be controlled by adjusting the electrospinning conditions. The in situ observations of FTIR spectra revealed that the crystallinity of the TPI fibers decreased with aging. While for TPI nanofibers aging at 45 ℃ for 24 h, a decrease in crystallinity as well as b to a transformation was observed with aging and these changings happened in the first 50 h during aging. The mechanism for b-TPI formation during electrospinning process and the reduced crystallinity with aging were proposed.
2016, 34(7): 805-819
doi: 10.1007/s10118-016-1808-2
Abstract:
Herein, functionalized graphene oxide (GO) was prepared by the covalent functionalization with amino acids (lysine, glycine, glutamic acid and tyrosine) in this study. Zeta potential results demonstrated that covalent functionalization of GO with amino acids was favourable for their homogeneous dispersion in water and organic solvents. Based on the higher absolute value of zeta potential and the better dipersion stability of GO-lysine, the PVDF/GO-lysine hybrid membranes were then prepared via the phase inversion induced by immersion precipitation technique. SEM images showed a better pore diameter and porosity distribution on the PVDF/GO-lysine membrane surface. The zeta potential absolute value of the PVDF/GO-lysine membrane surface was higher than that of the virgin PVDF membrane. Furthermore, the PVDF/GO-lysine membranes surface exhibited good hydrophilicity. The water flux of PVDF/GO-lysine membranes can reach two times of that of the virgin PVDF membrane. And the BSA adsorbed amount on PVDF/GO-lysine surface was decreased to 0.82 mg/cm2 for PVDF/GO-lysine-8% membrane. Filtration experiment results indicated that the fouling resistance was significantly improved for the PVDF/GO-lysine membranes. As a result, lysine functionalized GO will provide a promising method to fabricate graphene oxide based hybrid membranes with effective antifouling property and hydrophilicity.
Herein, functionalized graphene oxide (GO) was prepared by the covalent functionalization with amino acids (lysine, glycine, glutamic acid and tyrosine) in this study. Zeta potential results demonstrated that covalent functionalization of GO with amino acids was favourable for their homogeneous dispersion in water and organic solvents. Based on the higher absolute value of zeta potential and the better dipersion stability of GO-lysine, the PVDF/GO-lysine hybrid membranes were then prepared via the phase inversion induced by immersion precipitation technique. SEM images showed a better pore diameter and porosity distribution on the PVDF/GO-lysine membrane surface. The zeta potential absolute value of the PVDF/GO-lysine membrane surface was higher than that of the virgin PVDF membrane. Furthermore, the PVDF/GO-lysine membranes surface exhibited good hydrophilicity. The water flux of PVDF/GO-lysine membranes can reach two times of that of the virgin PVDF membrane. And the BSA adsorbed amount on PVDF/GO-lysine surface was decreased to 0.82 mg/cm2 for PVDF/GO-lysine-8% membrane. Filtration experiment results indicated that the fouling resistance was significantly improved for the PVDF/GO-lysine membranes. As a result, lysine functionalized GO will provide a promising method to fabricate graphene oxide based hybrid membranes with effective antifouling property and hydrophilicity.
2016, 34(7): 820-829
doi: 10.1007/s10118-016-1794-4
Abstract:
The mechanical properties and phase morphologies of cis-1,4-butadiene rubber (BR) blended with polyethylene (PE) at different blend ratios were studied. The tensile test results show that the PE exhibits excellent reinforcing capabilities towards BR. Blending BR with PE results in a remarkable enhancement of tensile strength, modulus and the elongation at break simultaneously. An increment of tensile strength from 1.11 MPa to 16.26 MPa was achieved by incorporation of 40 wt% PE in the blends. The modulus and elongation at break of 40/60 PE/BR blends are also about 5 times higher than those of the pure BR treated under exactly the same conditions. The tear test indicates that the tear strength also increases with the increase of PE content. It reaches 58.38 MPa for the 40/60 PE/BR blend, which is approximately 10 times higher than that of the pure BR. Morphological study demonstrates that the PE forms elongated microdomains finely dispersed in the BR matrix when its content is over 30 wt%, which corresponds to the remarkably enhanced mechanical properties. According to the results, reinforcement mechanism of PE toward BR dependent on the microstructure has been discussed and two different mechanisms have been proposed.
The mechanical properties and phase morphologies of cis-1,4-butadiene rubber (BR) blended with polyethylene (PE) at different blend ratios were studied. The tensile test results show that the PE exhibits excellent reinforcing capabilities towards BR. Blending BR with PE results in a remarkable enhancement of tensile strength, modulus and the elongation at break simultaneously. An increment of tensile strength from 1.11 MPa to 16.26 MPa was achieved by incorporation of 40 wt% PE in the blends. The modulus and elongation at break of 40/60 PE/BR blends are also about 5 times higher than those of the pure BR treated under exactly the same conditions. The tear test indicates that the tear strength also increases with the increase of PE content. It reaches 58.38 MPa for the 40/60 PE/BR blend, which is approximately 10 times higher than that of the pure BR. Morphological study demonstrates that the PE forms elongated microdomains finely dispersed in the BR matrix when its content is over 30 wt%, which corresponds to the remarkably enhanced mechanical properties. According to the results, reinforcement mechanism of PE toward BR dependent on the microstructure has been discussed and two different mechanisms have been proposed.
2016, 34(7): 830-837
doi: 10.1007/s10118-016-1793-5
Abstract:
A simple and effective polymer fluorescent thermosensitive system was successfully developed based on the synergistic effect of excimer/monomer interconversion of pyrene derivatives and electrostatic interaction between polyelectrolyte and charged fluorophore. As for the system, the excimer-monomer conversion, thermosensitive behavior and thermo-responsive reversibility were investigated experimentally. Temperature variation and temperature-distribution induced fluorescence changes can be observed directly by naked eyes. Thus, this polymer system holds promise for serving as a fluorescent thermometer.
A simple and effective polymer fluorescent thermosensitive system was successfully developed based on the synergistic effect of excimer/monomer interconversion of pyrene derivatives and electrostatic interaction between polyelectrolyte and charged fluorophore. As for the system, the excimer-monomer conversion, thermosensitive behavior and thermo-responsive reversibility were investigated experimentally. Temperature variation and temperature-distribution induced fluorescence changes can be observed directly by naked eyes. Thus, this polymer system holds promise for serving as a fluorescent thermometer.
2016, 34(7): 838-849
doi: 10.1007/s10118-016-1803-7
Abstract:
The self-assembly behavior of sphere-forming R5C30R5 triblock copolymers within a planar slit is studied by performing dissipative particle dynamics simulations. A sequence of novel structures which are not observed in bulk are formed within slits, including wetting layers, island-like structure, parallel cylinders, perpendicular cylinders and cross-cylindrical structures. Perpendicular cylinders are always formed before the increase in the layers of parallel cylinders. A phase diagram of the assembled structures with respective to the slit property and height is thus presented. The rod length is found to have a significant impact on the rod alignment, and a disordered-ordered transition of rod orientation occurs with an increase in the length of rod blocks. Some special structures, such as parallel half-cylinders and arrowhead-shaped morphology, are observed when the rod length increases to a certain extent. Our results show that the property and height of the slit and rod length all influence the self-assembly of rod-coil-rod triblock copolymers.
The self-assembly behavior of sphere-forming R5C30R5 triblock copolymers within a planar slit is studied by performing dissipative particle dynamics simulations. A sequence of novel structures which are not observed in bulk are formed within slits, including wetting layers, island-like structure, parallel cylinders, perpendicular cylinders and cross-cylindrical structures. Perpendicular cylinders are always formed before the increase in the layers of parallel cylinders. A phase diagram of the assembled structures with respective to the slit property and height is thus presented. The rod length is found to have a significant impact on the rod alignment, and a disordered-ordered transition of rod orientation occurs with an increase in the length of rod blocks. Some special structures, such as parallel half-cylinders and arrowhead-shaped morphology, are observed when the rod length increases to a certain extent. Our results show that the property and height of the slit and rod length all influence the self-assembly of rod-coil-rod triblock copolymers.
2016, 34(7): 850-857
doi: 10.1007/s10118-016-1809-1
Abstract:
A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer comprising poly-(propylene glycol) bis(2-aminopropyl) ether chains and 2-ureido-4[1H]-pyrimidinone moieties (UPy) self-assembled into spherical domains with sizes of 300 nm to 600 nm in diameter by micro phase separation in bulk epoxy matrixes. A significant improvement of 300% in impact resistance of the supramolecular polymer incorporated epoxy resin was obtained when the content of supramolecular polymer was 10 wt%. Tensile tests showed that the mechanical properties of the modified epoxy resin containing the hydrogen-bonded supramolecular polymers are also improved compared with those of the neat epoxy resin.
A bisphenol A based epoxy was incorporated with a quadruply hydrogen bonded supramolecular polymer as a toughening agent to prepare a composite epoxy resin with higher impact resistance. The supramolecular polymer comprising poly-(propylene glycol) bis(2-aminopropyl) ether chains and 2-ureido-4[1H]-pyrimidinone moieties (UPy) self-assembled into spherical domains with sizes of 300 nm to 600 nm in diameter by micro phase separation in bulk epoxy matrixes. A significant improvement of 300% in impact resistance of the supramolecular polymer incorporated epoxy resin was obtained when the content of supramolecular polymer was 10 wt%. Tensile tests showed that the mechanical properties of the modified epoxy resin containing the hydrogen-bonded supramolecular polymers are also improved compared with those of the neat epoxy resin.
2016, 34(7): 858-872
doi: 10.1007/s10118-016-1801-9
Abstract:
The dispersion and filler network of fibrillar silicate (FS) in elastomers were studied. The results showed that a good dispersion of FS in matrix during mechanical blending in unvulcanized composites contributed to a strong FS filler network, different from that of traditional reinforcing fillers. Meanwhile, the filler re-aggregation during vulcanization caused by the overlapping and intertwining of FS further strengthened the filler network. The factors including Mooney viscosity and molecular polarity of elastomer, type and amount of silane coupling agents used for filler modification, that may influence the filler network, were studied. Our study helps us to understand the mechanism for the formation of filler network of FS in elastomers and provides guidance for the preparation of high performance FS/elastomer composites.
The dispersion and filler network of fibrillar silicate (FS) in elastomers were studied. The results showed that a good dispersion of FS in matrix during mechanical blending in unvulcanized composites contributed to a strong FS filler network, different from that of traditional reinforcing fillers. Meanwhile, the filler re-aggregation during vulcanization caused by the overlapping and intertwining of FS further strengthened the filler network. The factors including Mooney viscosity and molecular polarity of elastomer, type and amount of silane coupling agents used for filler modification, that may influence the filler network, were studied. Our study helps us to understand the mechanism for the formation of filler network of FS in elastomers and provides guidance for the preparation of high performance FS/elastomer composites.
2016, 34(7): 873-888
doi: 10.1007/s10118-016-1805-5
Abstract:
A series of branched poly(butylene succinate) (PBS) were synthesized with several branching agents namely trimethylol propane (TMP), malic acid, trimesic acid, citric acid and glycerol propoxylate. The structure of the branched polymers was analyzed by SEC and 1H-NMR. The effect of branching agent structure on crystallization was also investigated and played a significant role. Isothermal studies showed that glycerol propoxylate could act as a nucleating agent. By contrast high content of TMP disturbed the regularity of the chain and hindered the crystallization of PBS. From the non-isothermal kinetic study, it was found that glycerol propoxylate increased noticeably the crystallization rate due to the flexible structure of the branching agent. A secondary nucleation was observed with glycerol propoxylate attributed to the crystallization of amorphous fraction included between crystallites formed at the primary crystallization. Chain topology was obtained through rheological investigations and the synthesized polymers showed a typical behavior of a mixture of linear and randomly branched PBS. The incorporation of branches improved the processability of PBS for film blowing application and the modulus and the stress at break of the resulting film were significantly increased.
A series of branched poly(butylene succinate) (PBS) were synthesized with several branching agents namely trimethylol propane (TMP), malic acid, trimesic acid, citric acid and glycerol propoxylate. The structure of the branched polymers was analyzed by SEC and 1H-NMR. The effect of branching agent structure on crystallization was also investigated and played a significant role. Isothermal studies showed that glycerol propoxylate could act as a nucleating agent. By contrast high content of TMP disturbed the regularity of the chain and hindered the crystallization of PBS. From the non-isothermal kinetic study, it was found that glycerol propoxylate increased noticeably the crystallization rate due to the flexible structure of the branching agent. A secondary nucleation was observed with glycerol propoxylate attributed to the crystallization of amorphous fraction included between crystallites formed at the primary crystallization. Chain topology was obtained through rheological investigations and the synthesized polymers showed a typical behavior of a mixture of linear and randomly branched PBS. The incorporation of branches improved the processability of PBS for film blowing application and the modulus and the stress at break of the resulting film were significantly increased.
2016, 34(7): 889-900
doi: 10.1007/s10118-016-1806-4
Abstract:
The open-cell structure foams of linear low-density polyethylene (LLDPE) and linear low-density polyethylene (LLDPE)/multi-wall carbon nanotubes (MWCNTs) composites are prepared by using supercritical carbon dioxide (sc-CO2) as a foaming agent. The effects of processing parameters (foaming temperature, saturation pressure, and depressurization rate) and the addition of MWCNTs on the evolution of cell opening are studied systematically. For LLDPE foaming, the foaming temperature and saturation pressure are two key factors for preparing open-cell foams. An increase in temperature and pressure promotes both the cell wall thinning and cell rupture, because a high temperature results in a decrease in the viscosity of the polymer, and a high pressure leads to a larger amount of cell nucleation. Moreover, for the given temperature and pressure, the high pressurization rate results in a high pressure gradient, favoring cell rupture. For LLDPE/MWCNTs foaming, the addition of MWCNTs not only promotes the cell heterogeneous nucleation, but also prevents the cell collapse during cell opening, which is critical to achieve the open-cell structures with small cell size and high cell density.
The open-cell structure foams of linear low-density polyethylene (LLDPE) and linear low-density polyethylene (LLDPE)/multi-wall carbon nanotubes (MWCNTs) composites are prepared by using supercritical carbon dioxide (sc-CO2) as a foaming agent. The effects of processing parameters (foaming temperature, saturation pressure, and depressurization rate) and the addition of MWCNTs on the evolution of cell opening are studied systematically. For LLDPE foaming, the foaming temperature and saturation pressure are two key factors for preparing open-cell foams. An increase in temperature and pressure promotes both the cell wall thinning and cell rupture, because a high temperature results in a decrease in the viscosity of the polymer, and a high pressure leads to a larger amount of cell nucleation. Moreover, for the given temperature and pressure, the high pressurization rate results in a high pressure gradient, favoring cell rupture. For LLDPE/MWCNTs foaming, the addition of MWCNTs not only promotes the cell heterogeneous nucleation, but also prevents the cell collapse during cell opening, which is critical to achieve the open-cell structures with small cell size and high cell density.
2016, 34(7): 901-909
doi: 10.1007/s10118-016-1811-7
Abstract:
In this work, a series of high performance bio-based polyurethanes (bio-PUs) were synthesized from polylactide (PLA)-based diols, different diisocyanates (TDI, MDI, HDI, IPDI) and chain extender 1, 4-butanediol, in which different soft and hard segments are used to adjust their transition temperatures and mechanical properties. Poly(lactide-co-caprolactone) copolymer diols (co-PLAols) instead of PLA diols as the soft segment improved the thermal stability and mechanical properties of the synthesized bio-PUs. Among them, MDI-based bio-PUs have the highest Tg (43.8℃), tensile strength (23.5 MPa) and modulus (380.8 MPa), while HDI-based bio-PUs have the lowest Tg (21.4℃) and highest elongation at break (580%). Especially, the bio-PUs synthesized from co-PLAols and MDI demonstrate better mechanical properties, closed to petroleum-based commodities. Furthermore, the obtained bio-PUs display good shape memory properties at body temperature and cytocompatibility. Therefore, these bio-PUs are promising for applications in biomedical fields.
In this work, a series of high performance bio-based polyurethanes (bio-PUs) were synthesized from polylactide (PLA)-based diols, different diisocyanates (TDI, MDI, HDI, IPDI) and chain extender 1, 4-butanediol, in which different soft and hard segments are used to adjust their transition temperatures and mechanical properties. Poly(lactide-co-caprolactone) copolymer diols (co-PLAols) instead of PLA diols as the soft segment improved the thermal stability and mechanical properties of the synthesized bio-PUs. Among them, MDI-based bio-PUs have the highest Tg (43.8℃), tensile strength (23.5 MPa) and modulus (380.8 MPa), while HDI-based bio-PUs have the lowest Tg (21.4℃) and highest elongation at break (580%). Especially, the bio-PUs synthesized from co-PLAols and MDI demonstrate better mechanical properties, closed to petroleum-based commodities. Furthermore, the obtained bio-PUs display good shape memory properties at body temperature and cytocompatibility. Therefore, these bio-PUs are promising for applications in biomedical fields.
2016, 34(7): 910-918
doi: 10.1007/s10118-016-1804-6
Abstract:
Homopolymer (PBIP) containing 2, 6-bis(1'-methylbenzimidazolyl)pyridine (MeBIP) ligands in the side chain was synthesized by RAFT polymerization and its kinetics was studied. Polymeric complex PBIP-Nd3+ was prepared by chelating PBIP with lanthanide ion Nd3+. The homopolymers and PBIP-Nd3+ complex were investigated by NMR, FTIR, GPC and TGA. The optical property of PBIP-Nd3+ complex was characterized by UV-Vis spectroscopy. The magnetic property of PBIP-Nd3+ complex was measured as a function of temperature (5 K to 300 K) and as a function of field (-3.98 × 106 A/m to 3.98 × 106 A/m). These results indicated that PBIP-Nd3+ complex is paramagnetic.
Homopolymer (PBIP) containing 2, 6-bis(1'-methylbenzimidazolyl)pyridine (MeBIP) ligands in the side chain was synthesized by RAFT polymerization and its kinetics was studied. Polymeric complex PBIP-Nd3+ was prepared by chelating PBIP with lanthanide ion Nd3+. The homopolymers and PBIP-Nd3+ complex were investigated by NMR, FTIR, GPC and TGA. The optical property of PBIP-Nd3+ complex was characterized by UV-Vis spectroscopy. The magnetic property of PBIP-Nd3+ complex was measured as a function of temperature (5 K to 300 K) and as a function of field (-3.98 × 106 A/m to 3.98 × 106 A/m). These results indicated that PBIP-Nd3+ complex is paramagnetic.
