It was found that traces of water in the reaction medium would result in a great increase of gel and a decrease of Molecular weight of the poly(2-methoxy,5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) during the pol...It was found that traces of water in the reaction medium would result in a great increase of gel and a decrease of Molecular weight of the poly(2-methoxy,5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) during the polymerization, which ultimately led to inferior film qualities and device properties. The device (ITO/PEDOT/MEH-PPV/Ba/Al) with MEH-PPV prepared under dry conditions has an external quantum efficiency of above 2.0%.展开更多
Both aliphatic and aromatic ketones are efficiently transfer-hydrogenated by propan-2-ol under mild conditions in the presence of a catalytic amount of poly(2,6-dimethyl-1,4-Phenylene oxide) (PPO) anchored ruthenium...Both aliphatic and aromatic ketones are efficiently transfer-hydrogenated by propan-2-ol under mild conditions in the presence of a catalytic amount of poly(2,6-dimethyl-1,4-Phenylene oxide) (PPO) anchored ruthenium complex and sodium hydroxide. An important feature of this polymer anchored catalyst is its stability in air.展开更多
A novel hyperbranched poly(phenylene oxide) (HPPO) with phenolic terminal groups was prepared from 4-bromo-4',4"-dihydroxytriphenylmethane as AB2 monomer in dimethylsulfoxide (DMSO) via a modified Ullmann reac...A novel hyperbranched poly(phenylene oxide) (HPPO) with phenolic terminal groups was prepared from 4-bromo-4',4"-dihydroxytriphenylmethane as AB2 monomer in dimethylsulfoxide (DMSO) via a modified Ullmann reaction. The molecular weight and polydispersity (PD) of the resulting polymers increased with increasing reaction time. In the presence of core molecules (bisphenol A and 1,3,5-trihydroxybenzene), which have the similar molecular backbones to the reactive monomer, the molecular weight could be controlled by varying the core-to-monomer ratio. Incorporation of a very small amount of core molecules could lead to a higher molecular weight as compared with that without the addition of core molecules. However, when the core content reached certain extent, the molecular weight would decrease with the further increase in the core content. A new similar behavior of control over the PD was also obtained. The resulting polymers were characterized by ^1H-NMR, ^13C-NMR, FT-IR, and GPC.展开更多
Poly(phenylene sulfide/ether) (PPSE) was synthesized from 4,4'-dihydroxydiphenyl sulfide and 4,4'-dichlorodiphenyl sulfide in solution by nucleophilic substitution reaction. The resulting polymer was characteriz...Poly(phenylene sulfide/ether) (PPSE) was synthesized from 4,4'-dihydroxydiphenyl sulfide and 4,4'-dichlorodiphenyl sulfide in solution by nucleophilic substitution reaction. The resulting polymer was characterized by viscosity measurement, elemental analysis, FT-IR, ^1H NMR, X-ray diffraction and thermal analysis. The results showed that the viscosities of the resulting polymer were above 0.68 dL/g, and the linear chain structure of product was confirmed. PPSE had the same reflex indices as poly(p-phenylene sulfide), an orthorhombic crystalline with unit cell a=0.853, b=0.562, c=1.026nm. The melting temperature, glass transition temperature and initial decomposition temperature were found to be 228℃, 85℃ and 325℃, respectively. The product was soluble in common organic solvents such as NMP, N, N'-dimethylformamide, N, N'-dimethylacetamide and 1,2-dichloroethane.展开更多
In this paper the percolation theory is employed to study the insulator-to-conductortransition in sulphonated poly(phenylene oxide)(SPPO) polymer membranes.The membranes withdifferent sulphonation degree were prep...In this paper the percolation theory is employed to study the insulator-to-conductortransition in sulphonated poly(phenylene oxide)(SPPO) polymer membranes.The membranes withdifferent sulphonation degree were prepared and infrared characterized.The transition thresholdwas calculated by the experimental data of membrane conductivities and the coordination numberwas thus estimated.The functional group-SO<sub>3</sub>H distribution in the membrane was evaluated inaccordance with the calculations and showed a non-random dispersion on the microscopic scale.展开更多
Poly(phenylene sulfide amide) (PPSA) has been synthesized by using sulfur as S source which reacts with dichlorobenzamide (DCBA) and alkali in polar organic solvent at the atmospheric pressure. The polymer structures ...Poly(phenylene sulfide amide) (PPSA) has been synthesized by using sulfur as S source which reacts with dichlorobenzamide (DCBA) and alkali in polar organic solvent at the atmospheric pressure. The polymer structures were determined by elemental analysis, FT-IR and H-1-NMR. It is shown that the yielded polymer has linear structure and its structure unit is -p-C6H4-CONH -p-C6H4-S-. The polymer morphology was studied by X-ray diffraction and polarized microscopy. The results show that PPSA is a crystalline polymer and its spherulites are the aggregation of nontwisting lamella or micro-thread structure. Under shearing force, these crystals are dispersed to form micro-fibrillar structure. The decomposition kinetics of PPSA was also studied at different heating rates. The decomposition energy of PPSA is higher than that of PPS.展开更多
A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecu...A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecules accumulated in the vicinity as recently reported by Na et al. [Nanotechnology 18 424001 (2007)]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H2O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H2O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H2O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.展开更多
The apparent solubility (S), concentration-average diffusivity (D), and permeability (P), for C0_2, CH_4 and N_2 through PPO and aryl-brominated PPO at 35℃ for pressure ranging from 1 to 26 atm are reported. It is fo...The apparent solubility (S), concentration-average diffusivity (D), and permeability (P), for C0_2, CH_4 and N_2 through PPO and aryl-brominated PPO at 35℃ for pressure ranging from 1 to 26 atm are reported. It is found that P, D, and S of the membranes to all the three gases vary with the extent of bromination. S increases with the increase of the percent of bromine in each case, but D to CO_2 increases remarkably only at higher degree of brominafion, and therefore, P to CO_2 is increased by more than 100% over a wide range ofpressure in the case. The solubility data are well described by the dual mode sorption model. It is found that the gas molecules sorbed by the Langmuir mode are relatively more immobilized and the contribution of the nonequilibrinm character of the polymer to gas permeation increases obviously for CO_2 and is hardly changed for CH_4 with increasing bromine content. These observations are interpreted in terms of changes in specific free volume (SFV)and the cohesive energy density (CED) of the polymers.展开更多
This paper investigates the possibility of attaining sulphonated poly(phenylene oxide) (SPPO) with a relativelyhigher sulfonation degree. To achieve this aim, the approach we adopt is to improve the solubility of the ...This paper investigates the possibility of attaining sulphonated poly(phenylene oxide) (SPPO) with a relativelyhigher sulfonation degree. To achieve this aim, the approach we adopt is to improve the solubility of the final product in themixed solvent so that the sulfonation may take place between the bulk solutions and PPO powders even at higher sulfonationdegree. It is shown that the addition of a proper amount of dimethyl formide (DMF) to the conventional PPO-chloroformsystem can actually enhance the sulfonation effect. The solvent composition is then correlated with the sulfonation degreebased on the solubility parameters. It is interesting to find that solubility parameters between the mixed solvent and theprecipitated products keep an approximately unchanged value at about 4.9, which is just equal to that when pure chloroformis used, though the solubility parameters of both solvents increase with the content of DMF in solution. This may be the mainreason why the addition of DMF can reduce the precipitation and improve the ion exchange capacity (IEC) of SPPOpolymer.展开更多
A soluble poly(meta-phenylene) derivative with rigid twisted biphenyl unit was synthesized by the Yamamoto coupling reaction. The polymer is soluble in common organic solvents, and the number-average molecular weigh...A soluble poly(meta-phenylene) derivative with rigid twisted biphenyl unit was synthesized by the Yamamoto coupling reaction. The polymer is soluble in common organic solvents, and the number-average molecular weight is about 6500. The UV-Vis and quantum chemical calculation indicate that the different conformation segments named "conformers" exist in the polymer backbones; it was also further confirmed by the single crystal X-ray diffraction study of the dimeric model compound. The π-π^* transition of biphenyl segments of twisted and planar conformations made the polymer exhibit a strong absorption around 256 nm and a weak absorption at about 300 nm. Furthermore, the polymer exhibits a strong UV photoluminescence at 372 nm when the excitation wavelengths are longer than 300 run. The ultraviolet-emitting electroluminescence(EL) device with the single layer structure shows EL λmax of the derivative at 370 nm.展开更多
A new process for preparing poly(phenylene sulfide amide, PPSA), which is by reaction of sulfur instead of sodium sulfide as S source with dichlorobenzamide (DCBA) and alkali in polar orga...A new process for preparing poly(phenylene sulfide amide, PPSA), which is by reaction of sulfur instead of sodium sulfide as S source with dichlorobenzamide (DCBA) and alkali in polar organic solvent at the atmospheric pressure (called sulfur solution route), is reported in the present paper. The influences of polymerization time, molar ratio of precursors, catalyst and solvent upon the polymer were investigated. To seek the best parameters of polymerization, orthogonal design was employed in the experiments. The results indicate that the molar ratio of precursors is the most significant effect on both of viscosity and yield of the polymer. The suitable parameters for preparing the related polymer are presented. The polymer was characterized by IRspectrum, 1HNMRspectrum and Raman spectrum, etc.展开更多
When α-ketothioanilide reacts with o-phenylenediamine,there are two competing reactions.One is condensation which forms substituted quinoxaline and the other is substitution which forms substituted quinoxaline-2-thio...When α-ketothioanilide reacts with o-phenylenediamine,there are two competing reactions.One is condensation which forms substituted quinoxaline and the other is substitution which forms substituted quinoxaline-2-thione·By controlling the reaction condition,we can obtain either quinoxaline or quinoxaline-2-thione as the main product.展开更多
The thermal stability of oil gels formed by styrene-butadiene-styrene triblock copolymer (SBS) was improved by adding a small amount of poly(phenylene ether) (PPE), which has a higher glass transition temperature (Tg)...The thermal stability of oil gels formed by styrene-butadiene-styrene triblock copolymer (SBS) was improved by adding a small amount of poly(phenylene ether) (PPE), which has a higher glass transition temperature (Tg). In naphthenic oil which is a good solvent for the butadiene blocks, but a non-solvent for the styrene blocks and PPE, PPE was selectively included into styrene blocks in SBS, and induced the increase of the Tg of these blocks. The melting temperature determined by viscoelastic measurements and softening temperature of the gels were elevated by adding PPE, while no significant change was detected by adding polystyrene. The gel became opaque by adding PPE, and partially separated phases were observed by field emission scanning electron microscopy (FE-SEM). The dependence of the viscoelastic behavior on the PPE concentration can be explained by the structural change observed by FE-SEM.展开更多
Kover and Batt [J. Magn. Reson., 73(1987), 512] first determined the distances between the quaternary carbons and the selected protons in a rigid sphere molecule by <sup>13</sup>C spinlattice relaxation ...Kover and Batt [J. Magn. Reson., 73(1987), 512] first determined the distances between the quaternary carbons and the selected protons in a rigid sphere molecule by <sup>13</sup>C spinlattice relaxation experiments (<sup>1</sup>H selective π pulse and <sup>13</sup>C π pulse were simultaneously used). We measure the selective <sup>13</sup>C spin-lattice relaxation rates of poly(2, 6-dimethyl-1, 4-phenylene oxide) by using the same experimental method. When the methyl protons are selectively π-excited, the <sup>13</sup>C spin-lattice relaxation rates of the quaternary carbon with 132.4展开更多
Achieving low friction and wear of poly(phenylene sulfide)(PPS) without using fillers or blending is a challenging task, but one of considerable practical importance. Here we describe how neat PPS with high tribologic...Achieving low friction and wear of poly(phenylene sulfide)(PPS) without using fillers or blending is a challenging task, but one of considerable practical importance. Here we describe how neat PPS with high tribological performance is achieved by manipulating processing parameters(pressure, flow and temperature). The key to achieving high tribological performance is comparatively high molecular chain orientation, realized in neat PPS, at high shear rates and low pressure. The friction coefficient and wear rate are as low as ~0.3 and~10^(-6) mm^(3)·N^(-1)·m^(-1), respectively, which break the record for neat PPS. These values are even better than those for PPS-based blends and comparable to PPS composites. Further studies show, for the first time, that wear rate decreases exponentially with increasing molecular chain orientation, prompting us to revise the classical Archard's law by including the effect of molecular chain orientation. These findings open the possibility of using neat PPS in highly demanding tribological applications.展开更多
Poly(phenylene ethynylene)s (P1) with 4-vinylaniline pendant groups were successfully prepared by the Sonogashira coupling polymerization bevween 1,4-diethynyl-2,5-bis(pentyloxy)benzene and 4-[2-(2,5-dibromophe...Poly(phenylene ethynylene)s (P1) with 4-vinylaniline pendant groups were successfully prepared by the Sonogashira coupling polymerization bevween 1,4-diethynyl-2,5-bis(pentyloxy)benzene and 4-[2-(2,5-dibromophenyl)vinyl]- aniline. In comparison with its analogue P2 without amino group, the emission of F'I is only enihanced by aggregation when adding n-hexane into its THF solution, exhibiting an aggregation-induced emission enhancement (AIEE) effect. When methanol or water instead of hexane was added into THF solution, P1, however, didn't show AII:~E. The results indicated that amino groups strengthen the inter-chain and intra-chain interactions in P1 and restrict the no^-radiative energy transition. This strategy can provide a platform for developing highly sensitive and efficient bio- and chemosensors.展开更多
Based on an analysis of the 1H NMR,FT-IR,UV-vis spectra,a chiral trimeric phenylene vinylene derivative(ChTPV) synthesized by a Wittig reaction was determined to have a trans-cis configuration, and it could be isome...Based on an analysis of the 1H NMR,FT-IR,UV-vis spectra,a chiral trimeric phenylene vinylene derivative(ChTPV) synthesized by a Wittig reaction was determined to have a trans-cis configuration, and it could be isomerized to the trans-trans isomer when treated with iodine.The melting point of ChTPV with a trans-trans configuration increased by 162.1℃compared to the trans-cis isomer,and the ChTPV with trans-trans configuration exhibited the typical liquid-crystalline texture of the smectic A in the heating process.The results indicated that the molecular configuration can influence the formation of the liquid crystalline phase of ChTPV.展开更多
Cholesteryl trimeric phenylene vinylene (ChoI-TPV) has been synthesized and characterized. The self- assembly behaviors of ChoI-TPV in THF/H20 system at different water content (water content: 40% and 80%) and di...Cholesteryl trimeric phenylene vinylene (ChoI-TPV) has been synthesized and characterized. The self- assembly behaviors of ChoI-TPV in THF/H20 system at different water content (water content: 40% and 80%) and different solute concentration (solute concentration: 1.0 ×10^-5 mol/L and saturated concentration) were studied using UV-vis spectrophotometry, photoluminescence spectrophotometry, and circular dichroism spectroscopy. Based on an analysis of the UV-vis and photoluminescence spectra, Chol-TPV shows the typical H-type aggregation at saturated concentration in 80% aqueous THF. However, ChoI-TPV shows the non-typical H-type aggregation under other conditions. The circular dichroism signal suggests that the Chol-TPV exists in the right handed helical architectures with high water content at a concentration of 1.0 × 10^-5 mol/L, and a helix inversion was found at saturated concentration.展开更多
基金This work were supported by the National Natural Science Foundation of China (Project No29992530-6) and the Natural Science Foundation of Guangdong Province (Grant No. 990623).
文摘It was found that traces of water in the reaction medium would result in a great increase of gel and a decrease of Molecular weight of the poly(2-methoxy,5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) during the polymerization, which ultimately led to inferior film qualities and device properties. The device (ITO/PEDOT/MEH-PPV/Ba/Al) with MEH-PPV prepared under dry conditions has an external quantum efficiency of above 2.0%.
文摘Both aliphatic and aromatic ketones are efficiently transfer-hydrogenated by propan-2-ol under mild conditions in the presence of a catalytic amount of poly(2,6-dimethyl-1,4-Phenylene oxide) (PPO) anchored ruthenium complex and sodium hydroxide. An important feature of this polymer anchored catalyst is its stability in air.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50473042)the Beijing Natural Science Foundation (No. 2042017).
文摘A novel hyperbranched poly(phenylene oxide) (HPPO) with phenolic terminal groups was prepared from 4-bromo-4',4"-dihydroxytriphenylmethane as AB2 monomer in dimethylsulfoxide (DMSO) via a modified Ullmann reaction. The molecular weight and polydispersity (PD) of the resulting polymers increased with increasing reaction time. In the presence of core molecules (bisphenol A and 1,3,5-trihydroxybenzene), which have the similar molecular backbones to the reactive monomer, the molecular weight could be controlled by varying the core-to-monomer ratio. Incorporation of a very small amount of core molecules could lead to a higher molecular weight as compared with that without the addition of core molecules. However, when the core content reached certain extent, the molecular weight would decrease with the further increase in the core content. A new similar behavior of control over the PD was also obtained. The resulting polymers were characterized by ^1H-NMR, ^13C-NMR, FT-IR, and GPC.
文摘Poly(phenylene sulfide/ether) (PPSE) was synthesized from 4,4'-dihydroxydiphenyl sulfide and 4,4'-dichlorodiphenyl sulfide in solution by nucleophilic substitution reaction. The resulting polymer was characterized by viscosity measurement, elemental analysis, FT-IR, ^1H NMR, X-ray diffraction and thermal analysis. The results showed that the viscosities of the resulting polymer were above 0.68 dL/g, and the linear chain structure of product was confirmed. PPSE had the same reflex indices as poly(p-phenylene sulfide), an orthorhombic crystalline with unit cell a=0.853, b=0.562, c=1.026nm. The melting temperature, glass transition temperature and initial decomposition temperature were found to be 228℃, 85℃ and 325℃, respectively. The product was soluble in common organic solvents such as NMP, N, N'-dimethylformamide, N, N'-dimethylacetamide and 1,2-dichloroethane.
基金Supported by the Chinese Postdoctoral Foundation.
文摘In this paper the percolation theory is employed to study the insulator-to-conductortransition in sulphonated poly(phenylene oxide)(SPPO) polymer membranes.The membranes withdifferent sulphonation degree were prepared and infrared characterized.The transition thresholdwas calculated by the experimental data of membrane conductivities and the coordination numberwas thus estimated.The functional group-SO<sub>3</sub>H distribution in the membrane was evaluated inaccordance with the calculations and showed a non-random dispersion on the microscopic scale.
文摘Poly(phenylene sulfide amide) (PPSA) has been synthesized by using sulfur as S source which reacts with dichlorobenzamide (DCBA) and alkali in polar organic solvent at the atmospheric pressure. The polymer structures were determined by elemental analysis, FT-IR and H-1-NMR. It is shown that the yielded polymer has linear structure and its structure unit is -p-C6H4-CONH -p-C6H4-S-. The polymer morphology was studied by X-ray diffraction and polarized microscopy. The results show that PPSA is a crystalline polymer and its spherulites are the aggregation of nontwisting lamella or micro-thread structure. Under shearing force, these crystals are dispersed to form micro-fibrillar structure. The decomposition kinetics of PPSA was also studied at different heating rates. The decomposition energy of PPSA is higher than that of PPS.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10804064 and 10674084)
文摘A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecules accumulated in the vicinity as recently reported by Na et al. [Nanotechnology 18 424001 (2007)]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H2O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H2O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H2O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.
文摘The apparent solubility (S), concentration-average diffusivity (D), and permeability (P), for C0_2, CH_4 and N_2 through PPO and aryl-brominated PPO at 35℃ for pressure ranging from 1 to 26 atm are reported. It is found that P, D, and S of the membranes to all the three gases vary with the extent of bromination. S increases with the increase of the percent of bromine in each case, but D to CO_2 increases remarkably only at higher degree of brominafion, and therefore, P to CO_2 is increased by more than 100% over a wide range ofpressure in the case. The solubility data are well described by the dual mode sorption model. It is found that the gas molecules sorbed by the Langmuir mode are relatively more immobilized and the contribution of the nonequilibrinm character of the polymer to gas permeation increases obviously for CO_2 and is hardly changed for CH_4 with increasing bromine content. These observations are interpreted in terms of changes in specific free volume (SFV)and the cohesive energy density (CED) of the polymers.
基金The authors graefully acknowledge financial support from the National Natural Science Foundation of China (29976040), Natural Science Foundation of Anhui Province (99045431), Key Foundation of Anhui Educational Comrnittee (2000j1255zd), the Foundation of
文摘This paper investigates the possibility of attaining sulphonated poly(phenylene oxide) (SPPO) with a relativelyhigher sulfonation degree. To achieve this aim, the approach we adopt is to improve the solubility of the final product in themixed solvent so that the sulfonation may take place between the bulk solutions and PPO powders even at higher sulfonationdegree. It is shown that the addition of a proper amount of dimethyl formide (DMF) to the conventional PPO-chloroformsystem can actually enhance the sulfonation effect. The solvent composition is then correlated with the sulfonation degreebased on the solubility parameters. It is interesting to find that solubility parameters between the mixed solvent and theprecipitated products keep an approximately unchanged value at about 4.9, which is just equal to that when pure chloroformis used, though the solubility parameters of both solvents increase with the content of DMF in solution. This may be the mainreason why the addition of DMF can reduce the precipitation and improve the ion exchange capacity (IEC) of SPPOpolymer.
基金Supported by the National Natural Science Foundation of China(Nos.20125421,90101026,50303007,20474024 and 50473001)Ministry of Science and Technology of China(No.2002CB6134003).
文摘A soluble poly(meta-phenylene) derivative with rigid twisted biphenyl unit was synthesized by the Yamamoto coupling reaction. The polymer is soluble in common organic solvents, and the number-average molecular weight is about 6500. The UV-Vis and quantum chemical calculation indicate that the different conformation segments named "conformers" exist in the polymer backbones; it was also further confirmed by the single crystal X-ray diffraction study of the dimeric model compound. The π-π^* transition of biphenyl segments of twisted and planar conformations made the polymer exhibit a strong absorption around 256 nm and a weak absorption at about 300 nm. Furthermore, the polymer exhibits a strong UV photoluminescence at 372 nm when the excitation wavelengths are longer than 300 run. The ultraviolet-emitting electroluminescence(EL) device with the single layer structure shows EL λmax of the derivative at 370 nm.
文摘A new process for preparing poly(phenylene sulfide amide, PPSA), which is by reaction of sulfur instead of sodium sulfide as S source with dichlorobenzamide (DCBA) and alkali in polar organic solvent at the atmospheric pressure (called sulfur solution route), is reported in the present paper. The influences of polymerization time, molar ratio of precursors, catalyst and solvent upon the polymer were investigated. To seek the best parameters of polymerization, orthogonal design was employed in the experiments. The results indicate that the molar ratio of precursors is the most significant effect on both of viscosity and yield of the polymer. The suitable parameters for preparing the related polymer are presented. The polymer was characterized by IRspectrum, 1HNMRspectrum and Raman spectrum, etc.
文摘When α-ketothioanilide reacts with o-phenylenediamine,there are two competing reactions.One is condensation which forms substituted quinoxaline and the other is substitution which forms substituted quinoxaline-2-thione·By controlling the reaction condition,we can obtain either quinoxaline or quinoxaline-2-thione as the main product.
文摘The thermal stability of oil gels formed by styrene-butadiene-styrene triblock copolymer (SBS) was improved by adding a small amount of poly(phenylene ether) (PPE), which has a higher glass transition temperature (Tg). In naphthenic oil which is a good solvent for the butadiene blocks, but a non-solvent for the styrene blocks and PPE, PPE was selectively included into styrene blocks in SBS, and induced the increase of the Tg of these blocks. The melting temperature determined by viscoelastic measurements and softening temperature of the gels were elevated by adding PPE, while no significant change was detected by adding polystyrene. The gel became opaque by adding PPE, and partially separated phases were observed by field emission scanning electron microscopy (FE-SEM). The dependence of the viscoelastic behavior on the PPE concentration can be explained by the structural change observed by FE-SEM.
文摘Kover and Batt [J. Magn. Reson., 73(1987), 512] first determined the distances between the quaternary carbons and the selected protons in a rigid sphere molecule by <sup>13</sup>C spinlattice relaxation experiments (<sup>1</sup>H selective π pulse and <sup>13</sup>C π pulse were simultaneously used). We measure the selective <sup>13</sup>C spin-lattice relaxation rates of poly(2, 6-dimethyl-1, 4-phenylene oxide) by using the same experimental method. When the methyl protons are selectively π-excited, the <sup>13</sup>C spin-lattice relaxation rates of the quaternary carbon with 132.4
基金financially supported by the National Natural Science Foundation of China (Nos. 21676217, 52003215, 21978240 and 52003219)Youth Project of Basic Research Program of Natural Science in Shaanxi Province (No. 2020JQ179)+1 种基金the Fundamental Research Funds for the Central Universities (Nos. 3102018AX004 and 3102017jc01001)the Open Testing Foundation of the Analytical & Testing Center of Northwestern Polytechnical University (No. 2020T020)。
文摘Achieving low friction and wear of poly(phenylene sulfide)(PPS) without using fillers or blending is a challenging task, but one of considerable practical importance. Here we describe how neat PPS with high tribological performance is achieved by manipulating processing parameters(pressure, flow and temperature). The key to achieving high tribological performance is comparatively high molecular chain orientation, realized in neat PPS, at high shear rates and low pressure. The friction coefficient and wear rate are as low as ~0.3 and~10^(-6) mm^(3)·N^(-1)·m^(-1), respectively, which break the record for neat PPS. These values are even better than those for PPS-based blends and comparable to PPS composites. Further studies show, for the first time, that wear rate decreases exponentially with increasing molecular chain orientation, prompting us to revise the classical Archard's law by including the effect of molecular chain orientation. These findings open the possibility of using neat PPS in highly demanding tribological applications.
基金financially supported by the National Natural Scientific Foundation of China(Nos.51073026 and 21004004)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Nos.2009110111003 l and 20101101120029)Excellent Young Scholars Research Fund of Beijing Institute of Technology(No.2009Y0914)
文摘Poly(phenylene ethynylene)s (P1) with 4-vinylaniline pendant groups were successfully prepared by the Sonogashira coupling polymerization bevween 1,4-diethynyl-2,5-bis(pentyloxy)benzene and 4-[2-(2,5-dibromophenyl)vinyl]- aniline. In comparison with its analogue P2 without amino group, the emission of F'I is only enihanced by aggregation when adding n-hexane into its THF solution, exhibiting an aggregation-induced emission enhancement (AIEE) effect. When methanol or water instead of hexane was added into THF solution, P1, however, didn't show AII:~E. The results indicated that amino groups strengthen the inter-chain and intra-chain interactions in P1 and restrict the no^-radiative energy transition. This strategy can provide a platform for developing highly sensitive and efficient bio- and chemosensors.
基金supported by the National Natural Science Foundation of China(No.51173155)the Hebei Province Science Foundation of China(No.E2010001182)
文摘Based on an analysis of the 1H NMR,FT-IR,UV-vis spectra,a chiral trimeric phenylene vinylene derivative(ChTPV) synthesized by a Wittig reaction was determined to have a trans-cis configuration, and it could be isomerized to the trans-trans isomer when treated with iodine.The melting point of ChTPV with a trans-trans configuration increased by 162.1℃compared to the trans-cis isomer,and the ChTPV with trans-trans configuration exhibited the typical liquid-crystalline texture of the smectic A in the heating process.The results indicated that the molecular configuration can influence the formation of the liquid crystalline phase of ChTPV.
基金supported by the National Science Foundation of China(No.51173155)the Hebei Province Science Foundation of China(No.F2011203160)
文摘Cholesteryl trimeric phenylene vinylene (ChoI-TPV) has been synthesized and characterized. The self- assembly behaviors of ChoI-TPV in THF/H20 system at different water content (water content: 40% and 80%) and different solute concentration (solute concentration: 1.0 ×10^-5 mol/L and saturated concentration) were studied using UV-vis spectrophotometry, photoluminescence spectrophotometry, and circular dichroism spectroscopy. Based on an analysis of the UV-vis and photoluminescence spectra, Chol-TPV shows the typical H-type aggregation at saturated concentration in 80% aqueous THF. However, ChoI-TPV shows the non-typical H-type aggregation under other conditions. The circular dichroism signal suggests that the Chol-TPV exists in the right handed helical architectures with high water content at a concentration of 1.0 × 10^-5 mol/L, and a helix inversion was found at saturated concentration.