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The static structure factor and the undulation dynamics of a solid-supported membrane stack have previously been calculated by Romanov and Ul'yanov [Romanov & Ul'yanov (2002). Phys. Rev. E, 66, 061701]. Based on this prior work, the calculation has been extended to cover the membrane dynamics, i.e. the intermediate scattering function as a Fourier transform of the van Hove correlation function of the membrane stack. Fortran code which calculates the intermediate scattering function for a membrane stack on a solid support is presented. It allows the static and dynamic scattering functions to be calculated according to the derivation of Romanov and Ul'yanov. The physical properties of supported phospholipid bilayers can be examined in this way and the results can be directly compared with results obtained from grazing-incidence neutron spin-echo spectroscopy experiments.

International journal of molecular sciences 23(13), 6969 (2022). doi:10.3390/ijms23136969 special issue: "Special Issue "Probing Protein Conformational Plasticity" / Special Issue Editor: Dr. Andreas Stadler, Guest Editor", Published by Molecular Diversity Preservation International, Basel

The use of technologies based on soft polymer particles represents an effective way to deliver target molecules with a specific function. To design a well-performing delivery system, it is fundamental to rationalize both the aggregation and the structural properties of such particles. In this study, we present the kinetic and structural characterization over time of poly(vinyl alcohol) (PVA) microgels obtained through a salting-out process in the presence of NaCl. We have analyzed how both the polymer and salt concentrations affect the aggregation process. The aggregation rate as well as the morphology and physico-chemical parameters, such as mass and chain density of the microgels, have been determined through static and dynamic light scattering and discussed in the framework of the diffusion-limited and reaction-limited colloid aggregation. Insights into the polymer chain arrangements and their dynamics have been gained by means of small-angle neutron scattering and neutron spin-echo measurements. As a result, it was found that NaCl induces a liquid phase separation in solution with the formation of spherical PVA microaggregates, which grow under a reaction-limited aggregation mechanism. The particles increase their size and compactness over time. Within the aggregate, the polymer chains are locally organized to form randomly oriented lamellae with a thickness of about 60 Å. The internal dynamics is a complex mixture of diffusion, Zimm dynamics, and possibly effects from crowding with the transition to a Rouse-like behavior. The microparticle preparation based on the salting-out process constitutes a novelty, if compared to the methods already existing and based on the use of chemical cross-linkers, and is a cheap and easy protocol that allows tuning both particle size and density by varying the salt concentration.

Ionic liquids are molten salts without an additional solvent and are discussed as innovative solvents and electrolytes in chemical processing and electrochemistry. A thorough microscopic understanding of the structure and ionic transport processes is essential for tailored applications. Here, we study the influence of "mild" nanoscopic confinement on the structure and diffusion properties of an ionic liquid, 1-ethyl-3-methylimidazolium acetate, using scattering techniques. The structure is analyzed by X-ray diffraction, while neutron backscattering spectroscopy is used for the study of the diffusion processes in these systems. Interpreting the diffusion processes in terms of a jump-diffusion model allowed us to deduce the confinement effects on the jump length and residence time, both increased at elevated temperatures in confinement. The applied "mild" confinement, which leaves room for 10-25 times the domain spacing, allows us to observe in great detail how the onset of domain distortion decelerates the dynamics.

Thermal fluctuations in soft matter systems take place on length- and time scales of nanometers and nanoseconds, accessible with neutron spin echo (NSE) spectroscopy. New developments in instrumentation as well as data treatment opened the door for new measurements with highest precision for subtle effects and gains in energy resolution. Superconducting main coils with optimized field shape have been installed at the J-NSE recently, providing better resolution and more flux for a given resolution. The magnetic shielding of the SNS-NSE provides unprecedented phase stability, which has been exploited to study tiniest effects of additives to membrane fluctuations in microemulsions. New software for data evaluation, DrSPINE provides the intermediate scattering function in an easy and robust way. Scientific highlights and trends in NSE spectroscopy will be discussed.

The continuous improvement of synthesis leads to a great variety in the internal architecture and functionality of colloidal hydrogels. A majority of envisioned applications use microgels as colloidal building blocks for layer formation at solid substrates. In this context, a fundamental understanding of the influence of these substrates on the internal structure and physical properties is essential. Especially, the nanomechanical properties of adsorbed poly(N-isopropylacrylamide) microgel particles are important for their application in cell cultivation, functional surface coatings, and others. Furthermore, these properties are closely related to the swelling behavior and the internal structure and dynamics of these microgels. However, the number of methods that are able to probe the viscoelasticity of adsorbed microgels over the entire vertical particle profile is limited. Grazing incidence neutron scattering techniques are suited to probe soft-matter samples with limited sample volumes at planar solid substrates and allow a resolution in the z-direction. We used neutron spin echo spectroscopy under grazing incidence to access fast thermal fluctuations (10–9 s) over the entire vertical particle profile. Atomic force microscopy nanoindentation was used to characterize the nanomechanical properties of adsorbed microgel particles prepared by batch and continuous monomer feeding methods. The resulting force maps revealed that batch microgels were “hard” and heterogeneous in their Young’s moduli, while the microgels from the continuous method were “soft” and homogeneous. Finally, neutron spin echo spectroscopy under grazing incidence revealed major differences in the vertical dynamic profile of both types of microgels.

Converting neutron scattering data to real-space time-dependent structures can only be achieved through suitable models, which is particularly challenging for geometrically disordered structures. We address this problem by introducing time-dependent clipped Gaussian field models. General expressions are derived for all space- and time-correlation functions relevant to coherent inelastic neutron scattering, for multiphase systems and arbitrary scattering contrasts. Various dynamic models are introduced that enable one to add time-dependence to any given spatial statistics, as captured e.g. by small-angle scattering. In a first approach, the Gaussian field is decomposed into localised waves that are allowed to fluctuate in time or to move, either ballistically or diffusively. In a second approach, a dispersion relation is used to make the spectral components of the field time-dependent. The various models lead to qualitatively different dynamics, which can be discriminated by neutron scattering. The methods of the paper are illustrated with oil/water microemulsion studied by small-angle scattering and neutron spin-echo. All available data - in both film and bulk contrasts, over the entire range of $q$ and $\tau$- are analyzed jointly with a single model. The analysis points to static large-scale structure of the oil and water domains, while the interfaces are subject to thermal fluctuations. The fluctuations have an amplitude around 6 nm and contribute to 30 % of the total interface area., Comment: The following article has been accepted by Journal of Chemical Physics. After it is published, it will be found at https://aip.scitation.org/journal/jcp/

Grazing Incidence Neutron Spin Echo Spectroscopy (GINSES) opens new possibilities for observing the thermally driven dynamics of macromolecules close to a rigid interface. The information about the dynamics can be retrieved as a function of scattering depth of the evanescent neutron wave, on the length scale in the range of some 10-100 nm. Using a classical neutron spin echo spectrometer with a laterally collimated beam, dynamics can be measured in grazing incidence geometry. We show examples of how the interface modifies the dynamics of microemulsions, membranes and microgels. Instrumental details and possible improvements for this technique will be presented. The key issue is the low intensity for dynamics measurements with an evanescent neutron wave. Conceptual questions how a specialised instrument could improve the experimental technique will be discussed.

Polymer-solvent interactions play a crucial role in the stimuli-responsive behaviour of polymer networks. They influence the swelling/deswelling behaviour as well as the dynamics of the polymer chains. Scattering experiments provide insight into the polymer-water interaction of poly(N-isopropylacrylamide) (PNIPAM) microgels cross-linked with N,N'-methylenebisacrylamide (BIS) in dried and humidified state. The water mobility is studied by means of neutron spin-echo spectroscopy and neutron backscattering spectroscopy. The residual water amount has been determined with Karl Fischer titration. For both degrees of humidification, the relaxation time of the water molecules is much larger than that of free water due to the strong interactions with the polymer network and is only weakly depending on temperature and length scale of observation. The possible influence of the water on methyl group rotations is discussed.

This work clarifies the self-similar dynamics of large polymer rings using pulsed-field gradient nuclear magnetic resonance and neutron spin echo spectroscopy. We find center of mass diffusion taking place in three dynamic regimes starting (i) with a strongly subdiffusive domain $⟨{r}^{2}(t){⟩}_{\mathrm{com}}\ensuremath{\sim}{t}^{\ensuremath{\alpha}}$ ($0.4\ensuremath{\le}\ensuremath{\alpha}\ensuremath{\le}0.65)$; (ii) a second subdiffusive region $⟨{r}^{2}(t){⟩}_{\mathrm{com}}\ensuremath{\sim}{t}^{0.75}$ that (iii) finally crosses over to Fickian diffusion. While the ${t}^{0.75}$ range previously has been found in simulations and was predicted by theory, we attribute the first to the effect of cooperative dynamics resulting from the correlation hole potential. The internal dynamics at scales below the elementary loop size is well described by ring Rouse motion. At larger scales the dynamics is self-similar and follows very well the predictions of the scaling models with preference for the self-consistent fractal loopy globule model.

β-casein undergoes a reversible endothermic self-association, forming protein micelles of limited size. In its functional state, a single β-casein monomer is unfolded, which creates a high structural flexibility, supposed to play a major role in preventing the precipitation of calcium phosphate particles. We characterize the structural flexibility in terms of nano-second molecular motions, depending on the temperature by quasi-elastic neutron scattering. Our major questions are: Does the self- association reduce the chain flexibility? How does the dynamic spectrum of disordered caseins differ from a compactly globular protein? How does the dynamic spectrum of β-casein in solution differ from that of a protein in hydrated powder states? We report on two relaxation processes on a nano-second and a sub-nano-second time scale for β-casein in solution. Both processes are analyzed by Brownian Oscillator model, by which the spring constant can be defined in the isotropic parabolic potential. The slower process, which is analyzed by neutron spin echo, seems a characteristic feature of the unfolded structure. It requires bulk solvent and is not seen in hydrated protein powders. The faster process, which is analyzed by neutron backscattering, has a smaller amplitude and requires hydration water, which is also observed with folded proteins in the hydrated state. The self-association had no significant influence on internal relaxation, and thus a β-casein protein monomer flexibility is preserved in the micelle. We derive spring constants of the faster and slower motions of β-caseins in solution, and compared them with those of some proteins in various states; folded or hydrated powder.

The preparation of poly(N-isopropylacrylamide) microgels via classical precipitation polymerization (batch method) and a continuous monomer feeding approach (feeding method) leads to different internal crosslinker distributions, i.e., from core–shell-like to a more homogeneous one. The internal structure and dynamics of these microgels with low and medium crosslinker concentrations are studied with dynamic light scattering and small-angle neutron scattering in a wide q-range below and above the volume phase transition temperature. The influence of the preparation method, and crosslinker and initiator concentration on the internal structure of the microgels is investigated. In contrast to the classical conception where polymer microgels possess a core–shell structure with the averaged internal polymer density distribution within the core part, a detailed view of the internal inhomogeneities of the PNIPAM microgels and the presence of internal domains even above the volume phase transition temperature, when polymer microgels are in the deswollen state, are presented. The correlation between initiator concentration and the size of internal domains that appear inside the microgel with temperature increase is demonstrated. Moreover, the influence of internal inhomogeneities on the dynamics of the batch- and feeding-microgels studied with neutron spin-echo spectroscopy is reported.

The molecular dynamics of the triphenylene-based discotic liquid crystal HAT6 is investigated by broadband dielectric spectroscopy, advanced dynamical calorimetry and neutron scattering. Differential scanning calorimetry in combination with X-ray scattering reveals that HAT6 has a plastic crystalline phase at low temperatures, a hexagonally ordered liquid crystalline phase at higher temperatures and undergoes a clearing transition at even higher temperatures. The dielectric spectra show several relaxation processes: a localized γ-relaxation at lower temperatures and a so called α2-relaxation at higher temperatures. The relaxation rates of the α2-relaxation have a complex temperature dependence and bear similarities to a dynamic glass transition. The relaxation rates estimated by Hyper DSC, Fast Scanning calorimetry and AC Chip calorimetry have a different temperature dependence than the dielectric α2-relaxation and follow the VFT-behavior characteristic for glassy dynamics. Therefore, this process is called α1-relaxation. Its relaxation rates show a similarity with that of polyethylene. For this reason, the α1-relaxation is assigned to the dynamic glass transition of the alkyl chains in the intercolumnar space. Moreover, this process is not observed by dielectric spectroscopy, which supports its assignment. The α2-relaxation is assigned to small scale translatorial and/or small angle fluctuations of the cores. The neutron scattering data reveal two relaxation processes. The process observed at shorter relaxation times is assigned to the methyl group rotation. The second relaxation process at longer time scales agree in the temperature dependence of its relaxation rates with that of the dielectric γ-relaxation.

Absrtract Adsorbed ethylene glycol based microgel particles on a silicon surface were studied. Neutron reflectometry (NR) and grazing incidence small-angle neutron scattering (GISANS) were performed to investigate their internal structure. Scattering experiments on soft matter systems such as adsorbed microgels often give only partial information about the inner structure of the polymer system. In this contribution, we discuss how the detailed inner structure of adsorbed microgel particles can be reconstructed by a combination of the specular Neutron Reflectivity (NR), Grazing Incidence Small Angle Neutron Scattering (GISANS), Atomic Force Microscopy (AFM) and a simulation in the framework of the Distorted Wave Born Approximation.

Surface-attached architectures of p(MEO2MA-co-OEGMA) copolymers are thermoresponsive PEG analogues with potential applications in biotechnology and medicine. In this respect, structure and dynamics of polymer brushes made of these copolymers are of great interest. In this work, the near surface dynamics of a p(MEO2MA-co-OEGMA) brush with a height of 250 nm was investigated with neutron spin echo spectroscopy under grazing incidence (GINSES) conditions. The brush dynamics was studied at two penetration depths of the neutrons. An influence of the distance from the confining surface on the collective diffusion was found. For the first time, the experiment demonstrates the feasibility of studying thermal fluctuations of macromolecules at a single planar liquid/solid interface by neutron spin echo spectroscopy under grazing incidence.

A general property of disordered proteins is their structural expansion that results in a high molecular flexibility. The structure and dynamics of bovine serum albumin (BSA) denatured by guanidinium hydrochloride (GndCl) were investigated using small-angle neutron scattering (SANS) and neutron spin-echo spectroscopy (NSE). SANS experiments demonstrated the relevance of intrachain interactions for structural expansion. Using NSE experiments, we observed a high internal flexibility of denatured BSA in addition to center-of-mass diffusion detected by dynamic light scattering. Internal motions measured by NSE were described using concepts based on polymer theory. The contribution of residue-solvent friction was accounted for using the Zimm model including internal friction (ZIF). Disulfide bonds forming loops of amino acids of the peptide backbone have a major impact on internal dynamics that can be interpreted with a reduced set of Zimm modes.

The high energy resolution of Neutron Spin Echo (NSE) Spectroscopy is perfectly suited for studying thermally driven membrane fluctuations in soft matter systems. Measuring membrane fluctuations allows determining the membrane bare bending rigidity of a membrane patch and is complementary to phase diagram measurements and Small Angle Neutron Scattering (SANS). The different aspects investigated with these three techniques will be elaborated, and some examples of how changes of the membrane composition will affect its elasticity. A recent topic in microemulsion membrane dynamics is the influence of a rigid interface to the surfactant membrane. Studies under grazing incidence conditions give a detailed insight into the effect of the interface to membrane elasticity.

Neutron spin echo (NSE) spectroscopy provides the ultimate energy resolution in quasi-elastic thermal and cold neutron scattering spectroscopy. A peculiarity of the SNS-NSE, the only NSE spectrometer at a pulsed beam port at the moment, is that the wavelength spread δλ/λ can be chosen during evaluation with an appropriate time channel binning. The Q-resolution can be adjusted in certain limits a posteriori by choosing the appropriate detector binning (as on a continuous source) and time channel binning. This can be exploited for samples with a strongly varying scattering function S (Q, t), e.g. due to Bragg peaks in a crystal or lamellar ordering in microemulsions. The data reduction software DrSpine allows for appropriate slicing and masking for this task. In this contribution the correlation function of microemulsions, thermodynamically stable mixtures of oil, water and surfactant, is measured with NSE on length scales where structural correlations are important, and data reduction strategies varying the Q-resolution by pixel and time channel grouping are discussed. The typical ”de Gennes narrowing” or structural narrowing is observed with a relaxation time proportional to I(Q). In these regions of strongly varying intensity it is shown that a too coarse grouping has an influence on the data reduction, with a broadened in Q of the apparent slowing down.

In this study, a protic ionic liquid (PIL), 2-Sulfoethylmethylammonium triflate [2-Sema][TfO] is considered as a potential new proton conducting electrolyte for future polymer membrane fuel cells capable of ambient air operation above 100 °C. The proton dynamics of the PIL with residual water are examined as a function of the hydration level on different time scales using pulsed field gradient nuclear magnetic resonance (PFG-NMR) and quasi-elastic neutron scattering (QENS). The separation of the different contributing relaxation processes enables a quantification of the proton fractions for the underlying hopping or vehicular motions. The hopping motion of the water in the time scale of picosecond and the vehicular motion in the time scale of nanosecond are detected by means of QENS. Such dynamic processes can be well described by the Chudley-Elliot jump model. This emphasised the presence of fixed jump lenghts. In the timescale of millisecond, the cooperative transport of the active protons of the acidic SO3H group and of the H2O molecules, as well as the vehicular transport of the PIL cations are detected by NMR. The different diffusion coefficients obtained by the NMR and QENS techniques are discussed in detail.

In this work, the structural properties of pristine and phosphoric acid doped poly(2,5-benzimidazole) membranes have been investigated by small angle neutron- and X-ray scattering, X-ray diffraction, polarized light microscopy and transmission electron microscopy. The results of our investigation demonstrate formation of crystalline regions with a fractal-like distribution upon aging on length scales ranging from sub-nm up to some micrometres. Transport properties of phosphoric acid doped poly(2,5-benzimidazole) membrane measured by pulsed-field-gradient nuclear magnetic resonance spectroscopy reveal proton self-diffusion coefficients of the system.

The structure and dynamic properties of poly(N-isopropylacrylamide) brushes at solid planar surfaces under good solvent conditions are studied. Polymer brushes with grafting densities in the concentrated and semidilute regime are prepared via surface-initiated atom transfer radical polymerization. The polymer brushes were removed from the substrates to determine the molar mass and molecular dispersity via size-exclusion chromatography to draw conclusions about the grafting density. The structure of the brushes was investigated with ellipsometry and neutron reflectometry measurements. We found an influence of the grafting density on the swelling properties of the poly(N-isopropylacrylamide) brushes. Furthermore, the brush dynamics at different neutron penetration depths was analyzed with neutron spin echo spectroscopy under grazing incidence. The evanescent intensity distribution was modeled with the BornAgain software package, which uses the distorted-wave Born approximation.

The present study focuses on quasielastic neutron scattering (QENS) of the proton dynamics in phosphoric acid (PA) inside the catalytic layer of high-temperature polymer electrolyte fuel cells (HT-PEFCs). The nanosecond proton dynamics is investigated on the local length scale around operating temperatures (300 K-430 K) using neutron backscattering spectroscopy. We have investigated the catalyst doped with different amounts of PA in order to understand the distribution of PA inside the layer. Three approaches are considered for the description of proton dynamics: the random jump diffusion model, distribution of diffusion constants and, finally, the trap model. Due to adsorption of the PA on the Pt particles the diffusion of protons in the catalytic layer is different in comparison to the bulk acid. The proton dynamics in the catalytic layer can be described by the random jump diffusion with traps. This diffusion is significantly slower than the diffusion of free PA; this also results in a lower conductivity, which is estimated from the obtained diffusion constant.

Domain motions in proteins are crucial for biological function. In the present manuscript, we present a neutron spin-echo spectroscopy (NSE) study of native bovine serum albumin (BSA) in solution. NSE allows to probe both global and internal dynamics of the BSA monomer and dimer equilibrium that is formed in solution. Using a model independent approach, we were able to identify an internal dynamic process in BSA that is visible in addition to global rigid-body diffusion of the BSA monomer and dimer mixture. The observed internal protein motion is characterised by a relaxation time of 43 ns. The overdamped Brownian oscillator was considered as an alternative analytical theory that was able to describe the internal process as first-order approximation. More detailed information on the physical nature of the internal protein motion was extracted from the q-dependent internal diffusion coefficients ΔDeff(q) that were detected by NSE in addition to global rigid-body translational and rotational diffusion. The ΔDeff(q) were interpreted using normal mode analysis based on the available crystal structures of the BSA monomer and dimer as structural test models. Normal mode analysis demonstrates that the observed internal dynamic process can be attributed to bending motion of the BSA dimer. The native BSA monomer does not show any internal dynamics on the time- and length-scales probed by NSE. An intermolecular disulphide bridge or a direct structural contact between the BSA monomers forms a localised link acting as a molecular hinge in the BSA dimer. The effect of that hinge on the observed motion of BSA in the used dimeric structural model is discussed in terms of normal modes in a molecular picture.

A novel set of superconducting main precession coils has been built and installed in the Julich-neutron spin-echo (J-NSE) spectrometer at the Heinz Maier-Leibnitz Zentrum (MLZ) in Garching. These unique new coils comprise a field-integral optimizing field shape, fringe field compensation, and high stability. They yield an enhancement of a factor of 2.5 in the intrinsic field-integral homogeneity, i.e., the resolution. The coil concept has been developed for the ESSENSE instrument proposal for the European Spallation Source. We report on the construction of and on the first results from the new superconducting neutron spin-echo spectrometer at the MLZ in Garching where the coils are the main part of a refurbishment of the J-NSE spectrometer after twenty years of operation.

Materials / Molecular Diversity Preservation International 13(6), 1474 (2020). doi:10.3390/ma13061474 special issue: "Special Issue "Soft and Nanostructured Materials for Energy Conversion" / Special Issue Editor: Prof. Dr. Patrizia Bocchetta, Guest Editor", Published by MDPI, Basel

Polymeric microgels with core–shell morphology provide promising properties for many applications such as controlled uptake and release of guest nanoparticles. In this work we investigated how the structure and dynamics of the core and the shell in the microgel are coupled using both experimental and computer simulation approaches. The studied core–shell model systems which consist of a collapsed core and a swollen shell (CCSS) and a swollen core and collapsed shell (SCCS) show a different behavior in both structure and dynamics. The intermediate scattering profiles obtained from neutron spin echo (NSE) spectroscopy of CCSS microgels show an initial fast decay similar to that of bare swollen microgels followed by a slow decay similar to that of a purely collapsed microgel. This is also reflected in mesoscale hydrodynamic simulations using the multiparticle collision dynamics method. In the case of CCSS microgels, the decay rate of the intermediate scattering functions shows a crossover from collective dif...

The present study focuses on structural and dynamical properties of the catalytic layer for high-temperature polymer electrolyte fuel cells (HT-PEFC). The catalytic layer is a composite material containing nanoporous carbon, poly(tetrafluoroethylene) (PTFE) and platinum (Pt) nanoparticles. The structure of the catalyst is investigated using small angle X-ray scattering (SAXS) following different preparation steps of the electrodes: pure carbon support, platinum/carbon (Pt/C) powder and finally, complete catalytic layer. The structural properties of the Pt/C powder containing different amounts of Pt are discussed along with the size distribution of Pt particles and their arrangement on the surface of the carbon support. Following the preparation sequence of the catalytic layer based on the Pt/C powders the electrodes with different final Pt loadings are analyzed in details. Investigation of the structure of the catalytic layer is accompanied by the study of nanosecond dynamics of the phosphoric acid (PA) in the catalytic layer containing different amount of Pt by means of neutron backscattering spectroscopy. The structure of the catalytic layer is mostly determined by the structure of the catalytic powder and does not vary significantly with Pt loading in the electrode. The behavior of the PA is sensitive to the Pt content in the electrode.

Microgels are flexible entities with a number of properties which can be tailored for a variety of applications. For redox-sensitive PNIPAM-based microgels involved in this study, the size and effective charge of microgels can be manipulated by electrochemical means. The electrochemical switching is implemented via interaction of redox-sensitive counterions (hexacyanoferrates: HCF) with oppositely charged (cationic) thermoresponsive microgels. Effects on the internal dynamics upon uptake of HCF and increased hydrophobicity with temperature are investigated with neutron spin echo spectroscopy. The polymer segmental dynamics is well described by the Zimm model. Unbalanced charges (in absence of HCF) apparently shorten the polymer length acting like confined discontinuity points (pinning). This effect vanishes in the presence of HCF. The ability of multivalent ferricyanides to bind several monovalent polymer charges at the same time produces an apparent secondary network. This effective bridging makes the dy...

Poly(N-isopropylacrylamide) microgel particles were prepared via a "classical" surfactant-free precipitation polymerization and a continuous monomer feeding approach. It is anticipated that this yields microgel particles with different internal structures, namely a dense core with a fluffy shell for the classical approach and a more even crosslink distribution in the case of the continuous monomer feeding approach. A thorough structural investigation of the resulting microgels with dynamic light scattering, atomic force microscopy and small angle neutron scattering was conducted and related to neutron spin echo spectroscopy data. In this way a link between structural and dynamic features of the internal polymer network was made.

The tunable properties of stimuli-responsive polymer coatings at solid surfaces inspire their application in different electronic devices, as functional tissue in regenerative medicine or even for drug release. Especially promising is the exploitation of thermo-responsive poly-N-isopropylacrylamide (PNIPAM) microgels as cell-surface adhesion control systems. In this context we present a morphological and internal structure investigation of thermo-responsive PNIPAM microgels adsorbed on a silicon-surface. By means of Grazing Incidence Small-Angle Neutron Scattering and Atomic Force Microscopy the swelling behaviour of adsorbed PNIPAM microgel particles and the influence of the N,N′-methylenebisacrylamide (cross-linker) content in the microgel network on the layer formation were investigated. The influence of the surface confinement on the responsivity of the polymer system is discussed.

Methods for efficient data extraction for neutron spin-echo spectroscopy with multipixel area detectors and – at a pulsed neutron source – multiple time-of-flight wavelength bins are presented., Neutron spin-echo spectrometers with a position-sensitive detector and operating with extended time-of-flight-tagged wavelength frames are able to collect a comprehensive set of data covering a large range of wavevector and Fourier time space with only a few instrumental settings in a quasi-continuous way. Extracting all the information contained in the raw data and mapping them to a suitable physical space in the most efficient way is a challenge. This article reports algorithms employed in dedicated software, DrSpine (data reduction for spin echo), that achieves this goal and yields reliable representations of the intermediate scattering function S(Q, t) independent of the selected ‘binning’.

We recently introduced a concept of a neutron waveguide for enhancing the intensity of the evanescent wave inside the sample next to the waveguide. This allows for studying tribology mechanisms of soft matter/solid interfaces using grazing incidence neutron spin echo spectroscopy (GINSES) and small angle neutron scattering (GISANS). In several experiments, the number of layer structures in the waveguide was chosen to be 1 and 3. Both waveguides increased the scattering intensity of GISANS (and GINSES) experiments successfully, while the simpler waveguide produced additional small angle scattering that was not rationalized so far. The roughness on the 100 nm and µm length scale may produce additional background at smaller angles. Comparisons are drawn using the Distorted Wave Born Approximation (DWBA), which is especially useful for the roughness discussion.

In this manuscript, we are investigating the contribution of dynamic membrane properties of phospholipid membranes to coherent scattering signals under grazing incidence. Spectroscopic measurements under grazing incidence can provide useful insight into the properties of biological membranes, however, they are often impeded by weak signals. By using grazing-incidence small-angle neutron scattering (GISANS) to identify a dynamic scattering contribution, we are able to independently corroborate the existence of a previously found dynamic mode, now measured by grazing-incidence neutron spin echo spectroscopy (GINSES). Additionally, by increasing the speed of measurement compared to GINSES from several days to hours, we were able to explore the temperature behavior of this mode in phospholipid membranes. These dynamic modes of the membranes show a wavelength of around 700 &Aring, in-plane of the membrane and are most pronounced around 37 ∘C and strongly decrease at lower temperatures below 25 ∘C before vanishing at 20 ∘C. We therefore speculate that they may be linked to biologically relevant functions of the membranes themselves. To our knowledge, this is the first report of an investigation of that membrane mode by means of GISANS.

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 dw and the Hausdorff dimension df have been determined on the length scales covered in the neutron scattering experiments.

We observe a change in the segmental dynamics of hydrogels based on hydrophobically modified ethoxylated urethanes (HEUR) when hydrophobic magnetite nanoparticles (MNPs) are embedded in the hydrogels. The dynamics of the nanocomposite hydrogels is investigated using dielectric relaxation spectroscopy (DRS) and neutron spin echo (NSE) spectroscopy. The magnetic nanoparticles within the hydrophobic domains of the HEUR polymer network increase the size of these domains and their distance. The size increase leads to a dilution of the polymers close to the hydrophobic domain, allowing higher mobility of the smallest polymer blobs close to the “center”. This is reflected in the decrease of the activation energy of the β-process detected in the DRS data. The increase in distance leads to an increase of the size of the largest hydrophilic polymer blobs. Therefore, the segmental dynamics of the largest blobs is slowed down. At short time scales, i.e. 10−9 s < τ < 10−3 s, the suppression of the segmental dynamics is reflected in the α-relaxation processes detected in the DRS data and in the decrease of the relaxation rate Γ of the segmental motion in the NSE data with increasing concentration of magnetic nanoparticles. The stepwise (multi-stage) freezing of the small blobs is only visible for the pure hydrogel at low temperatures. On the other hand, the glass transition temperature (Tg) decreases upon increasing the MNP loading, indicating an acceleration of the segmental dynamics at long time scales (τ ∼ 100 s). Therefore, it would be possible to tune the Tg of the hydrogels by varying the MNP concentration. The contribution of the static inhomogeneities to the total scattering function Sst(q) is extracted from the NSE data, revealing a more ordered gel structure than the one giving rise to the total scattering function S(q), with a relaxed correlation length ξNSE = (43 ± 5) Å which is larger than the fluctuating correlation length from a static investigation ξSANS = (17.2 ± 0.3) Å.

The adsorption of ethylene glycol (EG) based microgel particles at silicon surfaces was studied. Monodisperse p-MeO2MA-co-OEGMA microgel particles were synthesized by precipitation polymerization. Translational and inner dynamics of p-ME3O5 and p-ME3O26 microgels in bulk were investigated by dynamic light scattering (DLS) and neutron spin echo spectroscopy in transmission geometry (NSE). Here, cooperative diffusion and Zimm type dynamics were observed. The inner dynamics of these microgel particles in adsorbed state was explored by neutron spin echo spectroscopy under grazing incidence (GINSES). The reported GINSES experiments demonstrate the feasibility of these surface sensitive measurements. It indicates a slowing down of the inner dynamics in the vicinity of the substrate. At increasing distance from the substrate, the relaxation is comparable to the bulk.

High Temperature Polymer Electrolyte Fuel Cells (HT-PEFCs) have been studied with quasielastic neutron scattering, which gives access to the proton diffusion in the fuel cell on local length- and timescales. So far, the different components such as the proton conducting membrane and the electrode layers have been studied separately. Here we show that also operating fuel cells can be investigated and the proton diffusion can be measured under real working conditions. The proton diffusion during power production is compared to that “at rest” but at elevated temperatures.

High resolution neutron spin echo (NSE) spectroscopy is one of the most powerful techniques to study the dynamics of soft matter. For NSE spectroscopy at a pulsed source, the data reduction and analysis present new challenges and opportunities as compared to a steady (reactor) source experiment. We present a data reduction framework which extracts information of all time channels and detector images, grouping the results into S(q,t) for a series of q and t, also across different instrument settings (different q). This strategy helps to get the most out of an experiment (a set of scans at different diffraction angles) and also provides appropriate reporting on the quality of the evaluation. The same software is also capable of dealing with reactor source data, where no time-of-flight information is present.