Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited p...Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited pH dependant swelling and solute diffusivity due to the formation or disruption of hydrogen bonded complexation between methacrylic acid (MAA) and etheric (EO). In neutral and basic conditions (above the swelling transition pH), the copolymer swelling was greatly higher than acid condition. In complexed hydrogels, the diffusion coefficients of vitamin B12 (VB12) were in the range of 10-10 to 10-7 cm2s-1; While in uncomplexed hydrogels, the values were about 210-6 cm2s-1. The comonomer composition and synthesis conditions have great effect on the structure, and thereby, swelling and solute diffusion characteristics of the resultant hydrogels. For the copolymers with composition of less than or more than 1:1 MAA/EO molar ratio, the plot of lnD vs 1/H-1 followed two different linear equations of 慺ree volume theory? respectively.展开更多
A number of studies have been reported on the applications of supercritical fluids to polymeric processes. The presence of volatiles can affect the end-use properties of polymer materials. Therefore, these volatiles m...A number of studies have been reported on the applications of supercritical fluids to polymeric processes. The presence of volatiles can affect the end-use properties of polymer materials. Therefore, these volatiles must be reduced to a level below the maximum permissible limit. Conventional heat-relevant techniques for polymer devolatilization sometimes have limited effectiveness. Devolatilization with supercritical fluids, however, can enhance removal of volatiles from polymers. A model for diffusion-limited extraction is used to characterize dynamic supercritical fluid devolatilization of spherical polymer particles. The rate of supercritical fluid devolailization for styrene/polystyrene system is measured at 343 K and 18 MPa and at CO2 flow rate of 1.93, 3.27 and 5.62 L·min^-1, respectively. The model analysis, which is consistent with experimental results, indicates that the supercritical fluid devolatilization is not solubility-limited but diffusion-limited when CO2 flow rate is above 4.00 L·min^-1.展开更多
The diffusion of an antifogging agent, EO/PO (epoxyethane/epoxypropane) copolymer, through apolyethylene PE film was studied using a simple experimental system. It was found that the temperature, concentration of anti...The diffusion of an antifogging agent, EO/PO (epoxyethane/epoxypropane) copolymer, through apolyethylene PE film was studied using a simple experimental system. It was found that the temperature, concentration of antifogging agent, crystallinity of PE film and film thickness affect the diffusion process.展开更多
This paper describes the effects of fire on durability of reinforced concrete structures, and points out that fire not only damages the chemical composition and physical structure of concrete by high temperature, but ...This paper describes the effects of fire on durability of reinforced concrete structures, and points out that fire not only damages the chemical composition and physical structure of concrete by high temperature, but also leads to an additional risk due to the generation of polyvinyl chloride (PVC) combustion gases. A mathematical model is proposed to calculate chloride ingress profiles in fire damaged concrete, so as to explore the service life prediction of the structure. Rapid Chloride Migration (RCM) test was carried out to determine the chloride diffusion coefficients for the application of the mathematical model. Finally, the detected results of a reported case testified to the validity of the mathematical model.展开更多
The grand canonical Monte Carlo (GCMC), the canonical Monte Carlo by using equal probability perturbation, and the molecular dynamics (MD) methods were used to study the capillary phase-transition (capillary condensat...The grand canonical Monte Carlo (GCMC), the canonical Monte Carlo by using equal probability perturbation, and the molecular dynamics (MD) methods were used to study the capillary phase-transition (capillary condensation and evaporation) and self-diffusion for a simple Lennard-Jones model of ethylene confined in slit carbon pores of 2.109 nm at temperatures between 141.26 K and 201.80 K. The critical point of capillary phase-transition was extrapolated by the critical power law and the law of rectilinear diameter from the capillary phase-transition data in the near critical region. The effects of temperature and fluid density on the parallel self-diffusion coefficients of ethylene molecules confined in the slit carbon pores were examined. The results showed that the parallel selfdiffusion coefficients in the capillary phase transition area strongly depended on the fluids local densities in the slit carbon pores.展开更多
Structural manipulation of graphene oxide (GO) building blocks has been widely researched. Concerning GO membranes for separation applications, the validity and maintenance of their microscopic structures in the chemi...Structural manipulation of graphene oxide (GO) building blocks has been widely researched. Concerning GO membranes for separation applications, the validity and maintenance of their microscopic structures in the chemical environment are pivotal for effective separation at the molecular scale. Cationic interactions with both aromatic rings and oxygenated functional groups of GO make metal ions intriguing for physically and chemically structural reinforcement. By filtrating GO suspension through the substrate loaded with cations, stacking o f GO nanosheets and diffusion of cations steadily evolve simultaneously in an aqueous environment without flocculation. Thus, thin and homogeneous GO membrane is obtained. Divalent and monovalent cations were studied regarding their interactions with GO, and the performance of correspondingly functionalized membranes was evaluated. The divalent cation-stabilized membranes have favorable stability in the separation of water/ethanol. This facile fabrication and functionalization method may also be applicable for structure construction of other two-dimensional materials.展开更多
文摘Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited pH dependant swelling and solute diffusivity due to the formation or disruption of hydrogen bonded complexation between methacrylic acid (MAA) and etheric (EO). In neutral and basic conditions (above the swelling transition pH), the copolymer swelling was greatly higher than acid condition. In complexed hydrogels, the diffusion coefficients of vitamin B12 (VB12) were in the range of 10-10 to 10-7 cm2s-1; While in uncomplexed hydrogels, the values were about 210-6 cm2s-1. The comonomer composition and synthesis conditions have great effect on the structure, and thereby, swelling and solute diffusion characteristics of the resultant hydrogels. For the copolymers with composition of less than or more than 1:1 MAA/EO molar ratio, the plot of lnD vs 1/H-1 followed two different linear equations of 慺ree volume theory? respectively.
基金Supported by the National Natural Science Foundation of China (No. 20576123).
文摘A number of studies have been reported on the applications of supercritical fluids to polymeric processes. The presence of volatiles can affect the end-use properties of polymer materials. Therefore, these volatiles must be reduced to a level below the maximum permissible limit. Conventional heat-relevant techniques for polymer devolatilization sometimes have limited effectiveness. Devolatilization with supercritical fluids, however, can enhance removal of volatiles from polymers. A model for diffusion-limited extraction is used to characterize dynamic supercritical fluid devolatilization of spherical polymer particles. The rate of supercritical fluid devolailization for styrene/polystyrene system is measured at 343 K and 18 MPa and at CO2 flow rate of 1.93, 3.27 and 5.62 L·min^-1, respectively. The model analysis, which is consistent with experimental results, indicates that the supercritical fluid devolatilization is not solubility-limited but diffusion-limited when CO2 flow rate is above 4.00 L·min^-1.
基金Supported by the National Natural Science Foundation of China (No. 39830230).
文摘The diffusion of an antifogging agent, EO/PO (epoxyethane/epoxypropane) copolymer, through apolyethylene PE film was studied using a simple experimental system. It was found that the temperature, concentration of antifogging agent, crystallinity of PE film and film thickness affect the diffusion process.
基金Project (No. 50538070) supported by the National Natural ScienceFoundation of China
文摘This paper describes the effects of fire on durability of reinforced concrete structures, and points out that fire not only damages the chemical composition and physical structure of concrete by high temperature, but also leads to an additional risk due to the generation of polyvinyl chloride (PVC) combustion gases. A mathematical model is proposed to calculate chloride ingress profiles in fire damaged concrete, so as to explore the service life prediction of the structure. Rapid Chloride Migration (RCM) test was carried out to determine the chloride diffusion coefficients for the application of the mathematical model. Finally, the detected results of a reported case testified to the validity of the mathematical model.
基金the National Science Foundation of China (NSFC) the China Petrochemical Corporation (SINOPEC) (No. 29792077).
文摘The grand canonical Monte Carlo (GCMC), the canonical Monte Carlo by using equal probability perturbation, and the molecular dynamics (MD) methods were used to study the capillary phase-transition (capillary condensation and evaporation) and self-diffusion for a simple Lennard-Jones model of ethylene confined in slit carbon pores of 2.109 nm at temperatures between 141.26 K and 201.80 K. The critical point of capillary phase-transition was extrapolated by the critical power law and the law of rectilinear diameter from the capillary phase-transition data in the near critical region. The effects of temperature and fluid density on the parallel self-diffusion coefficients of ethylene molecules confined in the slit carbon pores were examined. The results showed that the parallel selfdiffusion coefficients in the capillary phase transition area strongly depended on the fluids local densities in the slit carbon pores.
基金financially supported by the National Natural Science Foundation of China (21476107, 21490585, 21776125 and 51861135203)the Innovative Research Team Program by the Ministry of Education of China (IRT17R54)the Topnotch Academic Programs Project of Jiangsu Higher Education Institutions (TAPP)
文摘Structural manipulation of graphene oxide (GO) building blocks has been widely researched. Concerning GO membranes for separation applications, the validity and maintenance of their microscopic structures in the chemical environment are pivotal for effective separation at the molecular scale. Cationic interactions with both aromatic rings and oxygenated functional groups of GO make metal ions intriguing for physically and chemically structural reinforcement. By filtrating GO suspension through the substrate loaded with cations, stacking o f GO nanosheets and diffusion of cations steadily evolve simultaneously in an aqueous environment without flocculation. Thus, thin and homogeneous GO membrane is obtained. Divalent and monovalent cations were studied regarding their interactions with GO, and the performance of correspondingly functionalized membranes was evaluated. The divalent cation-stabilized membranes have favorable stability in the separation of water/ethanol. This facile fabrication and functionalization method may also be applicable for structure construction of other two-dimensional materials.
