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A series of poly(ethylene oxide) nanocomposites with spherical silica was studied by proton NMR spectroscopy, identifying and characterizing reduced-mobility components arising from either roomtemperature lateral adsorption or possibly end-group mediated high-temperature bonding to the silica surface. The study complements earlier neutron-scattering results for some of the samples. The estimated thickness of a layer characterized by significant internal mobility resembling backbone rotation ranges from 2 nm for longer (20 k) chains adsorbed on 42 nm diameter particles to 0.5 nm and below for shorter (2 k) chains on 13 nm particles. In the latter case, even lower adsorbed amounts are found when hydroxy endgroups are replaced by methyl endgroups. Both heating and water addition do not lead to significant changes of the observables, in contrast to other systems such as acrylate polymers adsorbed to silica, where temperature- and solvent-induced softening associated with a glass transition temperature gradient was evidenced. We highlight the actual agreement and complementarity of NMR and neutron scattering results, with the earlier ambiguities mainly arising from different sensitivities to the component fractions and the details of their mobility. [ABSTRACT FROM AUTHOR]

The segmental dynamics of bottlebrush polymers with a stiff backbone and flexible side chains has been studied. The segmental relaxation time of side chains attached to a flexible backbone follows the same trend as linear polymers, an increase with the increasing molecular weight, but is slowed down compared to their linear counterparts. Theoretical work predicts a reversal of the molecular weight dependence of the relaxation time for stiff backbones. As a model for a stiff-g-flexible system, bottlebrushes with poly(norbornene) backbone and poly(propylene oxide) side chains, PNB-g-PPO, at a uniform grafting density have been synthesized and characterized with quasi-elastic neutron scattering. Indeed, the anticipated reversed dynamics was found. Increasing the side chain length decreases the segmental relaxation time. This indicates the importance of the characteristics of the grafting site beyond a simplified picture of an attached side chain. The mean square displacement shows a similar trend with longer side chains exhibiting a larger displacement. [ABSTRACT FROM AUTHOR]

We review the currently available material on the morphology and dynamics of phospholipids assembled into liposomes. Key information obtained from neutron scattering, nuclear magnetic resonance (NMR), and other techniques plays a crucial role in understanding the vital role of lipids in sustaining life in living organisms. We concentrate on the dynamics in the biologically important fluid phase in the time range from picoseconds to seconds, which includes a discussion of the center of mass diffusion of liposomes, membrane fluctuations; and lateral, rotational, and flip-flop motions of the lipids. We emphasize on the sensitivity of the dynamics on interactions with a variety of biologically relevant molecules such as cholesterol. By a comparison of data from literature, we witness a good agreement of the results from different techniques and studies. Image 1 • We discuss the morphology and dynamics of liposomes in the fluid phase. • We review universal behavior of lipid membranes at different length- and time scales and their relationship to barrier properties and biological function. • We discuss neutron scattering and existing models used to understand the motions associated with the lipid bilayer. • We review and compare popular experimental techniques and neutron scattering and summarize the impact on the understanding of the lipid bilayer. [ABSTRACT FROM AUTHOR]

The segmental dynamics of the side chains of poly(norbornene)‐g‐poly(propylene oxide) (PNB‐g‐PPO) bottlebrush polymer in comparison to PPO is studied by quasi‐elastic neutron scattering. Having experimental time and length scale information simultaneously allows to extract spatial information in addition to relaxation time. Tethering one end of the PPO side chain onto a stiff PNB backbone slows down the segmental relaxation, over the length and time scales investigated. The power law dependence of the relaxation time on the momentum transfer, Q, indicates a more heterogeneous relaxation pattern for the bottlebrush polymer, whereas the linear PPO has less deviations from a homogenous relaxation. Similar conclusions can be drawn from the time dependent mean square displacement, 〈r2(t)〉, and the non‐Gaussian parameter, α2(t). Herein, the bottlebrush polymer shows a more restricted dynamics, whereas the linear PPO reaches 〈r2(t)〉∝t0.5at the highest temperature. The deviations from Gaussian behavior are evident at the α2(t). Both samples show a decaying α2(t). The non‐Gaussian parameter supports the results from the power law dependence of the relaxation times, with lower α2(t) values for PPO compared to those for PNB‐g‐PPO, pointing to less deviations from Gaussian behavior. [ABSTRACT FROM AUTHOR]

The performance of fuel cells depends largely on the proton diffusion in the proton conducting membrane, the core of a fuel cell. High temperature polymer electrolyte fuel cells are based on a polymer membrane swollen with phosphoric acid as the electrolyte, where proton conduction takes place. We studied the proton diffusion in such membranes with neutron scattering techniques which are especially sensitive to the proton contribution. Time of flight spectroscopy and backscattering spectroscopy have been combined to cover a broad dynamic range. In order to selectively observe the diffusion of protons potentially contributing to the ion conductivity, two samples were prepared, where in one of the samples the phosphoric acid was used with hydrogen replaced by deuterium. The scattering data from the two samples were subtracted in a suitable way after measurement. Thereby subdiffusive behavior of the proton diffusion has been observed and interpreted in terms of a model of fractal diffusion. For this purpose, a scattering function for fractal diffusion has been developed. The fractal diffusion dimension d w and the Hausdorff dimension df have been determined on the length scales covered in the neutron scattering experiments. [ABSTRACT FROM AUTHOR]

Ultrasound irradiation is a commonly used technique for nondestructive diagnostics or targeted destruction. We report on a new versatile sonication device that fits in a variety of standard sample environments for neutron and X-ray scattering instruments. A piezoelectric transducer permits measuring of the time-dependent response of the sample in situ during or after sonication. We use small-angle neutron scattering (SANS) to demonstrate the effect of a time-dependent perturbation on the structure factor of micelles formed from sodium dodecyl sulfate surfactant molecules. We observe a substantial change in the micellar structure during and after exposure to ultrasonic irradiation. We also observe a time-dependent relaxation to the equilibrium values of the unperturbed system. The strength of the perturbation of the structure factor depends systematically on the duration of sonication. The relaxation behavior can be well reproduced after multiple times of sonication. Accumulation of the recorded intensities of the different sonication cycles improves the signal-to-noise ratio and permits reaching very short relaxation times. In addition, we present SANS data for the micellar form factor on alkyl-poly (ethylene oxide) surfactant molecules irradiated by ultrasound. Due to the flexibility of our new in situ sonication device, different experiments can be performed, e.g., to explore molecular potentials in more detail by introducing a systematic time-dependent perturbation. [ABSTRACT FROM AUTHOR]

Wehave investigated the dynamical processesα-relaxation,local motions of the side-groups, and methyl group rotationsinpoly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) in the dry stateand in mixtures (at 70 wt% polymer concentration) with tetrahydrofuran(THF) and water, to address the question as to how these polymer motionsare affected by plasticizers interacting in different ways with thepolymer. Differential scanning calorimetry, dielectric spectroscopy,and neutron scattering techniques on labeled samples (with deuteratedsolvents to isolate the signal of the polymer component) have beencombined. The α-relaxation is drastically affected, with similarshifts of the glass-transition temperature for both solvents. Effectsof compositional heterogeneities and reduction of the fragility arealso observed. On the contrary, methyl-group dynamics are unaffectedby the presence of solvent. Regarding side-group local motions (β-relaxation),two kinds of componentsa slow and a fast onecouldbe identified in the dry state. On the basis of the spatial informationprovided by neutron scattering, a model for the geometry of the motionsinvolved in the fast component has been proposed. Adding solvent,this process would remain essentially unaltered, but the populationinvolved in the slower one would be reduced. With THF as solvent,this reduction would be complete, but with water it would be onlypartial. This could be attributed to rather heterogeneous distributionof water molecules in the polymer likely associated with the presenceof water clusters. Such a scenario would also explain the much morepronounced broadening of the glass-transition region observed forthe polymer in the aqueous mixture with respect to that induced byTHF. [ABSTRACT FROM AUTHOR]

The interaction between proteins and hydration water stabilizes protein structure and promotes functional dynamics, with water translational motions enabling protein flexibility. Engineered solvent-free protein-polymer hybrids have been shown to preserve protein structure, function, and dynamics. Here, we used neutron scattering, protein and polymer perdeuteration, and molecular dynamics simulations to explore how a polymer dynamically replaces water. Even though relaxation rates and vibrational properties are strongly modified in polymer coated compared to hydrated proteins, liquidlike polymer dynamics appear to plasticize the conjugated protein in a qualitatively similar way as do hydration-water translational motions. [ABSTRACT FROM AUTHOR]