Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in a mathematical sense in continuum m...Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in a mathematical sense in continuum mechanics. A power law dependence of shear modulus of polymer melts on detC, referred to as envelope volume, is proposed. Based on those assumptions and the non-linear relation of shear modulus, a phenomenological viscoelastic model is derived. The model is tested in simple shear flow, simple elongational flow, oscillatory shear flow, and relaxation process after flow suddenly stopped. The results show that the model works well to predict the change of internal structure and viscoelastic performance of polymer melts in flow fields.展开更多
AM-AMPS-TAC polymers with different charge distribution are synthesized using acrylamide(AM),2-acrylamido-2-methylpropanesulfonate(AMPS)and 3-acrylamidopropyl trimethylammonium(TAC)at different feed ratios by polymeri...AM-AMPS-TAC polymers with different charge distribution are synthesized using acrylamide(AM),2-acrylamido-2-methylpropanesulfonate(AMPS)and 3-acrylamidopropyl trimethylammonium(TAC)at different feed ratios by polymerization in solution.The salt-responsive behavior,reasons leading to salt-responsiveness,and effects of polymers molecular structure on salt-responsiveness are studied by laboratory experiments to find out the adaptability of the polymers.Rheology test under stepwise shear mode shows that the AM-AMPS-TAC polymers have salt responsiveness,and the closer the feeds of AMPS and ATC,the more significant the salt responsiveness will be.Conformation change of polymers molecular chain under salt stimulus is studied by turbidity test and micro-morphology analysis,and the responsive mechanism is further investigated by intrinsic viscosity test and copolymer composition analysis.Results indicate that the salt-responsive behavior of AM-AMPS-TAC polymers derives from the"curled to expanded"transition of chain conformation under salt stimulus,and this transition is led by the screening effect of salt which weakens polymers intramolecular ionic bond.Application in saturated saltwater drilling fluid shows that the AM90-AMPS5-TAC5 polymer has the best salt-tolerance and temperature-tolerance when used together with fluid loss controller PAC-Lv.The drilling fluid saturated with NaCl can maintain stable viscosity,good dispersion and low fluid loss for long time under 150℃.展开更多
Hyperbranched polymer composed of G1 polyamidoamine (PAMAM) and branched with poly (propylene oxide) (PPO)-block-poly (ethylene oxide) (PEO) was investigated to interact with sodium dodecyl sulfate (SDS) and di-dodecy...Hyperbranched polymer composed of G1 polyamidoamine (PAMAM) and branched with poly (propylene oxide) (PPO)-block-poly (ethylene oxide) (PEO) was investigated to interact with sodium dodecyl sulfate (SDS) and di-dodecyl dimethyl ammonium bromide (DDAB), respectively, by the methods of turbidity titration and analysis, rheology measurements, dynamic light scattering (DLS) and transmission electron microscopy (TEM). It was noticeable that even at extremely low concentration of SDS (even far from the critical micelle concentration (cmc)), the system exhibits high turbidity, indicating that SDS molecules can insert into cationic amine groups and hydrophobic microenvironment, resulting in the formation of polymer-SDS complexes with large size. At the SDS concentration range of below 0.1 mM, the turbidity and cloud point (CP) temperature of the system keep almost invariable, mostly because of the repulsion between SDS molecules and the complexes. And, therefore, the size of the mixed aggregates retains almost constant. In the case of vesicle system of DDAB, the aggregates are in the size of 100 nm - 200 nm and 500 nm - 3000 nm at the concentrations of 30 mM and 100 mM, respectively. However, in the mixture of hyperbranched polymer with DDAB, by comparison, the size is smaller in a binary system than that of in DDAB system. So it is reasonable to infer that DDAB molecules remove from multilamellar vesicles of DDAB to the hydrophobic microenvironment of hyperbranched polymer aggregates, with the addition of the hyperbranched polymer. It leads to the destruction of the gel-like conformation in DDAB system, leading to the shear thinning of the mixture and, as a result, the viscoelastic character of the system is lost in a large degree.展开更多
A new statistical theory based on the rotational isomeric state model describing the chain conformational free energy has been proposed. This theory can be used to predict different tensions of rubber elongation for c...A new statistical theory based on the rotational isomeric state model describing the chain conformational free energy has been proposed. This theory can be used to predict different tensions of rubber elongation for chemically different polymers, and the energy term during the elongation of natural rubber coincides with the experimental one.展开更多
A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patt...A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocityprofiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction byusing the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation ofpolymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simpleshear flow, extensional flow, vortical flow, and mixed flow respectively.展开更多
There has been controversy as to whether the addition of nanoparticles to a polymer melt causes perturbed chain structure of polymers. In this work, the chain conformations of polydimethylsiloxane（PDMS） with additio...There has been controversy as to whether the addition of nanoparticles to a polymer melt causes perturbed chain structure of polymers. In this work, the chain conformations of polydimethylsiloxane（PDMS） with addition of polyhedral oligomeric silsesquioxane（POSS） nanoparticles have been studied using a classical density functional approach. Under the strong interactions of POSS-PDMS, the radius of gyration of PDMS in the nanocomposites can either increase or decline depending on particle loading. After adding nanoparticles with larger size or weaker interactions, both the increasing and the declining amplitudes can be largely suppressed. The results provide a deep understanding of chain conformation in polymer nanocomposites.展开更多
When a polymer chain has only one end group attaching to the boundary and all the other segments are located in the half-space divided by the boundary, it is defined as a tail chain~. Obviously, the model of tail chai...When a polymer chain has only one end group attaching to the boundary and all the other segments are located in the half-space divided by the boundary, it is defined as a tail chain~. Obviously, the model of tail chain represents the simplest form of展开更多
The hydrothermal reaction of Zn（NO3）2·4H2O, cyclohexane-1,2,3,4,5,6-hexacarboxylic acid hydrate （H6LI·H2O, cis-conformation LI： a,e,a,e,a,e） and 2,2＇-bpy yielded a new coordination polymer [Zn2（H2LII...The hydrothermal reaction of Zn（NO3）2·4H2O, cyclohexane-1,2,3,4,5,6-hexacarboxylic acid hydrate （H6LI·H2O, cis-conformation LI： a,e,a,e,a,e） and 2,2＇-bpy yielded a new coordination polymer [Zn2（H2LII）（2,2＇-bpy）]·2H2O（trans-conformation LII： e,e,e,e,e,e）, which was characterized by single-crystal X-ray diffraction, elemental analysis, IR and XRPD（X-ray powder diffraction）. This complex crystallized in the triclinic system, with P1 space group and parameters a=0.66922（5） nm, b=0.97291（8） nm, c=1.22184（9） nm, α=99.0020（10）°, β=99.1300（10）°, γ=99.1910（10）°, V= 0.76176（10） nm3 and Z=2. The structure is a three-dimensional supramolecular network based on linear coordination chains through π-π stacking and hydrogen bonding interactions. The confromation of the starting ligand H6LI transfromed to the H2LII. The complex emits strong luminescence at room temperature.展开更多
The SAW tail chains were studied.The permitted conformational number and the mean square end-to-end distance as a function of the chain length N for such a model tail chain were obtained by computer simulations,includ...The SAW tail chains were studied.The permitted conformational number and the mean square end-to-end distance as a function of the chain length N for such a model tail chain were obtained by computer simulations,including the exact enumeration and Monte Carlo method.These two basic quantities obeyed the relations deduced from the scaling law.The critical exponents and the lattice indexes were given by fitting the data of the computer experiments.It has been shown that there is a certain extension in the size of the SAW tail chains as well as the NRW tail chains in the direction normal to the wall.The normal component of the mean square end-to-end distance is almost twice as large as the parallel component of the short chain SAW.However,as N→∞,the effect of the wall on the chain conformation becomes a little weak because of the self-avoiding behavior for the model.That is quite different from the case of the NRW tail chain.展开更多
The hydrothermal reaction of Cd（OAc）2·2H2O, 4,4＇-bpy and cyclohexane-1,2,4,5-tetracarboxylic acid （H4L） yields a three-dimensional （3D） coordination porous framework [Cd2LI（4,4＇-bpy）1.5（H2O）2]n·2...The hydrothermal reaction of Cd（OAc）2·2H2O, 4,4＇-bpy and cyclohexane-1,2,4,5-tetracarboxylic acid （H4L） yields a three-dimensional （3D） coordination porous framework [Cd2LI（4,4＇-bpy）1.5（H2O）2]n·2nH2O, which was characterized by single-crystal X-ray diffraction （MoKα radiation, λ = 0.71073）, elemental analysis and IR. This complex crystallizes in the monoclinic system, space group C2/c with a = 25.951（3）, b = 11.6618（12）, c = 20.046（2） A, β = 114.863（2）o, V = 5504.4（10）A^3, Z = 8, Dc = 1.900 g/cm^3, Mr = 787.30, μ = 1.615 mm^-1, F（000） = 3128, the final R = 0.0978 and wR = 0.1780. The structure of the complex is a 3D coordination Cd-carboxylate framework consisting of 1D hexagonal channels along the c-axis filled with the bridging 4,4＇-bpy ligands. The 4,4＇-bpy ligands with two kinds of conformations are located alternately in the channels through coordination and hydrogen interactions to support the whole porous framework, in which the conformation-flexible cyclohexane-1,2,4,5-tetracarboxylate ligand adopts the I （e,a,a,e） conformation and acts as a pentadentate ligand to connect five Cd（Ⅱ） atoms via the carboxylate groups in different coordination modes.展开更多
The turbidity variation in artificial water and samples from a water plant was investigated in the presence of organics with different relative molecular mass.The results show that recessive turbidity existed when wat...The turbidity variation in artificial water and samples from a water plant was investigated in the presence of organics with different relative molecular mass.The results show that recessive turbidity existed when water chemical conditions were changing.The formation of turbidity depen-ded on organic relative molecular mass and their conforma-tions on particles.At higher pH and lower ionic strength,the organic chains with a more extended conformation resulted in rising turbidity of the suspension.At lower pH,the reconfor-mation of organics took place due to charge neutralization by the proton,resulting in a decline in turbidity.The addition of NaCl and MgCl_(2) at pH 7.00 also resulted in a decrease of turbidity in the suspension.It is believed that the occurrence of recessive turbidity has a significant influence on the stability of water supply quality.展开更多
The study of interactions between peptides and synthetic polymers has aroused considerable interest recently.In the present paper,the interaction mechanism between adsorbent DMAPAM and two pep-tides,VVRGCTWW(V8)and CT...The study of interactions between peptides and synthetic polymers has aroused considerable interest recently.In the present paper,the interaction mechanism between adsorbent DMAPAM and two pep-tides,VVRGCTWW(V8)and CTWW(C4),was investigated at molecular level by NMR and molecular stimulation.The results demonstrated that the conformation of oligopeptides played a vital role in their adsorption capacity on the adsorbent.Weak interactions could incorporate with each other between V8 and DMAPAM because there was a hydrophobic cleavage in α-helix conformation of V8.So the ad-sorption capacity of DMAPAM to V8 was higher.This was significant to explore the interaction mecha-nism between peptides and biomaterials.展开更多
基金This project is supported by the National Natural Science Foundation of China
文摘Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in a mathematical sense in continuum mechanics. A power law dependence of shear modulus of polymer melts on detC, referred to as envelope volume, is proposed. Based on those assumptions and the non-linear relation of shear modulus, a phenomenological viscoelastic model is derived. The model is tested in simple shear flow, simple elongational flow, oscillatory shear flow, and relaxation process after flow suddenly stopped. The results show that the model works well to predict the change of internal structure and viscoelastic performance of polymer melts in flow fields.
基金Supported by the China National Science and Technology Major Project(2017ZX05009-003,2016ZX05020-004,2016ZX05040-005)
文摘AM-AMPS-TAC polymers with different charge distribution are synthesized using acrylamide(AM),2-acrylamido-2-methylpropanesulfonate(AMPS)and 3-acrylamidopropyl trimethylammonium(TAC)at different feed ratios by polymerization in solution.The salt-responsive behavior,reasons leading to salt-responsiveness,and effects of polymers molecular structure on salt-responsiveness are studied by laboratory experiments to find out the adaptability of the polymers.Rheology test under stepwise shear mode shows that the AM-AMPS-TAC polymers have salt responsiveness,and the closer the feeds of AMPS and ATC,the more significant the salt responsiveness will be.Conformation change of polymers molecular chain under salt stimulus is studied by turbidity test and micro-morphology analysis,and the responsive mechanism is further investigated by intrinsic viscosity test and copolymer composition analysis.Results indicate that the salt-responsive behavior of AM-AMPS-TAC polymers derives from the"curled to expanded"transition of chain conformation under salt stimulus,and this transition is led by the screening effect of salt which weakens polymers intramolecular ionic bond.Application in saturated saltwater drilling fluid shows that the AM90-AMPS5-TAC5 polymer has the best salt-tolerance and temperature-tolerance when used together with fluid loss controller PAC-Lv.The drilling fluid saturated with NaCl can maintain stable viscosity,good dispersion and low fluid loss for long time under 150℃.
文摘Hyperbranched polymer composed of G1 polyamidoamine (PAMAM) and branched with poly (propylene oxide) (PPO)-block-poly (ethylene oxide) (PEO) was investigated to interact with sodium dodecyl sulfate (SDS) and di-dodecyl dimethyl ammonium bromide (DDAB), respectively, by the methods of turbidity titration and analysis, rheology measurements, dynamic light scattering (DLS) and transmission electron microscopy (TEM). It was noticeable that even at extremely low concentration of SDS (even far from the critical micelle concentration (cmc)), the system exhibits high turbidity, indicating that SDS molecules can insert into cationic amine groups and hydrophobic microenvironment, resulting in the formation of polymer-SDS complexes with large size. At the SDS concentration range of below 0.1 mM, the turbidity and cloud point (CP) temperature of the system keep almost invariable, mostly because of the repulsion between SDS molecules and the complexes. And, therefore, the size of the mixed aggregates retains almost constant. In the case of vesicle system of DDAB, the aggregates are in the size of 100 nm - 200 nm and 500 nm - 3000 nm at the concentrations of 30 mM and 100 mM, respectively. However, in the mixture of hyperbranched polymer with DDAB, by comparison, the size is smaller in a binary system than that of in DDAB system. So it is reasonable to infer that DDAB molecules remove from multilamellar vesicles of DDAB to the hydrophobic microenvironment of hyperbranched polymer aggregates, with the addition of the hyperbranched polymer. It leads to the destruction of the gel-like conformation in DDAB system, leading to the shear thinning of the mixture and, as a result, the viscoelastic character of the system is lost in a large degree.
基金This project is supported by the National Natural Science Foundation of China, 863 High Technology Project and the National Basic Research Project--Macromolecular Condensed State.
文摘A new statistical theory based on the rotational isomeric state model describing the chain conformational free energy has been proposed. This theory can be used to predict different tensions of rubber elongation for chemically different polymers, and the energy term during the elongation of natural rubber coincides with the experimental one.
基金This work was supported by the research grants from the National Nature Science Foundation of China (No. 20174024) and the Special Founds for Major State Basic Research Projects (G199906408)
文摘A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocityprofiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction byusing the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation ofpolymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simpleshear flow, extensional flow, vortical flow, and mixed flow respectively.
基金financial supports from the National Basic Research Program of China (No. 2015CB654700 (2015CB674704))the National Natural Science Foundation of China (Nos. 21476007, 51525301 and 51521062)the CHEMCLOUDCOMPUTING of Beijing University of Chemical Technology
文摘There has been controversy as to whether the addition of nanoparticles to a polymer melt causes perturbed chain structure of polymers. In this work, the chain conformations of polydimethylsiloxane（PDMS） with addition of polyhedral oligomeric silsesquioxane（POSS） nanoparticles have been studied using a classical density functional approach. Under the strong interactions of POSS-PDMS, the radius of gyration of PDMS in the nanocomposites can either increase or decline depending on particle loading. After adding nanoparticles with larger size or weaker interactions, both the increasing and the declining amplitudes can be largely suppressed. The results provide a deep understanding of chain conformation in polymer nanocomposites.
基金Project supported by the National Natural Science Foundation of China.
文摘When a polymer chain has only one end group attaching to the boundary and all the other segments are located in the half-space divided by the boundary, it is defined as a tail chain~. Obviously, the model of tail chain represents the simplest form of
基金Supported by the National Natural Science Foundation of China(No.20901018)the Natural Science Foundation of Guangdong Province, China(No.9451009101003177)
文摘The hydrothermal reaction of Zn（NO3）2·4H2O, cyclohexane-1,2,3,4,5,6-hexacarboxylic acid hydrate （H6LI·H2O, cis-conformation LI： a,e,a,e,a,e） and 2,2＇-bpy yielded a new coordination polymer [Zn2（H2LII）（2,2＇-bpy）]·2H2O（trans-conformation LII： e,e,e,e,e,e）, which was characterized by single-crystal X-ray diffraction, elemental analysis, IR and XRPD（X-ray powder diffraction）. This complex crystallized in the triclinic system, with P1 space group and parameters a=0.66922（5） nm, b=0.97291（8） nm, c=1.22184（9） nm, α=99.0020（10）°, β=99.1300（10）°, γ=99.1910（10）°, V= 0.76176（10） nm3 and Z=2. The structure is a three-dimensional supramolecular network based on linear coordination chains through π-π stacking and hydrogen bonding interactions. The confromation of the starting ligand H6LI transfromed to the H2LII. The complex emits strong luminescence at room temperature.
基金supported by the National Natural Science Foundation of China
文摘The SAW tail chains were studied.The permitted conformational number and the mean square end-to-end distance as a function of the chain length N for such a model tail chain were obtained by computer simulations,including the exact enumeration and Monte Carlo method.These two basic quantities obeyed the relations deduced from the scaling law.The critical exponents and the lattice indexes were given by fitting the data of the computer experiments.It has been shown that there is a certain extension in the size of the SAW tail chains as well as the NRW tail chains in the direction normal to the wall.The normal component of the mean square end-to-end distance is almost twice as large as the parallel component of the short chain SAW.However,as N→∞,the effect of the wall on the chain conformation becomes a little weak because of the self-avoiding behavior for the model.That is quite different from the case of the NRW tail chain.
基金Supported by the National Natural Science Foundation of China (No. 20901018)the Natural Science Foundation of Guangdong Province (No. 9451009101003177)
文摘The hydrothermal reaction of Cd（OAc）2·2H2O, 4,4＇-bpy and cyclohexane-1,2,4,5-tetracarboxylic acid （H4L） yields a three-dimensional （3D） coordination porous framework [Cd2LI（4,4＇-bpy）1.5（H2O）2]n·2nH2O, which was characterized by single-crystal X-ray diffraction （MoKα radiation, λ = 0.71073）, elemental analysis and IR. This complex crystallizes in the monoclinic system, space group C2/c with a = 25.951（3）, b = 11.6618（12）, c = 20.046（2） A, β = 114.863（2）o, V = 5504.4（10）A^3, Z = 8, Dc = 1.900 g/cm^3, Mr = 787.30, μ = 1.615 mm^-1, F（000） = 3128, the final R = 0.0978 and wR = 0.1780. The structure of the complex is a 3D coordination Cd-carboxylate framework consisting of 1D hexagonal channels along the c-axis filled with the bridging 4,4＇-bpy ligands. The 4,4＇-bpy ligands with two kinds of conformations are located alternately in the channels through coordination and hydrogen interactions to support the whole porous framework, in which the conformation-flexible cyclohexane-1,2,4,5-tetracarboxylate ligand adopts the I （e,a,a,e） conformation and acts as a pentadentate ligand to connect five Cd（Ⅱ） atoms via the carboxylate groups in different coordination modes.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.50238020 and 50378048)the National High-Tech Research and Development Program(863)of China(Grant No.2002AA601120).
文摘The turbidity variation in artificial water and samples from a water plant was investigated in the presence of organics with different relative molecular mass.The results show that recessive turbidity existed when water chemical conditions were changing.The formation of turbidity depen-ded on organic relative molecular mass and their conforma-tions on particles.At higher pH and lower ionic strength,the organic chains with a more extended conformation resulted in rising turbidity of the suspension.At lower pH,the reconfor-mation of organics took place due to charge neutralization by the proton,resulting in a decline in turbidity.The addition of NaCl and MgCl_(2) at pH 7.00 also resulted in a decrease of turbidity in the suspension.It is believed that the occurrence of recessive turbidity has a significant influence on the stability of water supply quality.
基金the National Natural Science Foundation of China(Grant Nos.50573034 and 20634030)
文摘The study of interactions between peptides and synthetic polymers has aroused considerable interest recently.In the present paper,the interaction mechanism between adsorbent DMAPAM and two pep-tides,VVRGCTWW(V8)and CTWW(C4),was investigated at molecular level by NMR and molecular stimulation.The results demonstrated that the conformation of oligopeptides played a vital role in their adsorption capacity on the adsorbent.Weak interactions could incorporate with each other between V8 and DMAPAM because there was a hydrophobic cleavage in α-helix conformation of V8.So the ad-sorption capacity of DMAPAM to V8 was higher.This was significant to explore the interaction mecha-nism between peptides and biomaterials.
