Poly(lithium propionate methyl siloxane )as a single-ion carrier source was synthesized. The crosslinked film showed lower lithium ionic conductivity at room temperature (about 10^(-10) S/cm). However,the lithium ioni...Poly(lithium propionate methyl siloxane )as a single-ion carrier source was synthesized. The crosslinked film showed lower lithium ionic conductivity at room temperature (about 10^(-10) S/cm). However,the lithium ionic conductivity was obviously increased by blending with high polar polymers such as polyethylene oxide, poly (methylsiloxane - co- ethylene oxide) and poly (methylsiloxane- g- ethylene oxide). In the blend system a high conductivity of 10^(-7)-10^(-5) Scm^(-1) at room temperature was obtained and the single-ion conductivity was deeply influenced by the content of the poly (lithium propionate methyl siioxane). The dc ionic conductivity of the flexible crosslinked films is more stable over time.展开更多
A new comblike polymer host for polymer electrolyte was synthesized by reacting monomethyl ether of poly(ethylene glycol) with poly(vinyl methyl ether-alt-maleic anhydride) and endcapping the residual carboxylic acid ...A new comblike polymer host for polymer electrolyte was synthesized by reacting monomethyl ether of poly(ethylene glycol) with poly(vinyl methyl ether-alt-maleic anhydride) and endcapping the residual carboxylic acid with methanol. Butanone was selected as a solvent for the esterification in order to obtain a completely soluble product. The synthesis process was traced through by LR. Compared with the model compounds, the presumed structure of this comblike polymer has been proved to be valid by C-13 NMR The comb polymer is a white rubbery solid. It can be dissolved in butanone and THF, and manifests good film forming ability.展开更多
Compatibility of poly (vinyl acetate) (PVAc) with poly (methyl methacrylate) (PMMA) mixtures has been studied by using nuclear magnetic relaxation, differential scanning calorimeter and small-angle X-ray scattering te...Compatibility of poly (vinyl acetate) (PVAc) with poly (methyl methacrylate) (PMMA) mixtures has been studied by using nuclear magnetic relaxation, differential scanning calorimeter and small-angle X-ray scattering techniques. The nuclear magnetic relaxation time T_1's were measured as a function of composition in blends of PMMA and PVAc prepared from chloroform solution. The results show that the system is miscible for casting from chloroform solution.展开更多
The piezoresistive behavior of carbon black (CB) filled poly(methyl vinyl siloxane) (PMVS) vulcanites under uniaxial compression was studied.At filler weight frac- tions φ slightly above the percolation threshold φc...The piezoresistive behavior of carbon black (CB) filled poly(methyl vinyl siloxane) (PMVS) vulcanites under uniaxial compression was studied.At filler weight frac- tions φ slightly above the percolation threshold φc,resistance first increased with pressure and then turned to decrease at a critical compressive stress,exhibiting a positive pressure co- efficient of resistance (PPCR) and a negative pressure coeffi- cient of resistance (NPCR) effects ,respectively.The NPCR effect became much more pronounced at φ>>φc,while com- pressive cycles facilitated the occurrence of the weak PPCR effect during compression.The PPCR-NPCR transition was a process related to true stress.It is believed that the changes of microstructure in the percolating network,i.e. the breakdown and the reformation of infinite conducting clusters,under pressure would be responsible for the uniaxial piezoresis- tance and the plastic deformation of the filled vulcanites.展开更多
Atomistic detailed hydration structures of poly(vinyl methyl ether)(PVME) have been investigated by molecular dynamics simulations under 300 K at various concentrations. Both radial distribution functions and the dist...Atomistic detailed hydration structures of poly(vinyl methyl ether)(PVME) have been investigated by molecular dynamics simulations under 300 K at various concentrations. Both radial distribution functions and the distance distributions between donors and acceptors in hydrogen bonds show that the hydrogen bonds between the polymer and water are shorter by 0.005 nm than those between water molecules. The Quasi-hydrogen bonds take only 7.2% of the van der Waals interaction pairs. It was found the hydrogen bonds are not evenly distributed along the polymer chain,and there still exists a significant amount(10%) of ether oxygen atoms that are not hydrogen bonded to water at a concentration as low as 3.3%. This shows that in polymer solutions close contacts occur not only between polymer chains but also between chain segments within the polymer,which leads to inefficient contacts between ether oxygen atoms and water molecules. Variation of the quasi-hydrogen bonds with the concentration is similar to that of hydrogen bonds,but the ratio of the repeat units forming quasi-hydrogen bonds to those forming hydrogen bonds approaches 0.2. A transition was found in the demixing enthalpy at around 30% measured by dynamic testing differential scanning calorimetry(DTDSC) for aqueous solutions of a mono-dispersed low molecular weight PVME,which can be related to the transition of the fractions of hydrogen bonds and quasi-hydrogen bonds at ～27%. The transition of the fractions of hydrogen bonds and quasi-hydrogen bonds at ～27% can be used to explain the demixing enthalpy transition at 30% at a molecular scale. In addition,at the concentration of 86%,each ether oxygen atom bonded with water is assigned 1.56 water molecules on average,and 'free' water molecules emerge at the concentration of around 54%.展开更多
The phase behavior of the aqueous solution of poly(vinyl methyl ether) (PVME) sensitive to temperature and the modification of the behavior by using poly(acrylic acid) (PAA) have been studied by ultrasonic attenuation...The phase behavior of the aqueous solution of poly(vinyl methyl ether) (PVME) sensitive to temperature and the modification of the behavior by using poly(acrylic acid) (PAA) have been studied by ultrasonic attenuation measurements and fluorescence probe techniques. It has been observed that PVME solution is transparent at room temperature and becomes turbid upon heating. The solution turns clear again as soon as the temperature is decreased to room temperature. The heating and cooling process can be repeated for many times. The phase behavior of the solution sensitive to temperature is attributed to the conformational changes of the polymer. PVME may adopt an open coil conformation at room temperature. With this conformation, the polymer is well miscible with the solvent, water, and thereby the system is a real solution. The polymer may adopt a compact coil conformation when the temperature is higher than a specific value, which is called the LCST (the lower critical solution temperature) of PVME. In this case, the polymer tangles to each other and forms various aggregates, which can scatter incident light and ultrasonic waves greatly, resulting in the phase separation. Introduction of PAA decreases the temperature sen-sitivity of the phase behavior of the polymer. The nature of the inhibition is attributed to the complexation of PAA with PVME and the strong hydrophilicity of PAA. Results from fluorescence probe studies are in accordance with those from ultrasonic attenuation measurements, indicating again that the ultrasonic attenuation method can be suc-cessfully used for the qualitative studies of polymer conformations and complexation between polymers.展开更多
Dynamic rheological properties of poly(methyl vinyl)siloxane(PMVS) filled with ultratra silica (SiO 2) were analyzed on an advanced rheometric expansion system(ARES) at 25 ℃ by varying the strain (γ) and the frequen...Dynamic rheological properties of poly(methyl vinyl)siloxane(PMVS) filled with ultratra silica (SiO 2) were analyzed on an advanced rheometric expansion system(ARES) at 25 ℃ by varying the strain (γ) and the frequency (ω). The results show that an incorporation of 5% SiO 2 into PMVS at 25 ℃ could be enough to impact a significant increase on the storage modulus (G′) of the uncured system, which is believed to be caused by the strong interactions among silica fillers. Meanwhile, γ dependence of G′ related to Payne effect was observed upon increasing γ amplitude, and no distinct “second plateau” was observed even the content of SiO 2 approached 20%. We owe this phenomenon partly to the surface esterification of silanols and partly to the unvulcanized PMVS.展开更多
The effect of crosslinking degree on the piezoresistive behavior of carbon black(CB) filled poly(methyl vinyl siloxane)(PMVS) vulcanites under uniaxial compression was studied.The results reveal that increasing the am...The effect of crosslinking degree on the piezoresistive behavior of carbon black(CB) filled poly(methyl vinyl siloxane)(PMVS) vulcanites under uniaxial compression was studied.The results reveal that increasing the amount of crosslinking agent could weaken the negative pressure coefficient of resistance(NPCR) effect at the late stage of compression and enhance the piezoresistivity intensity at a high stresses.The recovery property of resistance was related to the content of CB,the stress level and the degree of crosslinking.It was proved that repeated compression with the same maximum stress level could improve piezoresistive stability considerably.展开更多
基金This work was supported by the National Natural Science Foundation of China
文摘Poly(lithium propionate methyl siloxane )as a single-ion carrier source was synthesized. The crosslinked film showed lower lithium ionic conductivity at room temperature (about 10^(-10) S/cm). However,the lithium ionic conductivity was obviously increased by blending with high polar polymers such as polyethylene oxide, poly (methylsiloxane - co- ethylene oxide) and poly (methylsiloxane- g- ethylene oxide). In the blend system a high conductivity of 10^(-7)-10^(-5) Scm^(-1) at room temperature was obtained and the single-ion conductivity was deeply influenced by the content of the poly (lithium propionate methyl siioxane). The dc ionic conductivity of the flexible crosslinked films is more stable over time.
文摘A new comblike polymer host for polymer electrolyte was synthesized by reacting monomethyl ether of poly(ethylene glycol) with poly(vinyl methyl ether-alt-maleic anhydride) and endcapping the residual carboxylic acid with methanol. Butanone was selected as a solvent for the esterification in order to obtain a completely soluble product. The synthesis process was traced through by LR. Compared with the model compounds, the presumed structure of this comblike polymer has been proved to be valid by C-13 NMR The comb polymer is a white rubbery solid. It can be dissolved in butanone and THF, and manifests good film forming ability.
文摘Compatibility of poly (vinyl acetate) (PVAc) with poly (methyl methacrylate) (PMMA) mixtures has been studied by using nuclear magnetic relaxation, differential scanning calorimeter and small-angle X-ray scattering techniques. The nuclear magnetic relaxation time T_1's were measured as a function of composition in blends of PMMA and PVAc prepared from chloroform solution. The results show that the system is miscible for casting from chloroform solution.
基金This work was supported by the Key Program of the National Natural Science Foundation of China(Grant No.50133020)the National Science Foundation for Distinguished Young Scholars(Grant No.50125312).
文摘The piezoresistive behavior of carbon black (CB) filled poly(methyl vinyl siloxane) (PMVS) vulcanites under uniaxial compression was studied.At filler weight frac- tions φ slightly above the percolation threshold φc,resistance first increased with pressure and then turned to decrease at a critical compressive stress,exhibiting a positive pressure co- efficient of resistance (PPCR) and a negative pressure coeffi- cient of resistance (NPCR) effects ,respectively.The NPCR effect became much more pronounced at φ>>φc,while com- pressive cycles facilitated the occurrence of the weak PPCR effect during compression.The PPCR-NPCR transition was a process related to true stress.It is believed that the changes of microstructure in the percolating network,i.e. the breakdown and the reformation of infinite conducting clusters,under pressure would be responsible for the uniaxial piezoresis- tance and the plastic deformation of the filled vulcanites.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20474073, 20490220, 20674090 and 90612015)National Major Basic Research Project (Grant No. G1999064800)
文摘Atomistic detailed hydration structures of poly(vinyl methyl ether)(PVME) have been investigated by molecular dynamics simulations under 300 K at various concentrations. Both radial distribution functions and the distance distributions between donors and acceptors in hydrogen bonds show that the hydrogen bonds between the polymer and water are shorter by 0.005 nm than those between water molecules. The Quasi-hydrogen bonds take only 7.2% of the van der Waals interaction pairs. It was found the hydrogen bonds are not evenly distributed along the polymer chain,and there still exists a significant amount(10%) of ether oxygen atoms that are not hydrogen bonded to water at a concentration as low as 3.3%. This shows that in polymer solutions close contacts occur not only between polymer chains but also between chain segments within the polymer,which leads to inefficient contacts between ether oxygen atoms and water molecules. Variation of the quasi-hydrogen bonds with the concentration is similar to that of hydrogen bonds,but the ratio of the repeat units forming quasi-hydrogen bonds to those forming hydrogen bonds approaches 0.2. A transition was found in the demixing enthalpy at around 30% measured by dynamic testing differential scanning calorimetry(DTDSC) for aqueous solutions of a mono-dispersed low molecular weight PVME,which can be related to the transition of the fractions of hydrogen bonds and quasi-hydrogen bonds at ～27%. The transition of the fractions of hydrogen bonds and quasi-hydrogen bonds at ～27% can be used to explain the demixing enthalpy transition at 30% at a molecular scale. In addition,at the concentration of 86%,each ether oxygen atom bonded with water is assigned 1.56 water molecules on average,and 'free' water molecules emerge at the concentration of around 54%.
基金the National Natural Science Foundation of China (No. 20173035), the Ministry of Education (No. 03148), and the Natura
文摘The phase behavior of the aqueous solution of poly(vinyl methyl ether) (PVME) sensitive to temperature and the modification of the behavior by using poly(acrylic acid) (PAA) have been studied by ultrasonic attenuation measurements and fluorescence probe techniques. It has been observed that PVME solution is transparent at room temperature and becomes turbid upon heating. The solution turns clear again as soon as the temperature is decreased to room temperature. The heating and cooling process can be repeated for many times. The phase behavior of the solution sensitive to temperature is attributed to the conformational changes of the polymer. PVME may adopt an open coil conformation at room temperature. With this conformation, the polymer is well miscible with the solvent, water, and thereby the system is a real solution. The polymer may adopt a compact coil conformation when the temperature is higher than a specific value, which is called the LCST (the lower critical solution temperature) of PVME. In this case, the polymer tangles to each other and forms various aggregates, which can scatter incident light and ultrasonic waves greatly, resulting in the phase separation. Introduction of PAA decreases the temperature sen-sitivity of the phase behavior of the polymer. The nature of the inhibition is attributed to the complexation of PAA with PVME and the strong hydrophilicity of PAA. Results from fluorescence probe studies are in accordance with those from ultrasonic attenuation measurements, indicating again that the ultrasonic attenuation method can be suc-cessfully used for the qualitative studies of polymer conformations and complexation between polymers.
文摘Dynamic rheological properties of poly(methyl vinyl)siloxane(PMVS) filled with ultratra silica (SiO 2) were analyzed on an advanced rheometric expansion system(ARES) at 25 ℃ by varying the strain (γ) and the frequency (ω). The results show that an incorporation of 5% SiO 2 into PMVS at 25 ℃ could be enough to impact a significant increase on the storage modulus (G′) of the uncured system, which is believed to be caused by the strong interactions among silica fillers. Meanwhile, γ dependence of G′ related to Payne effect was observed upon increasing γ amplitude, and no distinct “second plateau” was observed even the content of SiO 2 approached 20%. We owe this phenomenon partly to the surface esterification of silanols and partly to the unvulcanized PMVS.
文摘The effect of crosslinking degree on the piezoresistive behavior of carbon black(CB) filled poly(methyl vinyl siloxane)(PMVS) vulcanites under uniaxial compression was studied.The results reveal that increasing the amount of crosslinking agent could weaken the negative pressure coefficient of resistance(NPCR) effect at the late stage of compression and enhance the piezoresistivity intensity at a high stresses.The recovery property of resistance was related to the content of CB,the stress level and the degree of crosslinking.It was proved that repeated compression with the same maximum stress level could improve piezoresistive stability considerably.
