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Background The importance of protein dynamics for their biological activity is now well recognized. Different experimental and computational techniques have been employed to study protein dynamics, hierarchy of different processes and the coupling between protein and hydration water dynamics. Yet, understanding the atomistic details of protein dynamics and the role of hydration water remains rather limited. Scoop of review Based on overview of neutron scattering, molecular dynamic simulations, NMR and dielectric spectroscopy results we present a general picture of protein dynamics covering time scales from faster than ps to microseconds and the influence of hydration water on different relaxation processes. Major conclusions Internal protein dynamics spread over a wide time range from faster than picosecond to longer than microseconds. We suggest that the structural relaxation in hydrated proteins appears on the microsecond time scale, while faster processes present mostly motion of side groups and some domains. Hydration water plays a crucial role in protein dynamics on all time scales. It controls the coupled protein-hydration water relaxation on 10–100 ps time scale. This process defines the friction for slower protein dynamics. Analysis suggests that changes in amount of hydration water affect not only general friction, but also influence significantly the protein's energy landscape. General significance The proposed atomistic picture of protein dynamics provides deeper understanding of various relaxation processes and their hierarchy, similarity and differences between various biological macromolecules, including proteins, DNA and RNA. This article is part of a Special Issue entitled “Science for Life” Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo”. [ABSTRACT FROM AUTHOR]

Despite potential significant advantages of polymer based batteries, the poor ionic conductivity of dry polymer electrolytes at ambient and low temperatures has limited their application. This review describes the approach for improving conductivity by decoupling ionic transport from polymer segmental relaxation. It is emphasized that the decoupling approach is the key for design of superionic polymer electrolytes. [ABSTRACT FROM AUTHOR]

Reports on the nature of the glass transition which remains an unsolved problem in the physics of condensed matter. Information on the mode-code coupling theory and crossover temperatures; Details on the dynamics at the mesoscopic frequency range.

Hybrid composites combine two or more different fillers to achieve multifunctional or advanced material properties, such as lightweight and enhanced mechanical properties. The properties of the composites significantly depend on their microstructures, which can be tailored via advanced 3D printing processes. Understanding the process-structure-property relationships is critical to enable the design and engineering of novel hybrid composites for applications in aerospace, automotive, and protective coatings. Here, we develop 3D printable and lightweight hybrid composites and leverage the conventional design of experiments, a theoretical hybrid model, and an image-driven machine learning (ML) method to investigate their mechanical behaviors. The hybrid composites are formulated with elastomer matrix, microfillers, and thin-shell particles, enabling a significant degree of design freedom of microstructures with densities and mechanical properties varying up to 70% and 91%, respectively. Our statistical analysis indicates that the 3D printing path direction and the microfibers fraction are dominating process parameters with contribution percentages of 45.3% and 57.7% on the specific stiffness and strength, respectively. A hybrid mechanics model is developed based on a simple Weibull distribution function and classical single-filler models to effectively capture the variations in mechanical properties, however, it overestimates the values due to its statistical constraints and idealization of experimental uncertainty. The image-driven ML model leverages the microscale images directly without losing the structural details, shows more accurate predictions with experimental data, and has 48.6% lower root mean square error than the theoretical model. [ABSTRACT FROM AUTHOR]

Abstract: A self-reduction of graphene oxide (GO) at room temperature after prolonged storage on a copper substrate is evidenced by decrease of oxygen content and a dramatic, 6 orders in magnitude, increase in dc conductivity. Experiments revealed that the stored GO film contains copper hydroxide phase embedded in the reduced GO structure. [Copyright &y& Elsevier]

Abstract Soiling of optical surfaces due to sand and dust accumulation is the main cause for decreased efficiency of concentrating solar power and photovoltaic installations in desert areas. Nanostructured coatings with tailored surface roughness can reduce the rate of soil accumulation and maintain the high optical performance of the solar mirrors and cover glass. Here, we investigate the correlation between the size and structure of the surface features of the coating and its anti-soiling and optical properties. To control the morphology of the surface features we developed two types of coating: (1) based on small size (30–50 nm) silica particles with nanostructured surface and (2) based on unstructured nanoparticles with bimodal size distribution (80 and 35 nm). We tailored the surface features of the coatings to achieve synergistic improvements over different length-scales and thus decrease the adhesion force between the soil particles and the surface. Adhesion force measurements were performed using atomic force microscopy. The adhesion force and energy required to separate a silica particle from the surface of coated solar glass was significantly lower than the respective values from the surface of uncoated solar glass. A falling sand abrasion test, modeled after the procedure in ASTM D968, was performed. The optical properties of coated and uncoated solar glass were measured before and after the soiling test. Coated solar mirror samples were tested in the field. The results of the field test provided evidence that the anti-soiling coating is effective at reducing soiling and improving the specular reflectances of the coated mirrors. The use of the developed anti-soiling coating can be extended to other power-grid applications where reducing the soil accumulation is valuable. Highlights • Anti-soiling coatings with tailored roughness that can retrofit solar mirrors and mitigate the soil accumulation. • Remarkable reductions in the soiling rate (up to 39%) of coated solar mirror samples that were tested in the field. • Mitigation of environmental pollutants such as dust particles is associated with the increased efficiency of solar power installations. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Star PolyIL arm dynamics are delayed relative to linear chains of similar size. • Stars have greater melt viscosity, increasing exponentially with arm length. • Nonlinear architecture has only secondary effects on segmental and ion dynamics. • Morphology and viscoelastic properties are tuned independently of ion transport. Abstract The viscoelastic and dielectric response of linear and star-shaped polymeric ionic liquids (PolyILs) based on imidazolium/bis(trifluoromethane)sulfonimide are probed over a broad range of frequencies and temperatures and are evaluated in connection to the polymer architecture and morphology. At longer timescales, the arm dynamics of star PolyILs are shown to be more sluggish and elastic relative to those of linear chains of comparable size. Arm retraction delays terminal relaxation in the melt, resulting in an enhanced zero-shear viscosity that increases exponentially with the arm length. Yet at shorter timescales, long-chain branching is shown to have only secondary effects on the segmental and ion motions. That is, star PolyIL melts are found to have a lower viscoelastic fragility, more frustrated secondary β fluctuations, and—for stars with the shortest arms—higher activation energies for ion hopping at low temperatures. Even so, all PolyILs ultimately exhibit nearly similar rates of segmental relaxation, ion disassociation, and dc conductivity over the investigated temperature range, regardless of polymer architecture including arm length. This study thus demonstrates how the disparity between chain, segmental, and ion dynamics in branched PolyILs can be exploited in the assembly of functional polymer electrolyte materials with divergent morphologies and controlled viscoelasticity properties, both can be varied independently of ion transport. [ABSTRACT FROM AUTHOR]

While PLA possesses modest to good strength and stiffness, broader application is hindered by its brittle nature. The aim of this study was to develop strong and tough polymeric materials from renewable biomaterials and understand the underlying interactions and mechanisms. Cellulose nanofibrils (CNFs) and epoxidized soybean oil (ESO) were compounded with poly(lactic acid) (PLA) to create a PLA-CNF-ESO tertiary nanocomposite system. Tensile and dynamic mechanical analyses were performed to see how variations in ESO and CNF content affect mechanical properties such as strength, modulus, ductility, and toughness. It was found that at low CNF levels (10 wt%) the addition of ESO can improve the ductility of the nanocomposites 5- to 10-fold with only slight losses in strength and modulus, while at higher CNF levels (20 and 30 wt%), ESO exhibited little effect on mechanical properties, possibly due to percolation of CNFs in the matrix, dominating stress transfer. Therefore, it is important to optimize CNF and ESO amounts in composites to achieve materials with both high strength and high toughness. Efforts have been made to understand the underlying mechanisms of the mechanical behavior of one class of these composites via thermal, dynamic mechanical, rheological, morphological, and Raman analyses. [ABSTRACT FROM AUTHOR]

Single-ion conducting polymer electrolytes (SCPE) are attractive candidates for high-performance energy storage devices. A star-shaped single lithium-ion conducting polymer electrolyte was synthesized by combining the “grafting to” and “grafting from” strategy utilizing a polyhedral oligomeric silsesquioxane (POSS) nanoparticle as the core. Carboxylic acid terminated polyethylene oxide (PEO) and Reversible Addition Fragmentation Chain Transfer Agent (RAFT-CTA) were attached to the POSS nanoparticle to form a POSS-cored macro RAFT CTA (PMR-CTA). The PMR-CTA was used to mediate the polymerization of potassium (styrene-4-sulfonyltrifluoromethyl-sulfonyl)imide (STF-K + ) and subsequent counter ion exchange resulted in a star-shaped single lithium-ion conducting copolymer (SSCP-Li + ). The grafting ratio of poly(STF-Li + ) and PEO per POSS nanoparticle can be tuned by modifying the feed ratio of the two polymer components. The synthesized star-shaped SCPE-Li + are characterized by 1 H NMR, FT-IR, UV-Vis, DLS, GPC and DSC, and their ionic conductivity is studied by broadband dielectric spectroscopy. The obtained results are compared to a conventional linear homopolymer poly(STF-Li + ) and block copolymer PEO- b -poly(STF-Li + ), and reveal a significant “decoupling” of ion conductivity from segmental dynamics for all of the studied SCPE-Li + . Blending extra PEOs with SCPE-Li + was also performed to improve the ionic conductivity. [ABSTRACT FROM AUTHOR]

In order to design more effective solid polymer electrolytes, it is important to decouple ion conductivity from polymer segmental motion. To that end, novel polymers based on oxanorbornene dicarboximide monomers with varying lengths of oligomeric ethylene oxide side chains have been synthesized using ring opening metathesis polymerization. These unique polymers have a fairly rigid and bulky backbone and were used to investigate the decoupling of ion motion from polymer segmental dynamics. Ion conductivity was measured using broadband dielectric spectroscopy for varying levels of added lithium salt. The conductivity data demonstrate six to seven orders of separation in timescale of ion conductivity from polymer segmental motion for polymers with shorter ethylene oxide side chains. However, commensurate changes in the glass transition temperatures T g reduce the effect of decoupling in ion conductivity and lead to lower conductivity at ambient conditions. These results suggest that both an increase in decoupling and a reduction in T g might be required to develop solid polymer electrolytes with high ion conductivity at room temperature. [ABSTRACT FROM AUTHOR]

We demonstrate the unprecedented chemical imaging of individual constituents in a four-component sample made of several carbon allotropes: single-wall carbon nanotubes, graphene oxide, C 60 fullerene, and an organic residue. This represents a significant advance with respect to previous works that were mainly limited to systems with one or two components having very different chemical composition. Despite the spectral and spatial overlap from different components, plasmon-based nanospectroscopy allows the discrimination of all individual carbon nanomaterials here investigated. Among other physical insights such as doping observed in carbon nanotubes, the detailed chemical imaging of graphene oxide reveals higher defect concentration at the flake edges similarly to the case of graphene. We found that the organic residue has either low adsorption or lack of resonant enhancement on GO, in contrast to graphene, suggesting a decreased van der Waals interaction. This report paves the way for routine nanoscale analysis of complex carbon systems with spatial resolution of 15 nm and below. [ABSTRACT FROM AUTHOR]

Replacing traditional liquid electrolytes by polymers will significantly improve electrical energy storage technologies. Despite significant advantages for applications in electrochemical devices, the use of solid polymer electrolytes is strongly limited by their poor ionic conductivity. The classical theory predicts that the ionic transport is dictated by the segmental motion of the polymer matrix. As a result, the low mobility of polymer segments is often regarded as the limiting factor for development of polymers with sufficiently high ionic conductivity. Here, we show that the ionic conductivity in many polymers can be strongly decoupled from their segmental dynamics, in terms of both temperature dependence and relative transport rate. Based on this principle, we developed several polymers with "superionic" conductivity. The observed fast ion transport suggests a fundamental difference between the ionic transport mechanisms in polymers and small molecules and provides a new paradigm for design of highly conductive polymer electrolytes. [ABSTRACT FROM AUTHOR]

Abstract: A self-complementary heteroditopic molecule composed of thymine and diamidopyridine end groups and a flexible aliphatic interconnecting chain has been synthesized. The glassy dynamics of this hydrogen-bonded supramolecule have been investigated by using dielectric and rheological measurements, in combination with infra-red spectroscopy and solid-state 13C NMR experiments. Decoupling of main dielectric relaxation from viscosity has been found in the vicinity of the glass transition and the temperature dependence of viscosity appears to be stronger than that of dielectric relaxation. The unusual dynamic decoupling phenomenon is ascribed to the chemical/dynamic heterogeneity and formation of hydrogen bonds in the supramolecules. [Copyright &y& Elsevier]

Abstract: A soluble π-conjugated polymer cis-PmPV is found to be twice as effective as its trans-PmPV isomer in dispersing SWNTs into organic solvents. The improved efficiency is related to the specific conformation of cis-vinylene-enriched PmPV, which facilitates a planar π–π interaction with SWNT surface and leads to improved nanotube dispersion. 1H NMR spectra indicate that the cis-CHare partially converted to the trans-CHby providing necessary conformational cavity for SWNT wrapping. Irradiation triggers a precipitation from SWNT dispersion, providing a purified SWNT/conjugated polymer composite. [Copyright &y& Elsevier]