Login In
2016 Volume 34 Issue 10
2016, 34(10): 1183-1195
doi: 10.1007/s10118-016-1826-0
Abstract:
In this study, a kind of fluorinated copolyfluorene, named poly[(4-(octyloxy)-9,9-diphenylfluorene-2,7-diyl)-alt-(2,3,5,6-tetrafluoro-1,4-phenylene)] (PODPF-TFP), is synthesized by facile palladium-based direct aromatization. Compared to the non-fluorinated counterpart, poly[(4-(octyloxy)-9,9-diphenylfluorene-2,7-diyl)-alt-(p-phenylene)] (PODPF-P), deeper HOMO/LUMO energy level combined with steric hindrance effect endow PODPF-TFP with excellent spectra and morphology stability. Finally, organic field-effect transistor (OFET) memory devices are fabricated with PODPF-P/PODPF-TFP as the dielectric layers, and they both exhibit flash type storage characteristic. Owing to the electronegativity of fluorine atom, the device based on PODPF-TFP exhibits larger memory window and more stable Ion/Ioff ratio during a retention time of 104 s as well as a better aging stability. The present study suggests that fluorinated p-n copolyfluorene electrets could enhance the capabilities of charge trapping and storage, which are promising for OFET memory devices.
In this study, a kind of fluorinated copolyfluorene, named poly[(4-(octyloxy)-9,9-diphenylfluorene-2,7-diyl)-alt-(2,3,5,6-tetrafluoro-1,4-phenylene)] (PODPF-TFP), is synthesized by facile palladium-based direct aromatization. Compared to the non-fluorinated counterpart, poly[(4-(octyloxy)-9,9-diphenylfluorene-2,7-diyl)-alt-(p-phenylene)] (PODPF-P), deeper HOMO/LUMO energy level combined with steric hindrance effect endow PODPF-TFP with excellent spectra and morphology stability. Finally, organic field-effect transistor (OFET) memory devices are fabricated with PODPF-P/PODPF-TFP as the dielectric layers, and they both exhibit flash type storage characteristic. Owing to the electronegativity of fluorine atom, the device based on PODPF-TFP exhibits larger memory window and more stable Ion/Ioff ratio during a retention time of 104 s as well as a better aging stability. The present study suggests that fluorinated p-n copolyfluorene electrets could enhance the capabilities of charge trapping and storage, which are promising for OFET memory devices.
2016, 34(10): 1196-1207
doi: 10.1007/s10118-016-1842-0
Abstract:
Using theoretical analysis and three-dimensional Langevin dynamics simulations, we investigate the influence of chain rigidity on the ejection dynamics of polymers from a nanochannel. We find that there exist two distinct dynamical regimes divided by a critical chain length for both flexible and semiflexible chains. At the short chain regime, semiflexible chains eject faster than flexible chains of the same chain length due to the longer occupying length. In contrast, at the long chain regime, semiflexible chains eject slower than flexible ones as the effective entropic driving force decreases. Based on these results, we propose that the nanochannels could be used to separate flexible and semiflexible chains effectively
Using theoretical analysis and three-dimensional Langevin dynamics simulations, we investigate the influence of chain rigidity on the ejection dynamics of polymers from a nanochannel. We find that there exist two distinct dynamical regimes divided by a critical chain length for both flexible and semiflexible chains. At the short chain regime, semiflexible chains eject faster than flexible chains of the same chain length due to the longer occupying length. In contrast, at the long chain regime, semiflexible chains eject slower than flexible ones as the effective entropic driving force decreases. Based on these results, we propose that the nanochannels could be used to separate flexible and semiflexible chains effectively
2016, 34(10): 1208-1219
doi: 10.1007/s10118-016-1835-z
Abstract:
Functionalized poly(phthalazinone ether sulfone ketone) was synthesized by successive chloromethylation and azidation, followed by curing reaction with the propargyl end-groups of various molecular weight crosslinking agents in the presence of Cu(I) catalyst via the azide-alkyne click reaction. The influences of the chain length of crosslinking agents on the poly(phthalazinone ether sulfone ketone) system were studied. FTIR and DSC tests demonstrated certain crosslinking by azide-alkyne reaction with the formation of triazole ring. DSC results showed that curing temperature shifted to lower temperatures considerably in the presence of Cu(I) catalyst. TGA showed cured polymers were of much higher thermal stability, including higher thermal decomposition temperatures and higher char-yielding properties. After being cured, the polymers became insoluble in organic solvents and the gel fraction of the cured polymers exceeded 71%. Wide-angle X-ray diffraction results indicated there was a short distance order in the poly(ether sulfone) (PES) main chain except for the azido methyl poly(phthalazinone ether sulfone ketone) and 4,4'-bis(2-propynyloxy) biphenyl ( AMPPESK-BP) system.
Functionalized poly(phthalazinone ether sulfone ketone) was synthesized by successive chloromethylation and azidation, followed by curing reaction with the propargyl end-groups of various molecular weight crosslinking agents in the presence of Cu(I) catalyst via the azide-alkyne click reaction. The influences of the chain length of crosslinking agents on the poly(phthalazinone ether sulfone ketone) system were studied. FTIR and DSC tests demonstrated certain crosslinking by azide-alkyne reaction with the formation of triazole ring. DSC results showed that curing temperature shifted to lower temperatures considerably in the presence of Cu(I) catalyst. TGA showed cured polymers were of much higher thermal stability, including higher thermal decomposition temperatures and higher char-yielding properties. After being cured, the polymers became insoluble in organic solvents and the gel fraction of the cured polymers exceeded 71%. Wide-angle X-ray diffraction results indicated there was a short distance order in the poly(ether sulfone) (PES) main chain except for the azido methyl poly(phthalazinone ether sulfone ketone) and 4,4'-bis(2-propynyloxy) biphenyl ( AMPPESK-BP) system.
2016, 34(10): 1220-1233
doi: 10.1007/s10118-016-1839-8
Abstract:
A simple non-isocyanate route is developed for synthesizing crystallizable aliphatic thermoplastic poly(ester urethane) elastomers (TPEURs) with good thermal and mechanical properties. Three prepolymers of 1,6-bis(hydroxyethyloxycarbonylamino) hexane (BHCH), i.e. PrePBHCHs, were prepared through the self-transurethane polycondensation of BHCH. A poly(butylene adipate) prepolymer (PrePBA) with terminal HO― groups was prepared and used as a polyester glycol. A series of TPEURs were prepared by the co-polycondensation of the PrePBHCHs with PrePBA at 170 ℃ under a reduced pressure of 399 Pa. The TPEURs were characterized by gel permeation chromatography, FTIR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction, atomic force microscopy, and tensile test. The TPEURs exhibited Mn up to 23300 g/mol, Mw up to 51100 g/mol, Tg ranging from -33.8 ℃ to -3.1 ℃, Tm from 94.3 ℃ to 111.9 ℃, initial decomposition temperature over 274.7 ℃, tensile strength up to18.8 MPa with a strain at break of 450.0%, and resilience up to 77.5%. TPU elastomers with good crystallization and mechanical properties were obtained through a non-isocyanate route.
A simple non-isocyanate route is developed for synthesizing crystallizable aliphatic thermoplastic poly(ester urethane) elastomers (TPEURs) with good thermal and mechanical properties. Three prepolymers of 1,6-bis(hydroxyethyloxycarbonylamino) hexane (BHCH), i.e. PrePBHCHs, were prepared through the self-transurethane polycondensation of BHCH. A poly(butylene adipate) prepolymer (PrePBA) with terminal HO― groups was prepared and used as a polyester glycol. A series of TPEURs were prepared by the co-polycondensation of the PrePBHCHs with PrePBA at 170 ℃ under a reduced pressure of 399 Pa. The TPEURs were characterized by gel permeation chromatography, FTIR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction, atomic force microscopy, and tensile test. The TPEURs exhibited Mn up to 23300 g/mol, Mw up to 51100 g/mol, Tg ranging from -33.8 ℃ to -3.1 ℃, Tm from 94.3 ℃ to 111.9 ℃, initial decomposition temperature over 274.7 ℃, tensile strength up to18.8 MPa with a strain at break of 450.0%, and resilience up to 77.5%. TPU elastomers with good crystallization and mechanical properties were obtained through a non-isocyanate route.
2016, 34(10): 1234-1239
doi: 10.1007/s10118-016-1828-y
Abstract:
Separation of oil/water mixtures, especially for the emulsified oil/water mixtures, is important because of the frequent occurrence of oil spill accidents. Utilizing superwetting porous membrane has become a promising approach to separate either surfactant-free or surfactant-stabilized emulsions. Herein we report a facile and versatile strategy for preparing hydrophobic/under-oil superhydrophobic membranes by coating the skeletons of the membranes with the poly[(3,3,3-trifluoropropyl)methylsiloxane] (PTFPMS) nanoparticles. The obtained membranes could be used to separate various water-in-oil emulsions with high flux and separation efficiency. In addition, owning to the outstanding resistance of PTFPMS to the most organic solvents or oils, the modified membranes exhibited the excellent reusability and the antifouling properties that were critical in the practical applications. Many commercially available membranes can be modified by such a simple method.
Separation of oil/water mixtures, especially for the emulsified oil/water mixtures, is important because of the frequent occurrence of oil spill accidents. Utilizing superwetting porous membrane has become a promising approach to separate either surfactant-free or surfactant-stabilized emulsions. Herein we report a facile and versatile strategy for preparing hydrophobic/under-oil superhydrophobic membranes by coating the skeletons of the membranes with the poly[(3,3,3-trifluoropropyl)methylsiloxane] (PTFPMS) nanoparticles. The obtained membranes could be used to separate various water-in-oil emulsions with high flux and separation efficiency. In addition, owning to the outstanding resistance of PTFPMS to the most organic solvents or oils, the modified membranes exhibited the excellent reusability and the antifouling properties that were critical in the practical applications. Many commercially available membranes can be modified by such a simple method.
2016, 34(10): 1240-1250
doi: 10.1007/s10118-016-1829-x
Abstract:
Cationic poly(styrene-co-N, N-dimethylaminoethyl methacrylate) (P(St-co-DMAEMA)) latexes were prepared in the absence of surfactant by using 2, 2'-azobis (2-methylpropionamidine) dihydrochloride (AIBA) as the initiator. The effects of the AIBA concentration, HCl/DMAEMA molar ratio and DMAEMA amount on the emulsion polymerization and the latex properties were investigated. The particle morphology and size, the zeta potential and the amino distribution of the P(St-co-DMAEMA) latexes were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS) and conductometric titration, respectively. Results showed that the emulsion polymerization performed smoothly with high monomer conversion and narrow particle size distribution under the optimized conditions with AIBA concentration of 1 wt%, HCl/DMAEMA molar ratio of 1.2 and DMAEMA content of 5 wt%. The diameter of the dried latex particles decreased and the density of amino groups on the particle surfaces increased with increasing the DMAEMA content. The zeta potential of the P(St-co-DMAEMA) latexes was pH-dependent and the zero point was around at pH 7.2. A facile method was developed to fabricate P(St-co-DMAEMA)/laponite hybrid nanoparticles via electrostatic adsorption, in which the loading capacity of laponite platelets reached 17.7 wt%, and the resultant hybrid nanoparticles showed good thermal stability.
Cationic poly(styrene-co-N, N-dimethylaminoethyl methacrylate) (P(St-co-DMAEMA)) latexes were prepared in the absence of surfactant by using 2, 2'-azobis (2-methylpropionamidine) dihydrochloride (AIBA) as the initiator. The effects of the AIBA concentration, HCl/DMAEMA molar ratio and DMAEMA amount on the emulsion polymerization and the latex properties were investigated. The particle morphology and size, the zeta potential and the amino distribution of the P(St-co-DMAEMA) latexes were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS) and conductometric titration, respectively. Results showed that the emulsion polymerization performed smoothly with high monomer conversion and narrow particle size distribution under the optimized conditions with AIBA concentration of 1 wt%, HCl/DMAEMA molar ratio of 1.2 and DMAEMA content of 5 wt%. The diameter of the dried latex particles decreased and the density of amino groups on the particle surfaces increased with increasing the DMAEMA content. The zeta potential of the P(St-co-DMAEMA) latexes was pH-dependent and the zero point was around at pH 7.2. A facile method was developed to fabricate P(St-co-DMAEMA)/laponite hybrid nanoparticles via electrostatic adsorption, in which the loading capacity of laponite platelets reached 17.7 wt%, and the resultant hybrid nanoparticles showed good thermal stability.
2016, 34(10): 1251-1260
doi: 10.1007/s10118-016-1837-x
Abstract:
Thermo-gelation polymers have attracted increasing attention over decades. However, rare facile tuning method of sol-gel transition temperature restricted the wider application. Preceding study indicated that supramolecular interactions demonstrated a powerful means to control the structure and property of polymeric materials. Here we designed an N-isopropylacrylamide (NIPAM) based thermo-sensitive copolymer with naphthyl (Np) on its side chain. Positive-charged side-chain ternary complex was formed with cucurbit[8]uril (CB[8]) and methylviologen (MV2+) via CB[8]-enhanced intermolecular charge-transfer (CT) interaction. Introducing the ternary complex CB[8]/MV2+/Np on side-chain altered microstructure of macromolecular chains and led to a strong tendency for thermo gelation. Altering content of CB[8] and MV2+ changed content of the positive-charged side-chain ternary complex and varied gelation temperature. Therefore, introducing supramolecular interaction endowed the hydrogel with tunable gelation property.
Thermo-gelation polymers have attracted increasing attention over decades. However, rare facile tuning method of sol-gel transition temperature restricted the wider application. Preceding study indicated that supramolecular interactions demonstrated a powerful means to control the structure and property of polymeric materials. Here we designed an N-isopropylacrylamide (NIPAM) based thermo-sensitive copolymer with naphthyl (Np) on its side chain. Positive-charged side-chain ternary complex was formed with cucurbit[8]uril (CB[8]) and methylviologen (MV2+) via CB[8]-enhanced intermolecular charge-transfer (CT) interaction. Introducing the ternary complex CB[8]/MV2+/Np on side-chain altered microstructure of macromolecular chains and led to a strong tendency for thermo gelation. Altering content of CB[8] and MV2+ changed content of the positive-charged side-chain ternary complex and varied gelation temperature. Therefore, introducing supramolecular interaction endowed the hydrogel with tunable gelation property.
2016, 34(10): 1261-1269
doi: 10.1007/s10118-016-1848-7
Abstract:
Poly(acrylamide-co-acrylic acid) nanocomposite physical (P(AAm-co-AAc)NCP) hydrogels have been prepared through the in situ free radical solution polymerization based on a “single network, dual cross-linkings” strategy. The P(AAm-co-AAc) NCP hydrogels are composed of nanobrushes of P(AAm-co-AAc) chains grafted on the surface of vinyl-hybrid silica nanoparticles (VSNPs). In the hydrogel system, the VSNPs act as the “analogous chemical cross-linking points” once the hydrogen bonds formed between the P(AAm-co-AAc) chains of the nanobrushes, thus leading to the fabrication of high-strength P(AAm-co-AAc) NCP hydrogels. Compared with conventional thermosensitive P(AAm-co-AAc) hydrogels, the P(AAm-co-AAc) NCP hydrogels have a broader range of phase transition temperature, which can be adjusted by altering the monomer ratio, the VSNPs concentration, the addition of urea and N, N-dimethylacrylamide (DMAAm). At the same time, the mechanical properties of the P(AAm-co-AAc) NCP hydrogels have been improved significantly by the introduction of VSNPs. Furthermore, both the phase transition and the tensile strength of the P(AAm-co-AAc) NCP hydrogels are largely influenced when Fe3+ ions are introduced as the ionic crosslinkers into the hydrogel networks.
Poly(acrylamide-co-acrylic acid) nanocomposite physical (P(AAm-co-AAc)NCP) hydrogels have been prepared through the in situ free radical solution polymerization based on a “single network, dual cross-linkings” strategy. The P(AAm-co-AAc) NCP hydrogels are composed of nanobrushes of P(AAm-co-AAc) chains grafted on the surface of vinyl-hybrid silica nanoparticles (VSNPs). In the hydrogel system, the VSNPs act as the “analogous chemical cross-linking points” once the hydrogen bonds formed between the P(AAm-co-AAc) chains of the nanobrushes, thus leading to the fabrication of high-strength P(AAm-co-AAc) NCP hydrogels. Compared with conventional thermosensitive P(AAm-co-AAc) hydrogels, the P(AAm-co-AAc) NCP hydrogels have a broader range of phase transition temperature, which can be adjusted by altering the monomer ratio, the VSNPs concentration, the addition of urea and N, N-dimethylacrylamide (DMAAm). At the same time, the mechanical properties of the P(AAm-co-AAc) NCP hydrogels have been improved significantly by the introduction of VSNPs. Furthermore, both the phase transition and the tensile strength of the P(AAm-co-AAc) NCP hydrogels are largely influenced when Fe3+ ions are introduced as the ionic crosslinkers into the hydrogel networks.
2016, 34(10): 1270-1280
doi: 10.1007/s10118-016-1836-y
Abstract:
In the field of polymer/graphene nanocomposites, massive production and commercial availability of graphene are essential. Exfoliation of graphite to obtain graphene is one of the most promising ways to large-scale production at extremely low cost. In this work we illustrate a facile strategy for mass production of few-layered (≤ 10) graphene (FLG) via the newly explored ball milling. The achieved FLG concentration was determined by UV/Vis spectroscopy. The formation of FLG was proved by measuring the flake thickness by atomic force microscopy (AFM). Further Raman spectral studies indicated that the crystal structure of exfoliated flakes was preserved satisfactorily during this shear-force dominating process. To increase the maximum concentration obtainable, it's critical to make a good parameter assessment. N-methylpyrrolidone (NMP) was used as a dispersing medium and the effect of milling parameters was systematically and quantitatively investigated, thus providing a criterion to optimize the milling process. We established the optimal values for solvent volume and initial weight of graphite. As for milling time, the production of FLG was enhanced with continuous milling according to the power law, but not linearly with increasing milling time. Moreover, the possible mechanism involved in milling process was also explored. Our work provides a simple method for graphite exfoliation and has great potential for improving thermal and electrical conductivity of polymer composites in the fields of engineering.
In the field of polymer/graphene nanocomposites, massive production and commercial availability of graphene are essential. Exfoliation of graphite to obtain graphene is one of the most promising ways to large-scale production at extremely low cost. In this work we illustrate a facile strategy for mass production of few-layered (≤ 10) graphene (FLG) via the newly explored ball milling. The achieved FLG concentration was determined by UV/Vis spectroscopy. The formation of FLG was proved by measuring the flake thickness by atomic force microscopy (AFM). Further Raman spectral studies indicated that the crystal structure of exfoliated flakes was preserved satisfactorily during this shear-force dominating process. To increase the maximum concentration obtainable, it's critical to make a good parameter assessment. N-methylpyrrolidone (NMP) was used as a dispersing medium and the effect of milling parameters was systematically and quantitatively investigated, thus providing a criterion to optimize the milling process. We established the optimal values for solvent volume and initial weight of graphite. As for milling time, the production of FLG was enhanced with continuous milling according to the power law, but not linearly with increasing milling time. Moreover, the possible mechanism involved in milling process was also explored. Our work provides a simple method for graphite exfoliation and has great potential for improving thermal and electrical conductivity of polymer composites in the fields of engineering.
2016, 34(10): 1281-1289
doi: 10.1007/s10118-016-1840-2
Abstract:
High strength cellulose composite films with antibacterial activities were prepared by dispersing montmorillonites (MMT) into cellulose solution in LiOH/urea aqueous solvent followed by regeneration in ethanol coagulation bath, and then by soaking in 5 wt% hexadecylpyridine bromide ethanol solutions to induce the antibacterial action. The cellulose/MMT composite films were characterized by field emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, FTIR, UV-spectra, wide angle X-ray diffraction and mechanical test. The results revealed that MMT was dispersed well in the cellulose matrix to form layer structure with a thickness of approximately 3 nm. The mechanical properties of the cellulose/MMT composite films were significantly improved to achieve 132 MP for tensile strength as a result of the MMT delamination. The hexadecylpyridine bromide was fixed well in the cellulose/MMT matrix through cation exchange, leading to the excellent antibacterial activities against Staphylococcus aureus and Escherichia coli, which is important in their practical applications.
High strength cellulose composite films with antibacterial activities were prepared by dispersing montmorillonites (MMT) into cellulose solution in LiOH/urea aqueous solvent followed by regeneration in ethanol coagulation bath, and then by soaking in 5 wt% hexadecylpyridine bromide ethanol solutions to induce the antibacterial action. The cellulose/MMT composite films were characterized by field emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, FTIR, UV-spectra, wide angle X-ray diffraction and mechanical test. The results revealed that MMT was dispersed well in the cellulose matrix to form layer structure with a thickness of approximately 3 nm. The mechanical properties of the cellulose/MMT composite films were significantly improved to achieve 132 MP for tensile strength as a result of the MMT delamination. The hexadecylpyridine bromide was fixed well in the cellulose/MMT matrix through cation exchange, leading to the excellent antibacterial activities against Staphylococcus aureus and Escherichia coli, which is important in their practical applications.
2016, 34(10): 1290-1300
doi: 10.1007/s10118-016-1847-8
Abstract:
The cure kinetics for two-component silicone rubber formed by addition reaction was studied by the rheological method. The influence of reaction temperature (T) on the cure kinetics was explored in detail. It was observed that the data of gel time (tgel, i.e. the time when the reaction reaches the gel point) or a specific reaction time (tnc) (defined as the reaction time before which time the influence of confinement of network on the diffusion of reaction components can be neglected) versus T obey certain functional relationship, which was well explained by the cure kinetics model of thermoset network. The cure kinetics for the two-component silicone rubber can be well fitted by the Kamal-Sourour(autocatalyst) reaction model rather than Kissinger model. When the reaction time was before or equal to tnc, the reaction order obtained by the Kamal-Sourour reaction model was 2, which was consistent with the reaction order inferred from the two components chemical reaction when the diffusion of reaction components was not influenced by the formed cross-linked polymer network. When the reaction time was larger than tnc, such as to the end of reaction (te), the influence of confinement of network on the diffusion of reaction components cannot be neglected, and the reaction order obtained by the Kamal-Sourour reaction model was larger than 2. It was concluded that the confinement effect of network had a greater influence on the cure kinetics of the silicone rubber. The reaction rate constants (kr) under different temperatures were also determined by Kamal-Sourour reaction model. The activation energy (E) for the two-component silicone rubber was also calculated from the results of lntgel, lntnc, and lnkr versus 1/T, respectively. The three values of E were close, which indicated that above analyses were self-consistent.
The cure kinetics for two-component silicone rubber formed by addition reaction was studied by the rheological method. The influence of reaction temperature (T) on the cure kinetics was explored in detail. It was observed that the data of gel time (tgel, i.e. the time when the reaction reaches the gel point) or a specific reaction time (tnc) (defined as the reaction time before which time the influence of confinement of network on the diffusion of reaction components can be neglected) versus T obey certain functional relationship, which was well explained by the cure kinetics model of thermoset network. The cure kinetics for the two-component silicone rubber can be well fitted by the Kamal-Sourour(autocatalyst) reaction model rather than Kissinger model. When the reaction time was before or equal to tnc, the reaction order obtained by the Kamal-Sourour reaction model was 2, which was consistent with the reaction order inferred from the two components chemical reaction when the diffusion of reaction components was not influenced by the formed cross-linked polymer network. When the reaction time was larger than tnc, such as to the end of reaction (te), the influence of confinement of network on the diffusion of reaction components cannot be neglected, and the reaction order obtained by the Kamal-Sourour reaction model was larger than 2. It was concluded that the confinement effect of network had a greater influence on the cure kinetics of the silicone rubber. The reaction rate constants (kr) under different temperatures were also determined by Kamal-Sourour reaction model. The activation energy (E) for the two-component silicone rubber was also calculated from the results of lntgel, lntnc, and lnkr versus 1/T, respectively. The three values of E were close, which indicated that above analyses were self-consistent.
