The shape of unperturbed polymer chains was studied using the Monte Carlo technique on a tetrahedral lattice. The asphericity A, the ratios <L-2(2)>/<L-1(2)> and <L-3(2)>/<L-1(2)> were calculat...The shape of unperturbed polymer chains was studied using the Monte Carlo technique on a tetrahedral lattice. The asphericity A, the ratios <L-2(2)>/<L-1(2)> and <L-3(2)>/<L-1(2)> were calculated for different Values of polymer chain length n, conformational energy epsilon (epsilon greater than or equal to 0) and temperature T. The asphericity A decreases with the increase of chain length and tends to reach its limiting value rapidly with the decrease of gamma (gamma = epsilon/k(B)T). For large n, A is about 0.525 +/- 0.005, the ratios <L-2(2)>/<L-1(2)> and <L-3(2)>/<L-1(2)> are about 2.7 and 12.0, respectively, and are almost independent of gamma, but for short chains, they depend on gamma.展开更多
By the so-called wormlike chain (WLC) model in polymer physics envision- ing an isotropic rod that is continuously flexible, the force-extension relations of semi- flexible polymer chains strongly constrained by var...By the so-called wormlike chain (WLC) model in polymer physics envision- ing an isotropic rod that is continuously flexible, the force-extension relations of semi- flexible polymer chains strongly constrained by various confinements are theoretically investigated, including a slab-like confinement where the polymer chains are sandwiched between two parallel impenetrable walls, and a capped nanochannel confinement with a circular or rectangular cross-section where the chains are bounded in three directions. The Brownian dynamics (BD) simulations based on the generalized bead-rod (GBR) model are performed to verify the theoretical predictions.展开更多
The behavior of three-dimensional bond fluctuation model chains tethered on an adsorbing fiat surface was simulated by the Monte Carlo method.The dependence of the number of surface contacts M on the interaction stren...The behavior of three-dimensional bond fluctuation model chains tethered on an adsorbing fiat surface was simulated by the Monte Carlo method.The dependence of the number of surface contacts M on the interaction strengthεand the chain length N was investigated by a finite-size scaling law M = N;[a;+a;N;κ+ O((N;κ);)]forεnear the critical adsorption pointε;,i.e.,κ=(ε-ε;)/ε;closes to 0.The critical adsorption point was estimated to beε;=0.93,and the exponentsφ= 0.49 and l/v= 0.57.展开更多
Polymer chain coils with entanglement is a crucial scale of structures in polymer materials since their relaxationtimes are matching practical processing times.Based on the phenomenological model of polymer chain coil...Polymer chain coils with entanglement is a crucial scale of structures in polymer materials since their relaxationtimes are matching practical processing times.Based on the phenomenological model of polymer chain coils and a new finiteelement approach,we have designed a computer software including solver,pre-and post-processing modules,and developeda digital analysis technology for the morphology of polymer chain coils in flow fields(DAMPC).Using this technology wemay simulate the morphology development of chain coils in various flow fields,such as simple shear flow,elongational flow,and any complex flow at transient or steady state.The applications made up to now show that the software predictions arecomparable with experimental results.展开更多
We use the pruned-enriched Rosenbluth method to investigate systematically the segment density profiles of compact polymer chains confined between two parallel plane walls. The non-adsorption case of adsorption intera...We use the pruned-enriched Rosenbluth method to investigate systematically the segment density profiles of compact polymer chains confined between two parallel plane walls. The non-adsorption case of adsorption interaction energy ε = 0 and the weak adsorption case of ε= -1 are considered for the compact polymer chains with different chain lengths N and different separation distances between two walls D. Several special entropy effects on the confined compact polymer chains, such as a damped oscillation in the segment density profile for the large separation distance D, are observed and discussed for different separation distances D in the non-adsorption case. In the weak adsorption case, investigations on the segment density profiles indicate that the competition between the entropy and adsorption effects results in an obvious depletion layer. Moreover, the scaling laws of the damped oscillation period Td and the depletion layer width Ld are obtained for the confined compact chains. Most of these results are obtained for the first time so far as we know, which are expected to understand the properties of the confined compact polymer chains more completely.展开更多
The correlation between shape and size of linear chains on the simple cubic lattice is investigated using a dynamicMonte Carlo technique. A positive correlation between the asphericity parameter A and the square of th...The correlation between shape and size of linear chains on the simple cubic lattice is investigated using a dynamicMonte Carlo technique. A positive correlation between the asphericity parameter A and the square of the end-to-end distanceR^2, as well as that between A and the square of the radius of gyration S^2, is found for both RW and SAW chains, indicatingthat a chain conformation of small size is usually more spherical than one of large size. The result can explain why the shapeof the SAW chain deviate much more from a sphere than that of the RW chain, and can also explain the similar dependenceof size and shape on chain stiffness and on the distance of the first bead of a chain from an infinitely large flat surface.展开更多
In this paper the influence of a knot on the structure of a polymethylene (PM) strand in the tensile process is investigated by using the steered molecular dynamics (SMD) method. The gradual increasing of end-to-e...In this paper the influence of a knot on the structure of a polymethylene (PM) strand in the tensile process is investigated by using the steered molecular dynamics (SMD) method. The gradual increasing of end-to-end distance, R, results in a tighter knot and a more stretched contour. That the break in a knotted rope almost invariably occurs at a point just outside the 'entrance' to the knot, which has been shown in a good many experiments, is further theoretically verified in this paper through the calculation of some structural and thermodynamic parameters. Moreover, it is found that the analyses on bond length, torsion angle and strain energy can facilitate to the study of the localization and the size of a knot in the tensile process. The symmetries of torsion angles, bond lengths and bond angles in the knot result in the whole symmetry of the knot in microstructure, thereby adapting itself to the strain applied. Additionally, the statistical property of the force-dependent average knot size illuminates in detail the change in size of a knot with force f, and therefore the minimum size of the knot in the restriction of the potentials considered in this work for a PM chain is deduced. At the same time, the difference in response to uniaxial strain, between a knotted PM strand and an unknotted one is also investigated. The force-extension profile is easily obtained from the simulation. As expected, for a given f, the knotted chain has an R significantly smaller than that of an unknotted polymer. However, the scaled difference becomes less pronounced for larger values of N, and the results for longer chains approach those of the unknotted chains.展开更多
The capture of circulating tumor cells(CTCs)is of great significance in reducing cancer mortality and complications.However,the nonspecific binding of proteins and white blood cells(WBCs)weakens the targeting capabili...The capture of circulating tumor cells(CTCs)is of great significance in reducing cancer mortality and complications.However,the nonspecific binding of proteins and white blood cells(WBCs)weakens the targeting capabilities of the capture surfaces,which critically hampers the efficiency and purity of the captured CTCs.Herein,we propose a liquid-like interface design strategy that consists of liquid-like polymer chains and anti-EpCAM modification processes for high-purity and high-efficiency capture of CTCs.The dynamic flexible feature of the liquid-like chains endows the modified surfaces with excellent antiadhesion property for proteins and blood cells.The liquid-like surfaces can capture the target CTCs and show high cell viability due to the environmentfriendly surface modification processes.When liquid-like surface designs were introduced in the deterministic lateral displacement(DLD)-patterned microfluidic chip,the nonspecific adhesion rate of WBCs was reduced by more than fivefold compared to that in the DLD chip without liquid-like interface design,while maintaining comparable capture efficiency.Overall,this strategy provides a novel perspective on surface design for achieving high purity and efficient capture of CTCs.展开更多
The catalysis of olefin polymerization through the chain-walking process is a subject of great interest. In this contribution, the successful synthesis of a Brookhart-type unsymmetrical α-diimine nickel catalyst Ni, ...The catalysis of olefin polymerization through the chain-walking process is a subject of great interest. In this contribution, the successful synthesis of a Brookhart-type unsymmetrical α-diimine nickel catalyst Ni, which contains both dibenzhydryl and phenyl groups, was determined by X-ray crystallography. The compound has a pseudo-tetrahedral geometry at the Ni center, showing pseudo-C2-symmetry. Upon activation with modified methylaluminoxane (MMAO), Ni1 exhibits high catalytic activity up to 1.02 × 107 g PE (mol Ni h)−1 toward ethylene polymerization, enabling the synthesis of high molecular weight branched polyethylene. The molecular weights and branching densities could be tuned over a very wide range. The polymerization results indicated the possibility of precise microstructure control, depending on the polymerization temperature. The branching densities were decreased with increasing the polymerization temperature.展开更多
The structural transition of a single polymer chain with chain length of 100,200 and 300 beads was investigated by parallel tempering MD simulation.Our simulation results can capture the structural change from random ...The structural transition of a single polymer chain with chain length of 100,200 and 300 beads was investigated by parallel tempering MD simulation.Our simulation results can capture the structural change from random coil to orientationally ordered structure with decreasing temperature.The clear transition was observed on the curves of radius of gyration and global orientational order parameter P as the function of temperature,which demonstrated structural formation of a single polymer chain.The linear relationships between three components of square radius of gyration R_(gx)~2,R_(gx)~2,R_(gz)~2 and global orientational order P can be obtained under the structurally transformational process.The slope of the linear relationship between x(or y-axis) component R_(gx)~2(or R_(gy)~2) and P is negative,while that of RL as the function of P is positive.The absolute value of slope is proportional to the chain length.Once the single polymer chain takes the random coil or ordered configuration,the linear relationship is invalid.The conformational change was also analyzed on microscopic scale.The polymer chain can be treated as the construction of rigid stems connecting by flexible loops.The deviation from exponentially decreased behavior of stem length distribution becomes prominent,indicating a stiffening of the chain arises leading to more and more segments ending up in the trans state with decreasing temperature.The stem length N_(tr) is about 21 bonds indicating the polymer chain is ordered with the specific fold length.So,the simulation results,which show the prototype of a liquid-crystalline polymer chain,are helpful to understand the crystallization process of crystalline polymers.展开更多
Elastic behavior of 4-branched star polymer chain with different chain length N adsorbed on attractive surface is investigated using steered molecular dynamics (SMD) simulation method based on the united-atom (UA)...Elastic behavior of 4-branched star polymer chain with different chain length N adsorbed on attractive surface is investigated using steered molecular dynamics (SMD) simulation method based on the united-atom (UA) model for branched alkanes. The simulation is realized by pulling up the chain via a linear spring with a constant velocity v = 0.005 nm/ps. At the beginning, the chain lies extensionally on adsorbed surface and suffers continuous deformations during the tensile process. Statistical parameters as mean-square radii of gyration 〈S2〉xy, 〈S2〉z, shape factor 〈δ〉, describing the conformational changes, sectional density 〈den〉 which gives the states of the chain, and average surface attractive energy 〈Ua〉, average total energy 〈U〉, average force 〈f〉 probed by the spring, which characterize the thermodynamic properties, are calculated in the stimulant process. Remarkably, distinguishing from the case in linear chains that there only exists one long plateau in the curve of 〈f 〉, the force plateau in our study for star chains is multiple, denoting different steps of desorption, and this agrees well with the experimental results in essence. We find during the tensile process, there are three characteristic distances Zc, Zt and Z0 from the attractive surface, and these values vary with N. When Z = Zc, the chain is stripped from the surface, but due to the form of wall-monomer interaction, the surface retains weak influence on the chain till Z = Zc. From Z = Zt, parameters 〈Ua〉, 〈U〉 and 〈f〉 respectively reach a stable value, while the shape and the size of the chain still need adjustments after Zt till Zo to reach their equilibrium states. Specifically, for short chain of N = 41, Zt and Z0 are incorporated. These results may help us to deepen the knowledge about the elastic behavior of adsorbed star polymer chains.展开更多
Distributed Lagrange Multiplier/Fictitious Domain (DLM/FD) method was employed to simulate the channel flow with polymer suspension. The polymer molecules were modeled as Finitely Extensible Nonlinear Elastic (FENE...Distributed Lagrange Multiplier/Fictitious Domain (DLM/FD) method was employed to simulate the channel flow with polymer suspension. The polymer molecules were modeled as Finitely Extensible Nonlinear Elastic (FENE) chains and FENE chain cluster. The coiled stretched transition of FENE chains was examined and the change in configuration of FENE chains was presented. The average velocity profile of the fully developed channel flow with 64 FENE chains was given and fitted well with the power-law curve. The change of chain cluster configuration was also simulated. These simulations show that DLM/FD method is capable of simulating the motion of not only FENE chain, but also FENE chain cluster.展开更多
A new AgO) coordination polymer, {[Ag(1,3-BIP)(H20)][Ag(1,3- BIP)(PMA)0.5.- 4H20}n (PMA = 1,2,4,5-benzenetricarboxylic acid, 1,3-BIP = 1,3-bis(imidazole)propane), have been synthesized and characterized b...A new AgO) coordination polymer, {[Ag(1,3-BIP)(H20)][Ag(1,3- BIP)(PMA)0.5.- 4H20}n (PMA = 1,2,4,5-benzenetricarboxylic acid, 1,3-BIP = 1,3-bis(imidazole)propane), have been synthesized and characterized by single-crystal X-ray diffraction, powder XRD, FTIR, TGA and elemental analysis techniques. The single-crystal X-ray diffraction reveals that the title complex is formed by 1D polymeric cationic chains of [Ag(1,3-BIP)(H2O)]n^n+ and 2D polymetric anionic layer of [Ag(1,3-BIP)(PMA)0.5]n^n-, which are further linked by intermolecular H-bonding to form a 3D supramolecular framework. In addition, the photoluminescence property of the title complex in the solid state at room temperature was also investigated.展开更多
Two novel coordination polymers with helical chains, {[Zn(L)(H2O)]·H2O}n(1) and {[Zn(L)(p-bix)]·3.5H2O}n(2), where H2 L = 5-(4-hydroxypyridinium-1-ylmethyl) isophthalic acid and p-bix = 1,4-bis...Two novel coordination polymers with helical chains, {[Zn(L)(H2O)]·H2O}n(1) and {[Zn(L)(p-bix)]·3.5H2O}n(2), where H2 L = 5-(4-hydroxypyridinium-1-ylmethyl) isophthalic acid and p-bix = 1,4-bis(imidazol-1-ylmethyl)benzene, have been hydrothermally synthesized, and charac-terized by elemental analysis, powder X-ray diffraction(PXRD), IR, thermal gravimetric analyses(TGA) and also by single-crystal X-ray diffraction. Both complexes 1 and 2 crystallize inmonoclinic, space group P21/c. Compound 1 displays a two-dimensional(2D) structure with two distinct types of helical chains; 2 shows a layered coordination polymer with two types of helical chains and features an interesting 2D→3D interdigitated architecture. Meanwhile, the luminescent properties of 1 and 2 have also been investigated in detail.展开更多
Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent.In the first step,free radical polymerization of methyl methac...Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent.In the first step,free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent,pentaerythritol tetrakis(3-mercaptopropinate).At appropriate monomer conversions,two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were o...展开更多
Reversible addition-fragmentation transfer (RAPT) miniemulsion polymerizations for PMMA with cumyl dithiobenzoate (CDB) as a chain transfer agent (CTA) has been carried out. Higher temperature made the polymeriz...Reversible addition-fragmentation transfer (RAPT) miniemulsion polymerizations for PMMA with cumyl dithiobenzoate (CDB) as a chain transfer agent (CTA) has been carried out. Higher temperature made the polymerization much faster and the PDI remained below 1.20, when the temperature was upon 70 ℃.展开更多
An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model stru...An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results展开更多
Reversible addition-fragmentation chain transfer(RAFT) mediated grafting of acrylonitrile onto Polyethylene/Poly(ethylene terephthalate)(PE/PET) composite fibers was performed using γ-irradiation as the initial sourc...Reversible addition-fragmentation chain transfer(RAFT) mediated grafting of acrylonitrile onto Polyethylene/Poly(ethylene terephthalate)(PE/PET) composite fibers was performed using γ-irradiation as the initial source at ambient temperature. Different initial concentrations of 2-cyanoprop-2-yl dithiobenzonate were used as the chain transfer agent. The kinetics of graft polymerization is in accordance with the living RAFT polymerization. The successful grafting of acrylonitrile is proved by Fourier transform infrared spectroscopy analysis.The results of monofilament tensile test show that mechanical properties of the fibers change slightly after grafting. Scanning electronic microscopy images of the fibers show that the surface of RAFT grafted fibers is smoother than that of fibers grafted conventionally.展开更多
Five kinds of side chain liquid crystalline polymers with a chiral component in the pendant group were synthesized and characterized by GPC, polarizing microscopy, DSC, X-ray diffraction ano Dielectric Relaxation Spec...Five kinds of side chain liquid crystalline polymers with a chiral component in the pendant group were synthesized and characterized by GPC, polarizing microscopy, DSC, X-ray diffraction ano Dielectric Relaxation Spectroscopy. The liquid crystalline behaviour of the polymers is affected by the length of flexible spacer, which links the mesogenic side chain to the polymer backbone and mesogenic moiety. The characteristic of smectic phase is observed for all the polymers.展开更多
基金This work was supported by the National Natural Science Foundation of China (No. 29736170).
文摘The shape of unperturbed polymer chains was studied using the Monte Carlo technique on a tetrahedral lattice. The asphericity A, the ratios <L-2(2)>/<L-1(2)> and <L-3(2)>/<L-1(2)> were calculated for different Values of polymer chain length n, conformational energy epsilon (epsilon greater than or equal to 0) and temperature T. The asphericity A decreases with the increase of chain length and tends to reach its limiting value rapidly with the decrease of gamma (gamma = epsilon/k(B)T). For large n, A is about 0.525 +/- 0.005, the ratios <L-2(2)>/<L-1(2)> and <L-3(2)>/<L-1(2)> are about 2.7 and 12.0, respectively, and are almost independent of gamma, but for short chains, they depend on gamma.
基金supported the National Natural Science Foundation of China(Nos.11032006,11072094,and11121202)the Ph.D.Program Foundation of Ministry of Education of China(No.20100211110022)+1 种基金the National Key Project of Magneto-Constrained Fusion Energy Development Program of China(No.2013GB110002)the Fundamental Research Funds for the Central Universities(No.lzujbky2013-1)
文摘By the so-called wormlike chain (WLC) model in polymer physics envision- ing an isotropic rod that is continuously flexible, the force-extension relations of semi- flexible polymer chains strongly constrained by various confinements are theoretically investigated, including a slab-like confinement where the polymer chains are sandwiched between two parallel impenetrable walls, and a capped nanochannel confinement with a circular or rectangular cross-section where the chains are bounded in three directions. The Brownian dynamics (BD) simulations based on the generalized bead-rod (GBR) model are performed to verify the theoretical predictions.
基金supported by the National Natural Science Foundation of China (No.20674074).
文摘The behavior of three-dimensional bond fluctuation model chains tethered on an adsorbing fiat surface was simulated by the Monte Carlo method.The dependence of the number of surface contacts M on the interaction strengthεand the chain length N was investigated by a finite-size scaling law M = N;[a;+a;N;κ+ O((N;κ);)]forεnear the critical adsorption pointε;,i.e.,κ=(ε-ε;)/ε;closes to 0.The critical adsorption point was estimated to beε;=0.93,and the exponentsφ= 0.49 and l/v= 0.57.
基金This work was supported by the research grants from the National Natural Science Foundation of China(No.50290090No.20204007+2 种基金No.20174024)National 863 project of China(No.2002AA336120)the Doctoral Foundation of National Education Committee of China(
文摘Polymer chain coils with entanglement is a crucial scale of structures in polymer materials since their relaxationtimes are matching practical processing times.Based on the phenomenological model of polymer chain coils and a new finiteelement approach,we have designed a computer software including solver,pre-and post-processing modules,and developeda digital analysis technology for the morphology of polymer chain coils in flow fields(DAMPC).Using this technology wemay simulate the morphology development of chain coils in various flow fields,such as simple shear flow,elongational flow,and any complex flow at transient or steady state.The applications made up to now show that the software predictions arecomparable with experimental results.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.20274040,20574052)the Program for New Century Excellent Talents in Universities(No.NCET-05-0538)+1 种基金the Natural Science Foundation of Zhejiang Province(Nos.R404047,Y405011,Y405553)China Postdoctoral Science Foundation(No.20060401064).
文摘We use the pruned-enriched Rosenbluth method to investigate systematically the segment density profiles of compact polymer chains confined between two parallel plane walls. The non-adsorption case of adsorption interaction energy ε = 0 and the weak adsorption case of ε= -1 are considered for the compact polymer chains with different chain lengths N and different separation distances between two walls D. Several special entropy effects on the confined compact polymer chains, such as a damped oscillation in the segment density profile for the large separation distance D, are observed and discussed for different separation distances D in the non-adsorption case. In the weak adsorption case, investigations on the segment density profiles indicate that the competition between the entropy and adsorption effects results in an obvious depletion layer. Moreover, the scaling laws of the damped oscillation period Td and the depletion layer width Ld are obtained for the confined compact chains. Most of these results are obtained for the first time so far as we know, which are expected to understand the properties of the confined compact polymer chains more completely.
基金This work was supported by the National Natural Science Foundation of China (No. 20076038 and No. 20204014).
文摘The correlation between shape and size of linear chains on the simple cubic lattice is investigated using a dynamicMonte Carlo technique. A positive correlation between the asphericity parameter A and the square of the end-to-end distanceR^2, as well as that between A and the square of the radius of gyration S^2, is found for both RW and SAW chains, indicatingthat a chain conformation of small size is usually more spherical than one of large size. The result can explain why the shapeof the SAW chain deviate much more from a sphere than that of the RW chain, and can also explain the similar dependenceof size and shape on chain stiffness and on the distance of the first bead of a chain from an infinitely large flat surface.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 20274040,20574052 and 20774066)the Program for New Century Excellent Talents in University,China (Grant No NCET-05-0538)the Natural Science Foundation of Zhejiang Province,China (Grant No R404047)
文摘In this paper the influence of a knot on the structure of a polymethylene (PM) strand in the tensile process is investigated by using the steered molecular dynamics (SMD) method. The gradual increasing of end-to-end distance, R, results in a tighter knot and a more stretched contour. That the break in a knotted rope almost invariably occurs at a point just outside the 'entrance' to the knot, which has been shown in a good many experiments, is further theoretically verified in this paper through the calculation of some structural and thermodynamic parameters. Moreover, it is found that the analyses on bond length, torsion angle and strain energy can facilitate to the study of the localization and the size of a knot in the tensile process. The symmetries of torsion angles, bond lengths and bond angles in the knot result in the whole symmetry of the knot in microstructure, thereby adapting itself to the strain applied. Additionally, the statistical property of the force-dependent average knot size illuminates in detail the change in size of a knot with force f, and therefore the minimum size of the knot in the restriction of the potentials considered in this work for a PM chain is deduced. At the same time, the difference in response to uniaxial strain, between a knotted PM strand and an unknotted one is also investigated. The force-extension profile is easily obtained from the simulation. As expected, for a given f, the knotted chain has an R significantly smaller than that of an unknotted polymer. However, the scaled difference becomes less pronounced for larger values of N, and the results for longer chains approach those of the unknotted chains.
基金supported by the National Natural Science Foundation of China(grant nos.52025132,21975209,22275156,21621091,22021001,22005255,and T2241022)the National Science Foundation of Fujian Province of China(grant no.2022J02059)+4 种基金the Fundamental Research Funds for the Central Universities of China(grant nos.20720220019 and 20720220085)the 111 Project(grant nos.B17027 and B16029)the Science and Technology Projects of Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(grant no.RD2022070601)the State Key Laboratory of Bio-Fibers and Eco-Textiles(Qingdao University)(grant no.KFKT202221)the Tencent Foundation(The XPLORER PRIZE).
文摘The capture of circulating tumor cells(CTCs)is of great significance in reducing cancer mortality and complications.However,the nonspecific binding of proteins and white blood cells(WBCs)weakens the targeting capabilities of the capture surfaces,which critically hampers the efficiency and purity of the captured CTCs.Herein,we propose a liquid-like interface design strategy that consists of liquid-like polymer chains and anti-EpCAM modification processes for high-purity and high-efficiency capture of CTCs.The dynamic flexible feature of the liquid-like chains endows the modified surfaces with excellent antiadhesion property for proteins and blood cells.The liquid-like surfaces can capture the target CTCs and show high cell viability due to the environmentfriendly surface modification processes.When liquid-like surface designs were introduced in the deterministic lateral displacement(DLD)-patterned microfluidic chip,the nonspecific adhesion rate of WBCs was reduced by more than fivefold compared to that in the DLD chip without liquid-like interface design,while maintaining comparable capture efficiency.Overall,this strategy provides a novel perspective on surface design for achieving high purity and efficient capture of CTCs.
文摘The catalysis of olefin polymerization through the chain-walking process is a subject of great interest. In this contribution, the successful synthesis of a Brookhart-type unsymmetrical α-diimine nickel catalyst Ni, which contains both dibenzhydryl and phenyl groups, was determined by X-ray crystallography. The compound has a pseudo-tetrahedral geometry at the Ni center, showing pseudo-C2-symmetry. Upon activation with modified methylaluminoxane (MMAO), Ni1 exhibits high catalytic activity up to 1.02 × 107 g PE (mol Ni h)−1 toward ethylene polymerization, enabling the synthesis of high molecular weight branched polyethylene. The molecular weights and branching densities could be tuned over a very wide range. The polymerization results indicated the possibility of precise microstructure control, depending on the polymerization temperature. The branching densities were decreased with increasing the polymerization temperature.
基金financially supported by the Science and Technology Planning Project of Zhejiang Province,China (No.2010R10022)Natural Science Foundation of Zhejiang Province,China(No.Y6110304)National Natural Science Foundation of China(No.20904047)
文摘The structural transition of a single polymer chain with chain length of 100,200 and 300 beads was investigated by parallel tempering MD simulation.Our simulation results can capture the structural change from random coil to orientationally ordered structure with decreasing temperature.The clear transition was observed on the curves of radius of gyration and global orientational order parameter P as the function of temperature,which demonstrated structural formation of a single polymer chain.The linear relationships between three components of square radius of gyration R_(gx)~2,R_(gx)~2,R_(gz)~2 and global orientational order P can be obtained under the structurally transformational process.The slope of the linear relationship between x(or y-axis) component R_(gx)~2(or R_(gy)~2) and P is negative,while that of RL as the function of P is positive.The absolute value of slope is proportional to the chain length.Once the single polymer chain takes the random coil or ordered configuration,the linear relationship is invalid.The conformational change was also analyzed on microscopic scale.The polymer chain can be treated as the construction of rigid stems connecting by flexible loops.The deviation from exponentially decreased behavior of stem length distribution becomes prominent,indicating a stiffening of the chain arises leading to more and more segments ending up in the trans state with decreasing temperature.The stem length N_(tr) is about 21 bonds indicating the polymer chain is ordered with the specific fold length.So,the simulation results,which show the prototype of a liquid-crystalline polymer chain,are helpful to understand the crystallization process of crystalline polymers.
基金supported by the National Natural Science Foundation of China(Nos.20904047,10947104).
文摘Elastic behavior of 4-branched star polymer chain with different chain length N adsorbed on attractive surface is investigated using steered molecular dynamics (SMD) simulation method based on the united-atom (UA) model for branched alkanes. The simulation is realized by pulling up the chain via a linear spring with a constant velocity v = 0.005 nm/ps. At the beginning, the chain lies extensionally on adsorbed surface and suffers continuous deformations during the tensile process. Statistical parameters as mean-square radii of gyration 〈S2〉xy, 〈S2〉z, shape factor 〈δ〉, describing the conformational changes, sectional density 〈den〉 which gives the states of the chain, and average surface attractive energy 〈Ua〉, average total energy 〈U〉, average force 〈f〉 probed by the spring, which characterize the thermodynamic properties, are calculated in the stimulant process. Remarkably, distinguishing from the case in linear chains that there only exists one long plateau in the curve of 〈f 〉, the force plateau in our study for star chains is multiple, denoting different steps of desorption, and this agrees well with the experimental results in essence. We find during the tensile process, there are three characteristic distances Zc, Zt and Z0 from the attractive surface, and these values vary with N. When Z = Zc, the chain is stripped from the surface, but due to the form of wall-monomer interaction, the surface retains weak influence on the chain till Z = Zc. From Z = Zt, parameters 〈Ua〉, 〈U〉 and 〈f〉 respectively reach a stable value, while the shape and the size of the chain still need adjustments after Zt till Zo to reach their equilibrium states. Specifically, for short chain of N = 41, Zt and Z0 are incorporated. These results may help us to deepen the knowledge about the elastic behavior of adsorbed star polymer chains.
文摘Distributed Lagrange Multiplier/Fictitious Domain (DLM/FD) method was employed to simulate the channel flow with polymer suspension. The polymer molecules were modeled as Finitely Extensible Nonlinear Elastic (FENE) chains and FENE chain cluster. The coiled stretched transition of FENE chains was examined and the change in configuration of FENE chains was presented. The average velocity profile of the fully developed channel flow with 64 FENE chains was given and fitted well with the power-law curve. The change of chain cluster configuration was also simulated. These simulations show that DLM/FD method is capable of simulating the motion of not only FENE chain, but also FENE chain cluster.
基金Supported by the National Natural Science Foundation of China(No.21373132)the Science Foundation of Shaanxi University of Technology(No.SLGKY-36)
文摘A new AgO) coordination polymer, {[Ag(1,3-BIP)(H20)][Ag(1,3- BIP)(PMA)0.5.- 4H20}n (PMA = 1,2,4,5-benzenetricarboxylic acid, 1,3-BIP = 1,3-bis(imidazole)propane), have been synthesized and characterized by single-crystal X-ray diffraction, powder XRD, FTIR, TGA and elemental analysis techniques. The single-crystal X-ray diffraction reveals that the title complex is formed by 1D polymeric cationic chains of [Ag(1,3-BIP)(H2O)]n^n+ and 2D polymetric anionic layer of [Ag(1,3-BIP)(PMA)0.5]n^n-, which are further linked by intermolecular H-bonding to form a 3D supramolecular framework. In addition, the photoluminescence property of the title complex in the solid state at room temperature was also investigated.
基金supported by Education Chamber of Henan Province(No.15A150068)
文摘Two novel coordination polymers with helical chains, {[Zn(L)(H2O)]·H2O}n(1) and {[Zn(L)(p-bix)]·3.5H2O}n(2), where H2 L = 5-(4-hydroxypyridinium-1-ylmethyl) isophthalic acid and p-bix = 1,4-bis(imidazol-1-ylmethyl)benzene, have been hydrothermally synthesized, and charac-terized by elemental analysis, powder X-ray diffraction(PXRD), IR, thermal gravimetric analyses(TGA) and also by single-crystal X-ray diffraction. Both complexes 1 and 2 crystallize inmonoclinic, space group P21/c. Compound 1 displays a two-dimensional(2D) structure with two distinct types of helical chains; 2 shows a layered coordination polymer with two types of helical chains and features an interesting 2D→3D interdigitated architecture. Meanwhile, the luminescent properties of 1 and 2 have also been investigated in detail.
文摘Heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent.In the first step,free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent,pentaerythritol tetrakis(3-mercaptopropinate).At appropriate monomer conversions,two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were o...
文摘Reversible addition-fragmentation transfer (RAPT) miniemulsion polymerizations for PMMA with cumyl dithiobenzoate (CDB) as a chain transfer agent (CTA) has been carried out. Higher temperature made the polymerization much faster and the PDI remained below 1.20, when the temperature was upon 70 ℃.
文摘An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results
基金Supported by the National Natural Science Foundation of China(Nos.11475246 and 11175234)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA02030205)
文摘Reversible addition-fragmentation chain transfer(RAFT) mediated grafting of acrylonitrile onto Polyethylene/Poly(ethylene terephthalate)(PE/PET) composite fibers was performed using γ-irradiation as the initial source at ambient temperature. Different initial concentrations of 2-cyanoprop-2-yl dithiobenzonate were used as the chain transfer agent. The kinetics of graft polymerization is in accordance with the living RAFT polymerization. The successful grafting of acrylonitrile is proved by Fourier transform infrared spectroscopy analysis.The results of monofilament tensile test show that mechanical properties of the fibers change slightly after grafting. Scanning electronic microscopy images of the fibers show that the surface of RAFT grafted fibers is smoother than that of fibers grafted conventionally.
文摘Five kinds of side chain liquid crystalline polymers with a chiral component in the pendant group were synthesized and characterized by GPC, polarizing microscopy, DSC, X-ray diffraction ano Dielectric Relaxation Spectroscopy. The liquid crystalline behaviour of the polymers is affected by the length of flexible spacer, which links the mesogenic side chain to the polymer backbone and mesogenic moiety. The characteristic of smectic phase is observed for all the polymers.