S. Srivastava, A. K. Kandar, J. K. Basu, M. K. Mukhopadhyay, L. B. Lurio, S. Narayanan, S. K. Sinha
Using X- ray photon correlation spectroscopy measurements on gold nanoparticles embedded in polymethylmethacrylate we provide evidence for existence of an intrinsic length scale for dynamic heterogeneity in polymer nanocomposites similar to that in other soft materials.We also show how the dynamics varies in a complex way with various parameters.
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Over the past two decades polymer nanocomposites have received tremendous interest from industry and academia due to their advanced properties comparative to polymer blends. Many computational studies have revealed that the macroscopic properties of polymer nanocomposites depend strongly on the microscopic polymer structure and conformations. In this article we review simulation studies of the fundamental problem of polymer structure and dimensions in nanocomposites containing bare spherical or rod nanoparticles. Experimentally, there is controversy over whether the addition of nanoparticles i…
Anomalous Molecular Weight Dependence Reveals the Origin of Mechanical Enhancement in Polymer Nanocomposite
该研究通过双峰分子量聚合物纳米复合材料实验，发现界面聚合物反常链伸长促进网络结构，降低平均分子量可使剪切模量最高提升103倍，揭示了力学增强的分子起源与通用拉伸因子。
Competitive Adsorption in Polymer Nanocomposites: The Molecular Weight and End-Group Effect Revealed by SANS and MD Simulations
本研究通过实验和分子动力学模拟揭示双分散PEG熔体中短链因端羟基氢键作用优先吸附于纳米颗粒，强调端基功能对界面行为的关键影响，为调控纳米复合材料性能提供新见解。
We present a numerical study of the slip link model introduced by Likhtman for describing the dy- namics of dense polymer melts. After reviewing the technical aspects associated with the implemen- tation of the model, we extend previous work in several directions. The dependence of the relaxation modulus with the slip link density and the slip link stiffness is reported. Then the nonlinear rheolog- ical properties of the model, for a particular set of parameters, are explored. Finally, we introduce excluded volume interactions in a mean field such as manner in order to describe inhomogeneous s…
In this work, we present a new model for the interpretation of the local dynamic behavior and the mechanical reinforcement mechanism in polymer nanocomposites. The temperature dependence of the dynamics in the glassy region is described by a new equation which assumes an Arrhenius component in the cooperative diffusion. By doing so, a characteristic temperature which can be identified as the glass transition temperature (Tg) emerges, while an additional parameter for the extension of the super-Arrhenius region is incorporated. Based on thermodynamic arguments, the dynamical heterogeneities are…
We demonstrate a simple and effective technique for dispersing pristine (unfunctionalized) graphene at high concentrations in a wide range of organic solvents by use of a stabilizing polymer (polyvinylpyrrolidone, PVP). These polymer-stabilized graphene dispersions are shown to be highly stable and readily redispersible even after freeze-drying. This technique yields significantly higher graphene concentrations as compared to prior studies. Excellent enhancement in thermal conductivity of the fluid by addition of pristine graphene is also demonstrated. These well-dispersed pristine graphene sh…
We have developed a coarse-grained (CG) model of a polymer-clay system consisting of organically modified montmorillonite nanoclay as the nanoparticle in accordance with the MARTINI forcefield. We have used mechanical properties and cleavage free energy of clay particle to respectively parameterize bonded and nonbonded interaction parameters for an organically modified montmorillonite (oMMT) clay particle where intergallery Na+ ions are replaced by tetramethylammonium (TMA) ions. The mechanical properties were determined from the slope of stress-strain curve and cleavage free energy was determ…
We report a novel class of polymer nanocomposite composed of organic nanoparticles dispersed in polymer matrix, with the particle sizes of 30-120 nm in radius. The organic nanoparticles were formed by the self-assembly of protonated poly(4-vinyl-pyridine)-r-poly(acrylonitrile) and amphiphilic metanil yellow dye molecules through electrostatic interactions in aqueous solution. A strongly broadened Raman shift band was probed, suggesting the presence of enhanced optoelectronic property from the polymer nanocomposite. Here, using random-copolymer polyelectrolytes and mesogenic amphiphiles as the …
While recent efforts have shown how local structure plays an essential role in the dynamic heterogeneity of homogeneous glass-forming materials, systems containing interfaces such as thin films or composite materials remain poorly understood. It is known that interfaces perturb the molecular packing nearby, however, numerous studies show the dynamics are modified over a much larger range. Here, we examine the dynamics in polymer nanocomposites (PNCs) using a combination of simulations and experiments and quantitatively separate the role of polymer packing from other effects on the dynamics, as…
We study the influence of spherical, triangular, and rod-like nanoparticles on the mechanical properties of a polymer nanocomposite (PNC), via coarse-grained molecular dynamics simulations. We focus on how the nanoparticle size, loading, mass, and shape influence the PNC's elastic modulus, stress at failure and resistance against cavity formation and growth, under external stress. We find that in the regime of strong polymer-nanoparticle interactions, the formation of a polymer network via temporary polymer-nanoparticle crosslinks has a predominant role on the PNC reinforcement. Spherical nano…
We report the mechanical response of a model nanocomposite system of poly(styrene) (PS)-silica to large-amplitude oscillatory shear deformations. Nonlinear behavior of PS nanocomposites is discussed with the changes in particle dispersion upon deformation to provide a complete physical picture of their mechanical properties. The elastic stresses for the particle and polymer are resolved by decomposing the total stress into its purely elastic and viscous components for composites at different strain levels within a cycle of deformation. We propose a mechanistic model which captures the deformat…
The permeability of certain polymer membranes with impenetrable nanoinclusions increases with the particle volume fraction (Merkel et al., Science, 296, 2002). This intriguing observation contradicts even qualitative expectations based on Maxwell's classical theory of conduction/diffusion in composites with homogeneous phases. This letter presents a simple theoretical interpretation based on classical models of diffusion and polymer physics. An essential feature of the theory is a polymer-segment depletion layer at the inclusion-polymer interface. The accompanying increase in free volume leads…
We study the structural and dynamical mechanisms of reinforcement of a polymer nanocomposite (PNC) via coarse-grained molecular dynamics simulations. In a regime of strong polymer-filler interactions, the stress at failure of the PNC is clearly correlated to structural quantities, such as the filler loading, the surface area of the polymer-filler interface, and the network structure. Additionally, we find that small fillers, of the size of the polymer monomers, are the most effective at reinforcing the matrix by surrounding the polymer chains and maximizing the number of strong polymer-filler …
Polymer nanocomposites based on 2D materials as fillers are the target in the industrial sector, but the ability to manufacture them on a large scale is very limited, and there is a lack of tools to scale up the manufacturing process of these nanocomposites. Here, for the first time, a systematic and fundamental study showing how 2D materials are inserted into the polymeric matrix in order to obtain nanocomposites using conventional and industrially scalable polymer processing machines leading to large-scale manufacturing are described. Two new strategies were used to insert pre-exfoliated 2D …
Enthalpic interactions at the interface between nanoparticles and matrix polymers is known to influence various properties of the resultant polymer nanocomposites (PNC). For athermal PNCs, consisting of grafted nanoparticles embedded in chemically identical polymers, the role and extent of the interface layer (IL) interactions in determining the properties of the nanocomposites is not very clear. Here, we demonstrate the influence of the interfacial layer dynamics on the fragility and dynamical heterogeneity (DH) of athermal and glassy PNCs. The IL properties are altered by changing the grafte…
Numerical modeling of viscoelastic properties is critical to developing the structure-property relationship of polymer nanocomposites. While it is recognized that the altered polymer region near filler particles, the interphase, significantly contributes to enhancements of composite properties, the spatial distribution of interphase properties is rarely considered due to lack of local property measurements. In recent years, the Atomic Force Microscopy (AFM) technique has begun to make local property measurements of the interphase available. In the light of the increasing availability of AFM da…
Central role of filler-polymer interplay in nonlinear reinforcement of elastomeric nanocomposites
本研究通过分子动力学模拟揭示，弹性体纳米复合材料的高应变增强源于纳米填料与聚合物的泊松比不匹配引发的反馈回路，明确了颗粒-颗粒接触对力学增强的核心作用。
This paper is an attempt to predict the thickness and modulus at the nanometric interphase region with the knowledge on the macroscopic Young's modulus in the polymer-clay nanocomposites. First, a systematic design of 20160 linear elastic finite element simulations are used to derive an analytical equation between the interphase thickness, the interphase modulus, the nanoclay content and the macroscopic Young's modulus of the nanocomposite. Four calibration parameters in this equation are calculated based on the reported data about NYLON6-MMT nanocomposite. Next, an analytical nanoscale equati…
Understanding process-structure-property relation for elastoplastic behavior of polymer nanocomposites with agglomeration anomalies and gradient interphase percolation
本研究开发了一种材料模型，结合微观结构实验设计，探索具有团聚和梯度界面渗透的聚合物纳米复合材料的加工-结构-性能关系，发现局部应力集中与界面性能衰减的平衡影响屈服应力改善，并提出局部屈服阻力图作为屈服过程预测和界面设计工具。
Nonlinear ferroelectric characteristics of barium titanate nanocrystals determined via a polymer nanocomposite approach
本文通过PVP/BTO聚合物纳米复合薄膜结合理论解卷积与非线性介电分析，提取了不同尺寸BTO纳米晶的Pp-Ep电滞回线，揭示了四方相与立方相BTO的铁电和顺电行为差异。
In this work, a coarse-grained (CG) model of carbon nanotube (CNT) reinforced polymer matrix composites is developed. A distinguishing feature of the CG model is the ability to capture interactions between polymer chains and nanotubes. The CG potentials for nanotubes and polymer chains are calibrated using the strain energy conservation between CG models and full atomistic systems. The applicability and efficiency of the CG model in predicting the elastic properties of CNT/polymer composites are evaluated through verification processes with molecular simulations. The simulation results reveal …
The crazing behavior of polymer nanocomposites formed by blending polymer grafted nanoparticles with an entangled polymer melt is studied by molecular dynamics simulations. We focus on the three key differences in the crazing behavior of a composite relative to the pure homopolymer matrix, namely, a lower yield stress, a smaller extension ratio and a grafted chain length dependent failure stress. The yield behavior is found to be mostly controlled by the local nanoparticle-grafted polymer interfacial energy, with the grafted polymer-polymer matrix interfacial structure being of little to no re…
This paper presents a study of the polymer-filler interfacial effects on filler dispersion and mechanical reinforcement in Polystyrene (PS) / silica nanocomposites by direct comparison of two model systems: un-grafted and PS-grafted silica dispersed in PS matrix. The structure of nanoparticles has been investigated by combining Small Angle Neutron Scattering (SANS) measurements and Transmission Electronic Microscopic (TEM) images. The mechanical properties were studied over a wide range of deformation by plate/plate rheology and uni-axial stretching. At low silica volume fraction, the particle…
Polymer composite materials are widely used for their exceptional mechanical properties, notably their ability to resist large deformations. Here we examine the failure stress and strain of rubbers reinforced by varying amounts of nano-sized silica particles. We find that small amounts of silica increase the fracture stress and strain, but too much filler makes the material become brittle and consequently fracture happens at small deformations. We thus find that as a function of the amount of filler there is an optimum in the breaking resistance at intermediate filler concentrations. We use a …
The present communication reports the first direct measurement of the conformation of a polymer corona grafted around silica nano-particles dispersed inside a nanocomposite, a matrix of the same polymer. This measurement constitutes an experimental breakthrough based on a refined combination of chemical synthesis, which permits to match the contribution of the neutron silica signal inside the composite, and the use of complementary scattering methods SANS and SAXS to extract the grafted polymer layer form factor from the inter-particles silica structure factor. The modelization of the signal o…
We demonstrate a novel in situ polymerization technique to develop localized polymer coatings on the surface of dispersed pristine graphene sheets. Graphene sheets show great promise as strong, conductive fillers in polymer nanocomposites; however, difficulties in dispersion quality and interfacial strength between filler and matrix have been a persistent problem for graphene-based nanocomposites, particularly for pristine graphene. To address this problem, a physisorbed polymer layer is used to stabilize graphene sheets in solution. To form this protective layer, an organic microenvironment i…
How Tuning Interfaces Impacts the Dynamics and Structure of Polymer Nanocomposites Simultaneously
本文通过宽带介电谱和小角X射线散射等方法，研究了表面修饰对聚(2-乙烯基吡啶)/二氧化硅纳米复合材料微观动力学与结构的影响，揭示了接枝密度如何调节聚合物-颗粒相互作用及界面层动力学。
The existence of magnetic dipolar nanoparticle chains at zero field has been predicted theoretically for decades, but these structures are rarely observed experimentally. A prerequisite is a permanent magnetic moment on the particles forming the chain. Here we report on the observation of magnetic dipolar chains of spherical iron oxide nanoparticles with a diameter of \SI{12.8}{\nano\meter}. The nanoparticles are embedded in an ultrathin polymer film. Due to the high viscosity of the polymer matrix, the dominating aggregation mechanism is driven by dipolar interactions. Smaller iron oxide nano…
Industrial and model polymer nanocomposites are often formulated with coating agents to improve polymer-nanoparticle (NP) compatibility. Here the localization of silane coating agents in styrene-butadiene nanocomposite is investigated through the segmental dynamics of the polymer matrix by broadband dielectric spectroscopy (BDS), allowing the detection of silanes in the matrix through their plasticization effect. This acceleration of dynamics was followed via the shift of $τ$max of the $α$-relaxation induced by the presence of coating agents of different molecular weight and quantity, for diff…
A new method based on the combination of small-anglescattering, reverse Monte Carlo simulations, and an aggregate recognition algorithm is proposed to characterize the structure of nanoparticle suspensions in solvents and polymer nanocomposites, allowing detailedstudies of the impact of different nanoparticle surface modifications.Experimental small-angle scattering is reproduced using simulated annealing of configurations of polydisperse particles in a simulation box compatible with the lowest experimental q-vector. Then, properties of interest likeaggregation states are extracted from these …
The structural features of polystyrene brushes grafted on spherical silica nanoparticles immersed in polystyrene are investigated by means of a Monte Carlo methodology based on polymer mean field theory. The nanoparticle radii (either 8 nm or 13 nm) are held constant, while the grafting density and the lengths of grafted and matrix chains are varied systematically in a series of simulations. The primary objective of this work is to simulate realistic nanocomposite systems of specific chemistry at experimentally accessible length scales and study the structure and scaling of the grafted brush. …
This work proposes an investigation of the fracturing behavior of polymer nanocomposites. Towards this end, the study leverages the analysis of a large bulk of fracture tests from the literature with the goal of critically investigating the effects of the nonlinear Fracture Process Zone (FPZ). It is shown that for most of the fracture tests the effects of the nonlinear FPZ are not negligible, leading to significant deviations from Linear Elastic Fracture Mechanics (LEFM) sometimes exceeding 150% depending on the specimen size and nanofiller content. To get a deeper understanding of the charact…
Resolving the Effects of the Mixing Process on Hierarchical Structures in Polymer Nanocomposites by Bayesian Ultra-Small-Angle X-ray Scattering Analysis
本研究通过贝叶斯统一拟合分析超小角X射线散射数据，解析了不同混合工艺对炭黑填充橡胶层级结构的影响，发现聚集体尺寸等结构参数与力学性能排序一致，为加工-结构-性能关系提供了不确定性感知的分析基础。
Some of our recent studies of the structure and mechanical properties of a special type of nanocomposite are reviewed here. In silica-latex systems, a latex film with silica inclusions is formed from a colloidal solution of both components. During drying of the solution, the formation of silica domains can be controlled via the physico-chemical properties of the solution. Well-defined silica aggregates embedded in a polymer matrix can be generated, and the mechanical properties of the resulting nanocomposite have been shown to be directly correlated to the average structure.
The structure of a polystyrene matrix filled with tightly cross-linked polystyrene nanoparticles, forming an athermal nanocomposite system, is investigated by means of a Monte Carlo sampling formalism. The polymer chains are represented as random walks and the system is described through a coarse grained Hamiltonian. This approach is related to self-consistent-field theory but does not invoke a saddle point approximation and is suitable for treating large three-dimensional systems. The local structure of the polymer matrix in the vicinity of the nanoparticles is found to be different in many w…
A large body of experimental work on the microstructure and dynamics of simplifiedindustrial nanocomposites made of disordered silica filler in a styrene-butadiene matrixby solid-phase mixing is regrouped and critically discussed in this feature article. Recentresults encompass systems with varying polymer mass, grafting functionality, and fillercontent. They have been obtained by simulation-based structural modelling of nanoparticleaggregate size and mass deduced from small-angle scattering and transmission electronmicroscopy. Our model has been validated by independent swelling experiments.C…
The antagonistic effect of processing and thermal annealing on both the filler structure and the polymer matrix is explored in polymer nanocomposites based on natural rubber with precipitated silica incorporated by coagulation from aqueous suspension followed by roll-milling. Their structure and linear and non-linear rheology have been studied, with a particular emphasis on the effect of high temperature thermal treatment and the number of milling passes. Small-angle X-ray scattering intensities show that the silica is organized in small, unbreakable aggregates containing ca. 50 primary nanopa…
We investigate the role played by the bidispersity of polymer chains on the local structure and the potential of mean force (PMF) between silica nanoparticles (NPs) in a polystyrene melt. We use the hybrid particle-field molecular dynamics technique which allows to efficiently relax polymer nanocomposites even with high molecular weights.The NPs we investigate are either bare or grafted with polystyrene chains immersed in a melt of free polystyrene chains, whereas the grafted and the free polystyrene chains are either monodisperse or bidisperse. The two-body PMF shows that a bidisperse distrib…
Characterization of Morphology Evolution in a Polymer-Clay Nanocomposite using Multiscale Simulations
本研究开发了与MARTINI力场兼容的有机改性蒙脱石粗粒化模型，用于模拟聚合物-粘土纳米复合材料的形态演化，发现纳米填料的主要影响源于粘土片层对聚合物链的限域和空间位阻效应。
Influence of the Graft Length on Nanocomposite Structure and Interfacial Dynamics
本文通过介电谱、X射线散射和模拟，研究了C8短链接枝对纳米粒子分散及聚合物界面动力学的影响，发现接枝可减弱动力学减速并实现渐进调控，界面层厚度约5纳米。
A study of the reinforcement effect of a soft polymer matrix by hard nanometric filler particles is presented. In the main part of this article, the structure of the silica filler in the matrix is studied by Small Angle Neutron Scattering (SANS), and stress-strain isotherms are measured to characterize the rheological properties of the composites. Our analysis allows us to quantify the degree of aggregation of the silica in the matrix, which is studied as a function of pH (4-10), silica volume fraction (3-15%) and silica bead size (average radius 78 A and 96 A). Rheological properties of the s…
Conducting polymers have wide technological applications in sensors, actuators, electric and optical devices, solar cells etc. To improve their operational performance, mechanical, thermal, electrical and optical properties, such polymers are doped with carbon allotrope nanofillers. Functionality of the novel nanocomposite polymers may be stipulated by size characteristics of nanoparticles and the polymer, different physical effects like charge transfer in such objects etc. We characterize and analyze structure, elastic, electric properties and of novel polymer nanocomposites, isotactic polypr…
Local dielectric spectroscopy is performed to study how relaxation dynamics of a poly-vinyl-acetate ultra-thin film is influenced by inorganic nano-inclusions of a layered silicate (montmorillonite). Dielectric loss spectra are measured by electrostatic force microscopy in the frequency-modulation mode in ambient air. Spectral changes in both shape and relaxation time are evidenced across the boundary between pure polymer and montmorillonite sheets. Dielectric loss imaging is also performed, evidencing spatial variations of dielectric properties near to nanostructures with nanometer scale reso…
Depth-dependent interplay of dynamical heterogeneity and chain dynamics at the surface of glass-forming polymers
研究揭示了玻璃形成聚合物表面深度依赖的动力学异质性与链动力学的相互作用，通过分子动力学模拟发现界面迁移梯度对链松弛的影响及Rouse缩放指数的变化。
The dynamics of structural relaxation in a model polymer glass subject to spatially-homogeneous, time-periodic shear deformation is investigated using molecular dynamics simulations. We study a coarse-grained bead-spring model of short polymer chains below the glass transition temperature. It is found that at small strain amplitudes, the segmental dynamics is nearly reversible over about $10^4$ cycles, while at strain amplitudes above a few percent, polymer chains become fully relaxed after a hundred cycles. At the critical strain amplitude, the transition from slow to fast relaxation dynamics…
The dynamics of polypropylene glycol, both neat and attached to silica nanoparticles, were investigated using elastic neutron backscattering and dielectric spectroscopy. The mean square displacement measured by the former is suppressed by the particles at temperatures corresponding to a dielectric secondary relaxation (that involves only a portion of the repeat unit) and the segmental relaxation (glass transition). Despite the suppression of the displacements, the motions are faster in the nanocomposite, primarily due to poorer packing (lower density) at the particle interface. At very low tem…
Amorphous materials exhibit peculiar mechanical and vibrational properties, including non-affine elastic responses and excess vibrational states, i.e., the so-called boson peak. For polymer glasses, these properties are considered to be affected by the bending rigidity of the constituent polymer chains. In our recent work [Tomoshige, et al., Sci. Rep. 9 19514 (2019)], we have revealed simple relationships between the variations of vibrational properties and the global elastic properties: the response of the boson peak scales only with that of the global shear modulus. This observation suggests…
Electrolytes as nanostructured materials are very attractive for batteries or other types of electronic devices. (PEO)8ZnCl2 polymer electrolytes and nanocomposites (PEO)8ZnCl2/TiO2 were prepared from PEO and ZnCl2 and with addition of TiO2 nanograins. The influence of TiO2 nanograins was studied by small-angle X-ray scattering (SAXS) simultaneously recorded with wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) at the synchrotron ELETTRA. It was shown by previous impedance spectroscopy (IS) that the room temperature conductivity of nanocomposite polymer electrolyt…
Large scale molecular dynamics simulations are used to study the dispersion of nanoparticles (NPs) in a polymer film during solvent evaporation. As the solvent evaporates, a dense polymer-rich skin layer forms at the liquid/vapor interface, which is either NP rich or poor depending on the strength of the NP/polymer interaction. When the NPs are strongly wet by the polymer, the NPs accumulate at the interface and form layers. However when the NPs are only partially wet by the polymer, most NPs are uniformly distributed in the bulk of the polymer film with the dense skin layer serving as a barri…
Soft nanocomposites represent both a theoretical and an experimental challenge due to the high number of the microscopic constituents that strongly influence the behaviour of the systems. An effective theoretical description of such systems invokes a reduction of the degrees of freedom to be analysed, hence requiring the introduction of an efficient, quantitative, coarse-grained description. We here report on a novel coarse graining approach based on a set of transferable potentials that quantitatively reproduces properties of mixtures of linear and star-shaped homopolymeric nanocomposites. By…
MARTINI Coarse-grained Force Field for Thermoplastic Starch Nanocomposites
本文基于全原子模拟开发了热塑性淀粉及TMA-MMT复合材料的MARTINI粗粒化力场，通过优化交叉相互作用准确复现结构与热力学性质，验证了模型的稳健性。
Nanocomposite films containing a high volume fraction (> 50vol%) of nanoparticles (NPs) in a polymer matrix are promising for their functionality and use as structural coatings, and also provide a unique platform to understand polymer behavior under strong confinement. Previously, we developed a novel technique to fabricate such nanocomposites at room temperature using solvent-driven infiltration of polymer (SIP) into NP packings. In the SIP process, a bilayer made of an underlying polymer film and a dense packing of NPs is exposed to solvent vapor which induces condensation of the solvent int…
Shearing of nanocomposites has shown to produce ordered nanostructures and orientation in the polymeric matrix. Due to the importance of the formation of an ordered structure of nanoparticles in a polymeric matrix to device wearable, flexible and photonic materials, its useful to get an insight of the shear-induced ordering and other properties of the polymeric nanocomposites. In this paper, we use a model Wormlike micellar matrix to study the arrangement and morphology of nanoparticles in the composite when the system is sheared using a hybrid multiparticle dynamics and molecular dynamics sim…
We investigate the local elastic properties of polystyrene doped with SiO2 nanoparticles by analyzing the local density fluctuations. The density fluctuations were established from coarse-grained molecular dynamics simulations performed with the MARTINI force field. A significant increase in polystyrene stiffness was revealed within a characteristic range of 1.4 nm from the nanoparticle, while polystyrene density saturates to the bulk value at significantly shorter distances. The enhancement of the local elastic properties of the polymer was attributed to the effect of non-affine deformations …
We study the effect of physical confinement on the capillary infiltration of polymers into cylindrical nanopores using molecular dynamics simulations. In particular, we probe whether the critical contact angle above which capillary rise infiltration ceases to occur changes for long chain polymers, possibly due to loss of conformation entropy induced by chain confinement. Surprisingly, the critical contact angle does not strongly depend on the length of polymer chains and stays constant for large N. A free energy model is developed to show that the critical angle for infiltration depends strong…
Designable media can control properties of nanocomposite materials by spatially organizing nanoparticles. Here we theoretically study particle organization by ultrathin polymer films of grafted chains (``brushes''). Polymer-soluble nanoparticles smaller than a brush-determined threshold disperse in the film to a depth scaling inversely with particle volume. In the polymer-insoluble case, aggregation is directed: provided particles are non-wetting at the film surface, the brush stabilizes the dispersion and selects its final morphology of giant elongated aggregates with a brush-selected width.
The dynamics of polymer-nanoparticle (NP) mixtures, which involves multiple scales and system-specific variables, has posed a long-standing challenge on its theoretical description. In this paper, we construct a microscopic theory for polymer diffusion in the mixtures based on a combination of generalized Langevin equation, mode-coupling approach, and polymer physics ideas. The parameter-free theory has an explicit expression and remains tractable on pair correlation level with system-specific equilibrium structures as input. Taking a minimal polymer-NP mixture as an example, our theory correc…
Magnetically Responsive Microprintable Soft Nanocomposites with Tunable Nanoparticle Loading
本文通过两光子聚合与铁氧化物纳米粒子共沉淀结合，制备出具有空间可调纳米粒子分布的3D打印微尺度纳米复合材料，实现了微尺度元材料和机器人应用中的精确机械与磁性控制。
Unraveling the glass-like dynamic heterogeneity in ring polymer melts: From semi-flexible to stiff chain
本研究通过分子动力学模拟探究链刚度与单体密度对环形聚合物熔体动静态行为的影响，发现非高斯性随密度和刚度增强，回转半径与密度的关系受链刚度调控，且键断裂动态非均匀性与非高斯性耦合，为理解其动力学机制提供新见解。
Depletion forces and macromolecular crowding govern the structure and function of biopolymers in biological cells and the properties of polymer nanocomposite materials. To isolate and analyze the influence of polymer shape fluctuations and penetrability on depletion-induced interactions and crowding by nanoparticles, we model polymers as effective penetrable ellipsoids, whose shapes fluctuate according to the probability distributions of the eigenvalues of the gyration tensor of an ideal random walk. Within this model, we apply Monte Carlo simulation methods to compute the depletion-induced po…
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