Dynamical Comparison of Different Polymer Architectures—Bottlebrush vs Linear Polymer
Not Available
36 MATERIALS SCIENCE↗
SEARCH · Engineering Papers
Results for “Dynamic polymer”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Fingerprinting Brownian Motions of Polymers under Flow
Here, we present a quantitative approach to the self-dynamics of polymers under steady flow by employing a set of complementary reference frames and extending the spherical harmonic expansion technique to dynamic density correlations. Application of this method to nonequilibrium molecular dynamics simulations of polymer melts reveals a number of universal features. For both unentangled and entangled melts, the center-of-mass motions in the flow frame are described by superdiffusive, anisotropic Gaussian distributions, whereas the isotropic component of monomer self-dynamics in the center-of-mass frame is strongly suppressed. Spatial correlation analysis shows that the heterogeneity of monomer self-dynamics increases significantly under flow.
36 MATERIALS SCIENCE↗
A Vitrimer Acts as a Compatibilizer for Polyethylene and Polypropylene Blends
Abstract Polymer compatibilization plays a critical role in achieving polymer blends with favorable mechanical properties and enabling efficient recycling of mixed plastic wastes. Nonetheless, traditional compatibilization methods often require tailored designs based on the specific chemical compositions of the blends. In this study, we propose a new approach for compatibilizing polymer blends using a dynamically crosslinked polymer network, known as vitrimers. By adding a relatively small amount (1–5 w/w%) of a vitrimer made of siloxane‐crosslinked high‐density polyethylene (HDPE), we successfully compatibilized unmodified HDPE and isotactic polypropylene (iPP). The vitrimer‐compatibilized blend exhibited enhanced elongation at break (120 %) and smaller iPP domain sizes (0.4 μm) compared to the control blend (22 % elongation at break, 0.9 μm iPP droplet size). Moreover, the vitrimer‐compatibilized blend showed significantly improved microphase stability during annealing at 180 °C. This straightforward method shows promise for applications across various polymer blend systems.
Yokoyama, Kosuke↗
A Vitrimer Acts as a Compatibilizer for Polyethylene and Polypropylene Blends
Polymer compatibilization plays a critical role in achieving polymer blends with favorable mechanical properties and enabling efficient recycling of mixed plastic wastes. Nonetheless, traditional compatibilization methods often require tailored designs based on the specific chemical compositions of the blends. In this study, we propose a new approach for compatibilizing polymer blends using a dynamically crosslinked polymer network, known as vitrimers. By adding a relatively small amount (1–5 w/w%) of a vitrimer made of siloxane‐crosslinked high‐density polyethylene (HDPE), we successfully compatibilized unmodified HDPE and isotactic polypropylene (iPP). The vitrimer‐compatibilized blend exhibited enhanced elongation at break (120 %) and smaller iPP domain sizes (0.4 μm) compared to the control blend (22 % elongation at break, 0.9 μm iPP droplet size). Moreover, the vitrimer‐compatibilized blend showed significantly improved microphase stability during annealing at 180 °C. This straightforward method shows promise for applications across various polymer blend systems.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Morphology–Diffusivity Relationships in Fluorine-Free Random Terpolymers for Proton-Exchange Membranes
Here, using atomistic molecular dynamics simulations, we investigate the morphology and transport properties of a new family of fluorine-free terpolymers designed as proton-exchange membranes. Simulated random terpolymers consist of three monomers with a 5-carbon backbone with a phenylsulfonate, phenyl, or no pendant group and have ion exchange capacities (IECs) ranging from 1.06–4.14 mmol/g. At a hydration level of 9, cluster analysis reveals macrophase separation between water and terpolymers with IEC < 2.1 mmol/g and continuous, percolated hydrophilic and hydrophobic nanoscale domains at higher IECs. Channel width distribution analysis of the percolated morphologies revealed that more hydrophobic units produce less uniform channels. Decreasing the surface area per sulfonate group and increasing the fractal dimension of the hydrophilic domains correlate with increased water diffusivity, due to a more acidic interface and more isotropic water channels. Relative to the previously studied phenylsulfonate homopolymer, these terpolymers with lower IECs have only modestly lower water diffusion, and we anticipate other advantages related to processability.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Surface-Functionalized Cellulose Nanocrystals as Nanofillers for Crosslinking Processes: Implications for Thermosetting Resins
Understanding the response of fillers in the epoxy resin crosslinking process and characterizing polymer–filler dynamics are the key features that guide the engineering of new thermosetting resin composites. Here, in this work, X-ray photon correlation spectroscopy (XPCS) is used as a thermal analysis tool to track the microscopic changes occurring during the cure of a functionalized cellulose nanocrystal (mCNC)–epoxy composite. In contrast, traditional methods such as differential scanning calorimetry (DSC) and curing rheology are used to understand the kinetics and properties on macroscopic length scales. Of interest is the influence of the mCNC on the curing kinetics and properties of the thermosetting resin. Two levels of modification (increasing hydrophobicity) were chosen to observe the effect of functionalization. Before cure, the highly functionalized CNC (mCNC3) shows a 44% increase in complex viscosity (η*), while the less functionalized CNC (mCNC2) shows a η* value similar to that of the neat resin. As the cure cycle progresses, results from DSC, rheology, and XPCS further show the enhancement in dispersion for mCNC3. The results show a clear difference in the maximum drift velocity, maximum heat flow, and complex viscosity during the ramp to the isothermal cure temperature (T cure ). Such results suggest that mCNC3 contains a well-dispersed network of particles due to the higher level of functionalization. During T cure , a transition in elastic modulus (G') occurs only for the highly functionalized CNC particle system. We believe that heat-induced aggregation occurs, and the crosslinked resin ultimately dominates the macroscopic properties of the final cured system for all samples. The results from the three techniques are in good agreement and showcase XPCS as a beneficial experimental tool for characterizing the microscopic dynamics of particulate-filled thermosetting resins. Hence, we envision this to be a fundamental curing study for the design of thermosetting resin composites.
36 MATERIALS SCIENCE↗
Capturing electronic decoherence in quantum-classical dynamics using the ring-polymer-surface-hopping–density-matrix approach
Simulations of coupled electronic and nuclear dynamics in molecules can be quite challenging due to the involved interplay of the many degrees of freedom. Because a full quantum treatment of both electrons and nuclei is computationally very demanding, it is generally restricted to model systems or rather small molecules and short timescales. Mixed quantum-classical dynamics methods such as Tully's fewest switches surface hopping (FSSH) can be used to overcome this limitation. However, FSSH is known to poorly describe electronic coherences and decoherence phenomena. Here, we present an approach that combines FSSH with ring-polymer molecular dynamics (RPMD) in a specific way that aims to alleviate the coherence problem. Termed the ring-polymer-surface-hopping–density-matrix approach, this method uses an electronic density-matrix formulation to calculate surface hopping rates. Additionally, this incorporates decoherence effects into FSSH in a natural way by taking into account the spatial spreading of the ring polymer that mimics the width of a nuclear wave packet in each RPMD trajectory. By applying our method to Tully's one-dimensional model system, we demonstrate that this method captures a crucial decoherence mechanism that is missing in FSSH. Furthermore, our method turns out to be superior at describing electronic coherences compared with earlier attempts at combining RPMD and FSSH.
74 ATOMIC AND MOLECULAR PHYSICS↗
Critical Role of the Interfacial Layer in Associating Polymers with Microphase Separation
Polymers with dynamic (transient) bonds, often called associating polymers, have been attracting significant attention in recent years due to their unique viscoelastic properties, self-healing ability, and recyclability. Nevertheless, understanding the mechanisms and the factors controlling their macroscopic properties remains limited due to the higher complexity introduced by the dynamic bonds. Here in this study, small-angle X-ray scattering (SAXS), broadband dielectric spectroscopy (BDS), and rheology were applied to unravel the structure and dynamics of telechelic associating polymers with different molecular weights. SAXS measurements revealed phase separation of the functional end groups with an average cluster size of ~2–3 nm and the distance between clusters controlled by the chain length. Borrowing the interfacial layer model analysis of BDS data from the polymer nanocomposite field, we demonstrated the presence of an interfacial polymer layer with a thickness of ~0.7–0.9 nm surrounding these clusters. Rheological measurements showed quantitatively that the presence of the interfacial layer significantly alters the viscoelastic behavior of these materials, indicating the crucial role of the interfacial layer in defining the macroscopic mechanical properties of the studied telechelic materials. The presented results emphasize that phase separation of the functional groups in associating polymers leads to very significant changes of the viscoelastic properties, opening a promising avenue in the design of novel functional materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Nanoscale Ion Transport Enhances Conductivity in Solid Polymer-Ceramic Lithium Electrolytes
The predictive design of flexible and solvent-free polymer electrolytes for solid-state batteries requires an understanding of the fundamental principles governing the ion transport. In this work, we establish a correlation among the composite structures, polymer segmental dynamics, and lithium ion (Li + ) transport in a ceramic-polymer composite. Elucidating this structure–property relationship will allow tailoring of the Li + conductivity by optimizing the macroscopic electrochemical stability of the electrolyte. The ion dissociation from the slow polymer segmental dynamics was found to be enhanced by controlling the morphology and functionality of the polymer/ceramic interface. The chemical structure of the Li + salt in the composite electrolyte was correlated with the size of the ionic cluster domains, the conductivity mechanism, and the electrochemical stability of the electrolyte. Polyethylene oxide (PEO) filled with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium bis(fluorosulfonyl) imide (LiFSI) salts was used as a matrix. A garnet electrolyte, aluminum substituted lithium lanthanum zirconium oxide (Al-LLZO) with a planar geometry, was used for the ceramic nanoparticle moieties. Further, the dynamics of the strongly bound and highly mobile Li + were investigated using dielectric relaxation spectroscopy. The incorporation of the Al-LLZO platelets increased the number density of more mobile Li + . The structure of the nanoscale ion-agglomeration was investigated by small-angle X-ray scattering, while molecular dynamics (MD) simulation studies were conducted to obtain the fundamental mechanism of the decorrelation of the Li + in the LiTFSI and LiFSI salts from the long PEO chain.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Structural and Dynamical Roles of Bound Polymer Chains in Rubber Reinforcement
The addition of nanofillers to rubber matrices is a powerful route to improve the mechanical properties. Here, we focus on a molecular understanding of basic mechanisms that are important for the reinforcement in rubbers. The key role in this process is ascribed to bound rubber (BR) that engages with the matrix as well as with adjacent nanofillers. To date, this understanding has been impeded by the lack of experimental tools to directly probe the BR chains buried in a polymer matrix composed of the same polymer. To tackle this challenge, we combine neutron scattering/spectroscopy techniques with isotope-labeling and molecular dynamics simulations. The system is a simplified carbon-black-filled polybutadiene. The combined experimental and computational results provide new insights into the local structural and dynamical heterogeneities of BR chains and their interactions with the matrix polymer, highlighting (i) the structural partition of the bound chains into three components (i.e., trains, loops, and tails) and their fractions; (ii) their dynamical hierarchies, i.e., the trains that remain immobile on the filler surface, the loops that are fairly large and hence allow the interdigitation of matrix chains, and the tails with their unique characteristics to reach far out into the matrix and entangle with matrix chains. These multiple roles of the constituent components of the BR chains promote the formation of a well-developed adhesive polymer–filler interface, enhancing the elastic property of a filled rubber. Finally, the comprehensive understanding derived and validated by the model rubber will be translatable to many other polymer nanocomposites.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Hydrodynamic Interactions in Topologically Linked Ring Polymers.
Despite decades of interdisciplinary research on topologically linked ring polymers, their dynamics remain largely unstudied. These systems represent a major scientific challenge as they are often subject to both topological and hydrodynamic interactions (HI), which render dynamical solutions either mathematically intractable or computationally prohibitive. Here we circumvent these limitations by preaveraging the HI of linked rings. We show that the symmetry of ring polymers leads to a hydrodynamic decoupling of ring dynamics. This decoupling is valid even for nonideal polymers and nonequilibrium conditions. Physically, our findings suggest that the effects of topology and HI are nearly independent and do not act cooperatively to influence polymer dynamics. We use this result to develop highly efficient Brownian dynamics algorithms that offer enormous performance improvements over conventional methods and apply these algorithms to simulate catenated ring polymers at equilibrium, confirming the independence of topological effects and HI. The methods developed here can be used to study and simulate large systems of linked rings with HI, including kinetoplast DNA, Olympic gels, and poly[n]catenanes.
Rauscher, Phillip M.↗
Universal dynamics of coarsening during polymer-polymer thin-film spinodal dewetting kinetics
The dewetting dynamics of a supported bilayer polymer thin film on a solid substrate is investigated using grazing incidence x-ray photon correlation spectroscopy. We find that the top layer dewets via the spinodal mechanism. The kinetics of the dewetting is studied by monitoring the time evolution of the surface diffuse x-ray scattering intensity. We study the time evolution of fluctuations about the average surface structure by measuring the two-time x-ray intensity fluctuation correlation functions. Using these two-time correlation functions we quantify the crossover from early-time diffusive dynamics to hydrodynamics. The early diffusive regime satisfies dynamic universality. The two-time correlation functions also quantify the onset of hydrodynamic effects. The hydrodynamic regime is observed during the spinodal dewetting process as these interactions are not screened.
36 MATERIALS SCIENCE↗
Charge transfer states impact the triplet pair dynamics of singlet fission polymers
Polymers are desirable optoelectronic materials, stemming from their solution processability, tunable electronic properties, and large absorption coefficients. An exciting development is the recent discovery that singlet fission (SF), the conversion of a singlet exciton to a pair of triplet states, can occur along the backbone of an individual conjugated polymer chain. Here, compared to other intramolecular SF compounds, the nature of the triplet pair state in SF polymers remains poorly understood, hampering the development of new materials with optimized excited state dynamics.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Accelerating ion transport by dynamic asymmetry of alternating polymer electrolytes
Polymer based electrolytes allow the absence of volatile components in batteries thus increasing their safety. Yet, they exhibit drawbacks based on their low conductivity. We have used an alternating polymer consisting of dimethyl siloxane (DMS) and ethylene glycol (EG) blocks to circumvent known disadvantages of the usually used polyethylene glycol (PEG). Incorporating dimethyl siloxane lowers the glass-transition temperature and thus reduces the segmental relaxation time, by dynamic asymmetry or internal plasticization of the constituting polymer blocks. The alternating structure ensures miscibility of the different components and hinders crystallization. Furthermore, the pure polymer, P(DMS 3 -alt-EG 4 ), shows a segmental relaxation time well in the range needed for polymer electrolytes. Mixtures of LiClO 4 and P(DMS 3 -alt-EG 4 ) show a drastically reduced temperature dependence of their DC conductivity in comparison to PEG based systems, resulting in an increase by two orders of magnitude at T = 5 °C and even three to four orders of magnitude at T = 0 °C. Addition of coordinating (acetonitrile) or non-coordinating (toluene) solvent increases conductivity either via additional plasticization or by weakening the Li-binding yet looking at the dynamics at low concentrations of additional solvent the mobility of the polymer is reduced. In conclusion, the solvent addition leads only at higher solvent concentration to a reduction in relaxation time.
Jakobi, Bruno [Louisiana State Univ., Baton Rouge,↗
Dynamical Ion Correlations in Polymer and Membrane Electrolytes: Recent Advances and Open Questions
Ion transport in polymer and membrane electrolytes is often described using uncorrelated models like the Nernst–Einstein (NE) approximation, which link conductivity, transference number, and salt diffusivity to individual ion mobilities. However, growing evidence shows that dynamical ion correlations─arising from ion pairing, polymer-mediated coupling, confinement, and electrostatic interactions─can substantially alter macroscopic transport properties. The Onsager transport formalism offers a rigorous framework to quantify these effects via cross-correlated ionic displacements. This Perspective highlights how such correlations manifest across dry and hydrated systems, including salt-doped polymers, block copolymers, hydrogels, and ion-exchange membranes. Here, we examine key physical origins, the influence of salt chemistry and polymer structure, and open questions in measuring and controlling correlated motion. Embracing correlation-aware design enables new pathways to optimize conductivity, transference number, and selectivity─shifting the focus from individual ion mobility to engineered collective dynamics for next-generation electrolytes in energy storage and separations.
Charge transport↗
Unexpected Slow Relaxation Dynamics in Pure Ring Polymers Arise from Intermolecular Interactions
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Origin of rate limitations in solid-state polymer batteries from constrained segmental dynamics within the cathode
Currently, one of the key challenges preventing the wide commercialization of polymer-based solid-state batteries is achieving high-rate capabilities. This work unravels chain structure and segmental dynamics in a polymer-based composite cathode consisting of LiFePO 4 (LFP), carbon, and poly(ethylene oxide) (PEO) with lithium bis(trifluoromethanesulfonyl)imide. Small-angle neutron scattering (SANS) data reveal that PEO chains are adsorbed on the surface of LFP particles during slurry processing to make the composite electrode. The strong interaction between LFP and PEO chains leads to greatly reduced segmental dynamics of PEO, as discovered by quasi-elastic neutron scattering (QENS). The reduced segmental dynamics results in 70% decreased Li + mobility of the polymer electrolyte in the composite cathode. The combined SANS and QENS study indicates that one of the key bottlenecks that limits the rate performance of PEO-based polymer batteries originates from molecular interactions within the cathode.
25 ENERGY STORAGE↗