Viscoelastic properties of entangled polymers - Ternary blends of monodisperse homopolymers
NASA Technical Reports Server (NTRS)
Soong, D.; Shen, M.; Hong, S. D.; Moacanin, J.; Shyu, S. S.
1979-01-01
In a previous publication from this laboratory, the Rouse-Bueche-Zimm molecular theory of viscoelasticity has been extended by using a transient network model to apply to binary blends of monodisperse polymers with chain entanglements. The dynamics of the entanglements were modeled both by the enhanced frictional coefficients and by the additional elastic couplings. It was recognized that entanglements not only may form between chains of the same lengths (intracomponent entanglements) but also between those of different lengths (intercomponent entanglements). At a given intercomponent entanglement, the longer chain was assumed to have the frictional coefficient of the shorter chain. Similarly, for blends consisting of several monodisperse components with different molecular weights, such modifications are also required to predict their linear viscoelastic behavior. The frequency of these interactions is assumed to be proportional to the weight ratio of the respective component chains in the blend. Equations of motion are formulated for each component and solved numerically for the relaxation time spectra. Linear viscoelastic properties such as the dynamic mechanical moduli, stress relaxation moduli, and zero-shear viscosity can then be computed for these systems by linear summation of those of the components.
Chitanvis, S.M.
1998-09-01
We have developed a theory of polymer entanglement using an extended Cahn-Hilliard functional with two extra terms. One is a nonlocal attractive term, operating over mesoscales, which is interpreted as giving rise to entanglement, and the other is a local repulsive term indicative of excluded volume interactions. This functional can be derived using notions from gauge theory. We go beyond the Gaussian approximation, to the one-loop level, to show that the system exhibits a crossover to a state of entanglement as the average chain length between points of entanglement decreases. This crossover is marked by {ital critical} slowing down, as the effective diffusion constant goes to zero. We have also computed the tensile modulus of the system, and we find a corresponding crossover to a regime of high modulus. The single parameter in our theory is obtained by fitting to available experimental data on polystyrene melts of various chain lengths. Extrapolation of this fit yields a model for the crossover to entanglement. The need for additional experiments detailing the crossover to the entangled state is pointed out. {copyright} {ital 1998} {ital The American Physical Society}
Entanglement swelling in polymer glasses
NASA Astrophysics Data System (ADS)
McGraw, Joshua D.; Dalnoki-Veress, Kari
2009-03-01
A polymer system in which the chains are much longer than the entanglement molecular weight, M+Me, is well entangled. When a thin, glassy polymer film is uniaxially strained, deformations which are almost visible to the naked eye called crazes may be formed. Measuring volume fractions of deformed to undeformed regions provides a method by which entanglement densities of similar systems can be comparedootnotetextACM Yang, EJ Kramer, CC Kuo, SL Phoenix, Macromolecules 19 2020 (1986). We present results of deformation experiments, probed using atomic force microscopy, in which well entangled polystyrene networks have been diluted with various weight fractions of polystyrene with molecular weight in the vicinity of Me. Upon dilution the system assumes an effective reduction in the entanglement density. The effective entanglement density is predicted by a conceptually simple model with Me as the only free parameter.
Entanglement swelling in polymer glasses
NASA Astrophysics Data System (ADS)
McGraw, Joshua; Dalnoki-Veress, Kari
2010-03-01
A polymer system in which the chains are much longer than the entanglement molecular weight is well entangled. When a glassy polymer film composed of such chains is uniaxially strained, deformations called crazes may be formed. It is well established that the study of crazes can reveal much about the nature of entanglements. Here, we present results of crazing experiments in which well entangled polystyrene networks have been diluted with various weight fractions of polystyrene with molecular weights in the vicinity of the entanglement molecular weight. Upon dilution, the systems assume an effective reduction in the entanglement density which is a function of both the weight fraction and molecular weight of the small chains. A model which combines simple ``chain packing'' with ``binary contact'' ideas is proposed. The model is found to quantitatively describe measurements in systems with two and three molecular weight components, and can easily be extended to polydisperse systems.
Swelling molecular entanglement networks in polymer glasses.
McGraw, Joshua D; Dalnoki-Veress, Kari
2010-08-01
Entanglements in a polymer network are like knots between the polymer chains, and they are at the root of many phenomena observed in polymer systems. When a polymer glass is strained, cracklike deformations called crazes may be formed and the study of these regions can reveal much about the nature of entanglements. We have studied crazes in systems that are blends of long polymer chains diluted with chains of various small molecular weights. The range of diluting chain lengths is such that a fraction of them have conformations leading to entanglements. It has been found that a system with more short chains added acts like one in which the entanglement density is smaller than that in an undiluted system. We propose a model that quantitatively predicts the density of effective entanglements of a polydisperse system of polymer chains which is consistent with our experimental data. PMID:20866829
Entanglements in quiescent and sheared polymer melts
NASA Astrophysics Data System (ADS)
Yamamoto, Ryoichi; Onuki, Akira
2004-10-01
We visualize entanglements in polymer melts using molecular dynamics simulation. A bead at an entanglement interacts persistently for long times with the nonbonded beads (those excluding the adjacent ones in the same chain). The interaction energy of each bead with the nonbonded beads is averaged over a time interval τ much longer than microscopic times but shorter than the onset time of tube constraints τe . Entanglements can then be detected as hot spots consisting of several beads with relatively large values of the time-averaged interaction energy. We next apply a shear flow with rate much faster than the disengagement motion of entangled chains. With increasing strain the chains take zigzag shapes and one-half of the hot spots become bent. The chains are first stretched as a network but, as the bends approach the chain ends, disentanglements subsequently occur, leading to stress overshoot observed experimentally.
Simplified tube models for entangled supramolecular polymers
NASA Astrophysics Data System (ADS)
Boudara, Victor; Read, Daniel
2015-03-01
This presentation describes current efforts investigating non-linear rheology of entangled, supramolecular polymeric materials. We describe two recently developed models: 1) We have developed a simplified model for the rheology of entangled telechelic star polymers. This is based on a pre-averaged orientation tensor, a stretch equation, and stretch-dependant probability of detachment of the sticker. In both linear and non-linear regimes, we produce maps of the whole parameter space, indicating the parameter values for which qualitative changes in response to flow are predicted. Results in the linear rheology regime are consistent with previous more detailed models and are in qualitative agreement with experimental data. 2) Using the same modelling framework, we investigate entangled linear polymers with stickers along the backbone. We use a set of coupled equations to describe the stretch between each stickers, and use equations similar to our star model for attachment/detachment of the sticky groups. This model is applicable to industrial polymers such as entangled thermoplastic elasomers, or functionalised model linear polymers. The work leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA Grant Agreement No. 607937 (SUPOLEN).
Packing and Entanglements in Polymer Melts
NASA Astrophysics Data System (ADS)
Ozisik, Rahmi; Sternstein, Sandy S.
2004-03-01
The idea of obtaining the properties of polymers simply from the chemical structure is a very attractive one. Recent work on entanglements and packing indicates that the entanglement molecular weight is related to packing length (= M/(ρ
Friction, Fracture and Entanglement Density of Polymers
NASA Astrophysics Data System (ADS)
Whitten, Philip; Brown, Hugh
2004-03-01
We have studied the fracture of a polymer surface due to friction, as observed by an afm. Friction experiments were made by sliding a smooth glass indenter over a polystyrene surface. The effective entanglement density of the material was changed by cross-linking it in an electron beam. The range of crosslink densities is known to change the deformation of thin films from crazing to shear deformation zones under tensile load. Without crosslinking ripples were formed by the accumulation of debris caused by cohesive failure. As the effective entanglement density was increased by crosslinking, the ripples ceased to form at a crosslink density equal to that required to suppress crazing. These observations demonstrate that the friction process causes extensive deformation at the polymer surface.
Entangled polymer complexes as Higgs phenomena.
Kim, Ki-Seok; Dutta, Sandipan; Jho, YongSeok
2015-10-28
We derive an effective Maxwell-London equation for entangled polymer complexes under topological constraints, borrowing the theoretical framework from topological field theory. We find that the transverse current flux of a test polymer chain, surrounded by entangled chains, decays exponentially from its centerline position with a finite penetration depth, which is analogous to the magnetic-field decay in a superconductor (SC), referred to as the Meissner effect. Just as the mass acquirement of photons in a SC is the origin of the magnetic-field decay, the polymer obtains uncrossable intersections along the chain due to the preservation of the linking number, which restricts the deviation of the transverse polymer current in the normal direction. The underlying physics is as follows: less flexible polymers have stronger current-current correlations, giving rise to a heavier effective mass of the gauge fields and resulting in a shorter decay length. Interestingly, this picture is well incorporated within the most successful phenomenological theory of the, so called, tube model, the microscopic origins of which researchers have long pursued. The correspondence of our equation of motion to the tube model claims that the confining tube potential is a consequence of the topological constraint (linking number). The tube radius is attributed to the decay length. On increasing the effective mass (by strengthening the interaction at an uncrossable intersection or a number of intersections), the tube becomes narrower. Using this argument, the exponential decay of the chain leakage out of the tube is well understood. PMID:26324955
Frozen Topology: Entanglements Control Nucleation and Crystallization in Polymers
NASA Astrophysics Data System (ADS)
Luo, Chuanfu; Sommer, Jens-Uwe
2014-05-01
Polymer chains form lamellar structures during crystallization which display a memory of thermal history. Using molecular dynamics simulations and primitive path analysis, we show a direct dependence of both density and crystalline stem length on the local entanglement length. The slow relaxation of the entanglement state after a change of external conditions can directly explain the role of thermal history for polymer crystallization, in particular memory effects. The analysis of the local entanglement state can be used to predict the occurrence of nucleation events. Our results present a fresh insight of the nonequilibrium properties of polymer crystals which might be identified as "frozen topology" of polymer melts.
Feasibility study: Monodisperse polymer particles containing laser-excitable dyes
NASA Technical Reports Server (NTRS)
Vanderhoff, John W.; Chen, Jing-Hong
1993-01-01
The objective was to determine the feasibility of the preparation of monodisperse spherical poly(methyl methacrylate) and polystyrene particles that contain laser-excitable dyes in the size range 0.1 microns to 1 cm. Poly(methyl methacrylate) and polystyrene were chosen because of their excellent optical properties. The sphericity was required for uniformity of spectral output of re-irradiated light from the dye-containing particles. The monodispersity was required to give each particle the same optical properties when exposed to laser light.
Phase stability and dynamics of entangled polymer-nanoparticle composites
Mangal, Rahul; Srivastava, Samanvaya; Archer, Lynden A.
2015-06-10
Nanoparticle–polymer composites, or polymer–nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.
Size-Dependent Particle Dynamics in Entangled Polymer Nanocomposites.
Mangal, Rahul; Srivastava, Samanvaya; Narayanan, Suresh; Archer, Lynden A
2016-01-19
Polymer-grafted nanoparticles with diameter d homogeneously dispersed in entangled polymer melts with varying random coil radius R0, but fixed entanglement mesh size a(e), are used to study particle motions in entangled polymers. We focus on materials in the transition region between the continuum regime (d > R0), where the classical Stokes-Einstein (S-E) equation is known to describe polymer drag on particles, and the noncontinuum regime (d < a(e)), in which several recent studies report faster diffusion of particles than expected from continuum S-E analysis, based on the bulk polymer viscosity. Specifically, we consider dynamics of particles with sizes d ≥ a(e) in entangled polymers with varying molecular weight M(w) in order to investigate how the transition from noncontinuum to continuum dynamics occur. We take advantage of favorable enthalpic interactions between SiO2 nanoparticles tethered with PEO molecules and entangled PMMA host polymers to create model nanoparticle-polymer composites, in which spherical nanoparticles are uniformly dispersed in entangled polymers. Investigation of the particle dynamics via X-ray photon correlation spectroscopy measurements reveals a transition from fast to slow particle motion as the PMMA molecular weight is increased beyond the entanglement threshold, with a much weaker M(w) dependence for M(w) > M(e) than expected from S-E analysis based on bulk viscosity of entangled PMMA melts. We rationalize these observations using a simple force balance analysis around particles and find that nanoparticle motion in entangled melts can be described using a variant of the S-E analysis in which motion of particles is assumed to only disturb subchain entangled host segments with sizes comparable to the particle diameter. PMID:26694953
Evolution of entanglements in crazing of glassy polymers
NASA Astrophysics Data System (ADS)
Hoy, Robert S.
2005-03-01
Highly entangled polymer glasses often fail via crazing [1]. The polymer expands by a large factor λ from an initial dense state to a craze network of fibrils and voids. The value of λ is found to correlate with the chemical distance between entanglements in both experiments [1] and simulations [2], indicating that the entanglements act like chemical bonds in limiting the expansion. We have applied the primitive path analysis method developed by Everaers et. al. [3] to follow the real space structure of entanglements in model polymer glasses during crazing. A wide range of initial states corresponding to melts with different Kuhn lengths and entanglement lengths was studied. In each case the primitive paths deform affinely and the number of entanglements remains constant during craze formation. Straining the craze past λ leads to a gradual reduction in the number of entanglements, and ultimately to craze fracture.1. E. Kramer and L. L. Berger, Adv. Polym. Sci. 91/92, 1 (1990).2. J. Rottler and M. O. Robbins, Phys. Rev. E 68, 011801 (2003).3. R. Everaers, et al., Science 203, 823 (2004).
Healing of polymer interfaces: Interfacial dynamics, entanglements, and strength
Ge, Ting; Robbins, Mark O.; Perahia, Dvora; Grest, Gary S.
2014-07-25
Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe the healing of polymer films and compare the results with those obtained for thermal welding of homopolymer slabs. These two processes differ from each other in their interfacial structure since damage leads to increased polydispersity and more short chains. A polymer sample was cut into two separate films that were then held together in the melt state. The recovery of the damaged film was followed as time elapsed and polymer molecules diffused across the interface. The mass uptake and formation of entanglements, as obtained from primitive path analysis, are extracted and correlated with the interfacial strength obtained from shear simulations. We find that the diffusion across the interface is signifcantly faster in the damaged film compared to welding because of the presence of short chains. Though interfacial entanglements increase more rapidly for the damaged films, a large fraction of these entanglements are near chain ends. As a result, the interfacial strength of the healing film increases more slowly than for welding. For both healing and welding, the interfacial strength saturates as the bulk entanglement density is recovered across the interface. However, the saturation strength of the damaged film is below the bulk strength for the polymer sample. At saturation, cut chains remain near the healing interface. They are less entangled and as a result they mechanically weaken the interface. When the strength of the interface saturates, the number of interfacial entanglements scales with the corresponding bulk entanglement density. Chain stiffness increases the density of entanglements, which increases the strength of the interface. Our results show that a few entanglements across the interface are sufficient to resist interfacial chain pullout and enhance the mechanical strength.
Healing of polymer interfaces: Interfacial dynamics, entanglements, and strength
Ge, Ting; Robbins, Mark O.; Perahia, Dvora; Grest, Gary S.
2014-07-25
Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe the healing of polymer films and compare the results with those obtained for thermal welding of homopolymer slabs. These two processes differ from each other in their interfacial structure since damage leads to increased polydispersity and more short chains. A polymer sample was cut into two separate films that were then held together in the melt state. The recovery of the damaged film was followed as time elapsed and polymer molecules diffused across the interface.more » The mass uptake and formation of entanglements, as obtained from primitive path analysis, are extracted and correlated with the interfacial strength obtained from shear simulations. We find that the diffusion across the interface is signifcantly faster in the damaged film compared to welding because of the presence of short chains. Though interfacial entanglements increase more rapidly for the damaged films, a large fraction of these entanglements are near chain ends. As a result, the interfacial strength of the healing film increases more slowly than for welding. For both healing and welding, the interfacial strength saturates as the bulk entanglement density is recovered across the interface. However, the saturation strength of the damaged film is below the bulk strength for the polymer sample. At saturation, cut chains remain near the healing interface. They are less entangled and as a result they mechanically weaken the interface. When the strength of the interface saturates, the number of interfacial entanglements scales with the corresponding bulk entanglement density. Chain stiffness increases the density of entanglements, which increases the strength of the interface. Our results show that a few entanglements across the interface are sufficient to resist interfacial chain pullout and enhance the mechanical
Stress Relaxation in Entangled Melts of Unlinked Ring Polymers
NASA Astrophysics Data System (ADS)
Milner, Scott T.; Newhall, Jillian D.
2010-11-01
Stress relaxation in unlinked ring polymer melts poses an important challenge to our theoretical understanding of entangled polymer dynamics. Recent experiments on entangled unlinked ring melts show power-law stress relaxation with no hint of a rubbery plateau, usually the hallmark of entangled polymers. Here we present a theory for stress relaxation in rings analogous to the successful approach for star polymers. We augment our theory with mesoscale Monte Carlo dynamics simulations of equivalent “lattice animal” configurations. We find a stress relaxation function G(t)˜t-α with α≈1/2 consistent with experiment, emerging ultimately from the disparate relaxation times of more- and less-central portions of ring conformations.
Almería, Begoña; Gomez, Alessandro
2014-03-01
This study reports on a methodology to control the size of polymer particles generated by the electrospray (ES) drying route, with emphasis on the generation of biodegradable polymer nanoparticles that are well suited for biomedical applications. The ability to produce spherical poly(lactic-co-glycolic) acid (PLGA) particles with and without encapsulated active agent, with relative standard deviation not exceeding 15%, was demonstrated over a remarkably broad (60 nm-2 μm) diameter range. By judiciously choosing ES parameters and solution properties, we can control the monodispersity and the size of the obtained particles, tailoring it to a specific application. The main parameters affecting particle size include solution electrical conductivity, flow rate and initial polymer volume fraction. Quasi-monodispersity at both the micro- and the more challenging nano-scale was achieved by avoiding Coulomb fission in the spray droplets, via entanglement of the polymer chains within the droplets rather than by charge neutralization. Guiding principles in the formulation of the solutions to satisfy a multiplicity of constraints are provided along with an extensive database of "recipes". PMID:24407667
Evolution of stress and entanglements during deformation of glassy polymers
NASA Astrophysics Data System (ADS)
Robbins, Mark
2007-03-01
Simulations of the mechanical properties of model polymer glasses have been performed over a wide range of entanglement densities, temperatures, strain rates and chain lengths. Primitive Path Analysis (PPA) is used to examine the corresponding changes in entanglement structure during deformation. Results for the initial yield stress, strain hardening and crazing will be presented. The initial yield stress is a function of strain rate and the thermal history of the sample. Strain hardening can be fit to entropic network models for the stress-strain curve. The stress shows a neo- Hookean response at low entanglement density ρe and Langevin strain-hardening at high ρe. As expected from network models, entangled polymers deform affinely at scales larger than the entanglement length. However simulations and experiments show strain hardening decreases with increasing temperature while entropic models predict a linear increase. Our results show that strain hardening scales with the flow stress rather than temperature and that substantial strain hardening occurs for unentangled chains. Studies of craze formation show that it does not lead to entanglement loss in our systems. Instead, small scale motions concentrate entanglements at the nodes between fibrils.
Entanglements and the Mechanical Properties of Glassy Polymers
NASA Astrophysics Data System (ADS)
Robbins, Mark
2011-03-01
The response of glassy polymers to shear or tensile strain is strongly influenced by the entanglement network that is inherited from the melt. Molecular dynamics simulations are used to probe the microscopic origins of stress-strain curves and their connection to entanglements. The latter are identified in real space by examining topological constraints along the primitive path. The first part of the talk will consider the process of craze formation, where the entanglement density is correlated to the volume increase during crazing. Simulations show that entanglements are preserved during crazing, but the craze density does not correspond to pulling chains taut between entanglements. The second part of the talk will examine the effect of entanglements on strain hardening under uniaxial strain. The stress is directly associated with the degree of orientational order along the strain axis, and nearly independent of order along perpendicular directions. Studies with mixtures of short and long chains show that the degree of order is independent of the surrounding chains. The final part of the talk will examine the strength of welds formed by diffusion across polymer interfaces. The shear stress follows the bulk response until chains are pulled taut on the scale of the length of segments that have diffused across the interface. When this length is several times the entanglement length, the maximum shear stress saturates at the bulk value and chains fail through scission. Similar trends are found for the fracture energy in tensile loading. This material is based upon work supported by NSF Grant DMR 108474.
Tang, Zonggui; Liu, Changbin; Wang, Jing; Li, Hongmin; Ji, Yong; Wang, Guohong; Lu, Chunxia
2016-04-01
Monodisperse molecularly imprinted polymers for oleanolic acid were successfully prepared by a precipitation polymerization method using oleanolic acid as a template, methacrylic acid as a functional monomer, and divinylbenzene/ethylene glycol dimethacrylate as a crosslinker in a mixture of acetonitrile and ethanol (3:1, v/v). The imprinted polymers and nonimprinted polymers were characterized by using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The resulting imprinted polymers had average diameters of 3.15 μm and monodispersity values of 1.024. The results clearly demonstrate that use of ethanol as a cosolvent is indeed exceedingly effective in promoting the dissolution of oleanolic acid and in obtaining uniform microspheres. Molecular recognition properties and binding capability to oleanolic acid were evaluated by adsorption testing, which indicated that the imprinted polymers displayed optimal binding performance with a maximum adsorption capacity of 17.3 mg/g and a binding saturation time of 80 min. Meanwhile, the produced imprinted polymers exhibited higher selectivity to oleanolic acid than that for ursolic acid and rhein. Herein, the studies can provide theoretical and experimental references for the oleanolic acid molecular imprinted system. PMID:27106769
Entanglements of End Grafted Polymer Brushes in a Polymeric Matrix
NASA Astrophysics Data System (ADS)
Grest, Gary S.; Hoy, Robert S.
2007-03-01
The entanglement of a polymer brush immersed in a melt of mobile polymer chains is studied by molecular dynamics simulations. A primitive path analysis (PPA) is carried out to identify the brush/brush, brush/melt and melt/melt entanglements as a function of distance from the substrate. The PPA characterizes the microscopic state of conformations of the polymer chain and is ideally suited to identify chain/chain entanglements. We use a new thin-chain PPA technique to eliminate spurious non-entangled inter chain contacts arising from excluded volume. As the grafting density of the brush increases we find that the entanglements of the brush with the melt decrease as the system crosses over from the wet to dry brush regime. Results are compared to brush/brush entanglements in an implicit solvent of varying solvent quality. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
Polymer Chain Reinforcement across Narrow Interfaces: Entanglements Versus Chain Friction
NASA Astrophysics Data System (ADS)
Benkoski, Jason J.; Fredrickson, Glenn H.; Kramer, Edward J.
2002-03-01
It is widely believed that entangled chains that bridge a glassy polymer/polymer interface solely determine its fracture energy (G_c). However, experiments show that while Gc increases with interfacial width (w), Gc vs. w/d_t, where dt is the tube diameter of the melt, is not universal. For some polymer pairs Gc increases dramatically even when w << d_t, while for others Gc does not increase until w >= d_t. We demonstrate that the friction stress for polymer loop pull-out from the interface is given by f_monoρ_merw/2 where f_mono is the static friction coefficient per mer and ρ_mer is the mer number density. Unlike interfaces with short block copolymers, where the friction stress for block pull-out is limited by a maximum areal density of block copolymer, the polymer/polymer friction stress grows linearly with w. For interfaces as narrow as 3 nm, it can be large enough to induce crazing. A model that includes both loop pull-out and chain entanglement shows that modest changes in f_mono can account for the fact that Gc versus w/dt is non-universal. A high areal density of bridging, entangled chains is therefore sufficient, but not necessary, to reinforce polymer interfaces.
Entanglements in polymer networks: two-state invariant
NASA Astrophysics Data System (ADS)
Müller-Nedebock, Kristian
2001-03-01
At the time of crosslinking of polymer chains, entanglements of these chains become permanent features of the resulting network. In a statistical physics formulation these constraints on the polymers can be dealt with by inclusion of invariants for the entangled states of chains. Analytical results are presented based upon an extension of a variational formalism for mechanical properties of entangled gels with a two-state invariant by Edwards and Müller-Nedebock (J. Phys. A: Math. Gen.32 3301 (1999)). Apart from showing Mooney-Rivlin-like behaviour of the reduced stress the theory is applied to olympic gels and discussed in the context of the limitations due to the approximations in this approach.
Percolation effects on entangled polymer rheology and the glass transition
NASA Astrophysics Data System (ADS)
Wool, Richard P.
2012-07-01
Current thinking on the fundamentals of entangled polymer melt rheology suggests that stress relaxation in the terminal zone occurs via Reptation, chain-end fluctuation and (convective) constraint release. This scenario is not correct. It is shown through a series of experiments with selectively deuterated model polymers that relaxation occurs through a percolation process which permits large clusters of entangled polymers to stress relax before their conformations are fully relaxed. The percolation model of entanglements (R.P. Wool, Macromolecules 26, 1564, 1993) makes unique predictions regarding the dynamics of polymer chains in the terminal relaxation zone. These include: (a) Reptating homopolymer chains with molecular weight M >> Mc appear to be non-Reptating as their ends and centers relax at the same rate in a Rouse-like manner during percolation. (b) The mechanical relaxation time τ(M) is related to the Reptation time Tr˜ M3 by τ(M) = Tr[(1-Mc/M)Me/Mc]2, which is the origin of the zero shear viscosity behaving as ηo˜M3.4 (c) The biggest surprise is that during stress relaxation, the random coil dimensions Rg(//) and Rg(⊥) are not fully relaxed when the stress and birefringence relax to zero. (d) Matrix molecular weight P effects on relaxation time τ(M) of the probe chain M are as follows: When the probe chain M>>P, the matrix P-chains percolate and Rouse-like dynamics is observed for the M-Reptating chains with τ(M) ˜ P1M2. (e) When the matrix P>>M, percolation does not occur for the M-chain and the relaxation time of the probe chain τ(M) ˜ PoM3 is in accord with DeGennes Reptation theory. These unusual results predicted by entanglement percolation are supported by extensive experimental data (NR, SANS, DSIMS, FTIR, BR) from selectively deuterated polystyrene chains HDH, DHD, HPS and DPS. These results clearly suggest that current notions of polymer rheology need to be reconsidered. Near Tg, a new perspective on the Glass Transition of amorphous
Evolution of Entanglements During Crazing of Glassy Polymers
NASA Astrophysics Data System (ADS)
Ge, Ting; Robbins, Mark O.; Hoy, Robert; Anogiannakis, Stefanos; Tzoumanekas, Christos; Theodorou, Doros
2011-03-01
Craze formation increases the fracture energy of glassy polymers by orders of magnitude. The polymer volume expands by an extension ratio which is assumed to be determined by the entanglement network. We test this assumption with molecular simulations that use the Contour Reduction Topological Analysis (CReTA) algorithm to follow topological constraints (TCs) associated with the entanglement network. The TCs are identified with contacts between chains after applying CReTA. Within systematic errors, crazing does not change the number of TCs or the distribution of chemical distances between them. Moreover, about 75% of the contacts remain between the same chains at nearly the same location. The 25% of contacts that change do not reflect a comparable loss of entanglements. Instead, small displacements within the tube change which chains contact after CReTA. This interpretation is tested by adding fixed crosslinks to a sparse entanglement network and crazing preoriented samples. This material is based upon work supported by NSF Grant DMR 108474.
Nonlinear rheology of entangled polymers at turning point.
Wang, Shi-Qing
2015-02-28
Thanks to extensive observations of strain localization upon startup or after stepwise shear, a conceptual framework for nonlinear rheology of entangled polymers appears to have emerged that has led to discovery of many new phenomena, which were not previously predicted by the standard tube model. On the other hand, the published theoretical and experimental attempts to test the limits of the tube model have largely demonstrated that the most experimental data appear consistent with the tube-model based theoretical calculations. Therefore, the field of nonlinear rheology of entangled polymers is at a turning point and is thus a rather crucial area in which further examinations are needed. In particular, more molecular dynamics simulations are needed to delineate the detailed molecular mechanisms for the various nonlinear rheological phenomena. PMID:25606850
Dynamics of nanoparticles in an entangled polymer matrix
NASA Astrophysics Data System (ADS)
Dhakal, Subas; Sureshkumar, Radhakrishna
2014-03-01
Quantitative description of the dynamics and rheology of the extracellular polymeric substance (EPS) of bacterial biofilms is still a major challenge due to their structural complexity. Recent experiments suggest that the viscoelasticity of EPS is not governed by entanglements in the polymer matrix. Here, we investigate the microstructure, dynamics and rheology of a Dextran EPS by probing the motion of nanoparticles embedded in the matrix using coarse-grained molecular dynamics simulations. Specifically, these simulations show that for particle diameter D >entanglement length le, the probe particles exhibit normal diffusion, while for D
Entanglement-Controlled Subdiffusion of Nanoparticles within Concentrated Polymer Solutions
Guo, Hongyu; Bourret, Gilles; Lennox, R. Bruce; Sutton, Mark; Harden, James L.; Leheny, Robert L.
2012-10-23
We describe x-ray photon correlation spectroscopy (XPCS) experiments tracking the motion of gold nanoparticles within solutions of high-molecular-weight polystyrene. Over displacements from nanometers to tens of nanometers, the particles undergo subdiffusive motion that is dictated by the temporal evolution of the entangled polymer mesh in the immediate vicinity of the particles. The results thus provide a novel microscopic dynamical characterization of this key structural property of polymers and more broadly demonstrate the capability of XPCS-based microrheology to interrogate heterogeneous mechanical environments in nanostructured soft materials.
Formation mechanism of monodispersed spherical core-shell ceria/polymer hybrid nanoparticles
Izu, Noriya; Uchida, Toshio; Matsubara, Ichiro; Itoh, Toshio; Shin, Woosuck; Nishibori, Maiko
2011-08-15
Graphical abstract: The formation mechanism for core-shell nanoparticles is considered to be as follows: nucleation and particle growth occur simultaneously (left square); very slow particle growth occurs (middle square). Highlights: {yields} The size of the resultant nanoparticles was strongly and complicatedly dependent on the set temperature used during reflux heating and the PVP molecular weight. {yields} The size of the nanoparticles increased by a 2-step process as the reflux heating time increased. {yields} The IR spectral changes with increasing reflux time indicated the increase in the number of cross-linked polymers in the shell. -- Abstract: Very unique core-shell ceria (cerium oxide)/polymer hybrid nanoparticles that have monodispersed spherical structures and are easily dispersed in water or alcohol without the need for a dispersant were reported recently. The formation mechanism of the unique nanoparticles, however, was not clear. In order to clarify the formation mechanism, these nanoparticles were prepared using a polyol method (reflux heating) under varied conditions of temperature, time, and concentration and molecular weight of added polymer (poly(vinylpyrrolidone)). The size of the resultant nanoparticles was strongly and complicatedly dependent on the set temperature used during reflux heating and the poly(vinylpyrrolidone) molecular weight. Furthermore, the size of the nanoparticles increased by a 2-step process as the reflux heating time increased. The IR spectral changes with increasing reflux time indicated the increase in the number of cross-linked polymers in the shell. From these results, the formation mechanism was discussed and proposed.
Molecular confinement accelerates deformation of entangled polymers during squeeze flow.
Rowland, Harry D; King, William P; Pethica, John B; Cross, Graham L W
2008-10-31
The squeezing of polymers in narrow gaps is important for the dynamics of nanostructure fabrication by nanoimprint embossing and the operation of polymer boundary lubricants. We measured stress versus strain behavior while squeezing entangled polystyrene films to large strains. In confined conditions where films were prepared to a thickness less than the size of the bulk macromolecule, resistance to deformation was markedly reduced for both solid-glass forging and liquid-melt molding. For melt flow, we further observed a complete inversion of conventional polymer viscosity scaling with molecular weight. Our results show that squeeze flow is accelerated at small scales by an unexpected influence of film thickness in polymer materials. PMID:18832609
Localization of chain dynamics in entangled polymer melts
NASA Astrophysics Data System (ADS)
Guenza, M. G.
2014-05-01
The dynamics of polymer melts in both the unentangled and entangled regimes is described by a Langevin equation for the correlated motion of a group of chains, interacting through both intra- and inter-molecular potentials. Entanglements are represented by an intermolecular monomer-monomer confining potential that has no effect on short chains, while interpolymer interactions, responsible for correlated motion and subdiffusive center-of-mass dynamics, are represented by an intermolecular center-of-mass potential derived from the Ornstein-Zernike equation. This potential ensures that the liquid of phantom chains reproduces the compressibility and free energy of the real samples. For polyethylene melts the calculated dynamic structure factor is found to be in quantitative agreement with neutron spin echo experiments of polyethylene melts with chain lengths that span both the unentangled and the entangled regimes. The theory shows a progressive localization of the cooperative chain dynamics at the crossover from the unentangled to the entangled regime, in the spirit of the reptation model.
Entangled polymer dynamics in equilibrium and flow modeled through slip links.
Schieber, Jay D; Andreev, Marat
2014-01-01
The idea that the dynamics of concentrated, high-molecular weight polymers are largely governed by entanglements is now widely accepted and typically understood through the tube model. Here we review alternative approaches, slip-link models, that share some similarities to and offer some advantages over tube models. Although slip links were proposed at the same time as tubes, only recently have detailed, quantitative mathematical models arisen based on this picture. In this review, we focus on these models, with most discussion limited to mathematically well-defined objects that conform to state-of-the-art beyond-equilibrium thermodynamics. These models are connected to each other through successive coarse graining, using nonequilibrium thermodynamics along the way, and with a minimal parameter set. In particular, the most detailed level of description has four parameters, three of which can be determined directly from atomistic simulations. Once the remaining parameter is determined for any system, all parameters for all members of the hierarchy are determined. We show how, using this hierarchy of slip-link models combined with atomistic simulations, we can make predictions about the nonlinear rheology of monodisperse homopolymer melts, polydisperse melts, or blends of different architectures. Mathematical details are given elsewhere, so these are limited here, and physical ideas are emphasized. We conclude with an outlook on remaining challenges that might be tackled successfully using this approach, including complex flow fields and polymer blends. PMID:24655135
Finite cohesion due to chain entanglement in polymer melts.
Cheng, Shiwang; Lu, Yuyuan; Liu, Gengxin; Wang, Shi-Qing
2016-04-14
Three different types of experiments, quiescent stress relaxation, delayed rate-switching during stress relaxation, and elastic recovery after step strain, are carried out in this work to elucidate the existence of a finite cohesion barrier against free chain retraction in entangled polymers. Our experiments show that there is little hastened stress relaxation from step-wise shear up to γ = 0.7 and step-wise extension up to the stretching ratio λ = 1.5 at any time before or after the Rouse time. In contrast, a noticeable stress drop stemming from the built-in barrier-free chain retraction is predicted using the GLaMM model. In other words, the experiment reveals a threshold magnitude of step-wise deformation below which the stress relaxation follows identical dynamics whereas the GLaMM or Doi-Edwards model indicates a monotonic acceleration of the stress relaxation dynamics as a function of the magnitude of the step-wise deformation. Furthermore, a sudden application of startup extension during different stages of stress relaxation after a step-wise extension, i.e. the delayed rate-switching experiment, shows that the geometric condensation of entanglement strands in the cross-sectional area survives beyond the reptation time τd that is over 100 times the Rouse time τR. Our results point to the existence of a cohesion barrier that can prevent free chain retraction upon moderate deformation in well-entangled polymer melts. PMID:26931322
Entanglement Density Changes in Free-Standing Thin Polymer Films
NASA Astrophysics Data System (ADS)
Stanzione, Joseph; Wool, Richard
2013-03-01
The entanglement molecular weight Me is obtained when a random walk chain crosses a plane three times to form a loop (R.P. Wool '83) such that for polymers with structure -CH2-CHX- where X is the side group, it is found that Me = 31 C∞ Mo/j, where C∞ is the characteristic ratio, Mo is the monomer mol weight and j =2 is the number of bonds per monomer. In thin films of thickness d < 2Rg, Me behaves as Me ~ d and this behavior is confirmed by computer simulation of random walks in thin films with reflecting boundary conditions. Thus, the entanglement density v ~ 1/Me increases as d decreases and rheological properties such as plateau modulus change as GNo ~ 1/d and plateau creep compliance Jo ~ d. The mechanical stiffening of thin films is in accord with recent experiments of McKenna et al (2012). The results are also in accord with the Packing model (Lin, Kavassil, Fetters 1983) where Me = 354 p3 in which p = Mo j/[C∞ bo2].The packing model is exactly derived from the Wool entanglement model for these polymers since C∞ = 1.36 [Mo/j]1/2. The empirical packing model with its excellent data correlation Me ~ p3 has been misinterpreted by many and such suggestions that v decreases due to nanoconfinement and GNo ~ d are incorrect.
Multiscale entanglement in ring polymers under spherical confinement.
Tubiana, Luca; Orlandini, Enzo; Micheletti, Cristian
2011-10-28
The interplay of geometrical and topological entanglement in semiflexible knotted polymer rings confined inside a spherical cavity is investigated by using advanced numerical methods. By using stringent and robust algorithms for locating knots, we characterize how the knot length l(k) depends on the ring contour length L(c) and the radius of the confining sphere R(c). In the no- and strong-confinement cases, we observe weak knot localization and complete knot delocalization, respectively. We show that the complex interplay of l(k), L(c), and R(c) that seamlessly bridges these two limits can be encompassed by a simple scaling argument based on deflection theory. The same argument is used to rationalize the multiscale character of the entanglement that emerges with increasing confinement. PMID:22107680
Sussman, Daniel; Schweizer, Kenneth
2013-01-01
The phenomenological reptation-tube model is based on a single chain perspective and was originally proposed to explain the remarkable viscoelastic properties of dense entangled polymer liquids. However, simulations over the last two decades have revealed a fundamental tension in the model: it assumes that bonded, single-chain backbone stresses are the sole polymer contribution to the slowly relaxing component of stress storage and elasticity, but mounting evidence suggests that at the local level of forces it is interchain contributions that dominate, as in simple liquids. Here we show that based on a chain model constructed at the level of self-consistently determined primitive paths, an explicit force-level treatment of the correlated intermolecular contributions to stress that arise from chain uncrossability can essentially quantitatively predict the entanglement plateau modulus associated with the soft rubbery response of polymer liquids. Analogies to transient localization and elasticity in glass-forming liquids are identified. Predictions for the effect of macroscopic deformation and anisotropic orientational order on the tube diameter are also made. Based on the interchain stress perspective the theory reproduces some aspects of the rheological response to shear and extensional deformations associated with the single chain tube model.
Microscopic theory for dynamics in entangled polymer nanocomposites
NASA Astrophysics Data System (ADS)
Yamamoto, Umi
New microscopic theories for describing dynamics in polymer nanocomposites are developed and applied. The problem is addressed from two distinct perspectives and using two different theoretical approaches. The first half of this dissertation studies the long-time and intermediate-time dynamics of nanoparticles in entangled and unentangled polymer melts for dilute particle concentrations. Using a combination of mode-coupling, Brownian motion, and polymer physics ideas, the nanoparticle long-time diffusion coefficients is formulated in terms of multiple length-scales, packing microstructures, and spatially-resolved polymer density fluctuation dynamics. The key motional mechanism is described via the parallel relaxation of the force exerted on the particle controlled by collective polymer constraint-release and the particle self-motion. A sharp but smooth crossover from the hydrodynamic to the non-hydrodynamic regime is predicted based on the Stokes-Einstein violation ratio as a function of all the system variables. Quantitative predictions are made for the recovery of the Stokes-Einstein law, and the diffusivity in the crossover regime agrees surprisingly well with large-scale molecular dynamics simulations for all particle sizes and chain lengths studied. The approach is also extended to address intermediate-time anomalous transport of a single nanoparticle and two-particle relative diffusion. The second half of this dissertation focuses on developing a novel dynamical theory for a liquid of infinitely-thin rods in the presence of hard spherical obstacles, aiming at a technical and conceptual extension of the existing paradigm for entangled polymer dynamics. As a fundamental theoretical development, the two-component generalization of a first-principles dynamic meanfield approach is presented. The theory enforces inter-needle topological uncrossability and needlesphere impenetrability in a unified manner, leading to a generalized theory of entanglements that
Chain entanglements and fracture energy in interfaces between immiscible polymers
NASA Astrophysics Data System (ADS)
Silvestri, Leonardo; Brown, Hugh R.; Carrà, Stefano; Carrà, Sergio
2003-10-01
It is a very well-known experimental fact that the toughness of interfaces obtained by joining pairs of immiscible glassy polymers is strongly correlated to the interfacial width. Several models have been proposed in the literature to estimate the fracture energy of these interfaces, but the agreement displayed with the experimental data cannot be considered satisfactory. In this paper a new model is proposed for polymers with molecular weight higher than the critical value for the onset of entanglements. The model is based on a precise and realistic calculation of the areal density of entangled strands across the interface, that is the crucial parameter determining the toughness of the glassy joints. In this paper a new fracture regime is also introduced, called "partial crazing," corresponding to a situation where, due to the fact that some of the load-bearing strands are broken during plastic deformation, the craze can start, but not fully develop. Model predictions are then compared with a series of literature fracture energy experimental data, showing excellent agreement.
Synthetic Polymers at Interfaces: Monodisperse Emulsions Multiple Emulsions and Liquid Marbles
NASA Astrophysics Data System (ADS)
Sun, Guanqing
The adsorption of polymeric materials at interfaces is an energetically favorable process which is investigated in much diversified fields, such as emulsions, bubbles, foams, liquid marbles. Pickering emulsion, which is emulsion stabilized by solid particles has been investigated for over one century and preparation of Pickering emulsion with narrow size distribution is crucial for both the theoretical study of the stabilization mechanism and practical application, such as templated fabrication of colloidosomes. The precise control over the size and functionality of polymer latices allows the preparation of monodisperse Pickering emulsions with desired sizes through SPG membrane emulsification at rather rapid rate compared to microfludic production. Double or multiple emulsions have long been investigated but its rapid destabilization has always been a major obstacle in applying them into practical applications. The modern living polymerization techniques allow us to prepare polymers with designed structure of block copolymers which makes it possible to prepare ultra-stable multiple emulsions. The precise tuning of the ratio of hydrophobic part over the hydrophilic can unveil the stabilization mechanism. Liquid marble is a new type of materials of which liquid droplets are coated by dry particles. The coating of an outer layer of dry particles renders the liquid droplets non-sticky at solid surface which is useful in transportation of small amount of liquid without leakage at extreme low friction force. The property of liquid marbles relies largely on the stabilizers and the drying condition of polymeric latices is shown to have great influence on the property of liquid marbles. Firstly, an introduction to the interfacial and colloidal science with special attention to topics on emulsions, multiple emulsion and liquid marbles is given in Chapter 1. The unique features of an interface and a discussion on the definition of colloids are introduced prior to the
Analysis of Entanglement Length and Segmental Order Parameter in Polymer Networks
NASA Astrophysics Data System (ADS)
Lang, M.; Sommer, J.-U.
2010-04-01
The tube model of entangled chains is applied to compute segment fluctuations and segmental orientational order in polymer networks. The entanglement length Ne is extracted directly from monomer fluctuations without constructing a primitive path. Sliding motion of monomers along the tube axis leads to reduction of segmental order along the chain. For network strands of length N≫Ne, the average segmental order decreases ˜(NeN)-1/2 in marked contrast to the 1/Ne contribution of entanglements to network elasticity. As a consequence, network modulus is not proportional to segmental order in entangled polymer networks. Monte Carlo simulations over a wide range of molecular weights are in quantitative agreement with our theoretical predictions. The impact of entanglements on these properties is directly tested by comparing with simulations where entanglement constraints are switched off.
Multiscale simulation of history-dependent flow in entangled polymer melts
NASA Astrophysics Data System (ADS)
Murashima, T.; Taniguchi, T.
2011-10-01
Predicting the flow of an entangled polymer melt is still difficult because of its multiscale characteristics. We have developed a novel multiscale simulation technique to investigate the history-dependent flow behavior of entangled polymer melts. The technique involves using a smoothed particle hydrodynamics simulation that is coupled at each fluid element to microscopic simulators that can accurately account for the dynamics of entangled polymers. The multiscale simulation is used to investigate the flow of an entangled polymer melt around a cylindrical obstacle subject to periodic boundary conditions. It is found that the macroscopic flow behavior is dependent on the history of the microscopic states of the polymers and that this memory causes nonlinear behavior even in the regions where the local Weissenberg number defined using the local strain-rate is less than unity. The spatial distribution of the entanglements langZrang suggests that, in a region around the obstacle, a slight depletion of the entanglements is observed and that this region broadens along the downstream direction. The totality of the presented results suggests that we have succeeded in describing the entangled polymer melt flow without using any constitutive equation.
Reduced Viscosity of Free Surface in Entangled Polymer Melt Films
NASA Astrophysics Data System (ADS)
Koga, Tad; Li, C.; Endoh, M.; Koo, J.; Rafailovich, M.; Narayanan, S.; Lee, D.; Lurio, L.; Sinha, S.
2010-03-01
The dynamics of polymer chains near the surface of a melt and within thin films remains a subject of inquiry along with the nature of the glass transition in these systems. By embedding ``dilute'' gold nanoparticles in single polystyrene thin films as ``markers'', we could probe the local viscosity of the free surface at temperatures far above the glass transition temperature (Tg). The technique used was X-ray photon correlation spectroscopy with resonance-enhanced X-ray scattering. The results clearly showed the viscosity was about 30 % lower than the rest of the film. We found that this reduction is strongly associated with chain entanglements at the free surface rather than the reduction in Tg.
Simulations on the number of entanglements of a polymer network using knot theory.
Michalke, W; Lang, M; Kreitmeier, S; Göritz, D
2001-07-01
Polymer networks, created on the computer using the Bond-Fluctuation-Algorithm, offer the possibility to count the number of entanglements. We generated networks consisting of 5000 chains that were cross linked at their end groups via tetra-functional cross linkers. The analysis of the topology was performed by computing the Homfly polynomial of the entanglements offering a much more precise determination of the knot and entanglement type than the Gaussian linking number. It also allows us to determine the influence of Brunnian links. Results concerning the connection between the chain length and the number of entanglements are shown. PMID:11461310
Evolution of non-equilibrium entanglement networks in spincast thin polymer films
NASA Astrophysics Data System (ADS)
Dalnoki-Veress, Kari; McGraw, Joshua; Fowler, Paul
2012-02-01
Measuring the rheology of non-equilibrium thin polymer films has received significant attention recently. Experiments are typically performed on thin polymer films that inherit their structure from spin coating. While the results of several rheological experiments paint a clear picture, details of molecular configurations in spincast polymer films are still unknown. Here we present the results of crazing measurements which demonstrate that the effective entanglement density of thin polymer films changes as a function of annealing toward a stable equilibrium value. The effective entanglement density plateaus with a time scale on the same order as the bulk reptation time.
NASA Astrophysics Data System (ADS)
Zartman, Gregory; Wang, Yangyang; Wang, Shi-Qing
2009-03-01
Large amplitude oscillatory shear (LAOS) experiments were carried out on a series of entangled monodisperse styrene-butadiene random copolymers (SBR). The deformation field during the measurements was monitored with a particle-tracking velocimetric technique. It was found that when the applied frequency was higher than the overall relaxation rate of the sample, the entangled melt would undergo uniform deformation at small strains, but exhibit shear banding at large strains. The inhomogeneity of the deformation field suggests that yielding through chain disentanglement cannot take place uniformly. This is the first report of shear banding in LAOS for melts and consequently rules out any speculation that shear banding could originate from concentration variation (due to shear induced phase separation) in entangled solutions.
Solid-like rheological response of non-entangled polymers in the molten state.
Mendil, H; Baroni, P; Noirez, L
2006-01-01
We show that non-entangled polymers display an elastic-like behaviour at a macroscopic scale (probed at some 0.100 mm thickness) up to at least hundred degrees above the glass transition temperature. This observation, found under non-slippage conditions, both for side-chain liquid crystalline polymers and ordinary polymers, is in contradiction with the typically found flow behaviour of polymer melt. Our measurements were carried out with a conventional rheometer at thicknesses of several tenths millimetres. Thus, we were probing bulk properties. The observed elasticity supposedly implies that even in the melt the chains experience a cohesive effect of macroscopic distances, involving collective motions over time scales longer than the individual relaxation time of an individual polymer chain. The detection of such a solid-like property of molten non-entangled polymers is of considerable importance for a better understanding of the polymer dynamics. PMID:16432635
Solid-like rheological response of non-entangled polymers in the molten state
NASA Astrophysics Data System (ADS)
Mendil, H.; Baroni, P.; Noirez, L.
2006-01-01
We show that non-entangled polymers display an elastic-like behaviour at a macroscopic scale (probed at some 0.100;mm thickness) up to at least hundred degrees above the glass transition temperature. This observation, found under non-slippage conditions, both for side-chain liquid crystalline polymers and ordinary polymers, is in contradiction with the typically found flow behaviour of polymer melt. Our measurements were carried out with a conventional rheometer at thicknesses of several tenths millimetres. Thus, we were probing bulk properties. The observed elasticity supposedly implies that even in the melt the chains experience a cohesive effect of macroscopic distances, involving collective motions over time scales longer than the individual relaxation time of an individual polymer chain. The detection of such a solid-like property of molten non-entangled polymers is of considerable importance for a better understanding of the polymer dynamics.
Failure behavior after stepwise uniaxial extension of entangled polymer melts
Sun, Hao; Lin, Panpan; Liu, Gengxin; Ntetsikas, Konstantinos; Misichronis, Konstantinos; Kang, Nam-Goo; Liu, Jianning; Avgeropoulos, Apostolos; Mays, Jimmy; Wang, Shi-Qing
2015-01-01
This work studies how stepwise extension of various well-entangled polymer melts produce mechanical/structural breakdowns during stress relaxation. Depending on how stepwise extension is imposed on five different styrene-butadiene random copolymers, two different forms of specimen failure are observed. When a step extension is produced with a low Hencky rate or to a low strain below some thresholds, the sample breaks up rather sharply after an appreciable period of induction during which the stress relaxes quiescently. After step extension, the sample draws and undergoes unsustainable necking due to shear yielding, if the step extension is produced with a Hencky rate highermore » than the Rouse relaxation rate and the magnitude is beyond a Hencky strain of 1.5. Moreover, introduction of long-chain branching suppresses the elastic breakup, postponing it to Hencky strains beyond 2.5. The clearly identifiable characteristics of the elastic yielding may be understood in terms of some speculative interpretations. More convincing explanations have yet to come from future computer experiments that hopefully the present work is able to motivate.« less
Failure behavior after stepwise uniaxial extension of entangled polymer melts
Sun, Hao; Lin, Panpan; Liu, Gengxin; Ntetsikas, Konstantinos; Misichronis, Konstantinos; Kang, Nam-Goo; Liu, Jianning; Avgeropoulos, Apostolos; Mays, Jimmy; Wang, Shi-Qing
2015-01-01
This work studies how stepwise extension of various well-entangled polymer melts produce mechanical/structural breakdowns during stress relaxation. Depending on how stepwise extension is imposed on five different styrene-butadiene random copolymers, two different forms of specimen failure are observed. When a step extension is produced with a low Hencky rate or to a low strain below some thresholds, the sample breaks up rather sharply after an appreciable period of induction during which the stress relaxes quiescently. After step extension, the sample draws and undergoes unsustainable necking due to shear yielding, if the step extension is produced with a Hencky rate higher than the Rouse relaxation rate and the magnitude is beyond a Hencky strain of 1.5. Moreover, introduction of long-chain branching suppresses the elastic breakup, postponing it to Hencky strains beyond 2.5. The clearly identifiable characteristics of the elastic yielding may be understood in terms of some speculative interpretations. More convincing explanations have yet to come from future computer experiments that hopefully the present work is able to motivate.
NASA Astrophysics Data System (ADS)
Grest, Gary S.
2008-03-01
Twenty years ago at the APS March Meeting, Kurt Kremer and I presented the first numerical evidence from computer simulations that the reptation model of Edwards and de Gennes correctly describes the dynamics of entangled linear polymer melts. For chains longer than the entanglement length Ne, the monomers of a chain move predominantly along their own contour. The distinctive signature of reptation dynamics, which we observed, was that on intermediate time scales, the mean squared displacement of a monomer increases with time as t^ 1/4. Though these early simulations were limited to chains of a few Ne, they demonstrated the potential of computer simulations to contribute to our understanding of polymer dynamics. Here I will review the progress over the past twenty years and present an outlook for the future in modeling entangled polymer melts and networks. With present day computers coupled with efficient parallel molecular dynamics codes, it is now possible to follow the equilibrium dynamics of chains of length 10-20Ne from the early Rouse regime to the long time diffusive regime. Result of these simulations support the earlier results obtained on chains of only a few Ne. Further evidence for the tube models of polymer dynamics has been obtained by identifying the primitive path mesh that characterizes the microscopic topological state of the computer- generated conformations of the chains. In particular, the plateau moduli derived on the basis of this analysis quantitatively reproduce experimental data for a wide spectrum of entangled polymer liquids including semi-dilute theta solutions of synthetic polymers, the corresponding dense melts, and solutions of semi-flexible (bio)polymers such as f-actin or suspensions of rodlike viruses. We also find that in agreement with the reptation model, the stress, end-to-end distance and entanglement length of an entangled melt subjected to uniaxial elongation, all relax on the same time scale.
NASA Astrophysics Data System (ADS)
Uneyama, Takashi; Akimoto, Takuma; Miyaguchi, Tomoshige
2012-09-01
In entangled polymer systems, there are several characteristic time scales, such as the entanglement time and the disengagement time. In molecular simulations, the longest relaxation time (the disengagement time) can be determined by the mean square displacement (MSD) of a segment or by the shear relaxation modulus. Here, we propose the relative fluctuation analysis method, which is originally developed for characterizing large fluctuations, to determine the longest relaxation time from the center of mass trajectories of polymer chains (the time-averaged MSDs). Applying the method to simulation data of entangled polymers (by the slip-spring model and the simple reptation model), we provide a clear evidence that the longest relaxation time is estimated as the crossover time in the relative fluctuations.
Huang, Xiaoxi; Zhou, Li-Jing; Voiry, Damien; Chhowalla, Manish; Zou, Xiaoxin; Asefa, Tewodros
2016-07-27
In our quest to make various chemical processes sustainable, the development of facile synthetic routes and inexpensive catalysts can play a central role. Herein we report the synthesis of monodisperse, polyaniline (PANI)-derived mesoporous carbon nanoparticles (PAMCs) that can serve as efficient metal-free electrocatalysts for the hydrogen peroxide reduction reaction (HPRR) as well as the oxygen reduction reaction (ORR) in fuel cells. The materials are synthesized by polymerization of aniline with the aid of (NH4)2S2O8 as oxidant and colloidal silica nanoparticles as templates, then carbonization of the resulting PANI/silica composite material at different high temperatures, and finally removal of the silica templates from the carbonized products. The PAMC materials that are synthesized under optimized synthetic conditions possess monodisperse mesoporous carbon nanoparticles with an average size of 128 ± 12 nm and an average pore size of ca. 12 nm. Compared with Co3O4, a commonly used electrocatalyst for HPRR, these materials show much better catalytic activity for this reaction. In addition, unlike Co3O4, the PAMCs remain relatively stable during the reaction, under both basic and acidic conditions. The nanoparticles also show good electrocatalytic activity toward ORR. Based on the experimental results, PAMCs' excellent electrocatalytic activity is attributed partly to their heteroatom dopants and/or intrinsic defect sites created by vacancies in their structures and partly to their high porosity and surface area. The reported synthetic method is equally applicable to other polymeric precursors (e.g., polypyrrole (PPY)), which also produces monodisperse, mesoporous carbon nanoparticles in the same way. The resulting materials are potentially useful not only for electrocatalysis of HPRR and ORR in fuel cells but also for other applications where high surface area, small sized, nanostructured carbon materials are generally useful for (e.g., adsorption
Goujon, Florent; Malfreyt, Patrice; Tildesley, Dominic J
2008-07-21
We use a simple spring-spring repulsion to model entanglements between polymers in dissipative particle dynamics (DPD) simulations. The model is applied to a polymer brushes system to study lubrication. We demonstrate that this method leads to mechanical equilibrium in polymer brushes using the normal DPD time step. The number of bond crossings is calculated to provide a quantitative description of the entanglement. We demonstrate that it is possible to avoid 99% of the bond crossings with the values of spring-spring repulsion that can be used without significantly decreasing the time step. A shear force is applied to the system to study the effect of the decrease in the bond crossings on the structure and rheological properties of the brushes. In particular, we show how the friction coefficient increases with the decrease in the bond crossings of the polymers. PMID:18647043
Horák, Daniel; Kučerová, Jana; Korecká, Lucie; Jankovičová, Barbora; Palarčík, Jiří; Mikulášek, Petr; Bílková, Zuzana
2012-05-01
Magnetic macroporous PGMA and PHEMA microspheres containing carboxyl groups are synthesized by multi-step swelling and polymerization followed by precipitation of iron oxide inside the pores. The microspheres are characterized by SEM, IR spectroscopy, AAS, and zeta-potential measurements. Their functional groups enable bioactive ligands of various sizes and chemical structures to couple covalently. The applicability of these monodisperse magnetic microspheres in biospecific catalysis and bioaffinity separation is confirmed by coupling with the enzyme trypsin and huIgG. Trypsin-modified magnetic PGMA-COOH and PHEMA-COOH microspheres are investigated in terms of their enzyme activity, operational and storage stability. The presence of IgG molecules on microspheres is confirmed. PMID:22411761
Visco-elasticity of bottlebrush polymer melts: Pushing the lower limit of the entanglement modulus
NASA Astrophysics Data System (ADS)
Daniel, William; Burdynska, Joanna; Dobrynin, Andrey; Matyjaszewski, Krzysztof; Rubinstein, Michael; Sheiko, Sergei; Materials Interdisciplinary Research Team @ UNC Chapel Hill Team
2015-03-01
Without swelling in a solvent, it is challenging to obtain materials with a modulus below ca.105 Pa, which is dictated by chain entanglements. Here we analyze the densely grafted molecular brush architecture to create solvent-free neat polymer melts and elastomers with plateau moduli down to hundred Pa. Such materials are theorized to behave as linear chains with rescaled dimensions of the entanglement strand due to the increase in both width and persistence length of polymer bottlebrushes. This simple rescaling leads to a prediction that entanglement modulus decreases with the degree of polymerization (DP) of the sidechains to the -1.5 power. Experimental evidence gives a remarkably close power of -1.38 +/- 0.05 with moduli in the hundreds of Pascals for long sidechains with DP ≅100. The experimental data have been fit using a combination of the Rouse relaxation and double reputation models lending further evidence that bottlebrush polymer behave as linear polymers with large entanglement weights and longer persistence lengths. With the addition of crystallizable block it will be possible to control the crosslinking density and design ultrasoft shapememory materials for use in mechanically sensitive applications. NSF DMR-1407645, DMR-1122483.
Apparatus for and method of producing monodisperse submicron polymer powders from solution
Noid, Donald W.; Otaigbe, Joshua U.; Barnes, Michael D.; Sumpter, Bobby G.; Kung, Chung-Yi
2002-01-01
This invention describes a method of producing polymer powders from solution in a compatible solvent using a new device referred to as a microdroplets on demand generator (MODG). The embodiment of this invention is the MODG apparatus and its relevance as a method to extensive application in materials science and technology. Proof of concept is demonstrated using poly(ethylene) glycol polymer microparticles generated with the MODG and captured in a microparticle levitation device.
Self-Similar Conformations and Dynamics of Non-Concatenated Entangled Ring Polymers
NASA Astrophysics Data System (ADS)
Ge, Ting
A scaling model of self-similar conformations and dynamics of non-concatenated entangled ring polymers is developed. Topological constraints force these ring polymers into compact conformations with fractal dimension D =3 that we call fractal loopy globules (FLGs). This result is based on the conjecture that the overlap parameter of loops on all length scales is equal to the Kavassalis-Noolandi number 10-20. The dynamics of entangled rings is self-similar, and proceeds as loops of increasing sizes are rearranged progressively at their respective diffusion times. The topological constraints associated with smaller rearranged loops affect the dynamics of larger loops by increasing the effective friction coefficient, but have no influence on the tubes confining larger loops. Therefore, the tube diameter defined as the average spacing between relevant topological constraints increases with time, leading to ``tube dilation''. Analysis of the primitive paths in molecular dynamics (MD) simulations suggests complete tube dilation with the tube diameter on the order of the time-dependent characteristic loop size. A characteristic loop at time t is defined as a ring section that has diffused a distance of its size during time t. We derive dynamic scaling exponents in terms of fractal dimensions of an entangled ring and the underlying primitive path and a parameter characterizing the extent of tube dilation. The results reproduce the predictions of different dynamic models of a single non-concatenated entangled ring. We demonstrate that traditional generalization of single-ring models to multi-ring dynamics is not self-consistent and develop a FLG model with self-consistent multi-ring dynamics and complete tube dilation. Various dynamic scaling exponents predicted by the self-consistent FLG model are consistent with recent computer simulations and experiments. We also perform MD simulations of nanoparticle (NP) diffusion in melts of non-concatenated entangled ring polymers
Distortion of chain conformation and reduced entanglement in polymer-graphene oxide nanocomposites
NASA Astrophysics Data System (ADS)
Weir, Michael; Boothroyd, Stephen; Johnson, David; Thompson, Richard; Coleman, Karl; Clarke, Nigel
Graphene and related two-dimensional materials are excellent candidates as filler materials in polymer nanocomposites due to their extraordinary physical properties and high aspect ratio. To explore the mechanism by which the filler affects the bulk properties of these unique systems, and to build understanding from the macromolecular level upwards, we use a combination of small-angle neutron scattering (SANS) and oscillatory rheology. Where a good dispersion is achieved in poly(methyl methacrylate)-graphene oxide (PMMA-GO) nanocomposites, we observe a reduction in the polymer radius of gyration with increasing GO concentration that is consistent with the predicted behavior of polymer melt chains at a solid interface. We use concepts from thin-film polymer physics to formulate a scaling relation for the reduction in entanglements caused by the GO interfaces. Using these scaling arguments, we utilize SANS results to directly estimate the changes to the elastic plateau modulus of the network of entangled polymer chains, and find a correlation with the measured bulk rheology. We present a direct link between interfacial confinement effects and the bulk polymer nanocomposite properties, whilst demonstrating a model system for measuring thin film polymer physics in the bulk.
Song, Yang; Du, Yi; Lv, Dachao; Ye, Gang; Wang, Jianchen
2014-06-15
Separation of strontium is of great significance for radioactive waste treatment and environmental remediation after nuclear accidents. In this work, a novel class of adsorbent (Crown-g-MPPPs) was synthesized by chemical grafting a macrocyclic ether receptor to monodisperse porous polymer particles (MPPPs) for strontium adsorption. Meanwhile, a counterpart material (Crown@MPPPs) with the receptor molecules immobilized to the MPPPs substrate by physical impregnation was prepared. To investigate how the immobilization manner and distribution of the receptors influence the adsorption ability, a comparative study on the adsorption behaviour of the two materials towards Sr(II) in HNO3 media was accomplished. Due to the shorter diffusion path and covalently-bonded structure, Crown-g-MPPPs showed faster adsorption kinetics and better stability for cycle use. While Crown@MPPPs had the advantages of facile synthesis and higher adsorption capacity, owing to the absence of conformational constraint to form complexation with Sr(II). Kinetic functions (Lagergren pseudo-first-order/pseudo-second-order functions) and adsorption isotherm models (Langmuir/Freundlich models) were used to fit the experimental data and examine the adsorption mechanism. On this basis, a chromatographic process was proposed by using Crown@MPPPs for an effective separation of Sr(II) (91%) in simulated high level liquid waste (HLLW). PMID:24794813
Leng, Yuxiao; Bai, Feifei; Ye, Gang; Wei, Jichao; Wang, Jianchen; Chen, Jing
2013-07-01
Strontium{sup 90} is one of the typical fission products that may be found in high level liquid waste (HLLW). Separation of Sr{sup 90} prior to the vitrification is beneficial to the final treatment of solid radioactive waste. In this study, a new class of sorbent for Sr(II) was developed by loading the macrocyclic ether DtBuCH18C6 into the monodisperse porous polymer particles (MPPPs). The MPPPs are well-known as a promising chromatographic material due to the uniform particle size, porous morphology, good compatibility with organic extractants, and rigid matrix. The structure and micro-morphology of the sorbent particles were characterized. The adsorption behavior towards Sr(II) in HNO{sub 3} media was investigated by both batch and column experiments. High adsorption efficiency and selective separation of Sr(II) was obtained. The sorbent particles can be recycled for at least several times before obvious lose of the adsorption ability. This kind of sorbent possesses the potential to be used for strontium separation in radioactive liquid waste.
Diffusion in Entangled and Surface Modified Polymer Systems
NASA Astrophysics Data System (ADS)
Tead, Stanley Fromm
Ion beam analysis techniques were used to measure the concentration vs. depth profiles of deuterium labelled polymer molecules in unlabeled and/or chemically dissimilar polymer melts, for several polymer systems. In the first polymer system, the tracer diffusion coefficient of deuterated polystyrene (d-PS) molecules was measured in polystyrene (PS) matrices which were blends of high molecular weight (volume fraction phi) and low molecular weight PS. The dependence of the d-PS diffusion coefficient on phi was quantitatively predicted by the models of reptation and constraint release. In the second polymer system, diffusion of polystyrenes was studied with ring shaped chains substituted (instead of linear ones) in the tracer and/or matrix roles. The diffusion of linear tracers into ring matrices was nearly identical to linear tracer diffusion in linear matrices, a result not predicted by any current theories. Dry etching of polystyrene by four different ion and plasma methods crosslinked the exposed surface monolayer, immobilizing it and reducing its permeability to diffusion by unetched tracer molecules. The integrated thickness of the immobile layer is decreased for an increased ratio of chain scission to crosslinking. The ratio is smallest for reactive ion beam etching, intermediate for reactive ion etching, and largest for the pure plasma techniques. Diffusion was investigated in systems of the polymer polyimide (PI), produced by the imidization of polyamic acid at a temperature T_{rm i }. The effects of thermal processing (imidization) of the polymer and exposure to solvents were studied. The diffusion of deuterated polyamic acid in PI was reduced to negligible levels for T_{rm i}'s at or above 200^circ C; purely thermally activated diffusion (in the absence of solvents) was not seen for any combination of annealing temperatures up to 400^circ C. Ion beam analysis methods were developed to measure the kinetics and depth dependence of the imidization reaction in
NASA Astrophysics Data System (ADS)
Larson, Ron
2007-03-01
Using concepts developed over the years by de Gennes, Doi, Edwards, Marrucci, Rubinstein, McLeish, Milner, and others, a kind of ``standard model'' for entangled polymer relaxation and rheology has been developed, which, like the ``standard model'' of high-energy physics, has a number of ad hoc assumptions and fitting parameters. The ``standard model'' of polymer relaxation is based on a phenomenological ``tube'' surrounding each polymer chain that represents the effect on that chain of non-crossability constraints imposed by surrounding chains. As a result of its confinement to the tube, the chain relaxes by reptation -- or sliding along the tube, accordion-like fluctuations of the chain within the tube, and movement of, or dilation of, the tube due to motion of the surrounding chains creating the tube-like region. Increasing computer speed and advanced simulation methods are now making possible the direct molecular dynamics simulations of entangled polymers resolved at the monomer scale, over time scales sufficient to test the underlying assumptions of the tube model and allow direct calculation of some of the phenomenological parameters. Here we illustrate how these simulations allow us to estimate the distribution of tube lengths, the average diameter of the tube, and the mobility of the branch point in a simple ``star'' branched polymer. These findings confirm the validity of the tube ansatz, but suggest that some corrections to the ``standard model'' may be needed.
Dynamic scaling in entangled mean-field gelation polymers.
Das, Chinmay; Read, Daniel J; Kelmanson, Mark A; McLeish, Tom C B
2006-07-01
We present a simple reaction kinetics model to describe the polymer synthesis used by Lusignan et al. [Phys. Rev. E 60, 5657 (1999)] to produce randomly branched polymers in the vulcanization class. Numerical solution of the rate equations gives probabilities for different connections in the final product, which we use to generate a numerical ensemble of representative molecules. All structural quantities probed in the experiments are in quantitative agreement with our results for the entire range of molecular weights considered. However, with detailed topological information available in our calculations, our estimate of the "rheologically relevant" linear segment length is smaller than that estimated from the experimental results. We use a numerical method based on a tube model of polymer melts to calculate the rheological properties of such molecules. Results are in good agreement with experiment, except that in the case of the largest molecular weight samples our estimate of the zero-shear viscosity is significantly lower than the experimental findings. Using acid concentration as an indicator for closeness to the gelation transition, we show that the high-molecular-weight polymers considered are at the limit of mean-field behavior--which possibly is the reason for this disagreement. For a truly mean-field gelation class of model polymers, we numerically calculate the rheological properties for a range of segment lengths. Our calculations show that the tube theory with dynamical dilation predicts that, very close to the gelation limit, the contribution to viscosity for this class of polymers is dominated by the contribution from constraint-release Rouse motion and the final viscosity exponent approaches a Rouse-like value. PMID:16907093
Structure and Entanglement Factors on Dynamics of Polymer Grafted Magnetic Nanoparticles
NASA Astrophysics Data System (ADS)
Liu, Siqi; Senses, Erkan; Jiao, Yang; Narayanan, Suresh; Akcora, Pinar
Magnetic nanoparticles functionalized with long polymer chains at low graft density are interesting systems to study structure-dynamic relationships in polymer nanocomposites since they are shown to aggregate into strings in both solution and melts, and also into spheres and branched aggregates in the presence of free polymer chains. This work investigates the structure, free volume and entanglement effects in composites of polystyrene grafted iron oxide nanoparticles by measuring particle dynamics with x-ray photon correlation spectroscopy technique. Particles of highly ordered strings and aggregated systems follow heterogeneous dynamics commonly observed in jammed soft glassy systems and other nanocomposites. On the other hand, particle dynamics becomes diffusive in branched structures which could be caused by the less penetration of long matrix chains into the brushes. These results show that particle dynamics is dictated through the strong interactions of low graft density chains with the host polymer.
Localization and elasticity in entangled polymer liquids as a mesoscopic glass transition
NASA Astrophysics Data System (ADS)
Schweizer, Kenneth
2010-03-01
The reptation-tube model is widely viewed as the correct zeroth order model for entangled linear polymer dynamics under quiescent conditions. Its key ansatz is the existence of a mesoscopic dynamical length scale that prohibits transverse chain motion beyond a tube diameter of order 3-10 nm. However, the theory is phenomenological and lacks a microscopic foundation, and many fundamental questions remain unanswered. These include: (i) where does the confining tube field come from and can it be derived from statistical mechanics? (ii) what is the microscopic origin of the magnitude, and power law scaling with concentration and packing length, of the plateau shear modulus? (iii) is the tube diameter time-dependent? (iv) does the confinement field contribute to elasticity ? (v) do entanglement constraints have a finite strength? Building on our new force-level theories for the dynamical crossover and activated barrier hopping in glassy colloidal suspensions and polymer melts, a first principles self-consistent theory has been developed for entangled polymers. Its basic physical elements, and initial results that address the questions posed above, will be presented. The key idea is that beyond a critical degree of polymerization, the chain connectivity and excluded volume induced intermolecular correlation hole drives temporary localization on an intermediate length scale resulting in a mesoscopic ``ideal kinetic glass transition.'' Large scale isotropic motion is effectively quenched due to the emergence of chain length dependent entropic barriers. However, the barrier height is not infinite, resulting in softening of harmonic localization at large displacements, temporal increase of the confining length scale, and a finite strength of entanglement constraints which can be destroyed by applied stress.
Protein encapsulation in and release from monodisperse double-wall polymer microspheres
Xia, Yujie; Xu, Qingxing; Wang, Chi-Hwa; Pack, Daniel W.
2014-01-01
Biodegradable polymer double-wall microspheres (DWMS) are promising vehicles for macromolecular therapeutics such as proteins and peptides. Using precision particle fabrication (PPF) technology, uniform DWMS with outer diameter ~55 μm were fabricated comprising poly(lactide-co-glycolide) cores encapsulating bovine serum albumin (BSA) and ~10 μm thick, drug-free, poly(lactic acid) shells of varying PLA molecular weight. Also, monolithic single-wall microspheres (SWMS) were fabricated to mimic the BSA-loaded core. The use of relatively fast extracting ethyl acetate and slowly extracting dichloromethane as shell- and core-phase solvents, respectively, was found to produce DWMS with well-defined core-shell structure, high BSA encapsulation efficiency, and the desired localization of protein in the particle core. Initial protein distribution, particle erosion, and in vitro protein release from DWMS and SWMS were examined. The presence of a BSA-free shell in DWMS decreased the protein release rate and extended the duration of release from ~50 days to 70-80 days, demonstrating the capacity of such DWMS to provide enhanced control of protein delivery rates. PMID:23529836
Liang, Guodong; Ni, Huan; Bao, Suping; Zhu, Fangming; Gao, Haiyang; Wu, Qing; Tang, Ben Zhong
2014-06-01
A class of new amphiphilic nanocapsules entangled with organometallic coordination polymers has been developed for the first time. Poly(2-(N,N-dimethyl amino)ethyl methacrylate)-b-polystyrene capped with β-cyclodextrin (β-CD) (CD-PDMAEMA-b-PS) is first synthesized using sequent RAFT polymerization of styrene and 2-(N,N-dimethyl amino)ethyl methacrylate with xanthate modified β-CD as chain transfer agent. The end group of β-CD is allowed to include 4,4'-bipyridine through host-guest inclusion to yield PDMAEMA-b-PS terminated with an inclusion complex of β-CD and bipyridine (bpy-PDMAEMA-b-PS), which is then used as surfactant to prepare emulsion droplets in toluene/water mixture. Upon addition of Ni(II), bipyridine coordinates with Ni(II) to form coordination polymers in the periphery of emulsion droplets, affording amphiphilic capsules entangled with organometallic coordination polymers, as confirmed by GPC, (1)H NMR, SEM, TEM, DLS, and so on. The organometallic coordination polymer capsules are capable of encapsulating organic cargoes. Interestingly, encapsulated cargoes can be extracted from the capsules without damaging the capsules. Such capsules are potential candidates for encapsulating and controlled release of organic cargoes. PMID:24828951
Relaxation of non-equilibrium entanglement networks in thin polymer films.
McGraw, Joshua D; Fowler, Paul D; Ferrari, Melissa L; Dalnoki-Veress, Kari
2013-01-01
It is known that polymer films, prepared by spin coating, inherit non-equilibrium configurations which can affect macroscopic film properties. Here we present the results of crazing experiments that support this claim; our measurements indicate that the as-cast chain configurations are strongly stretched as compared to equilibrium Gaussian configurations. The results of our experiments also demonstrate that the entanglement network equilibrates on a time scale comparable to one reptation time. Having established that films can be prepared with an equilibrium entanglement network, we proceed by confining polymers to films in which the thickness is comparable to the molecular size. By stacking two such films, a bilayer is created with a buried entropic interface. Such an interface has no enthalpic cost, only an entropic penalty associated with the restricted configurations of molecules that cannot cross the mid-plane of the bilayer. In the melt, the entropic interface heals as chains from the two layers mix and entangle with one another; crazing measurements allow us to probe the dynamics of two films becoming one. Healing of the entropic interface is found to take less than one bulk reptation time. PMID:23355094
NASA Astrophysics Data System (ADS)
Karim, Mir; Indei, Tsutomu; Schieber, Jay D.; Khare, Rajesh
2016-01-01
Particle rheology is used to extract the linear viscoelastic properties of an entangled polymer melt from molecular dynamics simulations. The motion of a stiff, approximately spherical particle is tracked in both passive and active modes. We demonstrate that the dynamic modulus of the melt can be extracted under certain limitations using this technique. As shown before for unentangled chains [Karim et al., Phys. Rev. E 86, 051501 (2012), 10.1103/PhysRevE.86.051501], the frequency range of applicability is substantially expanded when both particle and medium inertia are properly accounted for by using our inertial version of the generalized Stokes-Einstein relation (IGSER). The system used here introduces an entanglement length dT, in addition to those length scales already relevant: monomer bead size d , probe size R , polymer radius of gyration Rg, simulation box size L , shear wave penetration length Δ , and wave period Λ . Previously, we demonstrated a number of restrictions necessary to obtain the relevant fluid properties: continuum approximation breaks down when d ≳Λ ; medium inertia is important and IGSER is required when R ≳Λ ; and the probe should not experience hydrodynamic interaction with its periodic images, L ≳Δ . These restrictions are also observed here. A simple scaling argument for entangled polymers shows that the simulation box size must scale with polymer molecular weight as Mw3. Continuum analysis requires the existence of an added mass to the probe particle from the entrained medium but was not observed in the earlier work for unentangled chains. We confirm here that this added mass is necessary only when the thickness LS of the shell around the particle that contains the added mass, LS>d . We also demonstrate that the IGSER can be used to predict particle displacement over a given timescale from knowledge of medium viscoelasticity; such ability will be of interest for designing nanoparticle-based drug delivery.
Large-scale diffusion of entangled polymers along nanochannels
NASA Astrophysics Data System (ADS)
Saalwachter, Kay; Lange, Frank; Steinhart, Martin; Judeinstein, Patrick
2015-03-01
Confinement-induced changes in polymer mobility are still under active discussion. For weakly interacting poly(butadiene) chains in 100 μm long, 20 and 60 nm wide channels in anodic Al2O3, we here report on the study of the large-scale pore-averaged self diffusion on a μm scale by 1H pulsed-gradient NMR. We find weak indications of an acceleration due to surface-induced disentanglement. Unlike previous reports on polymer diffusion into particle nanocomposites of similar confinement scale, or start-up diffusivities out of even thinner films, we find an MW and temperature independent reduction of diffusivity that is solely determined by the confinement size. We rationalize this trend by a simple volume-average model, which suggests a 20-fold surface-enhanced monomeric friction on the scale of the packing length, which can be compared to a factor of 300 that our model predicts for comparable thin-film data of poly(styrene) on silica.
First-Passage Time in Entangled Star Polymers Melts
NASA Astrophysics Data System (ADS)
Cao, Jing; Zhu, Jian; Wang, Zuowei; Likhtman, Alexei
2015-03-01
For a single star polymer in a melt of extremely long linear chains, the stress of star polymer relaxes by arm-retraction in which the star arms explore new configurations by withdrawing along their tubes and stretching out towards a new direction. Pearson and Helfand proposed that the arm in the tube can be represented as a harmonic spring with an applied thermal tension such that the arm-end feels an entropic force if it fluctuates away from its equilibrium position. We have investigated the first-passage(FP) time of the destruction of tube segments by representing the arm as a one-dimensional Rouse chain. In contrast, we found that the disengagement of a tube segment is getting faster with more Rouse modes added in, which means the FP problem has to be modelled by a multi-dimensional Kramer's problem. We found a new way of solving the multi-dimensional FP problem by projecting the problem along the most probable trajectory termed ``minimal action trajectory'' and correcting it by entropy term. In addition, we performed direct and forward-flux simulations of Rouse chains of different lengths. A good agreement between the analytical calculations and simulations was achieved for both discrete and continuous Rouse chains.
Stress-Strain Relation of Tire Rubber Consist of Entangled Polymers, Fillers and Crosslink
NASA Astrophysics Data System (ADS)
Hagita, Katsumi; Bito, Y.; Minagawa, Y.; Omiya, M.; Morita, H.; Doi, M.; Takano, H.
2009-03-01
We presented a preliminary result of large scale coarse-grained Molecular Dynamics simulation of filled polymer melts with Sulfur-crosslink under an uni-axial deformation by using the Kremer-Grest Model. The size of simulation box under periodic boundary conditions (PBC) is set to about 66nm to consider length of entangled polymer chains, size and structure of fillers, and non-uniform distribution of crosslink. We put 640 polymer chains of 1024 particles and 32 fillers into the PBC box. Each filler consists of 1280 particles of the C1280 fullerene structure. A repulsive force from the center of the filler is applied to the particles. Here, the particles of the fillers are chosen to be the same as the particles of the polymers and the diameter of the filler is about 15nm. The distribution of the fillers used in this simulation is provided by the result of 2d pattern RMC analysis for 2D-USAXS experiments at SPring-8. Sulfur crosslink are randomly distributed in the system. It is found that stress-strain curves estimated by applying a certain uni-axial deformation to the system in simulations are in good agreement with those in experiments. It is successful to show difference on the S-S curve between existence / absence of fillers and qualitative dependence of attractive force between polymer and filler.
A Microscopic Model for Diffusion of a Polymer Chain in the Entangled Regime
NASA Astrophysics Data System (ADS)
Canpolat, Murat; Erzan, Ayþe; Pekcan, Önder
1997-01-01
In the entangled regime the reptation concept [1,2] is the most successful in describing the dynamical behavior of a single chain. Using scaling concepts some quantities such as translational diffussion coefficient for the polymer center of mass Dtr, and renewal time {t} [3] have been calculated in the reptation model. This model is used for representing the low-frequency motions of a polymer molecule in a fluid of entangled chains, neglecting rapid relaxation processes that are attributed to local conformal transitions of backbone. Helfand and collabrators have studied the kinetics of conformational transitions in chain molecules, and they find that single-bond rotations followed by the compensating rearrangement of neigboring units are predominantly responsible for local motions [4]. Such models have also been considered by Erman and co-workers [5]. The purpose of this study to understand reptation at a microscopic level. We consedir rapid relaxation processes, that are singlet- or double -bond rotations; motion along the contour of the chain is due to displacments caused by rearangements of the neighboring units. We recover the usual scaling behavior of the diffusion coefficients and relaxation times with the chain mass. Moreover, the effective activation energy that is found from the local jump model for translational motion of the chain center of mass compares favorably with experiment and is independent of the molecular weight for large enough chains [6]. We are also able to account for the apparent temperature of this "activation energy".
Relaxation of non-equilibrium entanglement networks in thin polymer films
NASA Astrophysics Data System (ADS)
Fowler, Paul; McGraw, Joshua; Ferrari, Melissa; Dalnoki-Veress, Kari
2013-03-01
It is well established that polymer films, prepared by spincoating, inherit non-equilibrium chain conformations which can affect macroscopic film properties. Here we present the results of crazing measurements that elucidate the non-equilibirum chain configurations in spin-cast films. Furthermore, we find that the entanglement network equilibrates on a time scale comparable to one reptation time. In a second set of experiments, we confine polymers to films with thickness comparable to the molecular size. By stacking two such films at room temperature, a glassy bilayer film with a buried entropic interface is created. According to Silberberg's reflection principle, such an interface has an entropic cost associated with the restricted configurations of molecules that cannot cross the mid-plane of the bilayer. In the melt, the interface heals as chains from the two layers mix and entangle with one another. Crazing measurements reveal that it takes less than one bulk reptation time for a bilayer to become indistinguishable from a single film.
Engineered monodisperse mesoporous materials
Saunders, R.S.; Small, J.H.; Lagasse, R.R.; Schroeder, J.L.; Jamison, G.M.
1997-08-01
Porous materials technology has developed products with a wide variety of pore sizes ranging from 1 angstrom to 100`s of microns and beyond. Beyond 15{angstrom} it becomes difficult to obtain well ordered, monodisperse pores. In this report the authors describe efforts in making novel porous material having monodisperse, controllable pore sizes spanning the mesoporous range (20--500 {angstrom}). They set forth to achieve this by using unique properties associated with block copolymers--two linear homopolymers attached at their ends. Block copolymers phase separate into monodisperse mesophases. They desired to selectively remove one of the phases and leave the other behind, giving the uniform monodisperse pores. To try to achieve this the authors used ring-opening metathesis polymerization to make the block copolymers. They synthesized a wide variety of monomers and surveyed their polymers by TGA, with the idea that one phase could be made thermally labile while the other phase would be thermally stable. In the precipitated and sol-gel processed materials, they determined by porosimetry measurements that micropores, mesopores, and macropores were created. In the film processed sample there was not much porosity present. They moved to a new system that required much lower thermal treatments to thermally remove over 90% of the labile phase. Film casting followed by thermal treatment and solvent extraction produced the desired monodisperse materials (based solely on SEM results). Modeling using Density Functional Theory was also incorporated into this project. The modeling was able to predict accurately the domain size and spacing vs. molecular weight for a model system, as well as accurate interfacial thicknesses.
NASA Astrophysics Data System (ADS)
Ma, Cheng; Zhang, Jinfang; Xu, Mingquan; Xia, Qingbing; Liu, Jiatu; Zhao, Shuai; Chen, Libao; Pan, Anqiang; Ivey, Douglas G.; Wei, Weifeng
2016-06-01
Nanohybrid polymer electrolytes (NHPE) with ceramic particles have attracted significant attention owing to their improvement in electrochemical performance. However, particle aggregation and weak nanoparticle/polymer matrix interaction restrict their further application in lithium-ion batteries (LIBs). We demonstrate a facile in-situ polymerization/crystallization method to synthesize a homogeneous TiO2-grafted NHPE with a cross-linked branching structure, comprised of ion-conducting poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and non-polar stearyl methacrylate (SMA). This technique is different from existing methods of blending functionalized ceramic particles into the polymer matrix. Highly monodispersed TiO2 nanocrystals enhance the effective interfacial interactions between particles and polymer matrix, which suppress the crystallization of ethylene oxide (EO) groups and facilitate forming continuously interconnected ion-conducting channels. Moreover, an increased dissociation degree of Li salt can also be achieved. The TiO2-grafted NHPE exhibits superior electrochemical properties with an ionic conductivity of 1.1 × 10-4 S cm-1 at 30 °C, a high lithium ion transference number and excellent interfacial compatibility with the lithium electrode. In particular, a lithium-ion battery based on TiO2-grafted NHPE demonstrates good C-rate performance, as well as excellent cycling stability with an initial discharge capacity of 153.5 mAh g-1 and a capacity retention of 96% after 300 cycles at 1 C (80 °C).
Liu, Dongfei; Zhang, Hongbo; Herranz-Blanco, Bárbara; Mäkilä, Ermei; Lehto, Vesa-Pekka; Salonen, Jarno; Hirvonen, Jouni; Santos, Hélder A
2014-05-28
We report an advanced drug delivery platform for combination chemotherapy by concurrently incorporating two different drugs into microcompoistes with ratiometric control over the loading degree. Atorvastatin and celecoxib were selected as model drugs due to their different physicochemical properties and synergetic effect on colorectal cancer prevention and inhibition. To be effective in colorectal cancer prevention and inhibition, the produced microcomposite contained hypromellose acetate succinate, which is insoluble in acidic conditions but highly dissolving at neutral or alkaline pH conditions. Taking advantage of the large pore volume of porous silicon (PSi), atorvastatin was firstly loaded into the PSi matrix, and then encapsulated into the pH-responsive polymer microparticles containing celecoxib by microfluidics in order to obtain multi-drug loaded polymer/PSi microcomposites. The prepared microcomposites showed monodisperse size distribution, multistage pH-response, precise ratiometric controlled loading degree towards the simultaneously loaded drug molecules, and tailored release kinetics of the loaded cargos. This attractive microcomposite platform protects the payloads from being released at low pH-values, and enhances their release at higher pH-values, which can be further used for colon cancer prevention and treatment. Overall, the pH-responsive polymer/PSi-based microcomposite can be used as a universal platform for the delivery of different drug molecules for combination therapy. PMID:24616278
Microscopic Theory for Entangled Polymer Dynamics in Rod-Sphere Nanocomposites
NASA Astrophysics Data System (ADS)
Yamamoto, Umi; Schweizer, Kenneth
2014-03-01
We have developed a self-consistent microscopic theory for the long-time dynamics of needles in an array of static spherical fillers. The approach exactly enforces the dynamical two-body rod topological uncrossability and sphere impenetrability constraints, leading to a generalized concept of entanglements that includes the filler excluded volume effect. How the diffusion anisotropy (transverse versus longitudinal motion) depends on the filler-needle aspect ratio, polymer concentration, and filler volume fraction is established. Due to the steric blocking of the longitudinal reptative motion by obstacles, a literal localization transition is predicted that is generically controlled by the ratio of filler diameter to the pure polymer tube diameter or needle length. For a window of filler sizes and loadings, the needle is predicted to diffuse via a ``renormalized'' reptation dynamics where the tube is compressed and the longitudinal motion is retarded in a manner that depends on all system variables. At high filler volume fractions the needle diffusivity is strongly suppressed, and localization ultimately occurs in the unentangled needle regime. Generalization of the approach to treat mobile fillers, flexible chains, and nonrandom microstructure is also possible.
Understanding entangled polymers: What we can learn from athermal chain packings
NASA Astrophysics Data System (ADS)
Karayiannis, Nikos
2012-02-01
The study of random and ordered packings (from atoms and colloidal particles to sand grains) has been the focus of extensive research. This is not surprising since an understanding of the mechanisms that control morphology and packing is the key to the design and synthesis of novel ``smart'' materials and functionalities. In particular, the study of packings of chain molecules presents challenges but also insights which are absent in monatomic systems and further allows for a direction comparison with them. In this contribution we give an overview of our work on very dense and nearly jammed packings of athermal polymers. We show that chain molecules can be as efficiently and as densely packed as monatomic analogs up to the same maximally random jammed state. We also show that an exact correspondence can be established between the statistical-mechanical ensembles of packings of monatomic, and chain systems, which yields insights on the universality of jamming. By studying the effect of concentration on polymer size and on the underlying network of topological hindrances we precisely identify the distinct universal scaling regimes and the corresponding exponents. An unsuspected connection, valid from dilute up to very dense assemblies, is established between knots (of intermolecular origin) and entanglements (intermolecular constraints). We finally show that, against expectations, entropy-driven crystallization can occur in dense systems of athermal polymers once a critical volume fraction is reached. Such phase transition is driven by the increase in translational entropy: ordered sites exhibit enhanced mobility as their local free volume becomes more spherical and symmetric. Incipient nuclei develop well defined, stack-faulted layered crystal morphologies with a single stacking direction. The ordering transition and the resulting complex morphologies are analyzed, highlighting similarities and differences with respect to monatomic crystallization.
Ramírez-Hernández, Abelardo; Peters, Brandon L; Andreev, Marat; Schieber, Jay D; de Pablo, Juan J
2015-12-28
A theoretically informed entangled polymer simulation approach is presented for description of the linear and non-linear rheology of entangled polymer melts. The approach relies on a many-chain representation and introduces the topological effects that arise from the non-crossability of molecules through effective fluctuating interactions, mediated by slip-springs, between neighboring pairs of macromolecules. The total number of slip-springs is not preserved but, instead, it is controlled through a chemical potential that determines the average molecular weight between entanglements. The behavior of the model is discussed in the context of a recent theory for description of homogeneous materials, and its relevance is established by comparing its predictions to experimental linear and non-linear rheology data for a series of well-characterized linear polyisoprene melts. The results are shown to be in quantitative agreement with experiment and suggest that the proposed formalism may also be used to describe the dynamics of inhomogeneous systems, such as composites and copolymers. Importantly, the fundamental connection made here between our many-chain model and the well-established, thermodynamically consistent single-chain mean-field models provides a path to systematic coarse-graining for prediction of polymer rheology in structurally homogeneous and heterogeneous materials. PMID:26723632
NASA Astrophysics Data System (ADS)
Ramírez-Hernández, Abelardo; Peters, Brandon L.; Andreev, Marat; Schieber, Jay D.; de Pablo, Juan J.
2015-12-01
A theoretically informed entangled polymer simulation approach is presented for description of the linear and non-linear rheology of entangled polymer melts. The approach relies on a many-chain representation and introduces the topological effects that arise from the non-crossability of molecules through effective fluctuating interactions, mediated by slip-springs, between neighboring pairs of macromolecules. The total number of slip-springs is not preserved but, instead, it is controlled through a chemical potential that determines the average molecular weight between entanglements. The behavior of the model is discussed in the context of a recent theory for description of homogeneous materials, and its relevance is established by comparing its predictions to experimental linear and non-linear rheology data for a series of well-characterized linear polyisoprene melts. The results are shown to be in quantitative agreement with experiment and suggest that the proposed formalism may also be used to describe the dynamics of inhomogeneous systems, such as composites and copolymers. Importantly, the fundamental connection made here between our many-chain model and the well-established, thermodynamically consistent single-chain mean-field models provides a path to systematic coarse-graining for prediction of polymer rheology in structurally homogeneous and heterogeneous materials.
Ramírez-Hernández, Abelardo Pablo, Juan J. de; Peters, Brandon L.; Andreev, Marat; Schieber, Jay D.
2015-12-28
A theoretically informed entangled polymer simulation approach is presented for description of the linear and non-linear rheology of entangled polymer melts. The approach relies on a many-chain representation and introduces the topological effects that arise from the non-crossability of molecules through effective fluctuating interactions, mediated by slip-springs, between neighboring pairs of macromolecules. The total number of slip-springs is not preserved but, instead, it is controlled through a chemical potential that determines the average molecular weight between entanglements. The behavior of the model is discussed in the context of a recent theory for description of homogeneous materials, and its relevance is established by comparing its predictions to experimental linear and non-linear rheology data for a series of well-characterized linear polyisoprene melts. The results are shown to be in quantitative agreement with experiment and suggest that the proposed formalism may also be used to describe the dynamics of inhomogeneous systems, such as composites and copolymers. Importantly, the fundamental connection made here between our many-chain model and the well-established, thermodynamically consistent single-chain mean-field models provides a path to systematic coarse-graining for prediction of polymer rheology in structurally homogeneous and heterogeneous materials.
Hu, Yougen; Zhao, Tao; Zhu, Pengli; Zhu, Yu; Liang, Xianwen; Sun, Rong; Wong, Ching-Ping
2016-09-01
Silver nanoparticles (AgNPs) were deposited onto the monodispersed carboxylic polystyrene (CPS) spheres by an improved in situ reduction method. The size and coverage density of the AgNPs on the surface of CPS spheres could be easily tailored by tuning the concentrations of carboxylic functional groups and silver precursor. The morphologies and structures of the resulting CPS/Ag hybrid particles were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis-NIR spectrometer and X-ray photoelectron spectroscopy (XPS), etc. The surface enhanced Raman scattering (SERS) performances of the resulting uniform CPS/Ag hybrid particles were investigated using 4-aminobenzenethiol (4-ABT) as the probe molecule. The optimized CPS/Ag hybrid particles show high enhancement factor (EF) of 2.71×10(7) , low limit of detection (LOD) of 10(-10) m and good reproducibility with relative standard deviation (RSD) of 9.64 %. The good SERS improvement properties demonstrate these hybrid particles could be employed as simple and effective substrates in the SERS spectroscopy. PMID:27511618
NASA Astrophysics Data System (ADS)
Wang, Chenxi; Kilfoil, Maria L.
2013-03-01
The high fidelity segregation of chromatin is the central problem in cell mitosis. The role of mechanics underlying this, however, is undetermined. Work in this area has largely focused on cytoskeletal elements of the process. Preliminary work in our lab suggests the mechanical properties of chromatin are fundamental in this process. Nevertheless, the mechanical properties of chromatin in the cellular context are not well-characterized. For better understanding of the role of mechanics in this cellular process, and of the chromatin mechanics in vivo generally, a systematic dynamical description of chromatin in vivo is required. Accordingly, we label specific sites on chromatin with fluorescent proteins of different wave lengths, enabling us to detect multiple spots separately in 3D and track their displacements in time inside living yeast cells. We analyze the pairwise cross-correlated motion between spots as a function of relative distance along the DNA contour. Comparison between the reptation model and our data serves to test our conjecture that chromatin in the cell is basically an entangled polymer network under constraints to thermal motion, and removal of constraints by non-thermal cellular processes is expected to affect its dynamic behavior.
Isolation and Characterization of Monodisperse Core-Shell Nanoparticle Fractions.
Sánchez-Ferrer, Antoni; Carney, Randy P; Stellacci, Francesco; Mezzenga, Raffaele; Isa, Lucio
2015-10-20
Monodispersity is a key property to control the self-assembly of colloidal particles, and is typically reached after fine-tuning of the synthesis conditions. Monodisperse particle fractions can also be separated from polydisperse suspensions via ultracentrifugation. This paper demonstrates the capability of isolating and characterizing suspensions of core-shell iron oxide-polymer nanoparticles with extremely low polydispersity (p < 0.01) and, thus, of complementing nanoparticle synthetic approaches in the pursuit of highly monodisperse materials. PMID:26406563
NASA Astrophysics Data System (ADS)
Steenbakkers, Rudi J. A.; Tzoumanekas, Christos; Li, Ying; Liu, Wing Kam; Kröger, Martin; Schieber, Jay D.
2014-01-01
We present a method to map the full equilibrium distribution of the primitive-path (PP) length, obtained from multi-chain simulations of polymer melts, onto a single-chain mean-field ‘target’ model. Most previous works used the Doi-Edwards tube model as a target. However, the average number of monomers per PP segment, obtained from multi-chain PP networks, has consistently shown a discrepancy of a factor of two with respect to tube-model estimates. Part of the problem is that the tube model neglects fluctuations in the lengths of PP segments, the number of entanglements per chain and the distribution of monomers among PP segments, while all these fluctuations are observed in multi-chain simulations. Here we use a recently proposed slip-link model, which includes fluctuations in all these variables as well as in the spatial positions of the entanglements. This turns out to be essential to obtain qualitative and quantitative agreement with the equilibrium PP-length distribution obtained from multi-chain simulations. By fitting this distribution, we are able to determine two of the three parameters of the model, which govern its equilibrium properties. This mapping is executed for four different linear polymers and for different molecular weights. The two parameters are found to depend on chemistry, but not on molecular weight. The model predicts a constant plateau modulus minus a correction inversely proportional to molecular weight. The value for well-entangled chains, with the parameters determined ab initio, lies in the range of experimental data for the materials investigated.
NASA Astrophysics Data System (ADS)
Lin, Y.-H.; Huang, C.-F.
2008-06-01
The dynamic structure factor (DSF) for single (labeled) chains well entangled in polymer melts has been developed based on the Rouse-Mooney picture; the DSF functions derived from the Langevin equations of the model in both discrete and continuous forms are given. It is shown that for all practical purposes, it is sufficient to use the continuous form to analyze experimental results in the ``safe'' q region (q being the magnitude of the scattering wave vector q) where the Rouse-segment-based theories are applicable. The DSF form reduces to the same limiting form as that of the free Rouse chain as q2a2 or q2R2-->∞ (a and R being the entanglement distance and the root mean square end-to-end distance, respectively), confirming what has been expected physically. The natural reduction to the limiting form allows the full range of DSF curves to be displayed in terms of the reduced Rouse variable q2(Zdt)0.5 in a unified way. The displayed full range represents a framework or ``map,'' with respect to which effects occurring in different regions of the DSF may be located and studied in a consistent manner. One effect is the significant or noticeable deviations of the theoretical DSF curves from the limiting curve in the region ~4>q2(Zdt)0.5>~0.1 (a time region where t<τ1e) to the faster side as qa is in the range 1-5. This is supported by the comparison of the experimental results of an entangled poly(vinylethylene) sample with the theoretical curves. The DSF functional forms predict plateaus with heights depending on the value of q-q-split plateaus-as can be experimentally observed in the time region greater than the relaxation time τ1e of the lowest Rouse-Mooney mode, when qa falls between ~1 and ~7. High sensitivity of the distribution of the q-split plateaus to a enables its value to be extracted from matching the calculated with the experimental results. The thus obtained a value for a well-entangled poly(ethylene-co-butene) polymer is in close agreement with the
Reduced Viscosity of the Free Surface in Entangled Polymer Melt Films
NASA Astrophysics Data System (ADS)
Koga, Tadanori; Li, C.; Endoh, M. K.; Koo, J.; Rafailovich, M.; Narayanan, S.; Lee, D. R.; Lurio, L. B.; Sinha, S. K.
2010-02-01
By embedding “dilute” gold nanoparticles in single polystyrene thin films as “markers”, we probe the local viscosity of the free surface at temperatures far above the glass transition temperature (Tg). The technique used was x-ray photon correlation spectroscopy with resonance-enhanced x-ray scattering. The results clearly showed the surface viscosity is about 30% lower than the rest of the film. We found that this reduction is strongly associated with chain entanglements at the free surface rather than the reduction in Tg.
Nematic effects and strain coupling in entangled polymer melts under strong flow.
Kirkensgaard, Jacob J K; Hengeller, Ludovica; Dorokhin, Andriy; Huang, Qian; Garvey, Christopher J; Almdal, Kristoffer; Hassager, Ole; Mortensen, Kell
2016-08-01
We use small-angle neutron scattering (SANS) to study labeled short chains with and without the influence of an entangled and highly stretched surrounding environment of longer chains. We find unequivocal evidence of nematic effects as the blend chains in steady state flow are stretched a factor ∼1.5 more from the presence of the long chain nematic field. In the pure melt we confirm that the nonaffine mean-field result ν=0.5 for the strain coupling is still valid for very fast flows, while in the nematic system our analysis predicts an increased coupling constant. We provide a structural explanation for the two first regimes of the nonlinear relaxation, particularly a transition regime where the long chains are relaxing in a sea of reptating short chains. PMID:27627228
The conformations of cyclic polymers in bidisperse blends of cyclic polymers
NASA Astrophysics Data System (ADS)
Lang, Michael
2013-03-01
The size of cyclic polymers in bidisperse blends of chemically identical molecules is analyzed by computer simulations. The compression of entangled rings can be explained by the changes in the penetrable fraction of the surface bounded by the ring. Corrections for small rings can be approximated by a concatenation probability 1 -POO that a cyclic polymer entraps at least one other cyclic polymer. Both results are in line with a previous work on the compression of entangled cyclic polymers in monodisperse melts. For entangled cyclic polymers, bond-bond correlations show a constant anti-correlation peak at a curvilinear distance of about ten segments that coincides with a horizontal tangent in the normalized mean square internal distances along the ring for sufficiently large degrees of polymerization. In consequence, the length scale of topological interactions must be considered as constant in contrast to a recent proposal by Sakaue. Our data is not in accord with an extension of the model of Cates and Deutsch to bidiperse blends of ring polymers.
NASA Astrophysics Data System (ADS)
Komlosh, M. E.; Callaghan, P. T.
1998-12-01
Pulsed gradient spin echo nuclear magnetic resonance (NMR) is used to investigate polymer mean-squared segmental displacements in semidilute solutions of high molar mass polystyrene in deuterio-toluene. Nine molar masses from 1 to 20 million daltons are studied at a fixed concentration of 5% w/v, and a range of concentrations from 5% to 20% at fixed molar mass of 3 million daltons. The distance and time scales accessed are 20 to 1000 nm and 10 to 3000 ms, respectively. Evidence for intrachain spin diffusion is found and its effect corrected for. The time dependence of mean-squared segmental displacements is fitted to the predictions of the Doi-Edwards model and tube disengagement times and tube diameters obtained.
Effects of Attractive Interactions on Nanoparticle Diffusion in Entangled Polymer Melts
NASA Astrophysics Data System (ADS)
Griffin, Philip; Clarke, Nigel; Composto, Russell; Winey, Karen
Developing a complete picture for the mechanism of nanoparticle diffusion in model polymer nanocomposites remains a great challenge, especially experimentally. Using Rutherford backscattering spectroscopy, we have measured the translational diffusion coefficient of spherical nanoparticles (diameter = 20 nm) infiltrated into poly(2-vinylpyridine) melts across a range of molecular weights (35-300 kg/mol). Our results reveal that the diffusion coefficient of nanoparticles in attractive nanocomposites is several times slower than what is predicted from the melt viscosity according to the Stokes-Einstein (SE) relation. This runs contrary to recent theoretical studies of non-attractive systems, where it is predicted that nanoparticle diffusion can be many orders of magnitude faster than SE predictions. Potential explanations for this unusual slowing of nanoparticle diffusion are discussed.
Monodisperse aerosol generator
Ortiz, Lawrence W.; Soderholm, Sidney C.
1990-01-01
An aerosol generator is described which is capable of producing a monodisperse aerosol within narrow limits utilizing an aqueous solution capable of providing a high population of seed nuclei and an organic solution having a low vapor pressure. The two solutions are cold nebulized, mixed, vaporized, and cooled. During cooling, particles of the organic vapor condense onto the excess seed nuclei, and grow to a uniform particle size.
Aoki, Hiroshi; Kubo, Takuya; Ikegami, Tohru; Tanaka, Nobuo; Hosoya, Ken; Tokuda, Daisuke; Ishizuka, Norio
2006-06-30
The preparation of polymer-based monolith capillary was examined by the use of glycerol dimethacrylate (GDMA) as monomer and monodisperse standard polystyrene (PS) solution in chlorobenzene as porogen. Poly-GDMA monoliths were prepared in situ in test tubes with standard PS having the variety of molecular weight (defined as Mw hereafter) from 50,000 to 3,840,000, and their morphology was compared to that of poly-GDMA monolith prepared in situ with a poor porogenic solvent of GDMA. According to scanning electron micrograph (SEM) observation, the structure of poly-GDMA monolith prepared in situ with toluene as a poor porogenic solvent showed a typical agglomerated globular structure, whereas the morphology of poly-GDMA monolith prepared in situ with the polymer (PS) porogenic solution was transformed from the aggregated globule form to three dimensionally (3D) continuous skeletal structure with the increase of Mw of standard PS utilized. Along with this morphological transformation or change, in the case of poly-GDMA monolith prepared in situ with ultra high Mw standard PS porogenic solution, the pore size distribution showed a sharp bimodal distribution, with one peak being located around 4 nm in the mesopore range (2-50 nm) and the other peak located around 1-2 microm in the macropore range (>50 nm), respectively. The poly-GDMA capillaries were prepared in situ with toluene, low Mw (50,000, 600,000) PS solution in chlorobenzene and the above mentioned ultra high Mw PS solution in chlorobenzene as a porogen, respectively, and measured by mu-HPLC with benzene and n-alkyl phenyl ketone as solutes for the evaluation in aqueous methanol (MeOH/H(2)O = 50/50-80/20, v/v). The permeability of capillaries prepared in situ with ultra high Mw standard PS polymer porogenic solution was much larger, compared to those of the capillaries prepared in situ with low Mw standard PS polymer porogenic solution or with toluene as porogen. On the other hand, the column efficiency was
NASA Astrophysics Data System (ADS)
Thapliyal, Ashish Vachaspati
Entanglement is an essential element of quantum mechanics. The aim of this work is to explore various properties of entanglement from the viewpoints of both physics and information science, thus providing a unique picture of entanglement from an interdisciplinary point of view. The focus of this work is on quantifying entanglement as a resource. We start with bipartite states, proposing a new measure of bipartite entanglement called entanglement of assistance, showing that bound entangled states of rank two cannot exist, exploring the number of members required in the ensemble achieving the entanglement of formation and the possibility of bound entangled states that are negative under partial transposition (NPT bound entangled states). For multipartite states we introduce the notions of reducibilities and equivalences under entanglement non-increasing operations and we study the relations between various reducibilities and equivalences such as exact and asymptotic LOCC, asymptotic LOCCq, cLOCC, LOc, etc. We use this new language to attempt to quantify entanglement for multiple parties. We introduce the idea of entanglement span and minimal entanglement generating set and entanglement coefficients associated with it which are the entanglement measures, thus proposing a multicomponent measure of entanglement for three or more parties. We show that the class of Schmidt decomposable states have only GHZM or Cat-like entanglement. Further we introduce the class of multiseparable states for quantification of their entanglement and prove that they are equivalent to the Schmidt decomposable states, and thus have only Cat-like entanglement. We further explore the conditions under which LOCO equivalences are possible for multipartite isentropic states. We define Cat-distillability, EPRB-distillability and distillability for multipartite mixed states and show that distillability implies EPRB-distillability. Further we show that all non-factorizable pure states are Cat
NASA Astrophysics Data System (ADS)
Rezayan, Ali Hossein; Mosavi, Majid; Kheirjou, Somayyeh; Amoabediny, Ghasem; Ardestani, Mehdi Shafiee; Mohammadnejad, Javad
2016-12-01
In this study, magnetic nanoparticles (MNPs) were synthesized via co-precipitation method. To enhance the biocompatibility and colloidal stability of the synthesized nanoparticles, they were modified with carboxyl functionalized PEG via dopamine (DPA) linker. Both modified and unmodified Fe3O4 nanoparticles exhibited super paramagnetic behavior (particle size below 20 nm). The saturation magnetization (Ms) of PEGdiacid-modified Fe3O4 was 45 emu/g, which was less than the unmodified Fe3O4 nanoparticles (70 emu/g). This difference indicated that PEGdiacid polymer was immobilized on the surface of Fe3O4 nanoparticles successfully. To evaluate the efficiency of the resulting nanoparticles as contrast agents for magnetic resonance imaging (MRI), different concentration of MNPs and different value of echo time TE were investigated. The results showed that by increasing the concentration of the nanoparticles, transverse relaxation time (T2) decreased, which subsequently resulted in MR signal enhancement. T2-weighted MR images of the different concentration of MNPs in different value of echo time TE indicated that MR signal intensity increased with increase in TE value up to 66 and then remained constant. The cytotoxicity effect of the modified and unmodified nanoparticles was evaluated in three different concentrations (12, 60 and 312 mg l-1) on MDA-MB-231 cancer cells for 24 and 48 h. In both tested time (24 and 48 h) for all three samples, the modified nanoparticles had long life time than unmodified nanoparticles. Cellular uptake of modified MNPs was 80% and reduced to 9% by the unmodified MNPs.
NASA Astrophysics Data System (ADS)
Fitzpatrick, Robert; Robertson-Anderson, Rae; Anderson Research Team
Actin is a ubiquitous structural protein in the cytoskeleton that gives cells shape and rigidity, and plays important roles in mechanical processes such as cell motility and division. Actin's diverse roles stem from its ability to polymerize into semiflexible filaments that are less than one persistence length (17 µm) in length, and form entangled networks that display unique viscoelastic properties. We previously found that entangled actin networks propagate microscale forces over several persistence lengths (>60 m) and takes minutes to relax. DNA, oppositely, has thousands of persistence lengths (50 nm) per chain, exhibits minimal force propagation, and takes only seconds to re-equilibrate. To directly determine the role of flexibility in mechanical response and force propagation of entangled networks, we use optical tweezers and fluorescence microscopy to investigate blends of actin and DNA. We use optically driven microspheres to perturb the network far from equilibrium and measure the force the network creates in response to the induced force. We simultaneously track partially labeled actin filaments during the perturbation and subsequent relaxation period. We characterize filament deformation and show explicitly how induced microscale forces propagate through the network.
Gualdi, Giulia; Giampaolo, Salvatore M; Illuminati, Fabrizio
2011-02-01
We introduce and discuss the concept of modular entanglement. This is the entanglement that is established between the end points of modular systems composed by sets of interacting moduli of arbitrarily fixed size. We show that end-to-end modular entanglement scales in the thermodynamic limit and rapidly saturates with the number of constituent moduli. We clarify the mechanisms underlying the onset of entanglement between distant and noninteracting quantum systems and its optimization for applications to quantum repeaters and entanglement distribution and sharing. PMID:21405382
Multipartite entanglement for entanglement teleportation
Lee, Jinhyoung; Min, Hyegeun; Oh, Sung Dahm
2002-11-01
A scheme for entanglement teleportation is proposed to incorporate multipartite entanglement of four qubits as a quantum channel. Based on the invariance of entanglement teleportation under an arbitrary two-qubit unitary transformation, we derive relations for the separabilities of joint measurements at a sending station and of unitary operations at a receiving station. From the relations of the separabilities it is found that an inseparable quantum channel always leads to total teleportation of entanglement with an inseparable joint measurement and/or a nonlocal unitary operation.
NASA Astrophysics Data System (ADS)
Schliemann, John
2014-09-01
We investigate further the relationship between the entanglement spectrum of a composite many-body system and the energy spectrum of a subsystem making use of concepts of canonical thermodynamics. In many important cases the entanglement Hamiltonian is, in the limit of strong coupling between subsystems, proportional to the energy Hamiltonian of the subsystem. The proportionality factor is an appropriately defined coupling parameter, suggesting to interpret the latter as a inverse temperature. We identify a condition on the entanglement Hamiltonian which rigorously guarantees this interpretation to hold and removes any ambiguity in the definition of the entanglement Hamiltonian regarding contributions proportional to the unit operator. Illustrations of our findings are provided by spin ladders of arbitrary spin length, and by bilayer quantum Hall systems at total filling factor ν = 2. Within mean-field description, the latter system realizes an entanglement spectrum of free fermions with just two levels of equal modulus where the analogies to canonical thermodynamics are particularly close.
Iwata, Kazuyoshi
1992-05-14
The local knot (LK) theory is tested by computer simulations in parts 1 and 2. Here, theoretical problems of the simulations are mainly discussed. The probe fluctuation found in part 1 is studied theoretically, and a method for separating the Markov motion of a LK from its probe fluctuation is proposed. A detailed discussions on the mechanism of the probe fluctuation and the uncertainty principal are given. A modified expression of the diffusion coefficient of a LK is derived that cancels the interference of the probe fluctuations, and its numerical calculation is performed. A correction for short memory effects of LK motion is also done. The theoretical value of d{sub 0} thus computed is 0.0393 bond{sup 2}/u.t. (u.t. - unit time) which is comparable to its simulation value 0.0172 bond{sup 2}/u.t. obtained in part 1. Finally, it is concluded that the LK theory is proved by the results of parts 1 and 2 and, by this, a true molecular theory of entanglement has been first established. 13 refs., 7 figs., 1 tab.
Phenomenological theory of the dynamics of polymer melts. I. Analytic treatment of self-diffusion
NASA Astrophysics Data System (ADS)
Skolnick, Jeffrey; Yaris, Robert; Kolinski, Andrzej
1988-01-01
In the context of dynamic Monte Carlo (MC) simulations on dense collections of polymer chains confined to a cubic lattice, the nature of the dynamic entanglements giving rise to the degree of polymerization n, dependence of the self-diffusion constant D˜n-2 is examined. Consistent with our previous simulation results, which failed to find evidence for reptation as the dominant mechanism of polymer melt motion [J. Chem. Phys. 86, 1567, 7164, 7174 (1987)], long-lived dynamic entanglement contacts between pairs of segments belonging to different chains are extremely rare and are mobile with respect to the laboratory fixed frame. It is suggested that dynamic entanglements involve the dragging of one chain by another through the melt for times on the order of the terminal relaxation time of the end-to-end vector. Employing the physical description provided by the MC simulation, the general expression of Hess [Macromolecules 19, 1395 (1986)] for the friction constant increment experienced by a polymer due to the other polymers forms the basis of a phenomenological derivation of D˜n-2 for monodisperse melts that does not require the existence of reptation. Rather, such behavior is dependent on the relatively benign assumptions that the long distance global motions of the chains are uncorrelated, that the dynamic contacts can be truncated at the pair level, and that the propagator describing the evolution between dynamic contacts contains a free Rouse chain component. The mean distance between dynamic entanglements is predicted to depend inversely on concentration, in agreement with experiment. Moreover, as the free Rouse component is frozen out, for chains greater than an entanglement length ne, a molecular weight independent glass transition is predicted. Extension to bidisperse melts predicts that the probe diffusion coefficient Dp depends on the matrix degree of polymerization, nm, as n-1m. Finally, comparison is made between the theoretical expressions and MC
Fast equilibration protocol for million atom systems of highly entangled linear polyethylene chains
NASA Astrophysics Data System (ADS)
Sliozberg, Yelena R.; Kröger, Martin; Chantawansri, Tanya L.
2016-04-01
Equilibrated systems of entangled polymer melts cannot be produced using direct brute force equilibration due to the slow reptation dynamics exhibited by high molecular weight chains. Instead, these dense systems are produced using computational techniques such as Monte Carlo-Molecular Dynamics hybrid algorithms, though the use of soft potentials has also shown promise mainly for coarse-grained polymeric systems. Through the use of soft-potentials, the melt can be equilibrated via molecular dynamics at intermediate and long length scales prior to switching to a Lennard-Jones potential. We will outline two different equilibration protocols, which use various degrees of information to produce the starting configurations. In one protocol, we use only the equilibrium bond angle, bond length, and target density during the construction of the simulation cell, where the information is obtained from available experimental data and extracted from the force field without performing any prior simulation. In the second protocol, we moreover utilize the equilibrium radial distribution function and dihedral angle distribution. This information can be obtained from experimental data or from a simulation of short unentangled chains. Both methods can be used to prepare equilibrated and highly entangled systems, but the second protocol is much more computationally efficient. These systems can be strictly monodisperse or optionally polydisperse depending on the starting chain distribution. Our protocols, which utilize a soft-core harmonic potential, will be applied for the first time to equilibrate a million particle system of polyethylene chains consisting of 1000 united atoms at various temperatures. Calculations of structural and entanglement properties demonstrate that this method can be used as an alternative towards the generation of entangled equilibrium structures.
Method for producing monodisperse aerosols
Ortiz, Lawrence W.; Soderholm, Sidney C.
1990-01-01
An aerosol generator is described which is capable of producing a monodisperse aerosol within narrow limits utilizing an aqueous solution capable of providing a high population of seed nuclei and an organic solution having a low vapor pressure. The two solutions are cold nebulized, mixed, vaporized, and cooled. During cooling, particles of the organic vapor condense onto the excess seed nuclei, and grow to a uniform particle size.
Rheology and morphology of no-slip sheared polymer nanocomposite under creep condition
NASA Astrophysics Data System (ADS)
Mortezapour, Saba; Eslami, Hossein; Nedaaee Oskoee, Ehsan
2015-07-01
Dissipative particle dynamics simulations are performed on wet polymer nanocomposite blends under the discrete imposed velocity profile and no-slip boundary conditions. To be able to study the chain length dependency of the rheological properties, a number of blends of mono-disperse polymer chains of lengths varying from 10 to 100 repeat units and nanoparticles of diameters 2.5 and 5 have been simulated. The wall velocity was imposed on a thin polymer layer (the no-slip layer). Linear velocity profiles for polymer confined in the pore were observed at the steady state. We found that the flow has a shear thinning effect on the chains with a radius of gyration less than the filler radius. Long chains (with a radius of gyration longer than the filler's radius), however, obey the Newtonian behavior over a much wider shear rate than that which causes shear thinning in short chains. The effect of particle-monomer interactions, polymer entanglements, chain morphology, and link formation on the shear rate dependency of the viscosity coefficient has been studied. Our results show that the particle-polymer interactions have no effect on shear thinning behavior of the blend. In contrast, the long range polymer-polymer interactions and the chain length have considerable effects on the rheological behavior of the blend. Finally, the phase diagram of the rheological properties of polymer nanocomposite as a function of strain rate and the chain length is extracted.
De Focatiis, Davide S. A.; Buckley, C. Paul; Embery, John
2008-07-07
This paper investigates the behaviour of a well-characterised monodisperse grade of entangled atactic polystyrene across a very wide temperature and strain rate range through linear and non-linear melt rheology and solid-state deformation. In an effort to construct a constitutive model for large deformations able to describe rheological response right across this wide timescale, two well-established rheological models are combined: the well known RoliePoly (RP) conformational melt model and the Oxford glass-rubber constitutive model for glassy polymers. Comparisons between experimental data and simulations from a numerical implementation of the model illustrate that the model can cope well with the range of deformations in which orientation is limited to length-scales longer than an entanglement length. One approach in which the model can be expanded to incorporate the effects of orientation on shorter length scales using anisotropic viscoplastic flow is briefly discussed.
Aerosol fabrication methods for monodisperse nanoparticles
Jiang, Xingmao; Brinker, C Jeffrey
2014-10-21
Exemplary embodiments provide materials and methods for forming monodisperse particles. In one embodiment, the monodisperse particles can be formed by first spraying a nanoparticle-containing dispersion into aerosol droplets and then heating the aerosol droplets in the presence of a shell precursor to form core-shell particles. By removing either the shell layer or the nanoparticle core of the core-shell particles, monodisperse nanoparticles can be formed.
Evolution of Entanglements During Craze Formation
NASA Astrophysics Data System (ADS)
Ge, Ting; Robbins, Mark; Hoy, Robert; Anogiannakis, Stefanos; Tzoumanekas, Christos; Theodorou, Doros
2009-03-01
Craze formation occurs during fracture of many polymers and leads to a substantial increase in the fracture energy. Models of craze formation usually assume that entanglements act like permanent chemical crosslinks.This model is tested by following the evolution of entanglements using the Contour Reduction Topological Analysis (CReTA) algorithm. The CReTA algorithm shortens each chain until further shortening would require chains to pass through each other. The contacts between chains that limit further shortening are identified as entanglements or topological constraints. Unlike related algorithms, the chain shortening has little effect on the craze structure, allowing the entanglements to be followed in real space, as well as along chains. CReTA is applied to molecular simulations of crazing using a coarse-grained bead-spring polymer model. The number of beads in each chain N and the entanglement length Ne are varied. Our results show that entanglements do not act like fixed chemical crosslinks. There is a systematic loss in entanglements during craze formation that does not occur when chains are deformed affinely and is nearly independent of N/Ne.The role of chain length, N, Ne, interchain friction and other parameters in determining the degree of entanglement loss is discussed.
Viscoelastic Properties of Entangled DNA Solutions: Dependence on Molecular Length and Concentration
NASA Astrophysics Data System (ADS)
Smith, Patrick; Dobrev, Veselin S.; Urbach, Jeff; Anderson, Rae
2014-03-01
We use macroscopic rheology to investigate the viscoelastic properties of solutions of monodisperse linear DNA, as a function of DNA length and concentration. We span from the unentangled to the entangled regime by using DNA lengths that vary from 11 to 115 kilobasepairs (3.7 to 39 μm) and solution concentrations that range between 0.5 and 4.0 mg/ml. We investigate the effects of oscillatory frequency on the linear elastic (G') and viscous (G'') moduli, with frequency values of 0.01 - 100 Hz. In addition, the dependence of viscosity on strain rate is studied with strain rates ranging from 0.01 to 100 Hz. Importantly, these studies are the first to examine the molecular length dependence of linear viscoelastic properties for concentrated DNA solutions. Results are compared to theoretical predictions based on the Rouse model and reptation model for unentangled and entangled polymer solutions, respectively. This research was funded by AFOSR YIP (Grant No. FA9550-12-1-0315) and NSF (Grant No. REU DMR-1004268).
Generation of a monodispersed aerosol
NASA Technical Reports Server (NTRS)
Schenck, H.; Mikasa, M.; Devicariis, R.
1974-01-01
The identity and laboratory test methods for the generation of a monodispersed aerosol are reported on, and are subjected to the following constraints and parameters; (1) size distribution; (2) specific gravity; (3) scattering properties; (4) costs; (5) production. The procedure called for the collection of information from the literature, commercial available products, and experts working in the field. The following topics were investigated: (1) aerosols; (2) air pollution -- analysis; (3) atomizers; (4) dispersion; (5) particles -- optics, size analysis; (6) smoke -- generators, density measurements; (7) sprays; (8) wind tunnels -- visualization.
Phase stability and dynamics of entangled polymer–nanoparticle composites
Mangal, Rahul; Srivastava, Samanvaya; Archer, Lynden A.
2015-01-01
Nanoparticle–polymer composites, or polymer–nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host. PMID:26044723
How do entangled polymeric liquids flow?
NASA Astrophysics Data System (ADS)
Sundar Ravindranath, Sham; Wang, Shi-Qing
2009-03-01
This work focused on investigating fundamental questions in polymer dynamics such as how entangled polymeric liquids respond to fast external deformation. By developing an effective particle tracking velocimetric (PTV) method, along with conventional rheometric measurements, new insights can be gained into the phenomenology of entangled polymers in presence of startup shear, step strain and large amplitude oscillatory shear (LAOS). During startup shear of well entangled systems, the shear field becomes inhomogeneous after the stress overshoot for a range of applied shear rates beyond the Newtonian region [1]. The emergence of shear banding after stress overshoot helped us to identify the stress overshoot as indicating yielding, whose characteristics obey some scaling laws. In step shear, contrary to the conventional perception that entangled polymers would undergo quiescent relaxation, the PTV observations reveal macroscopic motions after shear cessation [2]. The recoil-like macroscopic motions appears to reflect an elastic breakdown of the entanglement network due to sufficient build-up of retractive forces. LAOS experiments also demonstrate that entangled polymers cannot sustain a high magnitude of fast deformation without undergoing cohesive failure [3]. [1] Macromolecules 2008, 41, 2663 [2] Macromolecules 2007, 40, 8031 [3] J. Rheol. 2008, 52, 341.
Entanglement entropy of electronic excitations
NASA Astrophysics Data System (ADS)
Plasser, Felix
2016-05-01
A new perspective into correlation effects in electronically excited states is provided through quantum information theory. The entanglement between the electron and hole quasiparticles is examined, and it is shown that the related entanglement entropy can be computed from the eigenvalue spectrum of the well-known natural transition orbital (NTO) decomposition. Non-vanishing entanglement is obtained whenever more than one NTO pair is involved, i.e., in the case of a multiconfigurational or collective excitation. An important implication is that in the case of entanglement it is not possible to gain a complete description of the state character from the orbitals alone, but more specific analysis methods are required to decode the mutual information between the electron and hole. Moreover, the newly introduced number of entangled states is an important property by itself giving information about excitonic structure. The utility of the formalism is illustrated in the cases of the excited states of two interacting ethylene molecules, the conjugated polymer para-phenylene vinylene, and the naphthalene molecule.
Entanglement entropy of electronic excitations.
Plasser, Felix
2016-05-21
A new perspective into correlation effects in electronically excited states is provided through quantum information theory. The entanglement between the electron and hole quasiparticles is examined, and it is shown that the related entanglement entropy can be computed from the eigenvalue spectrum of the well-known natural transition orbital (NTO) decomposition. Non-vanishing entanglement is obtained whenever more than one NTO pair is involved, i.e., in the case of a multiconfigurational or collective excitation. An important implication is that in the case of entanglement it is not possible to gain a complete description of the state character from the orbitals alone, but more specific analysis methods are required to decode the mutual information between the electron and hole. Moreover, the newly introduced number of entangled states is an important property by itself giving information about excitonic structure. The utility of the formalism is illustrated in the cases of the excited states of two interacting ethylene molecules, the conjugated polymer para-phenylene vinylene, and the naphthalene molecule. PMID:27208936
Spatial distribution of entanglements in thin free-standing films.
Sussman, Daniel M
2016-07-01
We simulate entangled linear polymers in free-standing thin film geometries where the confining dimension is on the same scale as or smaller than the bulk chain dimensions. We compare both film-averaged and layer-resolved, spatially inhomogeneous measures of the polymer structure and entanglement network with theoretical models. We find that these properties are controlled by the ratio of both chain- and entanglement-strand length scales to the film thickness. While the film-averaged entanglement properties can be accurately predicted, we identify outstanding challenges in understanding the spatially resolved character of the heterogeneities in the entanglement network, particularly when the scale of both the entanglement strand and the chain end-to-end vector is comparable to or smaller than the film thickness. PMID:27575172
Spatial distribution of entanglements in thin free-standing films
NASA Astrophysics Data System (ADS)
Sussman, Daniel M.
2016-07-01
We simulate entangled linear polymers in free-standing thin film geometries where the confining dimension is on the same scale as or smaller than the bulk chain dimensions. We compare both film-averaged and layer-resolved, spatially inhomogeneous measures of the polymer structure and entanglement network with theoretical models. We find that these properties are controlled by the ratio of both chain- and entanglement-strand length scales to the film thickness. While the film-averaged entanglement properties can be accurately predicted, we identify outstanding challenges in understanding the spatially resolved character of the heterogeneities in the entanglement network, particularly when the scale of both the entanglement strand and the chain end-to-end vector is comparable to or smaller than the film thickness.
Polygamy of distributed entanglement
NASA Astrophysics Data System (ADS)
Buscemi, Francesco; Gour, Gilad; Kim, Jeong San
2009-07-01
While quantum entanglement is known to be monogamous (i.e., shared entanglement is restricted in multipartite settings), here we show that distributed entanglement (or the potential for entanglement) is by nature polygamous. By establishing the concept of one-way unlocalizable entanglement (UE) and investigating its properties, we provide a polygamy inequality of distributed entanglement in tripartite quantum systems of arbitrary dimension. We also provide a polygamy inequality in multiqubit systems and several trade-offs between UE and other correlation measures.
Polygamy of distributed entanglement
Buscemi, Francesco; Gour, Gilad; Kim, Jeong San
2009-07-15
While quantum entanglement is known to be monogamous (i.e., shared entanglement is restricted in multipartite settings), here we show that distributed entanglement (or the potential for entanglement) is by nature polygamous. By establishing the concept of one-way unlocalizable entanglement (UE) and investigating its properties, we provide a polygamy inequality of distributed entanglement in tripartite quantum systems of arbitrary dimension. We also provide a polygamy inequality in multiqubit systems and several trade-offs between UE and other correlation measures.
Lin, Jennifer S.; Albrecht, Jennifer Coyne; Meagher, Robert J.; Wang, Xiaoxiao; Barron, Annelise E.
2011-01-01
Protein-based polymers are increasingly being used in biomaterial applications due to their ease of customization and potential monodispersity. These advantages make protein polymers excellent candidates for bioanalytical applications. Here we describe improved methods for producing drag-tags for Free-Solution Conjugate Electrophoresis (FSCE). FSCE utilizes a pure, monodisperse recombinant protein, tethered end-on to a ssDNA molecule, to enable DNA size separation in aqueous buffer. FSCE also provides a highly sensitive method to evaluate the polydispersity of a protein drag-tag and thus its suitability for bioanalytical uses. This method is able to detect slight differences in drag-tag charge or mass. We have devised an improved cloning, expression, and purification strategy that enables us to generate, for the first time, a truly monodisperse 20 kDa protein polymer and a nearly monodisperse 38 kDa protein. These newly produced proteins can be used as drag-tags to enable longer read DNA sequencing by free-solution microchannel electrophoresis. PMID:21553840
Monodisperse atomizers for agricultural aviation applications
NASA Technical Reports Server (NTRS)
Christensen, L. S.; Steely, S. L.
1980-01-01
Conceptual designs of two monodisperse spray nozzles are described and the rationale used in each design is discussed. The nozzles were designed to eliminate present problems in agricultural aviation applications, such as ineffective plant coverage, drift due to small droplets present in the spray being dispersed, and nonuniform swath coverages. Monodisperse atomization techniques are reviewed and a synopsis of the information obtained concerning agricultural aviation spray applications is presented.
Monodisperse Uni- and Multicompartment Liposomes.
Deng, Nan-Nan; Yelleswarapu, Maaruthy; Huck, Wilhelm T S
2016-06-22
Liposomes are self-assembled phospholipid vesicles with great potential in fields ranging from targeted drug delivery to artificial cells. The formation of liposomes using microfluidic techniques has seen considerable progress, but the liposomes formation process itself has not been studied in great detail. As a result, high throughput, high-yielding routes to monodisperse liposomes with multiple compartments have not been demonstrated. Here, we report on a surfactant-assisted microfluidic route to uniform, single bilayer liposomes, ranging from 25 to 190 μm, and with or without multiple inner compartments. The key of our method is the precise control over the developing interfacial energies of complex W/O/W emulsion systems during liposome formation, which is achieved via an additional surfactant in the outer water phase. The liposomes consist of single bilayers, as demonstrated by nanopore formation experiments and confocal fluorescence microscopy, and they can act as compartments for cell-free gene expression. The microfluidic technique can be expanded to create liposomes with a multitude of coupled compartments, opening routes to networks of multistep microreactors. PMID:27243596
Synthesis of substantially monodispersed colloids
NASA Technical Reports Server (NTRS)
Klabunde, Kenneth J. (Inventor); Stoeva, Savka (Inventor); Sorensen, Christopher (Inventor)
2003-01-01
A method of forming ligated nanoparticles of the formula Y(Z).sub.x where Y is a nanoparticle selected from the group consisting of elemental metals having atomic numbers ranging from 21-34, 39-52, 57-83 and 89-102, all inclusive, the halides, oxides and sulfides of such metals, and the alkali metal and alkaline earth metal halides, and Z represents ligand moieties such as the alkyl thiols. In the method, a first colloidal dispersion is formed made up of nanoparticles solvated in a molar excess of a first solvent (preferably a ketone such as acetone), a second solvent different than the first solvent (preferably an organic aryl solvent such as toluene) and a quantity of ligand moieties; the first solvent is then removed under vacuum and the ligand moieties ligate to the nanoparticles to give a second colloidal dispersion of the ligated nanoparticles solvated in the second solvent. If substantially monodispersed nanoparticles are desired, the second dispersion is subjected to a digestive ripening process. Upon drying, the ligated nanoparticles may form a three-dimensional superlattice structure.
NASA Astrophysics Data System (ADS)
Wang, Feng; Luo, MingXing; Chen, XiuBo; Yang, YiXian; Wang, XiaoJun
2014-10-01
A universal entangler is a very powerful fault-tolerant entangling device for generating quantum entanglements from any joint states. Our paper aims to address the construction of universal entanglers. We prove that universal entanglers may be obtained from random unitary gates according to the Harr measure. The success probability is close to 1 for large system spaces. This result represents the typical density of entanglement subspaces in large state spaces. It also partially solves an open problem of universal bipartite entanglers and is explained by some experiment simulations.
ERIC Educational Resources Information Center
Tucker, David C.
1986-01-01
Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)
Allahverdyan, A.E.; Khrennikov, A.; Nieuwenhuizen, Th.M.
2005-09-15
For two classical Brownian particles an analog of continuous-variable quantum entanglement is presented: The common probability distribution of the two coordinates and the corresponding coarse-grained velocities cannot always be prepared via mixing of any factorized distributions referring to the two particles separately. This is possible for particles which have interacted in the past, but do not interact at present. Three factors are crucial for the effect: (1) separation of time scales of coordinate and momentum which motivates the definition of coarse-grained velocities; (2) the resulting uncertainty relations between the coordinate of the Brownian particle and the change of its coarse-grained velocity; (3) the fact that the coarse-grained velocity, though pertaining to a single Brownian particle, is defined on a common context of two particles. The Brownian entanglement is a consequence of a coarse-grained description and disappears for a finer resolution of the Brownian motion. Analogies with the quantum situation are discussed, as well as possibilities of experimental realization of the effect in examples of macroscopic Brownian motion.
NASA Astrophysics Data System (ADS)
Boyd, Jeffrey
2011-04-01
The double slit and Innsbruck experiments are thought to be the premier experiments establishing the need for the idea of ``non-locality'' in quantum mechanics. In the Innsbruck experiments it is said that two photons at a distance are ``entangled'' without there being any means of communication between them. But the interpretation of these experiments are based on the incorrect idea of wave particle duality. According to the Theory of Elementary Waves (TEW) waves are independent of particles. Waves are ubiquitous in nature. In the Innsbruck experiments two waves traveling at the speed of light in opposite directions impinge on the photon source from the two fiberoptic cables. The waves pass through the source. Wave interference is spread over a wide distance: from one polarizer to the other. This stimulates the emission of a photon pair such that, when detected at a polarizer at angle θ 1 and another polarizer at angle θ 2, the probability density is sin2(θ 1 - θ 2). This is true for any θ 1 and θ 2, and it doesn't matter when the polarizers are rotated. Thus local wave interference accounts for the experimental results, without any need for the exotic theory of ``entanglement.'' See http://Elwave.org
Fundamentals and applications of monodisperse carbon-based nanomaterials
NASA Astrophysics Data System (ADS)
Hersam, Mark
2011-03-01
Carbon-based nanomaterials have attracted significant attention due to their potential to enable and/or improve applications such as transistors, transparent conductors, solar cells, batteries, water purification systems, infrastructure materials, drug delivery, and biosensors. This talk will delineate chemical strategies for tuning and enhancing the properties of these promising nanomaterials. For example, we have developed and commercialized a scalable technique for sorting single-walled carbon nanotubes (SWCNTs) by their physical and electronic structure using density gradient ultracentrifugation (DGU). The resulting monodisperse SWCNTs possess unprecedented uniformity in their electronic and optical properties, which enables the fabrication of high performance thin film field-effect transistors, optoelectronic devices, and transparent conductors. The DGU technique also enables multi-walled carbon nanotubes to be sorted by the number of walls, and solution phase graphene to be sorted by thickness, thus expanding the suite of monodisperse carbon-based nanomaterials. By recently extending our DGU efforts to SWCNTs and graphene dispersed in biocompatible polymers (e.g., DNA, poloxamers, etc.), new opportunities have emerged in biomedical applications. Ultimately, the ability to control structure and surface chemistry with sub-nanometer precision enables optimized properties for a diverse range of technologies that employ carbon-based nanomaterials.
Renormalizing Entanglement Distillation
NASA Astrophysics Data System (ADS)
Waeldchen, Stephan; Gertis, Janina; Campbell, Earl T.; Eisert, Jens
2016-01-01
Entanglement distillation refers to the task of transforming a collection of weakly entangled pairs into fewer highly entangled ones. It is a core ingredient in quantum repeater protocols, which are needed to transmit entanglement over arbitrary distances in order to realize quantum key distribution schemes. Usually, it is assumed that the initial entangled pairs are identically and independently distributed and are uncorrelated with each other, an assumption that might not be reasonable at all in any entanglement generation process involving memory channels. Here, we introduce a framework that captures entanglement distillation in the presence of natural correlations arising from memory channels. Conceptually, we bring together ideas from condensed-matter physics—ideas from renormalization and matrix-product states and operators—with those of local entanglement manipulation, Markov chain mixing, and quantum error correction. We identify meaningful parameter regions for which we prove convergence to maximally entangled states, arising as the fixed points of a matrix-product operator renormalization flow.
Influence of entanglements on glass transition temperature of polystyrene
NASA Astrophysics Data System (ADS)
Ougizawa, Toshiaki; Kinugasa, Yoshinori
2013-03-01
Chain entanglement is essential behavior of polymeric molecules and it seems to affect many physical properties such as not only viscosity of melt state but also glass transition temperature (Tg). But we have not attained the quantitative estimation because the entanglement density is considered as an intrinsic value of the polymer at melt state depending on the chemical structure. Freeze-drying method is known as one of the few ways to make different entanglement density sample from dilute solution. In this study, the influence of entanglements on Tg of polystyrene obtained by the freeze-dried method was estimated quantitatively. The freeze-dried samples showed Tg depression with decreasing the concentration of precursor solution due to the lower entanglement density and their depressed Tg would be saturated when the almost no intermolecular entanglement was formed. The molecular weight dependence of the maximum value of Tg depression was discussed.
Enzyme Induced Formation of Monodisperse Hydrogel Nanoparticles Tunable in Size
Bocharova, Vera; Sharp, Danna; Jones, Aaron; Cheng, Shiwang; Griffin, Philip J.; Agapov, Alexander L.; Voylov, Dmitry; Wang, Yangyang; Kisliuk, Alexander; Melman, Artem; Sokolov, Alexei P.
2015-03-09
Here, we report a novel approach to synthesize monodisperse hydrogel nanoparticles that are tunable in size. The distinctive feature of our approach is the use of a multicopper oxidase enzyme, laccase, as both a biocatalyst and template for nanoparticle growth. We utilize the ferroxidase activity of laccase to initiate localized production of iron(III) cations from the oxidation of iron(II) cations. We demonstrate that nanoparticles are formed in a dilute polymer solution of alginate as a result of cross-linking between alginate and enzymatically produced iron(III) cations. Exerting control over the enzymatic reaction allows for nanometer-scale tuning of the hydrogel nanoparticle radii in the range of 30–100 nm. Moreover, the nanoparticles and their growth kinetics were characterized via dynamic light scattering, atomic force microscopy, and UV–vis spectroscopy. Our finding opens up a new avenue for the synthesis of tunable nanoscale hydrogel particles for biomedical applications.
Hussain, Irshad; Graham, Susan; Wang, Zhenxin; Tan, Bien; Sherrington, David C; Rannard, Steven P; Cooper, Andrew I; Brust, Mathias
2005-11-30
We report here a simple one-step protocol for the preparation of near-monodisperse gold hydrosols in the small size regime (<5 nm). The particle size can be controlled by varying the concentration of the stabilizing polymer, which can be readily displaced by thiol ligands to yield monolayer protected clusters of the usual type. PMID:16305218
Interface-mediated growth of monodispersed nanostructures.
Wang, Xun; Peng, Qing; Li, Yadong
2007-08-01
This Account focuses on the recent development of interface-mediated growth of monodispersed nanostructures in our laboratory. By rationally tuning the chemical reactions at various gas-liquid, solid-solid, liquid-liquid, and liquid-solid-solution interfaces, we could readily synthesize nanostructures such as hollow microspheres, core-shell nanoparticles, and monodispersed nanocrystals. These advances in interface-mediated synthesis could lead to progress in the development of nanocrystal crystallography and encourage some more unique and exciting research and applications to nanoscience and nanotechnology. PMID:17500508
Spatial multipartite entanglement and localization of entanglement
Daems, D.; Cerf, N. J.
2010-09-15
We present a simple model together with its physical implementation which allows one to generate multipartite entanglement between several spatial modes of the electromagnetic field. It is based on parametric down-conversion with N pairs of symmetrically tilted plane waves serving as a pump. The characteristics of this spatial entanglement are investigated in the cases of zero as well as nonzero phase mismatch. Furthermore, the phenomenon of entanglement localization in just two spatial modes is studied in detail and shown to result in an enhancement of the entanglement by a factor {radical}(N).
NASA Astrophysics Data System (ADS)
Watanabe, Hiroshi; Matsumiya, Yumi
Viscoelastic relaxation was examined for entangled miscible blends of cis-polyisoprene (PI) and poly(ptert-butylstyrene) (PtBS). The terminal relaxation times of PI and PtBS therein, τPI and τPtBS, changed with the composition wPI and the molecular weights MPI and MPtBS. This ratio became unity when the wPI, MPI, and MPtBS values were chosen adequately. For example, in a blend with wPI = 0.75, MPI = 321k, and MPtBS = 91k at T = 40ûC, τPI/τPtBS = 1 and M/Me = 55 and 8.3 for PI and PtBS. Under small strains, this blend exhibited sharp, single-step terminal relaxation as similar to monodisperse homopolymers, thereby behaving as a ``quasi-monodisperse'' material. Under large step strains, the blend exhibited moderate nonlinear damping known as the type-A damping for entangled monodisperse homopolymers. Nevertheless, PI had M/Me = 55 in that blend, and homopolymers having such a large M/Me ratio exhibit very strong type-C damping. Thus, as compared to homopolymers, the nonlinearity was suppressed in the PI/PtBS blend having the large M/Me ratio. This suppression is discussed in relation to the slow Rouse retraction of the coexisting PtBS chains (having M/Me = 8.3 in the blend).
Generalized entanglement entropy
NASA Astrophysics Data System (ADS)
Taylor, Marika
2016-07-01
We discuss two measures of entanglement in quantum field theory and their holographic realizations. For field theories admitting a global symmetry, we introduce a global symmetry entanglement entropy, associated with the partitioning of the symmetry group. This quantity is proposed to be related to the generalized holographic entanglement entropy defined via the partitioning of the internal space of the bulk geometry. Thesecond measure of quantum field theory entanglement is the field space entanglement entropy, obtained by integrating out a subset of the quantum fields. We argue that field space entanglement entropy cannot be precisely realised geometrically in a holographic dual. However, for holographic geometries with interior decoupling regions, the differential entropy provides a close analogue to the field space entanglement entropy. We derive generic descriptions of such inner throat regions in terms of gravity coupled to massive scalars and show how the differential entropy in the throat captures features of the field space entanglement entropy.
Charged topological entanglement entropy
NASA Astrophysics Data System (ADS)
Matsuura, Shunji; Wen, Xueda; Hung, Ling-Yan; Ryu, Shinsei
2016-05-01
A charged entanglement entropy is a new measure which probes quantum entanglement between different charge sectors. We study symmetry-protected topological (SPT) phases in (2+1)-dimensional space-time by using this charged entanglement entropy. SPT phases are short-range entangled states without topological order and hence cannot be detected by the topological entanglement entropy. We demonstrate that the universal part of the charged entanglement entropy is nonzero for nontrivial SPT phases and therefore it is a useful measure to detect short-range entangled topological phases. We also discuss that the classification of SPT phases based on the charged topological entanglement entropy is related to that of the braiding statistics of quasiparticles.
Nonequilibrium thermal entanglement
Quiroga, Luis; Rodriguez, Ferney J.; Ramirez, Maria E.; Paris, Roberto
2007-03-15
Results on heat current, entropy production rate, and entanglement are reported for a quantum system coupled to two different temperature heat reservoirs. By applying a temperature gradient, different quantum states can be found with exactly the same amount of entanglement but different purity degrees and heat currents. Furthermore, a nonequilibrium enhancement-suppression transition behavior of the entanglement is identified.
Extremal extensions of entanglement witnesses: Finding new bound entangled states
Sengupta, R.; Arvind
2011-09-15
In this paper, we discuss extremal extensions of entanglement witnesses based on Choi's map. The constructions are based on a generalization of the Choi map, from which we construct entanglement witnesses. These extremal extensions are powerful in terms of their capacity to detect entanglement of positive under partial transpose (PPT) entangled states and lead to unearthing of entanglement of new PPT states. We also use the Cholesky-like decomposition to construct entangled states which are revealed by these extremal entanglement witnesses.
Tunable stability of monodisperse secondary O/W nano-emulsions
NASA Astrophysics Data System (ADS)
Vecchione, R.; Ciotola, U.; Sagliano, A.; Bianchini, P.; Diaspro, A.; Netti, P. A.
2014-07-01
Stable and biodegradable oil in water (O/W) nano-emulsions can have a huge impact on a wide range of bio-applications, from food to cosmetics and pharmaceuticals. Emulsions, however, are immiscible systems unstable over time; polymer coatings are known to be helpful, but an effective procedure to stabilize monodisperse and biodegradable O/W nano-emulsions is yet to be designed. Here, we coat biodegradable O/W nano-emulsions with a molecular layer of biodegradable polyelectrolytes such as polysaccharides - like chitosan - and polypeptides - like polylysine - and effectively re-disperse and densify the polymer coating at high pressure, thus obtaining monodisperse and stable systems. In particular, focusing on chitosan, our tests show that it is possible to obtain unprecedented ultra-stable O/W secondary nano-emulsions (diameter sizes tunable from ~80 to 160 nm and polydispersion indices below 0.1) by combining this process with high concentrations of polymers. Depending on the polymer concentration, it is possible to control the level of coating that results in a tunable stability ranging from a few weeks to several months. The above range of concentrations has been investigated using a fluorescence-based approach with new insights into the coating evolution.Stable and biodegradable oil in water (O/W) nano-emulsions can have a huge impact on a wide range of bio-applications, from food to cosmetics and pharmaceuticals. Emulsions, however, are immiscible systems unstable over time; polymer coatings are known to be helpful, but an effective procedure to stabilize monodisperse and biodegradable O/W nano-emulsions is yet to be designed. Here, we coat biodegradable O/W nano-emulsions with a molecular layer of biodegradable polyelectrolytes such as polysaccharides - like chitosan - and polypeptides - like polylysine - and effectively re-disperse and densify the polymer coating at high pressure, thus obtaining monodisperse and stable systems. In particular, focusing on
Li, Zhen; Tan, Bien; Allix, Mathieu; Cooper, Andrew I; Rosseinsky, Matthew J
2008-02-01
Water-soluble monodisperse superparamagnetic Fe3O4 nanocrystals decorated with two distinct functional groups are prepared in a single-step procedure by injecting iron precursors into a refluxing aqueous solution of a polymer ligand, trithiol-terminated poly(methacrylic acid) (PMAA-PTTM), bearing both carboxylate and thiol functionalities. The ratio of carboxylic acid groups in the polymer-protecting ligand to the iron precursors plays a key role in determining the particle size and particle size distribution. The surface functionalities of the ligands allow post-synthesis modification of the materials to produce water-soluble fluorescent magnetic nanocrystals. PMID:18213671
Gaussian entanglement of formation
Wolf, M.M.; Giedke, G.; Krueger, O.; Werner, R. F.; Cirac, J.I.
2004-05-01
We introduce a Gaussian version of the entanglement of formation adapted to bipartite Gaussian states by considering decompositions into pure Gaussian states only. We show that this quantity is an entanglement monotone under Gaussian operations and provide a simplified computation for states of arbitrary many modes. For the case of one mode per site the remaining variational problem can be solved analytically. If the considered state is in addition symmetric with respect to interchanging the two modes, we prove additivity of the considered entanglement measure. Moreover, in this case and considering only a single copy, our entanglement measure coincides with the true entanglement of formation.
Entanglement monogamy and entanglement evolution in multipartite systems
Bai Yankui; Ye Mingyong; Wang, Z. D.
2009-10-15
We analyze the entanglement distribution and the two-qubit residual entanglement in multipartite systems. For a composite system consisting of two cavities interacting with independent reservoirs, it is revealed that the entanglement evolution is restricted by an entanglement monogamy relation derived here. Moreover, it is found that the initial cavity-cavity entanglement evolves completely to the genuine four-partite cavities-reservoirs entanglement in the time interval between the sudden death of cavity-cavity entanglement and the birth of reservoir-reservoir entanglement. In addition, we also address the relationship between the genuine block-block entanglement form and qubit-block form in the interval.
Threefold entanglement matching
NASA Astrophysics Data System (ADS)
Roa, Luis; Muñoz, Ariana; Hutin, Alice; Hecker, Matthias
2015-11-01
We address the problem of entanglement matching in the probabilistic teleportation scheme by considering two independent levels of entanglement in the measurement basis. The probability of a successful teleportation has an upper bound which only depends on the amount of entanglement of the quantum channel. However, we found that each entanglement of the measurement basis contributes independently to the success probability as long as it is weaker than the entanglement of the channel. Accordingly, the teleportation process reaches its optimal probability when both entanglements of the measurement basis match the entanglement of the channel. Additionally, we study the probabilistic scheme for extracting an unknown state from a partially known state. We characterize the success probability and the concurrence involved in that process.
Polymer Physics Prize Talk: Our Love Story with Polymers or ``Is This Really Physics?''
NASA Astrophysics Data System (ADS)
Rubinstein, Michael
2010-03-01
Some recent results and remaining open questions in several areas of polymer physics ranging from polymer entanglements to reversible gels and polyelectrolytes will be reviewed and put into historical and sociological perspective.
Surfactant-assisted synthesis of mono-dispersed cubic BaTiO{sub 3} nanoparticles
Hai, Chunxi; Inukai, Koji; Takahashi, Yosuke; Izu, Noriya; Akamatsu, Takafumi; Itoh, Toshio; Shin, Woosuck
2014-09-15
Mono-dispersed BaTiO{sub 3} nanoparticles have been prepared via the assistance of capping agent poly(vinylpyrrolidone) (PVP). - Highlights: • BaTiO{sub 3} nanoparticles with single cubic crystal structure. • Poor dispersibility of nanoparticles has been overcome by in situ modification way. • Growth competition between BaTiO3 core and polymer shell. - Abstract: In this study, poly(vinylpyrrolidone)-assisted synthesis of mono-dispersed BaTiO{sub 3} nanoparticles have been reported. The various processing parameters, namely, refluxing temperature, KOH concentration, and poly(vinylpyrrolidone) concentration, have been varied, and the effects on the growth of BaTiO{sub 3} particles have been analyzed systematically. X-ray diffraction studies indicated that poly(vinylpyrrolidone) did not affect the crystal structure, but rather influenced the crystal lattice structure. In addition, the use of surfactant poly(vinylpyrrolidone) hindered the agglomeration of the nanoparticles, and facilitated the formation of mono-dispersed core–shell organic/inorganic hybrid nanocomposite. Furthermore, the mineralizer KOH promoted the dissolution of reactants and promoted the crystallization of BaTiO{sub 3} particles. Accordingly, the dissolution-precipitation scheme was believed to be the mechanism underlying the formation of BaTiO{sub 3} particles. This was further substantiated by the experimental observations, which indicated that the nucleation and crystallization of the particles was affected by the KOH concentration in the reaction system. Finally, the formation of mono-dispersed core–shell nanocomposites proceeded via reaction limited cluster aggregation. We believe that the method proposed in this study could be extended for the synthesis of mono-dispersed nanoparticles for industrial applications.
Entanglement - From Particles to Consciousness
NASA Astrophysics Data System (ADS)
Teodorani, M.
2007-06-01
This book, which is entirely devoted to the description and discussion of the mechanism of quantum entanglement, is divided into three main parts: a) canonical entanglement in the realm of elementary particles; b) entanglement in the biological environment (DNA and microtubules); c) entanglement in the psychic realm. Cosmological entanglement and non-local SETI are discussed as well.
Viscoelastic Properties of Polymer Blends
NASA Technical Reports Server (NTRS)
Hong, S. D.; Moacanin, J.; Soong, D.
1982-01-01
Viscosity, shear modulus and other viscoelastic properties of multicomponent polymer blends are predicted from behavior of individual components, using a mathematical model. Model is extension of two-component-blend model based on Rouse-Bueche-Zimm theory of polymer viscoelasticity. Extension assumes that probabilities of forming various possible intracomponent and intercomponent entanglements among polymer molecules are proportional to relative abundances of components.
Pollutant Formation in Monodisperse Fuel Spray Combustion
NASA Technical Reports Server (NTRS)
Cernansky, N. P.; Sarv, H.
1983-01-01
The combustion of liquid sprays represents an extremely important class of combustion processes. In the transition region, encompassing droplet sizes in the range of 25-80 micron diameter, the mixing and evaporation processes are both incomplete at the flame front and burning occurs in a combined diffusive and premixed fashion. Under these conditions, the relative importance of heterogeneous and homogeneous effects in dominating the combustion process is switched and gives rise to a number of interesting phenomena. NO (sub x) formation in monodisperse spray combustion was investigated with the following specific objectives: (1) to quantitatively determine the effect of droplet size, number density, etc. on NO sub x formation in monodisperse fuel spray combustion; and (2) to isolate the important physical and chemical phenomena in NO sub x formation in these combustion systems.
Monodisperse functional colloidosomes with tailored nanoparticle shells.
Sander, J S; Studart, A R
2011-04-01
We report the assembly of monodisperse colloidosomes containing a wide range of functional nanoparticles in the outer shell using a double emulsion templating method in a microfluidic device. By selecting nanoparticles of specific functionalities, hollow capsules with inert, magnetic, photocatalytic, and potentially biocompatible and piezoelectric shells are easily obtained. Proper control over the surface chemistry of the nanoparticles forming the shell and of the liquid interfaces involved is key to enable the assembly of colloidosomes using this double emulsification route. PMID:21384846
Spectral conditions for entanglement witnesses versus bound entanglement
Chruscinski, Dariusz; Kossakowski, Andrzej; Sarbicki, Gniewomir
2009-10-15
It is shown that entanglement witnesses constructed via the family of spectral conditions are decomposable, i.e., cannot be used to detect bound entanglement. It supports several observations that bound entanglement reveals highly nonspectral features.
Chain entanglements. I. Theory
NASA Astrophysics Data System (ADS)
Fixman, Marshall
1988-09-01
A model of concentrated polymer solution dynamics is described. The forces in a linear generalized Langevin equation for the motion of a probe chain are derived on the assumption that all relaxation of the forces is due to motion of the surrounding matrix. Vicinal chain displacements are classified as viscoelastic deformation, reptation, and minor residual fluctuations. The latter provide a torsional relaxation of the primitive path that minimizes the significance of transverse forces on the probe chain. All displacements of vicinal segments are assumed proportional to the forces that they exert on the probe chain. In response to an external force, the displacement of the probe chain relative to a laboratory frame is increased by viscoelastic deformation of the matrix, but reptative diffusion relative to the deforming matrix is slowed down. The net effect on translational diffusion is negligible if the probe and vicinal chains have the same chain length N, but the friction constant for reptative motion is increased by a factor N1-xs. xs=1/2 if Gaussian conformational statistics applies during the disengagement process, while xs =0.6 if excluded volume statistics applies. The translational friction constant is βp ˜N2, as in reptation theory, but the viscosity is η˜N4-xs . The persistence of entanglements during the translational diffusion of the probe chain across many radii of gyration is rationalized pictorially in terms of correlated reptative motion of the probe and vicinal chains.
Falzone, Tobias T; Blair, Savanna; Robertson-Anderson, Rae M
2015-06-14
We drive optically trapped microspheres through entangled F-actin at constant speeds and distances well beyond the linear regime, and measure the microscale force response of the entangled filaments during and following strain. Our results reveal a unique crossover to appreciable nonlinearity at a strain rate of [small gamma, Greek, dot above]c ≈ 3 s(-1) which corresponds remarkably well with the theoretical rate of relaxation of entanglement length deformations 1/τent. Above [small gamma, Greek, dot above]c, we observe stress stiffening which occurs over very short time scales comparable to the predicted timescale over which mesh size deformations relax. Stress softening then takes over, yielding to an effectively viscous regime over a timescale comparable to the entanglement length relaxation time, τent. The viscous regime displays shear thinning but with a less pronounced viscosity scaling with strain rate compared to flexible polymers. The relaxation of induced force on filaments following strain shows that the relative relaxation proceeds more quickly for increasing strain rates; and for rates greater than [small gamma, Greek, dot above]c, the relaxation displays a complex power-law dependence on time. Our collective results reveal that molecular-level nonlinear viscoelasticity is driven by non-classical dynamics of individual entanglement segments that are unique to semiflexible polymers. PMID:25920523
Entangling power and operator entanglement in qudit systems
Wang Xiaoguang; Sanders, Barry C.; Berry, Dominic W.
2003-04-01
We establish the entangling power of a unitary operator on a general finite-dimensional bipartite quantum system with and without ancillas, and give relations between the entangling power based on the von Neumann entropy and the entangling power based on the linear entropy. Significantly, we demonstrate that the entangling power of a general controlled unitary operator acting on two equal-dimensional qudits is proportional to the corresponding operator entanglement if linear entropy is adopted as the quantity representing the degree of entanglement. We discuss the entangling power and operator entanglement of three representative quantum gates on qudits: the SUM, double SUM, and SWAP gates.
Theory of entanglement and entanglement-assisted communication
NASA Astrophysics Data System (ADS)
Bennett, Charles H.
2011-03-01
Protocols such as quantum teleportation and measurement-based quantum computation highlight the importance of entanglement as a resource to be quantified and husbanded. Unlike classical shared randomness, entanglement has a profound effect on the capacity of quantum channels: a channel's entanglement-assisted capacity can be much greater than its unassisted capacity, and in any case is given by much a simpler formula, paralleling Shannon's original formula for the capacity of a classical channel. We review the differences between entanglement and weaker forms of correlation, and the theory of entanglement distillation and entanglement-assisted communication, including the role of strong forms of entanglement such as entanglement-embezzling states.
Thermalization of entanglement.
Zhang, Liangsheng; Kim, Hyungwon; Huse, David A
2015-06-01
We explore the dynamics of the entanglement entropy near equilibrium in highly entangled pure states of two quantum-chaotic spin chains undergoing unitary time evolution. We examine the relaxation to equilibrium from initial states with either less or more entanglement entropy than the equilibrium value, as well as the dynamics of the spontaneous fluctuations of the entanglement that occur in equilibrium. For the spin chain with a time-independent Hamiltonian and thus an extensive conserved energy, we find slow relaxation of the entanglement entropy near equilibration. Such slow relaxation is absent in a Floquet spin chain with a Hamiltonian that is periodic in time and thus has no local conservation law. Therefore, we argue that slow diffusive energy transport is responsible for the slow relaxation of the entanglement entropy in the Hamiltonian system. PMID:26172682
Unlocking fermionic mode entanglement
NASA Astrophysics Data System (ADS)
Friis, Nicolai
2016-06-01
Aside from other puzzling features of entanglement, it has been debated whether a physically meaningful notion of entanglement requires two (or more) particles as carriers of the correlated degrees-of-freedom, or if a single particle could be considered to be entangled as well. While the usefulness of single-boson entanglement has been demonstrated some time ago, the restrictions of superselection rules have previously thwarted attempts at similar arguments for single fermions. In Dasenbrook et al (2016 New J. Phys. 18 043036) this obstacle is overcome. The authors propose a scheme for a Bell test on two copies of single-electron states whose entanglement is individually not accessible. The discussed scheme, which makes use of recent progress in electronic quantum optics, provides an experimentally viable and theoretically unambiguous way to assert that certain single-electron states can be considered to be entangled.
Geometric measures of entanglement
Uyanik, K.; Turgut, S.
2010-03-15
The geometric measure of entanglement, which expresses the minimum distance to product states, has been generalized to distances to sets that remain invariant under the stochastic reducibility relation. For each such set, an associated entanglement monotone can be defined. The explicit analytical forms of these measures are obtained for bipartite entangled states. Moreover, the three-qubit case is discussed and it is argued that the distance to the W states is a new monotone.
Multipartite entanglement measures
NASA Astrophysics Data System (ADS)
Szalay, Szilárd
2015-10-01
The main concern of this paper is how to define proper measures of multipartite entanglement for mixed quantum states. Since the structure of partial separability and multipartite entanglement is getting complicated if the number of subsystems exceeds two, one cannot expect the existence of an ultimate scalar entanglement measure, which grasps even a small part of the rich hierarchical structure of multipartite entanglement, and some higher-order structure characterizing that is needed. In this paper we make some steps in this direction. First, we reveal the lattice-theoretic structure of the partial separability classification, introduced earlier [Sz. Szalay and Z. Kökényesi, Phys. Rev. A 86, 032341 (2012), 10.1103/PhysRevA.86.032341]. It turns out that, mathematically, the structure of the entanglement classes is the up-set lattice of the structure of the different kinds of partial separability, which is the down-set lattice of the lattice of the partitions of the subsystems. It also turns out that, physically, this structure is related to the local operations and classical communication convertibility: If a state from a class can be mapped into another one, then that class can be found higher in the hierarchy. Second, we introduce the notion of multipartite monotonicity, expressing that a given set of entanglement monotones, while measuring the different kinds of entanglement, shows also the same hierarchical structure as the entanglement classes. Then we construct such hierarchies of entanglement measures and propose a physically well-motivated one, being the direct multipartite generalization of the entanglement of formation based on the entanglement entropy, motivated by the notion of statistical distinguishability. The multipartite monotonicity shown by this set of measures motivates us to consider the measures to be the different manifestations of some "unified" notion of entanglement.
Hopping Diffusion of Nanoparticles in Polymer Matrices
2016-01-01
We propose a hopping mechanism for diffusion of large nonsticky nanoparticles subjected to topological constraints in both unentangled and entangled polymer solids (networks and gels) and entangled polymer liquids (melts and solutions). Probe particles with size larger than the mesh size ax of unentangled polymer networks or tube diameter ae of entangled polymer liquids are trapped by the network or entanglement cells. At long time scales, however, these particles can diffuse by overcoming free energy barrier between neighboring confinement cells. The terminal particle diffusion coefficient dominated by this hopping diffusion is appreciable for particles with size moderately larger than the network mesh size ax or tube diameter ae. Much larger particles in polymer solids will be permanently trapped by local network cells, whereas they can still move in polymer liquids by waiting for entanglement cells to rearrange on the relaxation time scales of these liquids. Hopping diffusion in entangled polymer liquids and networks has a weaker dependence on particle size than that in unentangled networks as entanglements can slide along chains under polymer deformation. The proposed novel hopping model enables understanding the motion of large nanoparticles in polymeric nanocomposites and the transport of nano drug carriers in complex biological gels such as mucus. PMID:25691803
NASA Astrophysics Data System (ADS)
Xiao, Yunlong; Jing, Naihuan; Li-Jost, Xianqing; Fei, Shao-Ming
2016-08-01
We present several criteria for genuine multipartite entanglement from universal uncertainty relations based on majorization theory. Under non-negative Schur-concave functions, the vector-type uncertainty relation generates a family of infinitely many detectors to check genuine multipartite entanglement. We also introduce the concept of k-separable circles via geometric distance for probability vectors, which include at most ( k-1)-separable states. The entanglement witness is also generalized to a universal entanglement witness which is able to detect the k-separable states more accurately.
Multipartite entanglement of superpositions
NASA Astrophysics Data System (ADS)
Cavalcanti, D.; Terra Cunha, M. O.; Acín, A.
2007-10-01
The entanglement of superpositions [Linden , Phys. Rev. Lett. 97, 100502 (2006)]is generalized to the multipartite scenario: an upper bound to the multipartite entanglement of a superposition is given in terms of the entanglement of the superposed states and the superposition coefficients. This bound is proven to be tight for a class of states composed of an arbitrary number of qubits. We also extend the result to a large family of quantifiers, which includes the negativity, the robustness of entanglement, and the best separable approximation measure.
Multipartite entanglement of superpositions
Cavalcanti, D.; Terra Cunha, M. O.; Acin, A.
2007-10-15
The entanglement of superpositions [Linden et al., Phys. Rev. Lett. 97, 100502 (2006)]is generalized to the multipartite scenario: an upper bound to the multipartite entanglement of a superposition is given in terms of the entanglement of the superposed states and the superposition coefficients. This bound is proven to be tight for a class of states composed of an arbitrary number of qubits. We also extend the result to a large family of quantifiers, which includes the negativity, the robustness of entanglement, and the best separable approximation measure.
NASA Astrophysics Data System (ADS)
Xiao, Yunlong; Jing, Naihuan; Li-Jost, Xianqing; Fei, Shao-Ming
2016-03-01
We present several criteria for genuine multipartite entanglement from universal uncertainty relations based on majorization theory. Under non-negative Schur-concave functions, the vector-type uncertainty relation generates a family of infinitely many detectors to check genuine multipartite entanglement. We also introduce the concept of k-separable circles via geometric distance for probability vectors, which include at most (k-1)-separable states. The entanglement witness is also generalized to a universal entanglement witness which is able to detect the k-separable states more accurately.
Renormalizing Entanglement Distillation.
Waeldchen, Stephan; Gertis, Janina; Campbell, Earl T; Eisert, Jens
2016-01-15
Entanglement distillation refers to the task of transforming a collection of weakly entangled pairs into fewer highly entangled ones. It is a core ingredient in quantum repeater protocols, which are needed to transmit entanglement over arbitrary distances in order to realize quantum key distribution schemes. Usually, it is assumed that the initial entangled pairs are identically and independently distributed and are uncorrelated with each other, an assumption that might not be reasonable at all in any entanglement generation process involving memory channels. Here, we introduce a framework that captures entanglement distillation in the presence of natural correlations arising from memory channels. Conceptually, we bring together ideas from condensed-matter physics-ideas from renormalization and matrix-product states and operators-with those of local entanglement manipulation, Markov chain mixing, and quantum error correction. We identify meaningful parameter regions for which we prove convergence to maximally entangled states, arising as the fixed points of a matrix-product operator renormalization flow. PMID:26824532
Feasibility study: Monodisperse polymer particles containing laser-excitable dyes
NASA Technical Reports Server (NTRS)
Venkateswarlu, Putcha; He, K. X.; Sharma, A.
1993-01-01
The optical properties associated with small particles, which include aerosols, hydrosols and solid microspheres have an impact on several areas of science and engineering. Since the advent of high-speed computers and lasers, the interaction of light with matter in the form of small particles with a discontinuous optical boundary relative to the surroundings has been much better understood. Various nonlinear optical effects have been observed involving interaction of a laser beam with both solid microspheres and liquid microdroplets. These include observation of second and third harmonic generation, four wave mixing, optical visibility, two photon absorption, observation of stimulated emission and lasing, and Stimulated Raman Scattering. Many of these effects are observed with laser intensities which are orders of magnitude less than that required by threshold condition for interactions in macroscopic bulk medium. The primary reason for this is twofold. The front surface of the microsphere acts as a thick lens to enhance the internal intensity of the input laser radiation, and the spherical shape of the droplet acts as an optical cavity to provide feedback at specific wavelengths corresponding to the whispering gallery modes or the morphology dependent resonances (MDR's). The most interesting and significant recent finding in this field is undoubtedly the existence of resonance peaks in linear and nonlinear optical spectra. Such resonance peaks are only dependent on the particle morphology, which means the size, shape and refractive index of the particle. Because of the simultaneous presence of these resonances, they have been referred to by many names, including structural resonances, whispering modes or whispering gallery modes, creeping waves, circumferential waves, surfaces modes, and virtual modes. All of these names refer to the same phenomena, i.e. morphology dependent resonances (MDR's) which has already been described and predicted precisely by electromagnetic theory and Loentz-Mie theory since 1908. MDR's can become important when the particle size (radius a) approaches and exceeds the wavelength of the electromagnetic wave (lambda) and the refractive index of the particle is greater than that of the surrounding medium. Such resonances are easiest to observe from a single particle with high symmetry, such as a sphere, spheroid, or cylinder. MDR's correspond to solutions of the characteristic equations of the electromagnetic fields in the presence of a sphere.
Fluorescence enhancement of Rhodamine B by monodispersed silver nanoparticles
NASA Astrophysics Data System (ADS)
Suslov, A.; Lama, P. T.; Dorsinville, R.
2015-06-01
A strong enhancement in fluorescence of Rhodamine B dye in the vicinity of silver monodisperse nanoparticles is presented. The fluorescence of the dye increased as much as by 23 times in the presence of monodispersed silver nanoparticles. The fluorescence enhancement due to monodispersed silver nanoparticles was about 2-3 times larger than in the presence of polydispersed silver nanoparticles. The additional enhancement is explained in terms of emergence of uniform and large local electromagnetic field induced by surface plasmon resonance around an ensemble of monodispersed silver nanoparticles.
Emerging Methods for Producing Monodisperse Graphene Dispersions
Green, Alexander A.; Hersam, Mark C.
2010-01-01
With the recent burst of activity surrounding solution phase production of graphene, comparatively little progress has been made towards the generation of graphene dispersions with tailored thickness, lateral area, and shape. The polydispersity of graphene dispersions, however, can lead to unpredictable or non-ideal behavior once they are incorporated into devices, since the properties of graphene vary as a function of its structural parameters. In this brief perspective, we overview the problem of graphene polydispersity, the production of graphene dispersions, and the methods under development to produce dispersions of monodisperse graphene. PMID:20657758
Causality & holographic entanglement entropy
NASA Astrophysics Data System (ADS)
Headrick, Matthew; Hubeny, Veronika E.; Lawrence, Albion; Rangamani, Mukund
2014-12-01
We identify conditions for the entanglement entropy as a function of spatial region to be compatible with causality in an arbitrary relativistic quantum field theory. We then prove that the covariant holographic entanglement entropy prescription (which relates entanglement entropy of a given spatial region on the boundary to the area of a certain extremal surface in the bulk) obeys these conditions, as long as the bulk obeys the null energy condition. While necessary for the validity of the prescription, this consistency requirement is quite nontrivial from the bulk standpoint, and therefore provides important additional evidence for the prescription. In the process, we introduce a codimension-zero bulk region, named the entanglement wedge, naturally associated with the given boundary spatial region. We propose that the entanglement wedge is the most natural bulk region corresponding to the boundary reduced density matrix.
Mechanism of entanglement preservation
Tong Qingjun; An Junhong; Luo Honggang; Oh, C. H.
2010-05-15
We study the entanglement preservation of two qubits locally interacting with their reservoirs. We show that the existence of a bound state of the qubit and its reservoir and the non-Markovian effect are two essential ingredients and their interplay plays a crucial role in preserving the entanglement in the steady state. When the non-Markovian effect is neglected, the entanglement sudden death (ESD) is reproduced. On the other hand, when the non-Markovian is significantly strong but the bound state is absent, the phenomenon of the ESD and its revival is recovered. Our formulation presents a unified picture about the entanglement preservation and provides a clear clue on how to preserve the entanglement in quantum information processing.
Monodisperse PEGylated Spheres: An Aqueous Colloidal Model System
2014-01-01
Fluorinated core–shell spheres have been synthesized using a novel semibatch emulsion polymerization protocol employing slow feeding of the initiator. The synthesis results in aqueous dispersions of highly monodisperse spheres bearing a well-defined poly(ethylene glycol) graft (PEGylation). Measurements are consistent with the synthesis achieving a high grafting density that moreover consists of a single PEG layer with the polymer significantly elongated beyond its radius of gyration in bulk. The fluorination of the core of the particles confers a low index of refraction such that the particles can be refractive index matched in water through addition of relatively small amounts of a cosolvent, which enables the use of optical and laser-based methods for studies of concentrated systems. The systems exhibit an extreme stability in NaCl solutions, but attractions among particles can be introduced by addition of other salts, in which case aggregation is shown to be reversible. The PEGylated sphere dispersions are expected to be ideally suited as model systems for studies of the effect of PEG-mediated interactions on, for instance, structure, dynamics, phase behavior, and rheology. PMID:24533774
Enzyme Induced Formation of Monodisperse Hydrogel Nanoparticles Tunable in Size
Bocharova, Vera; Sharp, Danna; Jones, Aaron; Cheng, Shiwang; Griffin, Philip J.; Agapov, Alexander L.; Voylov, Dmitry; Wang, Yangyang; Kisliuk, Alexander; Melman, Artem; et al
2015-03-09
Here, we report a novel approach to synthesize monodisperse hydrogel nanoparticles that are tunable in size. The distinctive feature of our approach is the use of a multicopper oxidase enzyme, laccase, as both a biocatalyst and template for nanoparticle growth. We utilize the ferroxidase activity of laccase to initiate localized production of iron(III) cations from the oxidation of iron(II) cations. We demonstrate that nanoparticles are formed in a dilute polymer solution of alginate as a result of cross-linking between alginate and enzymatically produced iron(III) cations. Exerting control over the enzymatic reaction allows for nanometer-scale tuning of the hydrogel nanoparticle radiimore » in the range of 30–100 nm. Moreover, the nanoparticles and their growth kinetics were characterized via dynamic light scattering, atomic force microscopy, and UV–vis spectroscopy. Our finding opens up a new avenue for the synthesis of tunable nanoscale hydrogel particles for biomedical applications.« less
Monodisperse PEGylated spheres: an aqueous colloidal model system.
Ulama, Jeanette; Zackrisson Oskolkova, Malin; Bergenholtz, Johan
2014-03-01
Fluorinated core-shell spheres have been synthesized using a novel semibatch emulsion polymerization protocol employing slow feeding of the initiator. The synthesis results in aqueous dispersions of highly monodisperse spheres bearing a well-defined poly(ethylene glycol) graft (PEGylation). Measurements are consistent with the synthesis achieving a high grafting density that moreover consists of a single PEG layer with the polymer significantly elongated beyond its radius of gyration in bulk. The fluorination of the core of the particles confers a low index of refraction such that the particles can be refractive index matched in water through addition of relatively small amounts of a cosolvent, which enables the use of optical and laser-based methods for studies of concentrated systems. The systems exhibit an extreme stability in NaCl solutions, but attractions among particles can be introduced by addition of other salts, in which case aggregation is shown to be reversible. The PEGylated sphere dispersions are expected to be ideally suited as model systems for studies of the effect of PEG-mediated interactions on, for instance, structure, dynamics, phase behavior, and rheology. PMID:24533774
Monodisperse hard rods in external potentials
NASA Astrophysics Data System (ADS)
Bakhti, Benaoumeur; Karbach, Michael; Maass, Philipp; Müller, Gerhard
2015-10-01
We consider linear arrays of cells of volume Vc populated by monodisperse rods of size σ Vc,σ =1 ,2 ,... , subject to hardcore exclusion interaction. Each rod experiences a position-dependent external potential. In one application we also examine effects of contact forces between rods. We employ two distinct methods of exact analysis with complementary strengths and different limits of spatial resolution to calculate profiles of pressure and density on mesoscopic and microscopic length scales at thermal equilibrium. One method uses density functionals and the other statistically interacting vacancy particles. The applications worked out include gravity, power-law traps, and hard walls. We identify oscillations in the profiles on a microscopic length scale and show how they are systematically averaged out on a well-defined mesoscopic length scale to establish full consistency between the two approaches. The continuum limit, realized as Vc→0 ,σ →∞ at nonzero and finite σ Vc , connects our highest-resolution results with known exact results for monodisperse rods in a continuum. We also compare the pressure profiles obtained from density functionals with the average microscopic pressure profiles derived from the pair distribution function.
Monodisperse Magnetic Nanoparticles for Theranostic Applications
Ho, Don; Sun, Xiaolian; Sun, Shouheng
2011-01-01
Conspectus The development of highly effective medicine requires the on-time monitoring of the medical treatment process. This combination of monitoring and therapeutics allows a large degree of control on the treatment efficacy and is now commonly referred to as “theranostics”. Magnetic nanoparticles (NPs) provide a unique nano-platform for theranostic applications due to their comparable sizes with various functional biomolecules, their biocompatibility and their responses to the external magnetic field. Recent efforts in studying magnetic NPs for both imaging and therapeutic applications have led to great advances in NP fabrication with controls in dimension, surface functionalization and magnetic property. These magnetic NPs have been proven to be robust agents that can be target-specific for enhancing magnetic resonance imaging sensitivity and magnetic heating efficiency. These, plus the deep tissue penetration of magnetic field, make magnetic NPs the most promising candidates for successful theranostics in the future. In this Account, we review the recent advances in the synthesis of magnetic NPs of iron oxide, Fe, as well as FePt and FeCo NPs for imaging and therapeutic applications. We will first introduce briefly nanomagnetism, magnetic resonance imaging (MRI), and magnetic fluid hyperthermia (MFH). We will then focus on chemical synthesis of monodisperse magnetic NPs with controlled sizes, morphologies, and magnetic properties. Typical examples in using monodisperse magnetic NPs for MRI and MFH are highlighted. PMID:21661754
Reexamination of entanglement of superpositions
NASA Astrophysics Data System (ADS)
Gour, Gilad
2007-11-01
We find tight lower and upper bounds on the entanglement of a superposition of two bipartite states in terms of the entanglement of the two states constituting the superposition. Our upper bound is dramatically tighter than the one presented by Linden [Phys. Rev. Lett. 97, 100502 (2006)] and our lower bound can be used to provide lower bounds on different measures of entanglement such as the entanglement of formation and the entanglement of subspaces. We also find that in the case in which the two states are one-sided orthogonal, the entanglement of the superposition state can be expressed explicitly in terms of the entanglement of the two states in the superposition.
Entanglement negativity in the multiverse
Kanno, Sugumi; Shock, Jonathan P.; Soda, Jiro
2015-03-10
We explore quantum entanglement between two causally disconnected regions in the multiverse. We first consider a free massive scalar field, and compute the entanglement negativity between two causally separated open charts in de Sitter space. The qualitative feature of it turns out to be in agreement with that of the entanglement entropy. We then introduce two observers who determine the entanglement between two causally disconnected de Sitter spaces. When one of the observers remains constrained to a region of the open chart in a de Sitter space, we find that the scale dependence enters into the entanglement. We show that a state which is initially maximally entangled becomes more entangled or less entangled on large scales depending on the mass of the scalar field and recovers the initial entanglement in the small scale limit. We argue that quantum entanglement may provide some evidence for the existence of the multiverse.
Entanglement negativity in the multiverse
NASA Astrophysics Data System (ADS)
Kanno, Sugumi; Shock, Jonathan P.; Soda, Jiro
2015-03-01
We explore quantum entanglement between two causally disconnected regions in the multiverse. We first consider a free massive scalar field, and compute the entanglement negativity between two causally separated open charts in de Sitter space. The qualitative feature of it turns out to be in agreement with that of the entanglement entropy. We then introduce two observers who determine the entanglement between two causally disconnected de Sitter spaces. When one of the observers remains constrained to a region of the open chart in a de Sitter space, we find that the scale dependence enters into the entanglement. We show that a state which is initially maximally entangled becomes more entangled or less entangled on large scales depending on the mass of the scalar field and recovers the initial entanglement in the small scale limit. We argue that quantum entanglement may provide some evidence for the existence of the multiverse.
Facile production of monodisperse nanoparticles on a liquid surface.
Anantha, P; Cheng, T; Tay, Y Y; Wong, C C; Ramanujan, R V
2015-10-28
The emergence of monodispersity during particle growth on a liquid substrate was investigated both by experimental methods and by computer simulation. Monodispersity arises through a novel mechanism (termed "shared coarsening"), associated with the spatial distribution of the particles; smaller particles are simultaneously consumed by several larger particles. Particle monodispersity was predicted by kinetic Monte Carlo simulation for suitable substrate adsorption probability and adatom diffusion length conditions. High particle monodispersity is predicted for low adsorption probability and low/intermediate diffusion length values. Experimentally, the formation of uniformly sized copper nanoparticles by physical vapor deposition on a liquid substrate was demonstrated. These results demonstrate, by experiment and simulation, the facile production of monodisperse particles on liquid substrates. PMID:26399544
Multipartite Entanglement And Firewalls
NASA Astrophysics Data System (ADS)
Luo, Shengqiao; Stoltenberg, Henry; Albrecht, Andreas
2016-03-01
Black holes offer an exciting area to explore the nature of quantum gravity. The classic work on Hawking radiation indicates that black holes should decay via quantum effects, but our ideas about how this might work at a technical level are incomplete. Recently Almheiri-Marolf-Polchinski-Sully AMPS have noted an apparent paradox in reconciling fundamental properties of quantum mechanics with standard beliefs about black holes. One way to resolve the paradox is to postulate the existence of a ``firewall'' inside the black hole horizon which prevents objects from falling smoothly toward the singularity. A fundamental limitation on the behavior of quantum entanglement known as ``monogamy'' plays a key role in the AMPS argument. Our goal is to study and apply many-body entanglement theory to consider the entanglement among different parts of Hawking radiation and black holes. We identified an example which could change the AMPS accounting of quantum entanglement and perhaps eliminating the need for a firewall. Looking at different many body entanglement measures and their monogamy properties can tell us subtle ways in which different subsystems can share their entanglement. Specific measures we consider include negativity, concurrence, and mutual information. Taking insights from these different measures, we constructed toy models for black hole decay which have different entanglement behaviors than those assumed by AMPS. We hope to use our effective toy model to demonstrate interesting new ways of thinking about black holes.
Highly entangled tensor networks
NASA Astrophysics Data System (ADS)
Gu, Yingfei; Bulmash, Daniel; Qi, Xiao-Liang
Tensor network states are used to represent many-body quantum state, e.g., a ground state of local Hamiltonian. In this talk, we will provide a systematic way to produce a family of highly entangled tensor network states. These states are entangled in a special way such that the entanglement entropy of a subsystem follows the Ryu-Takayanagi formula, i.e. the entropy is proportional to the minimal area geodesic surface bounding the boundary region. Our construction also provide an intuitive understanding of the Ryu-Takayanagi formula by relating it to a wave propagation process. We will present examples in various geometries.
Multipartite Fully Entangled Fraction
NASA Astrophysics Data System (ADS)
Xu, Jianwei
2016-06-01
Fully entangled fraction is a definition for bipartite states, which is tightly related to bipartite maximally entangled states, and has clear experimental and theoretical significance. In this work, we generalize it to multipartite case, we call the generalized version multipartite fully entangled fraction (MFEF). MFEF measures the closeness of a state to GHZ states. The analytical expressions of MFEF are very difficult to obtain except for very special states, however, we show that, the MFEF of any state is determined by a system of finite-order polynomial equations. Therefore, the MFEF can be efficiently numerically computed.
Constructing optimal entanglement witnesses
Chruscinski, Dariusz; Pytel, Justyna; Sarbicki, Gniewomir
2009-12-15
We provide a class of indecomposable entanglement witnesses. In 4x4 case, it reproduces the well-known Breuer-Hall witness. We prove that these witnesses are optimal and atomic, i.e., they are able to detect the 'weakest' quantum entanglement encoded into states with positive partial transposition. Equivalently, we provide a construction of indecomposable atomic maps in the algebra of 2kx2k complex matrices. It is shown that their structural physical approximations give rise to entanglement breaking channels. This result supports recent conjecture by Korbicz et al. [Phys. Rev. A 78, 062105 (2008)].
NASA Astrophysics Data System (ADS)
Olson Reichhardt, C. J.; Hastings, M. B.
2004-04-01
We propose an experiment for directly constructing and locally probing topologically entangled states of superconducting vortices which can be performed with present-day technology. Calculations using an elastic string vortex model indicate that as the pitch (the winding angle divided by the vertical distance) increases, the vortices approach each other. At values of the pitch higher than a maximum value the entangled state becomes unstable to collapse via a singularity of the model. We provide predicted experimental signatures for both vortex entanglement and vortex cutting. The local probe we propose can also be used to explore a wide range of other quantities.
Probabilistic Teleportation via Entanglement
NASA Astrophysics Data System (ADS)
Li, De-Chao; Shi, Zhong-Ke
2008-10-01
With an arbitrary bi-particle entangled mixed state which is shared by Alice (the sender) and Bob (the receiver) acted as a quantum channel, at first, a teleportation protocol that Alice successfully transmits an unknown mixed state to Bob based on a positive operator-valued measurement (POVM) is presented. The upper bound of probability to teleport successfully an unknown mixed state is then investigated, and conclude that it completely depends on the entanglement degree of the bi-particle entangled mixed state as a resource.
Effect of molecular weight on polymer processability
Karg, R.F.
1983-01-01
Differences in rheological behavior due to the polymer molecular weight and molecular weight distribution have been shown with the MPT. SBR polymers having high molecular weight fractions develop higher stress relaxation time values due to the higher degree of polymer entanglements. Tests conducted at increasing temperatures show the diminishing influence of the polymer entanglements upon stress relaxation time. EPDM polymers show stress relaxation time and head pressure behavior which correlates with mill processability. As anticipated, compounded stock of EPDM have broad molecular weight distribution has higher stress relaxation time values than EPDM compounds with narrow molecular weight distribution.
Monodisperse microdroplet generation and stopping without coalescence
Beer, Neil Reginald
2015-04-21
A system for monodispersed microdroplet generation and trapping including providing a flow channel in a microchip; producing microdroplets in the flow channel, the microdroplets movable in the flow channel; providing carrier fluid in the flow channel using a pump or pressure source; controlling movement of the microdroplets in the flow channel and trapping the microdroplets in a desired location in the flow channel. The system includes a microchip; a flow channel in the microchip; a droplet maker that generates microdroplets, the droplet maker connected to the flow channel; a carrier fluid in the flow channel, the carrier fluid introduced to the flow channel by a source of carrier fluid, the source of carrier fluid including a pump or pressure source; a valve connected to the carrier fluid that controls flow of the carrier fluid and enables trapping of the microdroplets.
Monodisperse microdroplet generation and stopping without coalescence
Beer, Neil Reginald
2016-02-23
A system for monodispersed microdroplet generation and trapping including providing a flow channel in a microchip; producing microdroplets in the flow channel, the microdroplets movable in the flow channel; providing carrier fluid in the flow channel using a pump or pressure source; controlling movement of the microdroplets in the flow channel and trapping the microdroplets in a desired location in the flow channel. The system includes a microchip; a flow channel in the microchip; a droplet maker that generates microdroplets, the droplet maker connected to the flow channel; a carrier fluid in the flow channel, the carrier fluid introduced to the flow channel by a source of carrier fluid, the source of carrier fluid including a pump or pressure source; a valve connected to the carrier fluid that controls flow of the carrier fluid and enables trapping of the microdroplets.
Monodisperse cluster crystals: Classical and quantum dynamics.
Díaz-Méndez, Rogelio; Mezzacapo, Fabio; Cinti, Fabio; Lechner, Wolfgang; Pupillo, Guido
2015-11-01
We study the phases and dynamics of a gas of monodisperse particles interacting via soft-core potentials in two spatial dimensions, which is of interest for soft-matter colloidal systems and quantum atomic gases. Using exact theoretical methods, we demonstrate that the equilibrium low-temperature classical phase simultaneously breaks continuous translational symmetry and dynamic space-time homogeneity, whose absence is usually associated with out-of-equilibrium glassy phenomena. This results in an exotic self-assembled cluster crystal with coexisting liquidlike long-time dynamical properties, which corresponds to a classical analog of supersolid behavior. We demonstrate that the effects of quantum fluctuations and bosonic statistics on cluster-glassy crystals are separate and competing: Zero-point motion tends to destabilize crystalline order, which can be restored by bosonic statistics. PMID:26651695
Converting Nonclassicality into Entanglement.
Killoran, N; Steinhoff, F E S; Plenio, M B
2016-02-26
Quantum mechanics exhibits a wide range of nonclassical features, of which entanglement in multipartite systems takes a central place. In several specific settings, it is well known that nonclassicality (e.g., squeezing, spin squeezing, coherence) can be converted into entanglement. In this work, we present a general framework, based on superposition, for structurally connecting and converting nonclassicality to entanglement. In addition to capturing the previously known results, this framework also allows us to uncover new entanglement convertibility theorems in two broad scenarios, one which is discrete and one which is continuous. In the discrete setting, the classical states can be any finite linearly independent set. For the continuous setting, the pertinent classical states are "symmetric coherent states," connected with symmetric representations of the group SU(K). These results generalize and link convertibility properties from the resource theory of coherence, spin coherent states, and optical coherent states, while also revealing important connections between local and nonlocal pictures of nonclassicality. PMID:26967398
Quantifying entanglement with witness operators
Brandao, Fernando G.S.L.
2005-08-15
We present a unifying approach to the quantification of entanglement based on entanglement witnesses, which includes several already established entanglement measures such as the negativity, the concurrence, and the robustness of entanglement. We then introduce an infinite family of new entanglement quantifiers, having as its limits the best separable approximation measure and the generalized robustness. Gaussian states, states with symmetry, states constrained to super-selection rules, and states composed of indistinguishable particles are studied under the view of the witnessed entanglement. We derive new bounds to the fidelity of teleportation d{sub min}, for the distillable entanglement E{sub D} and for the entanglement of formation. A particular measure, the PPT-generalized robustness, stands out due to its easy calculability and provides sharper bounds to d{sub min} and E{sub D} than the negativity in most of the states. We illustrate our approach studying thermodynamical properties of entanglement in the Heisenberg XXX and dimerized models.
Anomalies and entanglement entropy
NASA Astrophysics Data System (ADS)
Nishioka, Tatsuma; Yarom, Amos
2016-03-01
We initiate a systematic study of entanglement and Rényi entropies in the presence of gauge and gravitational anomalies in even-dimensional quantum field theories. We argue that the mixed and gravitational anomalies are sensitive to boosts and obtain a closed form expression for their behavior under such transformations. Explicit constructions exhibiting the dependence of entanglement entropy on boosts is provided for theories on spacetimes with non-trivial magnetic fluxes and (or) non-vanishing Pontryagin classes.
Entanglement of mesoscopic systems
NASA Astrophysics Data System (ADS)
Narnhofer, Heide; Thirring, Walter
2002-11-01
The entanglement of clouds of N=1011 atoms recently experimentally verified is expressed in terms of the fluctuation algebra introduced by [P. Goderis, A. Verbeure, and P. Vets, Commun. Phys. 128, 533 (1990)]. A mean-field Hamiltonian describing the coupling to a laser beam leads to different time evolutions if considered on microscopic or mesoscopic operators. Only the latter creates nontrivial correlations that finally after a measurement lead to entanglement between the clouds.
Entanglement Renormalization and Wavelets.
Evenbly, Glen; White, Steven R
2016-04-01
We establish a precise connection between discrete wavelet transforms and entanglement renormalization, a real-space renormalization group transformation for quantum systems on the lattice, in the context of free particle systems. Specifically, we employ Daubechies wavelets to build approximations to the ground state of the critical Ising model, then demonstrate that these states correspond to instances of the multiscale entanglement renormalization ansatz (MERA), producing the first known analytic MERA for critical systems. PMID:27104687
Entanglement Renormalization and Wavelets
NASA Astrophysics Data System (ADS)
Evenbly, Glen; White, Steven R.
2016-04-01
We establish a precise connection between discrete wavelet transforms and entanglement renormalization, a real-space renormalization group transformation for quantum systems on the lattice, in the context of free particle systems. Specifically, we employ Daubechies wavelets to build approximations to the ground state of the critical Ising model, then demonstrate that these states correspond to instances of the multiscale entanglement renormalization ansatz (MERA), producing the first known analytic MERA for critical systems.
Entangling power and operator entanglement of nonunitary quantum evolutions
NASA Astrophysics Data System (ADS)
Kong, Fan-Zhen; Zhao, Jun-Long; Yang, Ming; Cao, Zhuo-Liang
2015-07-01
We propose a method to calculate the operator entanglement and entangling power of a noisy nonunitary operation in terms of linear entropy. By decomposing the Kraus operators of noisy evolution as the sum of products of Pauli matrices, we derive the analytical expression of the operator entanglement for a general nonunitary operation. The definition of entangling power is extended from the ideal unitary operation case to the nonunitary case via a Kraus operator representation and the analytical expression of the entangling power for a general nonunitary operation is derived. To demonstrate the effectiveness of the above method, we investigate the properties of operator entanglement and entangling power of nonunitary operations caused by phase damping noise. Our findings imply that the pure phase damping noise has its own operator entanglement and entangling power, which increase exponentially with time and asymptotically approach their respective upper bounds. In addition, when the phase damping noise is added to an ideal operation, such as an iswap operation or a controlled-Z operation, it can make the operation's entangling power grow exponentially with the strength of noise, but leave its operator entanglement invariant. In this sense, we can conclude that, for a general operation, operator entanglement is a more intrinsic property than entangling power.
Browne, Christine; Tabor, Rico F; Grieser, Franz; Dagastine, Raymond R
2015-08-01
Structural forces play an important role in the rheology, processing and stability of colloidal systems and complex fluids, with polyelectrolytes representing a key class of structuring colloids. Here, we explore the interactions between soft colloids, in the form of air bubbles, in solutions of monodisperse sodium poly(styrene sulfonate) as a model polyelectrolyte. It is found that by self-consistently modelling the force oscillations due to structuring of the polymer chains along with deformation of the bubbles, it is possible to precisely predict the interaction potential between approaching bubbles. In line with polyelectrolyte scaling theory, two distinct regimes of behaviour are seen, corresponding to dilute and semi-dilute polymer solutions. It is also seen that by blending monodisperse systems to give a bidisperse sample, the interaction forces between soft colloids can be controlled with a high degree of precision. At increasing bubble collision velocity, it is revealed that hydrodynamic flow overwhelms oscillatory structural interactions, showing the important disparity between equilibrium behaviour and dynamic interactions. PMID:25881266
Large-size monodisperse latexes as a commercial space product
NASA Technical Reports Server (NTRS)
Kornfeld, D. M.
1977-01-01
Proposed spacelab production of large-size (2-40 micron diameter) monodispersed latexes is discussed. Explanations are given for the present lack of monodisperse particles in this size range. The four main topics discussed are: (1) the potential uses of these large particle size latexes, (2) why it is necessary for the particles to have a very narrow size distribution, (3) why large amounts of these monodisperse latexes are needed, and (4) why it is necessary to go to microgravity to prepare these latexes.
NASA Astrophysics Data System (ADS)
Hoy, Robert S.; Foteinopoulou, Katerina; Kröger, Martin
2009-09-01
Primitive path analyses of entanglements are performed over a wide range of chain lengths for both bead spring and atomistic polyethylene polymer melts. Estimators for the entanglement length Ne which operate on results for a single chain length N are shown to produce systematic O(1/N) errors. The mathematical roots of these errors are identified as (a) treating chain ends as entanglements and (b) neglecting non-Gaussian corrections to chain and primitive path dimensions. The prefactors for the O(1/N) errors may be large; in general their magnitude depends both on the polymer model and the method used to obtain primitive paths. We propose, derive, and test new estimators which eliminate these systematic errors using information obtainable from the variation in entanglement characteristics with chain length. The new estimators produce accurate results for Ne from marginally entangled systems. Formulas based on direct enumeration of entanglements appear to converge faster and are simpler to apply.
NASA Astrophysics Data System (ADS)
Han, Junwon; Semler, James J.
2005-03-01
High performance liquid chromatography techniques have been developed for characterizing complex polymers that are often heterogeneous in molecular weight, molecular architecture, and chemical composition. Recently, interaction chromatography (IC) techniques have been developed, which facilitate separation of polymers based on enthalpic ``attraction'' difference among the chemical constituents of the molecule. Here, we use IC for characterizing the composition and monomer sequence distribution in statistical copolymers of poly(styrene-co-4-bromostyrene) (PBrxS). The PBrxS copolymers were synthesized by brominating monodisperse polystyrenes; the degree of bromination (x) and the sequence distribution have been adjusted by varying the bromination time and the solvent quality, respectively. Both normal-phase (bare silica) and reversed-phase (C18-bonded silica) columns are used at different combinations of solvents and non-solvents to monitor the content of the 4-bromostyrene units in the copolymer and their average monomer sequence distribution.
Benito-Peña, Elena; Navarro-Villoslada, Fernando; Carrasco, Sergio; Jockusch, Steffen; Ottaviani, M Francesca; Moreno-Bondi, Maria C
2015-05-27
The effect of the cross-linker on the shape and size of molecular imprinted polymer (MIP) beads prepared by precipitation polymerization has been evaluated using a chemometric approach. Molecularly imprinted microspheres for the selective recognition of fluoroquinolone antimicrobials were prepared in a one-step precipitation polymerization procedure using enrofloxacin (ENR) as the template molecule, methacrylic acid as functional monomer, 2-hydroxyethyl methacrylate as hydrophilic comonomer, and acetonitrile as the porogen. The type and amount of cross-linker, namely ethylene glycol dimethacrylate, divinylbenzene or trimethylolpropane trimethacrylate, to obtain monodispersed MIP spherical beads in the micrometer range was optimized using a simplex lattice design. Particle size and morphology were assessed by scanning electron microscopy, dynamic light scattering, and nitrogen adsorption measurements. Electron paramagnetic resonance spectroscopy in conjunction with a nitroxide as spin probe revealed information about the microviscosity and polarity of the binding sites in imprinted and nonimprinted polymer beads. PMID:25942541
Entanglement swapping of two arbitrarily degraded entangled states
NASA Astrophysics Data System (ADS)
Kirby, Brian T.; Santra, Siddhartha; Malinovsky, Vladimir S.; Brodsky, Michael
2016-07-01
We consider entanglement swapping, a key component of quantum network operations and entanglement distribution. Pure entangled states, which are the desired input to the swapping protocol, are typically mixed by environmental interactions, causing a reduction in their degree of entanglement. Thus an understanding of entanglement swapping with partially mixed states is of importance. Here we present a general analytical solution for entanglement swapping of arbitrary two-qubit states. Our result provides a comprehensive method for analyzing entanglement swapping in quantum networks. First, we show that the concurrence of a partially mixed state is conserved when this state is swapped with a Bell state. Then, we find upper and lower bounds on the concurrence of the state resulting from entanglement swapping for various classes of input states. Finally, we determine a general relationship between the ranks of the initial states and the rank of the final state after swapping.
Entangled graphs: a classification of four-qubit entanglement
NASA Astrophysics Data System (ADS)
Ghahi, Masoud Gharahi; Akhtarshenas, Seyed Javad
2016-03-01
We use the concept of entangled graphs with weighted edges to present a classification for four-qubit entanglement which is based neither on the LOCC nor the SLOCC. Entangled graphs, first introduced by Plesch et al. [Phys. Rev. A 67, 012322 (2003)], are structures such that each qubit of a multi-qubit system is represented as a vertex and an edge between two vertices denotes bipartite entanglement between the corresponding qubits. Our classification is based on the use of generalized Schmidt decomposition of pure states of multi-qubit systems. We show that for every possible entangled graph one can find a pure state such that the reduced entanglement of each pair, measured by concurrence, represents the weight of the corresponding edge in the graph. We also use the concept of tripartite and quadripartite concurrences as a proper measure of global entanglement of the states. In this case a circle including the graph indicates the presence of global entanglement.
Entanglement under restricted operations: Analogy to mixed-state entanglement
Bartlett, Stephen D.; Doherty, Andrew C.; Spekkens, Robert W.; Wiseman, H. M.
2006-02-15
We show that the classification of bipartite pure entangled states when local quantum operations are restricted yields a structure that is analogous in many respects to that of mixed-state entanglement. Specifically, we develop this analogy by restricting operations through local superselection rules, and show that such exotic phenomena as bound entanglement and activation arise using pure states in this setting. This analogy aids in resolving several conceptual puzzles in the study of entanglement under restricted operations. In particular, we demonstrate that several types of quantum optical states that possess confusing entanglement properties are analogous to bound entangled states. Also, the classification of pure-state entanglement under restricted operations can be much simpler than for mixed-state entanglement. For instance, in the case of local Abelian superselection rules all questions concerning distillability can be resolved.
Sustainable synthesis of monodispersed spinel nano-ferrites
A sustainable approach for the synthesis of various monodispersed spinel ferrite nanoparticles has been developed that occurs at water-toluene interface under both conventional and microwave hydrothermal conditions. This general synthesis procedure utilizes readily available and ...
Electromagnetically Induced Entanglement
NASA Astrophysics Data System (ADS)
Yang, Xihua; Xiao, Min
2015-08-01
Quantum entanglement provides an essential resource for quantum computation, quantum communication, and quantum network. How to conveniently and efficiently produce entanglement between bright light beams presents a challenging task to build realistic quantum information processing networks. Here, we present an efficient and convenient way to realize a novel quantum phenomenon, named electromagnetically induced entanglement, in the conventional Λ-type three-level atomic system driven by a strong pump field and a relatively weak probe field. Nearly perfect entanglement between the two fields can be achieved with a low coherence decay rate between the two lower levels, high pump-field intensity, and large optical depth of the atomic ensemble. The physical origin is quantum coherence between the lower doublet produced by the pump and probe fields, similar to the well-known electromagnetically induced transparency. This method would greatly facilitate the generation of nondegenerate narrow-band continuous-variable entanglement between bright light beams by using only coherent laser fields, and may find potential and broad applications in realistic quantum information processing.
Electromagnetically Induced Entanglement.
Yang, Xihua; Xiao, Min
2015-01-01
Quantum entanglement provides an essential resource for quantum computation, quantum communication, and quantum network. How to conveniently and efficiently produce entanglement between bright light beams presents a challenging task to build realistic quantum information processing networks. Here, we present an efficient and convenient way to realize a novel quantum phenomenon, named electromagnetically induced entanglement, in the conventional Λ-type three-level atomic system driven by a strong pump field and a relatively weak probe field. Nearly perfect entanglement between the two fields can be achieved with a low coherence decay rate between the two lower levels, high pump-field intensity, and large optical depth of the atomic ensemble. The physical origin is quantum coherence between the lower doublet produced by the pump and probe fields, similar to the well-known electromagnetically induced transparency. This method would greatly facilitate the generation of nondegenerate narrow-band continuous-variable entanglement between bright light beams by using only coherent laser fields, and may find potential and broad applications in realistic quantum information processing. PMID:26314514
Monodispersed Spray Generation from Convex Surfaces
NASA Astrophysics Data System (ADS)
Shroff, Shilpa; Liepmann, Dorian
1999-11-01
Flow of a fluid sheet over a concave surface has been found to amplify streamwise vorticity leading to a new mechanism for droplet formation. An instability leading to waves that travel in the streamwise direction is also observed. The resultant grid-like structure produces monodispersed droplets at the intersections of the two instabilities as the flow develops. The presentation will focus on the dominant physics associated with the interaction between the solid surface and the fluid sheet and discuss how these control the formation of the droplets. The cross-stream ridges result from a wave instability that depends on the curvature of the bed and the Froude Number. There has been some analytical work done on determining the stability characteristic of flow in curved beds by Eagles, which indicates a weak instability even at Reynolds numbers approaching zero. The possibility of streamwise vortices was also investigated as the source of the streamwise ridges. This vorticity may be introduced into the flow by the angle between the jet and the sheet during the initial contact. An analytic model as well as experimental work has been developed to determine the physical phenomena that influence the dynamics of this flow. In addition, work has been done to identify important scaling parameters, especially those that control the development of the surface deformation and droplet formation.
Multipartite entanglement in quantum algorithms
Bruss, D.; Macchiavello, C.
2011-05-15
We investigate the entanglement features of the quantum states employed in quantum algorithms. In particular, we analyze the multipartite entanglement properties in the Deutsch-Jozsa, Grover, and Simon algorithms. Our results show that for these algorithms most instances involve multipartite entanglement.
Estimating concurrence via entanglement witnesses
Jurkowski, Jacek; Chruscinski, Dariusz
2010-05-15
We show that each entanglement witness detecting a given bipartite entangled state provides an estimation of its concurrence. We illustrate our result with several well-known examples of entanglement witnesses and compare the corresponding estimation of concurrence with other estimations provided by the trace norm of partial transposition and realignment.
Lithography using quantum entangled particles
NASA Technical Reports Server (NTRS)
Williams, Colin (Inventor); Dowling, Jonathan (Inventor); della Rossa, Giovanni (Inventor)
2003-01-01
A system of etching using quantum entangled particles to get shorter interference fringes. An interferometer is used to obtain an interference fringe. N entangled photons are input to the interferometer. This reduces the distance between interference fringes by n, where again n is the number of entangled photons.
Lithography using quantum entangled particles
NASA Technical Reports Server (NTRS)
Williams, Colin (Inventor); Dowling, Jonathan (Inventor)
2001-01-01
A system of etching using quantum entangled particles to get shorter interference fringes. An interferometer is used to obtain an interference fringe. N entangled photons are input to the interferometer. This reduces the distance between interference fringes by n, where again n is the number of entangled photons.
Topological entanglement entropy.
Kitaev, Alexei; Preskill, John
2006-03-24
We formulate a universal characterization of the many-particle quantum entanglement in the ground state of a topologically ordered two-dimensional medium with a mass gap. We consider a disk in the plane, with a smooth boundary of length L, large compared to the correlation length. In the ground state, by tracing out all degrees of freedom in the exterior of the disk, we obtain a marginal density operator rho for the degrees of freedom in the interior. The von Neumann entropy of rho, a measure of the entanglement of the interior and exterior variables, has the form S(rho) = alphaL - gamma + ..., where the ellipsis represents terms that vanish in the limit L --> infinity. We show that - gamma is a universal constant characterizing a global feature of the entanglement in the ground state. Using topological quantum field theory methods, we derive a formula for gamma in terms of properties of the superselection sectors of the medium. PMID:16605802
NASA Astrophysics Data System (ADS)
Brand, J.; Flach, S.; Fleurov, V.; Schulman, L. S.; Tolkunov, D.
2008-08-01
We study the localization of bosonic atoms in an optical lattice, which interact in a spatially confined region. The classical theory predicts that there is no localization below a threshold value for the strength of interaction that is inversely proportional to the number of participating atoms. In a full quantum treatment, however, we find that localized states exist for arbitrarily weak attractive or repulsive interactions for any number (>1) of atoms. We further show, using an explicit solution of the two-particle bound state and an appropriate measure of entanglement, that the entanglement tends to a finite value in the limit of weak interactions. Coupled with the non-existence of localization in an optimized quantum product state, we conclude that the localization exists by virtue of entanglement.
NASA Astrophysics Data System (ADS)
Graydon, Matthew A.; Appleby, D. M.
2016-08-01
We describe a connection between entanglement and designs. It involves the conical two-designs introduced in a previous paper. These are a generalization of projective two-designs which includes full sets of arbitrary rank mutually unbiased measurements (mums) and arbitrary rank symmetric informationally complete measurements (sims), as well as the more familiar mubs and sics. We show that a povm is a conical two-design if and only if there exists what we call a regular entanglement monotone whose restriction to the pure states is a function of the norm of the probability vector. In that case the concurrence is such a monotone. We also generalize and develop previous work on designs and entanglement detection.
Entangling and assisted entangling power of bipartite unitary operations
NASA Astrophysics Data System (ADS)
Chen, Lin; Yu, Li
2016-08-01
Nonlocal unitary operations can create quantum entanglement between distributed particles, and the quantification of created entanglement is a hard problem. It corresponds to the concepts of entangling and assisted entangling power when the input states are, respectively, product and arbitrary pure states. We analytically derive them for Schmidt-rank-two bipartite unitary and some complex bipartite permutation unitaries. In particular, the entangling power of permutation unitary of Schmidt rank three can take only one of two values: log29 -16 /9 or log23 ebits. The entangling power, assisted entangling power, and disentangling power of 2 ×dB permutation unitaries of Schmidt rank four are all 2 ebits. These quantities are also derived for generalized Clifford operators. We further show that any bipartite permutation unitary of Schmidt rank greater than two has entangling power greater than 1.223 ebits. We construct the generalized controlled-not (cnot) gates whose assisted entangling power reaches the maximum. We quantitatively compare the entangling power and assisted entangling power for general bipartite unitaries and their connection to the disentangling power by proposing a probabilistic protocol for implementing bipartite unitaries.
Images in quantum entanglement
NASA Astrophysics Data System (ADS)
Bowden, G. J.
2009-08-01
A system for classifying and quantifying entanglement in spin 1/2 pure states is presented based on simple images. From the image point of view, an entangled state can be described as a linear superposition of separable object wavefunction ΨO plus a portion of its own inverse image. Bell states can be defined in this way: \\Psi = 1/\\sqrt 2 (\\Psi _O \\pm \\Psi _I ). Using the method of images, the three-spin 1/2 system is discussed in some detail. This system can exhibit exclusive three-particle ν123 entanglement, two-particle entanglements ν12, ν13, ν23 and/or mixtures of all four. All four image states are orthogonal both to each other and to the object wavefunction. In general, five entanglement parameters ν12, ν13, ν23, ν123 and phi123 are required to define the general entangled state. In addition, it is shown that there is considerable scope for encoding numbers, at least from the classical point of view but using quantum-mechanical principles. Methods are developed for their extraction. It is shown that concurrence can be used to extract even-partite, but not odd-partite information. Additional relationships are also presented which can be helpful in the decoding process. However, in general, numerical methods are mandatory. A simple roulette method for decoding is presented and discussed. But it is shown that if the encoder chooses to use transcendental numbers for the angles defining the target function (α1, β1), etc, the method rapidly turns into the Devil's roulette, requiring finer and finer angular steps.
Fabrication of monodispersed silver nanoparticles and their optical characterizations
NASA Astrophysics Data System (ADS)
Lama, Pemba
This dissertation is about the fabrication of monodispersed (same size, shape, composition, structure, etc.) silver nanoparticles in gas media and their optical characterizations such as optical absorption, nonlinear optical response and plasmon assisted fluorescence. The first part of the thesis presents the fabrication method used to prepare monodispersed silver (Ag) nanoparticles (NPs) using heterogeneous condensation in gas media. Well defined and charged Ag NPs were separated based on their sizes by applying an electric field on unipolar charged Ag NPs and were collected on quartz substrates. Thin films consisting of monodispersed Ag NPs with size ranging from 35 nm to 120 nm were prepared by varying an applied electric field during the fabrication process. Scanning electron microscope (SEM) results showed that the samples have a uniform size distribution. In the second part of the thesis, optical characterization, including linear and nonlinear optical properties, are performed on monodispersed and polydispersed Ag NPs and analyzed. A strong plasmon resonance was observed for the monodispersed Ag NPs due to the coherent oscillations of the conduction band electrons, owing to the uniform size of the Ag NPs. Narrow extinction widths (~ 41 nm to ~ 69 nm) were observed for the Ag NPs compared to the width of the polydispersed Ag sample. Nonlinear optical characterizations were also performed on monodispersed silver (Ag) nanoparticles (NPs) of various sizes using a picosecond Z-scan technique with excitation wavelengths at 532 nm and 1064 nm. The nonlinear refraction values were higher for the monodispersed Ag NPs whose surface plasmon resonance (SPR) peak is closer to the excitation wavelength. The higher nonlinear optical response is explained in terms of an electric field enhancement near the SPR. Finally, plasmon assisted fluorescence of Rhodamine B dye was also investigated. Higher fluorescence quantum yield was obtained from Rhodamine B when using
Valence bond entanglement entropy.
Alet, Fabien; Capponi, Sylvain; Laflorencie, Nicolas; Mambrini, Matthieu
2007-09-14
We introduce for SU(2) quantum spin systems the valence bond entanglement entropy as a counting of valence bond spin singlets shared by two subsystems. For a large class of antiferromagnetic systems, it can be calculated in all dimensions with quantum Monte Carlo simulations in the valence bond basis. We show numerically that this quantity displays all features of the von Neumann entanglement entropy for several one-dimensional systems. For two-dimensional Heisenberg models, we find a strict area law for a valence bond solid state and multiplicative logarithmic corrections for the Néel phase. PMID:17930468
NASA Astrophysics Data System (ADS)
Baez, John C.; Vicary, Jamie
2014-11-01
Maldacena and Susskind have proposed a correspondence between wormholes and entanglement, dubbed ER=EPR. We study this in the context of three-dimensional topological quantum field theory (TQFT), where we show that the formation of a wormhole is the same process as creating a particle-antiparticle pair. A key feature of the ER=EPR proposal is that certain apparently entangled degrees of freedom turn out to be the same. We name this phenomenon ‘fake entanglement’, and show how it arises in our TQFT model.
Entanglement monogamy relations of qubit systems
NASA Astrophysics Data System (ADS)
Zhu, Xue-Na; Fei, Shao-Ming
2014-08-01
We investigate the monogamy relations related to the concurrence and the entanglement of formation. General monogamy inequalities given by the αth power of concurrence and entanglement of formation are presented for N-qubit states. The monogamy relation for entanglement of assistance is also established. Based on these general monogamy relations, the residual entanglement of concurrence and entanglement of formation are studied. Some relations among the residual entanglement, entanglement of assistance, and three tangle are also presented.
Recovering entanglement by local operations
D’Arrigo, A.; Lo Franco, R.; Benenti, G.; Paladino, E.; Falci, G.
2014-11-15
We investigate the phenomenon of bipartite entanglement revivals under purely local operations in systems subject to local and independent classical noise sources. We explain this apparent paradox in the physical ensemble description of the system state by introducing the concept of “hidden” entanglement, which indicates the amount of entanglement that cannot be exploited due to the lack of classical information on the system. For this reason this part of entanglement can be recovered without the action of non-local operations or back-transfer process. For two noninteracting qubits under a low-frequency stochastic noise, we show that entanglement can be recovered by local pulses only. We also discuss how hidden entanglement may provide new insights about entanglement revivals in non-Markovian dynamics.
Reexamination of entanglement of superpositions
Gour, Gilad
2007-11-15
We find tight lower and upper bounds on the entanglement of a superposition of two bipartite states in terms of the entanglement of the two states constituting the superposition. Our upper bound is dramatically tighter than the one presented by Linden et al. [Phys. Rev. Lett. 97, 100502 (2006)] and our lower bound can be used to provide lower bounds on different measures of entanglement such as the entanglement of formation and the entanglement of subspaces. We also find that in the case in which the two states are one-sided orthogonal, the entanglement of the superposition state can be expressed explicitly in terms of the entanglement of the two states in the superposition.
A general and robust strategy for the synthesis of nearly monodisperse colloidal nanocrystals
NASA Astrophysics Data System (ADS)
Pang, Xinchang; Zhao, Lei; Han, Wei; Xin, Xukai; Lin, Zhiqun
2013-06-01
Colloidal nanocrystals exhibit a wide range of size- and shape-dependent properties and have found application in myriad fields, incuding optics, electronics, mechanics, drug delivery and catalysis, to name but a few. Synthetic protocols that enable the simple and convenient production of colloidal nanocrystals with controlled size, shape and composition are therefore of key general importance. Current strategies include organic solution-phase synthesis, thermolysis of organometallic precursors, sol-gel processes, hydrothermal reactions and biomimetic and dendrimer templating. Often, however, these procedures require stringent experimental conditions, are difficult to generalize, or necessitate tedious multistep reactions and purification. Recently, linear amphiphilic block co-polymer micelles have been used as templates to synthesize functional nanocrystals, but the thermodynamic instability of these micelles limits the scope of this approach. Here, we report a general strategy for crafting a large variety of functional nanocrystals with precisely controlled dimensions, compositions and architectures by using star-like block co-polymers as nanoreactors. This new class of co-polymers forms unimolecular micelles that are structurally stable, therefore overcoming the intrinsic instability of linear block co-polymer micelles. Our approach enables the facile synthesis of organic solvent- and water-soluble nearly monodisperse nanocrystals with desired composition and architecture, including core-shell and hollow nanostructures. We demonstrate the generality of our approach by describing, as examples, the synthesis of various sizes and architectures of metallic, ferroelectric, magnetic, semiconductor and luminescent colloidal nanocrystals.
Universal nonlinear entanglement witnesses
Kotowski, Marcin; Kotowski, Michal
2010-06-15
We give a universal recipe for constructing nonlinear entanglement witnesses able to detect nonclassical correlations in arbitrary systems of distinguishable and/or identical particles for an arbitrary number of constituents. The constructed witnesses are expressed in terms of expectation values of observables. As such, they are, at least in principle, measurable in experiments.
Entanglement Created by Dissipation
Alharbi, Abdullah F.; Ficek, Zbigniew
2011-10-27
A technique for entangling closely separated atoms by the process of dissipative spontaneous emission is presented. The system considered is composed of two non-identical two-level atoms separated at the quarter wavelength of a driven standing wave laser field. At this atomic distance, only one of the atoms can be addressed by the laser field. In addition, we arrange the atomic dipole moments to be oriented relative to the inter-atomic axis such that the dipole-dipole interaction between the atoms is zero at this specific distance. It is shown that an entanglement can be created between the atoms on demand by tuning the Rabi frequency of the driving field to the difference between the atomic transition frequencies. The amount of the entanglement created depends on the ratio between the damping rates of the atoms, but is independent of the frequency difference between the atoms. We also find that the transient buildup of an entanglement between the atoms may differ dramatically for different initial atomic conditions.
Postcolonial Entanglements: Unruling Stories
ERIC Educational Resources Information Center
Pacini-Ketchabaw, Veronica
2012-01-01
In this article, I use Donna Haraway's philosophy to think about postcolonial encounters between different species. I follow entangled stories of the deer/settler-child figure to trouble colonialisms and untangle the histories and trajectories that we inhabit with other species through colonial histories. I shy away from generalizations and…
Evolution equation for entanglement of assistance
Li Zongguo; Liu, W. M.; Zhao Mingjing; Fei Shaoming
2010-04-15
We investigate the time evolution of the entanglement of assistance when one subsystem undergoes the action of local noisy channels. A general factorization law is presented for the evolution equation of entanglement of assistance. Our results demonstrate that the dynamics of the entanglement of assistance is determined by the action of a noisy channel on the pure maximally entangled state, in which the entanglement reduction turns out to be universal for all quantum states entering the channel. This single quantity will make it easy to characterize the entanglement dynamics of entanglement of assistance under unknown channels in the experimental process of producing entangled states by assisted entanglement.
Are all maximally entangled states pure?
NASA Astrophysics Data System (ADS)
Cavalcanti, D.; Brandão, F. G. S. L.; Terra Cunha, M. O.
2005-10-01
We study if all maximally entangled states are pure through several entanglement monotones. In the bipartite case, we find that the same conditions which lead to the uniqueness of the entropy of entanglement as a measure of entanglement exclude the existence of maximally mixed entangled states. In the multipartite scenario, our conclusions allow us to generalize the idea of the monogamy of entanglement: we establish the polygamy of entanglement, expressing that if a general state is maximally entangled with respect to some kind of multipartite entanglement, then it is necessarily factorized of any other system.
Are all maximally entangled states pure?
Cavalcanti, D.; Brandao, F.G.S.L.; Terra Cunha, M.O.
2005-10-15
We study if all maximally entangled states are pure through several entanglement monotones. In the bipartite case, we find that the same conditions which lead to the uniqueness of the entropy of entanglement as a measure of entanglement exclude the existence of maximally mixed entangled states. In the multipartite scenario, our conclusions allow us to generalize the idea of the monogamy of entanglement: we establish the polygamy of entanglement, expressing that if a general state is maximally entangled with respect to some kind of multipartite entanglement, then it is necessarily factorized of any other system.
General polygamy inequality of multiparty quantum entanglement
NASA Astrophysics Data System (ADS)
Kim, Jeong San
2012-06-01
Using entanglement of assistance, we establish a general polygamy inequality of multiparty entanglement in arbitrary-dimensional quantum systems. For multiparty closed quantum systems, we relate our result with the monogamy of entanglement, and clarify that the entropy of entanglement bounds both monogamy and polygamy of multiparty quantum entanglement.
Bipyramid-templated synthesis of monodisperse anisotropic gold nanocrystals
NASA Astrophysics Data System (ADS)
Lee, Jung-Hoon; Gibson, Kyle J.; Chen, Gang; Weizmann, Yossi
2015-06-01
Much of the interest in noble metal nanoparticles is due to their plasmonic resonance responses and local field enhancement, both of which can be tuned through the size and shape of the particles. However, both properties suffer from the loss of monodispersity that is frequently associated with various morphologies of nanoparticles. Here we show a method to generate diverse and monodisperse anisotropic gold nanoparticle shapes with various tip geometries as well as highly tunable size augmentations through either oxidative etching or seed-mediated growth of purified, monodisperse gold bipyramids. The conditions employed in the etching and growth processes also offer valuable insights into the growth mechanism difficult to realize with other gold nanostructures. The high-index facets and more complicated structure of the bipyramid lead to a wider variety of intriguing regrowth structures than in previously studied nanoparticles. Our results introduce a class of gold bipyramid-based nanoparticles with interesting and potentially useful features to the toolbox of gold nanoparticles.
Morphological Control and Characterization of Monodispersed Ceria Particles
Minamidate, Y.; Yin, S.; Devaraju, M. K.; Sato, T.
2010-11-24
The morphological control of cerium oxide particles was carried out by a homogeneous precipitation followed by calcination in air at 400 deg. C. The effects of pre-aging temperature, aging time and precipitation reagents on the morphologies of final products were investigated. When urea was used as a precipitation reagent, monodispersed spherical and flake-like cerium carbonate hydroxide precursor was precipitated in the solution at 90 deg. C for 2 h after pre-aging at 25 deg. C - 50 deg. C for 24-72 h. On the other hand, monodispersed nanosize rod-like cerium hydroxide particles were obtained using triethanolamine as precipitation reagent. Ceria particles with the same morphologies and slightly smaller particle size than those of as-prepared cerium precursor could be obtained after calcination in air at 400 deg. C. Physical-chemical characteristics of the monodispersed cerium oxide particles were evaluated.
NASA Astrophysics Data System (ADS)
Teng, Chao; He, Jie; Zhu, Lili; Ren, Lianbing; Chen, Jiwei; Hong, Mei; Wang, Yong
2015-10-01
A facile and efficient hard-templating strategy is reported for the preparation of porous nickel microspheres with excellent uniformity and strong magnetism. The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction. The morphology, structure, and the property of the Ni microspheres were characterized by scanning electron microscopy, X-ray powder diffraction, N2 adsorption-desorption isotherms, thermogravimetric analysis, and magnetic hysteresis measurement. The obtained porous nickel microspheres were monodispersed with a particle size of 0.91 μm and crystallite size of 52 nm. Their saturation magnetization was much higher than that of Ni nanoparticles. The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol. The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration.
Monodisperse red blood cell-like particles via consolidation of charged droplets.
Park, Chul Ho; Chung, Nae-Oh; Lee, Jonghwi
2011-09-15
Recently, researchers have tried to produce non-spherical and anisotropic particles to be used in the next generation of multi-functional materials. Of key interest is the red blood cell-like particle. The torus structure was produced under the relatively fast consolidation of monodisperse droplets, and its parameters were found to be tunable by temperature as well as solvent type and concentration. The observation of consolidation demonstrated that the polymers were accumulated and solidified in the torus structure, naturally, whereas there was the critical droplet size to induce the asymmetry diffusivities. The torus structures could be simply tuned by the flow rate and concentration. The coaxial nozzle system produced the core/shell torus particles. These results state that the consolidation mechanism can hold important clues to enhance the range of tuning capabilities. PMID:21719020
Teng, Chao; He, Jie; Zhu, Lili; Ren, Lianbing; Chen, Jiwei; Hong, Mei; Wang, Yong
2015-12-01
A facile and efficient hard-templating strategy is reported for the preparation of porous nickel microspheres with excellent uniformity and strong magnetism. The strategy involves impregnation of porous polymer microspheres with nickel precursors, calcination to remove the template, followed by thermal reduction. The morphology, structure, and the property of the Ni microspheres were characterized by scanning electron microscopy, X-ray powder diffraction, N2 adsorption-desorption isotherms, thermogravimetric analysis, and magnetic hysteresis measurement. The obtained porous nickel microspheres were monodispersed with a particle size of 0.91 μm and crystallite size of 52 nm. Their saturation magnetization was much higher than that of Ni nanoparticles. The unique porous nanostructured Ni microspheres possess catalytic activity and excellent recyclability, as demonstrated in the catalytic reduction of 4-nitrophenol to 4-aminophenol. The micropherical Ni catalysts could be easily separated either by an external magnetic field or by simple filtration. PMID:26437654
Entanglement and quantum teleportation via decohered tripartite entangled states
Metwally, N.
2014-12-15
The entanglement behavior of two classes of multi-qubit system, GHZ and GHZ like states passing through a generalized amplitude damping channel is discussed. Despite this channel causes degradation of the entangled properties and consequently their abilities to perform quantum teleportation, one can always improve the lower values of the entanglement and the fidelity of the teleported state by controlling on Bell measurements, analyzer angle and channel’s strength. Using GHZ-like state within a generalized amplitude damping channel is much better than using the normal GHZ-state, where the decay rate of entanglement and the fidelity of the teleported states are smaller than those depicted for GHZ state.
Triclosan antimicrobial polymers
Petersen, Richard C.
2016-01-01
Triclosan antimicrobial molecular fluctuating energies of nonbonding electron pairs for the oxygen atom by ether bond rotations are reviewed with conformational computational chemistry analyses. Subsequent understanding of triclosan alternating ether bond rotations is able to help explain several material properties in Polymer Science. Unique bond rotation entanglements between triclosan and the polymer chains increase both the mechanical properties of polymer toughness and strength that are enhanced even better through secondary bonding relationships. Further, polymer blend compatibilization is considered due to similar molecular relationships and polarities. With compatibilization of triclosan in polymers a more uniform stability for nonpolar triclosan in the polymer solid state is retained by the antimicrobial for extremely low release with minimum solubility into aqueous solution. As a result, triclosan is projected for long extended lifetimes as an antimicrobial polymer additive. Further, triclosan rapid alternating ether bond rotations disrupt secondary bonding between chain monomers in the resin state to reduce viscosity and enhance polymer blending. Thus, triclosan is considered for a polymer additive with multiple properties to be an antimicrobial with additional benefits as a nonpolar toughening agent and a hydrophobic wetting agent. The triclosan material relationships with alternating ether bond rotations are described through a complete different form of medium by comparisons with known antimicrobial properties that upset bacterial cell membranes through rapid fluctuating mechanomolecular energies. Also, triclosan bond entanglements with secondary bonding can produce structural defects in weak bacterial lipid membranes requiring pliability that can then interfere with cell division. Regarding applications with polymers, triclosan can be incorporated by mixing into a resin system before cure, melt mixed with thermoplastic polymers that set on cooling
Feng, Lili; Stuart, Martien Cohen; Adachi, Yasuhisa
2015-12-01
The dynamic behavior of polyelectrolytes just after their encounter with the surface of bare colloidal particles is analyzed, using the flocculation properties of mono-dispersed polystyrene latex (PSL) particles. Applying a Standardized Colloid Mixing (SCM) approach, effects of ionic strength and charge density of polymer chain on the rate of flocculation, the electrophoretic mobility of particle coated with polyelectrolyte, and the thickness of adsorbed polymer layer were analyzed, focusing on distinguishing features of two modes of flocculation, namely bridging formation and charge neutralization. In the case of excess polymer dosage, the bridging flocculation clearly highlights the transient behavior of polymer conformation from random-coil-like in bulk solution to increasingly flatten on the surface. The adsorption of polymer chains leads to a stagnant layer of solvent near the solid wall, which is confirmed by electrokinetic data. In the regime near optimum dosage two cases emerge. For high charge density polymer, charge neutralization is dominant and advantageous for the continuous progress of flocculation by heterogeneous double layer interaction. As a function of elapsed time after the onset of mixing, crossover from bridging to charge neutralization is found. In the case of low charge density polymer, bridging flocculation is the mechanism. Fluid mixing is concluded to have an essential role in the formation of bridges. PMID:26456137
Methods for producing monodispersed particles of barium titanate
Hu, Zhong-Cheng
2001-01-01
The present invention is a low-temperature controlled method for producing high-quality, ultrafine monodispersed nanocrystalline microsphere powders of barium titanate and other pure or composite oxide materials having particles ranging from nanosized to micronsized particles. The method of the subject invention comprises a two-stage process. The first stage produces high quality monodispersed hydrous titania microsphere particles prepared by homogeneous precipitation via dielectric tuning in alcohol-water mixed solutions of inorganic salts. Titanium tetrachloride is used as an inorganic salt precursor material. The second stage converts the pure hydrous titania microsphere particles into crystalline barium titanate microsphere powders via low-temperature, hydrothermal reactions.
High-dimensional entanglement certification.
Huang, Zixin; Maccone, Lorenzo; Karim, Akib; Macchiavello, Chiara; Chapman, Robert J; Peruzzo, Alberto
2016-01-01
Quantum entanglement is the ability of joint quantum systems to possess global properties (correlation among systems) even when subsystems have no definite individual property. Whilst the 2-dimensional (qubit) case is well-understood, currently, tools to characterise entanglement in high dimensions are limited. We experimentally demonstrate a new procedure for entanglement certification that is suitable for large systems, based entirely on information-theoretics. It scales more efficiently than Bell's inequality and entanglement witness. The method we developed works for arbitrarily large system dimension d and employs only two local measurements of complementary properties. This procedure can also certify whether the system is maximally entangled. We illustrate the protocol for families of bipartite states of qudits with dimension up to 32 composed of polarisation-entangled photon pairs. PMID:27311935
High-dimensional entanglement certification
Huang, Zixin; Maccone, Lorenzo; Karim, Akib; Macchiavello, Chiara; Chapman, Robert J.; Peruzzo, Alberto
2016-01-01
Quantum entanglement is the ability of joint quantum systems to possess global properties (correlation among systems) even when subsystems have no definite individual property. Whilst the 2-dimensional (qubit) case is well-understood, currently, tools to characterise entanglement in high dimensions are limited. We experimentally demonstrate a new procedure for entanglement certification that is suitable for large systems, based entirely on information-theoretics. It scales more efficiently than Bell’s inequality and entanglement witness. The method we developed works for arbitrarily large system dimension d and employs only two local measurements of complementary properties. This procedure can also certify whether the system is maximally entangled. We illustrate the protocol for families of bipartite states of qudits with dimension up to 32 composed of polarisation-entangled photon pairs. PMID:27311935
Sudden death of effective entanglement
Roszak, K.; Horodecki, P.; Horodecki, R.
2010-04-15
Sudden death of entanglement is a well-known effect resulting from the finite volume of separable states. We study the case when the observer has a limited measurement capability and analyze the effective entanglement (i.e., entanglement minimized over the output data). We show that in the well-defined system of two quantum dots monitored by single-electron transistors, one may observe a sudden death of effective entanglement when real, physical entanglement is still alive. For certain measurement setups, this occurs even for initial states for which sudden death of physical entanglement is not possible at all. The principles of the analysis may be applied to other analogous scenarios, such as estimation of the parameters arising from quantum process tomography.
High-dimensional entanglement certification
NASA Astrophysics Data System (ADS)
Huang, Zixin; Maccone, Lorenzo; Karim, Akib; Macchiavello, Chiara; Chapman, Robert J.; Peruzzo, Alberto
2016-06-01
Quantum entanglement is the ability of joint quantum systems to possess global properties (correlation among systems) even when subsystems have no definite individual property. Whilst the 2-dimensional (qubit) case is well-understood, currently, tools to characterise entanglement in high dimensions are limited. We experimentally demonstrate a new procedure for entanglement certification that is suitable for large systems, based entirely on information-theoretics. It scales more efficiently than Bell’s inequality and entanglement witness. The method we developed works for arbitrarily large system dimension d and employs only two local measurements of complementary properties. This procedure can also certify whether the system is maximally entangled. We illustrate the protocol for families of bipartite states of qudits with dimension up to 32 composed of polarisation-entangled photon pairs.
Entanglement structures in qubit systems
NASA Astrophysics Data System (ADS)
Rangamani, Mukund; Rota, Massimiliano
2015-09-01
Using measures of entanglement such as negativity and tangles we provide a detailed analysis of entanglement structures in pure states of non-interacting qubits. The motivation for this exercise primarily comes from holographic considerations, where entanglement is inextricably linked with the emergence of geometry. We use the qubit systems as toy models to probe the internal structure, and introduce some useful measures involving entanglement negativity to quantify general features of entanglement. In particular, our analysis focuses on various constraints on the pattern of entanglement which are known to be satisfied by holographic sates, such as the saturation of Araki-Lieb inequality (in certain circumstances), and the monogamy of mutual information. We argue that even systems as simple as few non-interacting qubits can be useful laboratories to explore how the emergence of the bulk geometry may be related to quantum information principles.
Local cloning of entangled qubits
Choudhary, Sujit K.; Kunkri, Samir; Rahaman, Ramij; Roy, Anirban
2007-11-15
We discuss the exact cloning of orthogonal but entangled qubits under local operations and classical communication. The amount of entanglement necessary in a blank copy is obtained for various cases. Surprisingly, this amount is more than 1 ebit for certain sets of two nonmaximal but equally entangled states of two qubits. To clone any three Bell states, at least log{sub 2} 3 ebit is necessary.
All maximally entangling unitary operators
Cohen, Scott M.
2011-11-15
We characterize all maximally entangling bipartite unitary operators, acting on systems A and B of arbitrary finite dimensions d{sub A}{<=}d{sub B}, when ancillary systems are available to both parties. Several useful and interesting consequences of this characterization are discussed, including an understanding of why the entangling and disentangling capacities of a given (maximally entangling) unitary can differ and a proof that these capacities must be equal when d{sub A}=d{sub B}.
Relative Entropy and Squashed Entanglement
NASA Astrophysics Data System (ADS)
Li, Ke; Winter, Andreas
2014-02-01
We are interested in the properties and relations of entanglement measures. Especially, we focus on the squashed entanglement and relative entropy of entanglement, as well as their analogues and variants. Our first result is a monogamy-like inequality involving the relative entropy of entanglement and its one-way LOCC variant. The proof is accomplished by exploring the properties of relative entropy in the context of hypothesis testing via one-way LOCC operations, and by making use of an argument resembling that by Piani on the faithfulness of regularized relative entropy of entanglement. Following this, we obtain a commensurate and faithful lower bound for squashed entanglement, in the form of one-way LOCC relative entropy of entanglement. This gives a strengthening to the strong subadditivity of von Neumann entropy. Our result improves the trace-distance-type bound derived in Brandão et al. (Commun Math Phys, 306:805-830, 2011), where faithfulness of squashed entanglement was first proved. Applying Pinsker's inequality, we are able to recover the trace-distance-type bound, even with slightly better constant factor. However, the main improvement is that our new lower bound can be much larger than the old one and it is almost a genuine entanglement measure. We evaluate exactly the relative entropy of entanglement under various restricted measurement classes, for maximally entangled states. Then, by proving asymptotic continuity, we extend the exact evaluation to their regularized versions for all pure states. Finally, we consider comparisons and separations between some important entanglement measures and obtain several new results on these, too.
Inter-Universal Quantum Entanglement
NASA Astrophysics Data System (ADS)
Robles-Pérez, S. J.; González-Díaz, P. F.
2015-01-01
The boundary conditions to be imposed on the quantum state of the whole multiverse could be such that the universes would be created in entangled pairs. Then, interuniversal entanglement would provide us with a vacuum energy for each single universe that might be fitted with observational data, making testable not only the multiverse proposal but also the boundary conditions of the multiverse. Furthermore, the second law of the entanglement thermodynamics would enhance the expansion of the single universes.