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Butyl acrylate polymer networks were synthesized to understand the effect of permanent cross-links on large, anisotropic dye diffusion. The average degree of polymerization between cross-links (Nx)...

The connection between slow activated relaxation in glass-forming liquids and various equilibrium thermodynamic properties remains intensely debated. The microscopic elastically collective nonlinea...

Hyaluronan is a biopolymer that is essential for many biological processes in the human body, like the regulation of tissue lubrication and inflammatory responses. Here, we study the behavior of hyaluronan at aqueous surfaces using heterodyne-detected vibrational sum-frequency generation spectroscopy (HD-VSFG). Low-molecular-weight hyaluronan (similar to 150 I(Da) gradually covers the water-air interface within hours, leading to a negatively charged surface and a reorientation of interfacial water molecules. The rate of surface accumulation strongly increases when the bulk concentration of low-molecular-weight hyaluronan is increased. In contrast, high-molecular-weight hyaluronan (>1 MDa) cannot be detected at the surface, even hours after the addition of the polymer to the aqueous solution. The strong dependence on the polymer molecular weight can be explained by entanglements of the hyaluronan polymers. We also find that for low-molecular-weight hyaluronan the migration kinetics of hyaluronan in aqueous media shows an anomalous dependence on the pH of the solution, which can be explained from the interplay of hydrogen bonding and electrostatic interactions of hyaluronan polymers.

The effects, that glycine (Gly) has on the local chain conformation and internal backbone dynamics (IBD) of polypeptides, were investigated by comparing the fluorescence response of a series of pyr...

The dynamics of adsorption and desorption of counterions on a polyelectrolyte chain in aqueous solution is studied at a single molecular level. The investigation is through the process of fluoresce...

It is now generally agreed that the most dramatic influence of a free surface on local relaxation dynamics occurs over the first 10 nm from the surface. Using the cooperative free volume (CFV) rate...

Although experimental evidence for shear-banding flows in concentrated polymer solutions has accumulated over the last 20 years, the origin of such shear-banding flows is still under heated debate....

We use molecular dynamics simulations to study how the chain length affects the structure and segmental dynamics of polymer–nanoparticle (NP) composites at semidilute NP concentrations. For NPs hav...

We investigated the dynamics of the topological network formed by rotaxane-type movable crosslinks consisting of a poly(ethyl acrylate) backbone threaded through peracetylated cyclodextrins, which ...

Though the strong transformation in mechanical properties of glass-forming materials such as amorphous polymers near the glass transition, Tg, has long been recognized and exploited, efforts to und...

We present the results from an extensive atomistic molecular dynamics simulation study of poly(ethylene oxide) (PEO) doped with various amounts of lithium-bis(trifluoromethane)sulfonimide (LiTFSI) salt under the influence of external electric field strengths up to $1\,$V/nm. The motivation stems from recent experimental reports on the nonlinear response of mobilities to the application of an electric field in such electrolyte systems and arising speculations on field-induced alignment of the polymer chains, creating channel-like structures that facilitate ion passage. Hence, we systematically examine the electric field impact on the lithium coordination environment, polymer structure as well as ionic transport properties and further present a procedure to quantify the susceptibility of both structural and dynamical observables to the external field. Our investigation reveals indeed a coiled-to-stretched transformation of the PEO strands along with a concurrent nonlinear behavior of the dynamic properties. However, from studying the temporal response of the unperturbed electrolyte system to field application we are able to exclude a structurally conditioned enhancement of ion transport and surprisingly observe a slowing down. A microscopic understanding is supplied., Main manuscript comprises 30 pages and 13 figures, supplementary information section comprises 30 pages and 28 figures

Despite being the most ubiquitous compound on Earth, the fundamental properties of water are not fully understood, especially in nanoconfinement. Densely grafted polyelectrolyte (PE) molecules atta...

We employ molecular dynamics (MD) simulations to study the spreading and imbibition of a liquid drop on a porous, soft, solvophilic, and responsive surface represented by a layer of polymer molecul...

The dynamics of different blocks in block copolymers are expected to affect the other blocks due to compositional heterogeneity, thus influencing their bulk structure and performance. It is signifi...

Dendronized polymers (denpols) are thick polymers comprising a linear backbone with grafted treelike structures (dendrons). The latter give rise to a molecular thickness that is a function of dendr...

Well-dispersed polymer-tethered silica nanoparticles exhibit soft glassy rheology and caging behaviors due to chain interpenetration driven by entropic attraction and geometric confinement. In this...

The fluorescence blob model (FBM) was applied to analyze the fluorescence decays of a series of pyrene-labeled polypeptides to better understand how the amino acid (aa) composition of a polypeptide...

Recently, Hor et al. [Hor, J. L., Wang, H., Fakhraai, Z., & Lee, D. (2018). Macromolecules 51 (14), 5069–5078] reported a set of interesting results for the viscosity of unentangled polystyrene of ...

The effect of functionality on the migration behaviors, structural, and dynamical properties of star polymers in Poiseuille flow are investigated by multiparticle collision dynamics integrated with...

Ring polymers are a unique class of macromolecules that lack free ends and show qualitatively different dynamics compared to linear chains. Despite recent progress, the nonequilibrium flow behavior...

The dynamics of two polyrotaxanes with different ring component sizes were compared through viscoelastic measurements. An improved polyrotaxane synthesis was used to develop a glass-forming polyrot...

The acceleration of structural relaxation or physical aging by deformation, known as overaging, has been reported in experiments and simulations of polymer and colloid glasses, and correct accounti...

The dynamics of nanostructured soft materials crucially impact their associated macroscopic material properties, yet they are often difficult to measure due to spatiotemporal limitations of convent...

Dynamic bonds have been widely incorporated into polymeric materials for achieving self-healing, recycling, and stimuli-responsive properties. As a result, these polymeric chains often exhibit dive...

Three series of pyrene-labeled polypeptides, namely, poly(l-lysine) (Py-PLL), poly(l-glutamic acid) (Py-PLGA), and poly(d,l-glutamic acid) (Py-PDLGA), were studied in dimethyl sulfoxide (DMSO) by m...

The effects of interphase topology, entanglements, and chain dynamics on the mechanical response of semicrystalline polyethylene have been examined using atomistic simulations. In particular, the prevalence of the cavitation and melting/recrystallization mechanisms for yield and plastic flow were found to depend on both topological and dynamical properties of the molecular segments in the semicrystalline interphase. First, two different protocols were used during preparation of the interphase ensemble to modulate the distribution of (i) loops, bridges, and tails and (ii) entanglements within the noncrystalline domain. A protocol denoted “step-wise cooling” produced structures having a large fraction of long, entangled segments that yielded by the melting/recrystallization mechanism about 50% of the time. By contrast, the protocol denoted “instantaneous quench” produced structures that yielded by melting/recrystallization about 73% of the time. Second, two different united atom force fields, PYS and TraPPE-UA, that exhibit nearly identical topological characteristics of the noncrystalline domain but different mobilities were used to study the effect of chain dynamics on yield mechanisms. At the slower strain rate used in this work, yield and plastic flow proceeded exclusively via cavitation for the model using the TraPPE-UA force field, whereas both cavitation and melting/recrystallization were observed for the model using the PYS force field. The greater prevalence of melting/recrystallization in the latter case is attributed to faster chain-sliding dynamics in the crystalline domain. The dependences of the yield mechanism on topology and dynamics are found to be related. ISSN:1520-5835 ISSN:0024-9297

We investigate single chain dynamics of an entangled linear poly(ethylene oxide) melt in the presence of well-dispersed attractive nanoparticles using high-resolution neutron spectroscopy at partic...

We systematically investigate the effects of surface roughness on the static and dynamic properties of polymer chains in confined films by using molecular dynamics simulations, in which the roughne...

We investigate tank-treading and breathing dynamics of individual star molecules under shear flow and their relation with the macromolecule architecture. Tank-treading consists of the rotation of t...

Processability of vitrimers strongly relies on the temperature dependence of viscosity. In this study, we analyzed temperature-dependent viscoelasticity of vitrimers based on the dioxaborolane meta...

Macromolecules in an entangled environment are constrained to wriggle predominantly along a confining tube, giving rise to the so-called reptation or tube-like motion. While the principles of polymer physics were well developed to understand its conformational dynamics, the quantitative characterization of the tube diameter and resulting reptation remains an open question. Here, using highly confined parallel plate geometry nanoslits down to sub-30 nm, we directly observe reptation in a one-dimensional (1D) confined nanoenvironment. We provide a quantitative analysis scheme, by introducing the segmental tangential vector and its associated correlation function, to characterize the strand reptation and connect it to the confinement degree. Our analysis shows that the amplitude of the transverse fluctuations (the virtual 2D "tube") exhibits the typical scaling of fluctuating interfaces, contact lines, or charge density waves, with a roughness exponent, which depends on the slit height. Our results are shown to lead to less rough DNA profiles in shallower nanoslits. We anticipate our analysis to be a starting point for a more detailed understanding of the relationship between polymer physics and other nonequilibrium physical systems.

The dynamics of polymer nanocomposites (PNCs) are dictated by two intertwining components, the polymer matrix and the nanoparticle network, whose characteristics have not been elucidated. Here, we ...

We combine 1H, 7Li, and 19F NMR methods to selectively investigate polymer, cation, and anion dynamics in polymer electrolytes on various length and time scales and over broad temperature ranges. B...

Although numerous studies have been conducted to describe the gelation of multi-arm star polymers, reports on the relationship among rheological quantities, overlap concentration (c*), and microstr...

We analyze the dynamics from microsecond-long, atomistic molecular dynamics (MD) simulations of a series of precise poly(ethylene-co-acrylic acid) ionomers neutralized with lithium, with three diff...

Simulations of coarse-grained models are used to study relationships among chain motion, composition fluctuations, and stress relaxation in unentangled melts of symmetric diblock copolymers. Measur...

The rotation of Ni nanorods, dispersed in dilute and semidilute poly(ethylene oxide) solutions, is investigated. Ni nanorods with similar diameter but different lengths are synthesized using the an...

Atomic force microscopy (AFM) imaging was used to study the in situ swelling of terraced poly(styrene-block-methyl methacrylate) (PS-b-PMMA) thin films under cyclohexane, a selective solvent for PS...