Search

By using time-of-flight neutron spectroscopy with polarization analysis, we have separated coherent and incoherent contributions to the scattering of deuterated tetrahydrofuran in a wide scattering vector (Q)-range from meso- to inter-molecular length scales. The results are compared with those recently reported for water to address the influence of the nature of inter-molecular interactions (van der Waals vs hydrogen bond) on the dynamics. The phenomenology found is qualitatively similar in both systems. Both collective and self-scattering functions are satisfactorily described in terms of a convolution model that considers vibrations, diffusion, and a Q-independent mode. We observe a crossover in the structural relaxation from being dominated by the Q-independent mode at the mesoscale to being dominated by diffusion at inter-molecular length scales. The characteristic time of the Q-independent mode is the same for collective and self-motions and, contrary to water, faster and with a lower activation energy (≈1.4 Kcal/mol) than the structural relaxation time at inter-molecular length scales. This follows the macroscopic viscosity behavior. The collective diffusive time is well described by the de Gennes narrowing relation proposed for simple monoatomic liquids in a wide Q-range entering the intermediate length scales, in contraposition to the case of water.

We have combined X-ray diffraction, neutron diffraction with polarization analysis, small-angle neutron scattering (SANS), neutron elastic fixed window scans (EFWS), and differential scanning calorimetry (DSC) to investigate polymeric blends of industrial interest composed by isotopically labeled styrene–butadiene rubber (SBR) and polystyrene (PS) oligomers of size smaller than the Kuhn length. The EFWS are sensitive to the onset of liquid-like motions across the calorimetric glass transition, allowing the selective determination of the “microscopic” effective glass transitions of the components. These are compared with the “macroscopic” counterparts disentangled by the analysis of the DSC results in terms of a model based on the effects of thermally driven concentration fluctuations and self-concentration. At the microscopic level, the mixtures are dynamically heterogeneous for blends with intermediate concentrations or rich in PS, while the sample with highest content of the fast SBR component looks as dynamically homogeneous. Moreover, the combination of SANS and DSC has allowed determining the relevant length scale for the α-relaxation through its loss of equilibrium to be ≈30 Å. This is compared with the different characteristic length scales that can be identified in these complex mixtures from structural, thermodynamical, and dynamical points of view because of the combined approach followed. We also discuss the sources of the non-Gaussian effects observed for the atomic displacements and the applicability of a Lindemann-like criterion in these materials. We thank Marc Couty for fruitful discussions and Karine Vernay (Michelin Advanced Research) for dSBR synthesis. The authors acknowledge Grant PID2021-123438NB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”, as well as financial support of Eusko Jaurlaritza (code: IT1566-22) and from the IKUR Strategy under the collaboration agreement between Ikerbasque Foundation and the Materials Physics Center on behalf of the Department of Education of the Basque Government. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

We have disentangled the contributions to the glass transition as observed by differential scanning calorimetry (DSC) on simplified systems of industrial interest consisting of blends of styrene–butadiene rubber (SBR) and polystyrene (PS) oligomer. To do this, we have started from a model previously proposed to describe the effects of blending on the equilibrium dynamics of the α-relaxation as monitored by broadband dielectric spectroscopy (BDS). This model is based on the combination of self-concentration and thermally driven concentration fluctuations (TCFs). Considering the direct insight of small-angle neutron scattering on TCFs, blending effects on the α-relaxation can be fully accounted for by using only three free parameters: the self-concentration of the components φselfSBR and φselfPS) and the relevant length scale of segmental relaxation, 2Rc. Their values were determined from the analysis of the BDS results on these samples, being that obtained for 2Rc ≈ 25Å in the range usually reported for this magnitude in glass-forming systems. Using a similar approach, the distinct contributions to the DSC experiments were evaluated by imposing the dynamical information deduced from BDS and connecting the component segmental dynamics in the blend above the glass-transition temperature Tg (at equilibrium) and the way the equilibrium is lost when cooling toward the glassy state. This connection was made through the α-relaxation characteristic time of each component at Tg, τg. The agreement of such constructed curves with the experimental DSC results is excellent just assuming that τg is not affected by blending., A. Alegría, A. Arbe, and J. Colmenero acknowledge the Grant PID2021-123438NB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”, as well as financial support of Eusko Jaurlaritza, codes IT-1175-19 and IT-1566-22, and from the IKUR Strategy under the collaboration agreement between Ikerbasque Foundation and the Materials Physics Center on behalf of the Department of Education of the Basque Government., Open Access funding provided by University of Basque Country.

The main challenge for the preparation of protein single-chain nanoparticles (SCNPs) is the natural complexity of these macromolecules. Herein, we report the suitable conditions to produce “neat” bovine serum albumin (BSA) single-chain nanoparticles (SCNPs) from partially denatured BSA, which involves denaturation in urea and intramolecular cross-linking below the overlap concentration. We use two disuccinimide ester linkers containing three and six methylene spacer groups: disuccinimidyl glutarate (DSG) and disuccinimidyl suberate (DSS), respectively. Remarkably, the degree of internal cross-linking can be followed simply and efficiently via 1H NMR spectroscopy. The associated structural changes─as probed by small-angle neutron scattering (SANS)─reveal that the denatured protein has a random-like coil conformation, which progressively shrinks with the addition of DSG or DSS, thus allowing for size control of the BSA-SCNPs with radii of gyration down to 5.4 nm. The longer cross-linker exhibits slightly more efficiency in chain compaction with a somewhat stronger size reduction but similar reactivity at a given cross-linker concentration. This reliable method is applicable to a wide range of compact proteins since most proteins have appropriate reactive amino acids and denature in urea. Critically, this work paves the way to the synthesis of “neat”, biodegradable protein SCNPs for a range of applications including nanomedicine., The authors acknowledge the financial support received from the IKUR Strategy under the collaboration agreement between the Ikerbasque Foundation and the Materials Physics Center on behalf of the Department of Education of the Basque Government. Financial support by MCIN/AEI/10.13039/ 501100011033 and “ERDF−A way of making Europe” (grant PID2021-123438NB-I00), Eusko Jaurlaritza−Basque Government (grantIT-1566-22) and the Gipuzkoako Foru Aldundia, Programa Red Gipuzkoana de Ciencia, Tecnología e Innovación (2021-CIEN-000010-01) is gratefully acknowledged. A.I. thanks MICINN for a Personal Técnico de Apoyo contract (PTA2017-14359-I).

The development of simple, efficient, and robust strategies affording the facile construction of biomimetic organocatalytic nano-objects is currently a subject of great interest. Herein, a new pathway to artificial organocatalysts based on partially collapsed individual soft nano-objects displaying useful and diverse biomimetic catalytic functions is reported. Single-chain polymer nanoparticles endowed with enzyme-mimetic activity synthesized following this new route display (i) a relatively extended morphology under good solvent conditions, as revealed by small angle neutron scattering and coarse-grained molecular dynamics simulation results, (ii) multiple, compartmentalized, and accessible catalytic sites in which borane catalytic units are retained via B···O interactions, and (iii) unprecedented reductase and polymerase enzyme-mimetic properties. © 2013 American Chemical Society., Financial support from the projects MAT2012-31088 (MINECO) and IT-654-13 (GV) is acknowledged. I. P.-B. acknowledges CSIC for her JAE-PREDOC grant. This work is based on has been supported by the European Commission under the 7th Framework Programme through the 'Research Infrastructures' action of the 'Capacities' Programme, NMI3-II Grant number 283883.

In this work, high-resolution inelastic neutron scattering (INS) has been used to provide novel insights into the properties of confined poly(ethylene oxide) (PEO) chains. Two limits have been explored in detail, namely, single-layer 2D-polymer intercalation into graphite oxide (GO) and surface polymer adsorption onto thermally reduced and exfoliated graphite oxide, that is, graphene (G) sheets. Careful control over the degree of GO oxidation and exfoliation reveals three distinct cases of spatial confinement: (i) subnanometer 2D-confinement; (ii) frustrated absorption; and (iii) surface immobilization. Case (i) results in drastic changes to PEO conformational (800–1000 cm–1) and collective (200–600 cm–1) vibrational modes as a consequence of a preferentially planar zigzag (trans–trans–trans) chain conformation in the confined polymer phase. These changes give rise to peculiar thermodynamic behavior, whereby confined PEO chains are unable to either crystallize or display a calorimetric glass transition. In case (ii), GO is thermally reduced resulting in a disordered pseudo-graphitic structure. As a result, we observe minimal PEO absorption owing to a dramatic reduction in the abundance of hydrophilic groups inside the distorted graphitic galleries. In case (iii), the INS data unequivocally show that PEO chains adsorb firmly onto the G sheets, with a substantial increase in the population of gauche conformers. Well-defined glass and melting transitions associated with the confined polymer phase are recovered in case (iii), albeit at significantly lower temperatures than those of the bulk., The support by Spanish Ministry of Education (MAT2007-63681), Basque Government (IT-436-07), Gipuzkoako Foru Aldundia (2011-CIEN-000085-01) and UK Science and Technology Facilities Council is gratefully acknowledged. F.B.B. acknowledges financial support by BERC-MPC.

Mimicking the substrate specificity and catalytic activity of enzymes is of great interest for different fields (e.g., chemistry, biology, nanomedicine). Enhanced reaction rates using artificial, enzyme-mimic catalysts based on a variety of molecular structures and nanoentities (e.g., macrocyclic compounds, star and helical polymers, dendrimers) have been previously reported. However, examples of enzyme-sized soft entities displaying substrate specificity are certainly scarce. Herein, we report the synthesis and characterization of single-chain nanoparticles based on metallo-folded polymer chains containing complexed Cu(II) ions showing catalytic specificity during the oxidative coupling of mixtures of chemically related terminal acetylene substrates. This work paves the way for the easy and efficient construction of other Pd-, Ni-, Co-, Fe-, Mn-, or Mo-containing soft nanoentities approaching the substrate specificity of natural enzymes for a variety of organic reactions. © 2014 American Chemical Society., Financial support from the Projects MAT2012-31088 (MINECO), T-654-13 (GV) and S-PE13UN034 (GV) is acknowledged. A. S.-S. thanks the Ph.D. grant support of Basque Government. This work has been supported by the European Commission under the 7th Framework Programme through the “Research Infra-structures” action of the “Capacities” Programme, NMI3-II Grant Number 283883.

Recent efforts, fostered by a pioneering work by us, have shown the of multiple steps in the recovery of equilibrium of glasses. Jin and McKenna raise concerns regarding the validity of such scenario alleging that the multiple recovery steps would be an artifact arising from poor temperature control in the oven used for isothermal glass equilibration. We critically discuss Jin and McKenna arguments from both the viewpoints of scrutinizing previous literature data and that of the temperature control in the oven. In doing so, we provide compelling arguments that Jin and McKenna conjectures are unjustified and point out the need for efforts to describe glass dynamics significantly below the glass transition temperature, Tg, by accounting for the presence of different relaxation mechanisms active in glass equilibration.

QENS/WINS 2022 – 15th Edition of the QENS Series and 10th of the WINS Workshops., This work is focused on atomistic molecular dynamics (MD) simulations of water carried out at 300 K. The main goal is to better understand the experimental results of the coherent dynamic structure factor S(Q,ν) of D2O that were obtained by means of neutron scattering with polarization analysis and previously reported by us [A. Arbe et al. Phys. Rev. Res. 2, 022015 (2020)]. From the simulations, we have calculated the coherent dynamic structure factor in the time domain S(Q,t) as well as its selfand distinctcontributions. We have also calculated S(Q,t) corresponding to a H2O sample. The main results obtained are: (i) The Q-independent relaxation process identified in S(Q,ν) in the mesoscopic range (Q0-mode) is the responsible of the restructuring of the hydrogen bond (HB) network at times shorter than that corresponding to the molecular diffusion; (ii) the vibrational contribution identified at high frequency in S(Q,ν) corresponds to a hydrodynamic-like mode propagating in an elastic medium (fixed HB bonding pattern); (iii) in the crossover range from mesoscopic to intermolecular scales, diffusion also progressively contributes to the decay of density fluctuations; (iv) MD-simulations suggest that it would be basically impossible to measure S(Q,ν,) of H2O in the mesoscopic range with the current neutron scattering capabilities., We acknowledge the Grant PID2021-123438NB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. We also acknowledge financial support of Eusko Jaurlaritza, code: and IT1566-22, as well as from the IKUR Strategy under the collaboration agreement between Ikerbasque Foundation and the Materials Physics Center on behalf of the Department of Education of the Basque Government.

QENS/WINS 2022 – 15th Edition of the QENS Series and 10th of the WINS Workshops., We present a combined study by quasielastic neutron scattering (QENS), differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS) on poly(tetrahydrofuran-co-epichlorohydrin) copolymers, to see how their composition can be used to tune their crystallizability and to elucidate the impact of this factor on the dynamical properties. QENS reveals a strong effect on the local dynamics upon cooling down, where the local motions of a sample that remains in the supercooled state at lower temperatures are less Gaussian and slower than those in a sample that crystallizes a few degrees below. This can be attributed to the enhancement of local heterogeneities in the former, which could be a determining factor preventing crystallization., We acknowledge the Grant PID2021-123438NB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. We also acknowledge the financial support of Eusko Jaurlaritza, code : IT-1566-22 and from the IKUR Strategy under the collaboration agreement between Ikerbasque Foundation and the Materials Physics Center on behalf of the Department of Education of the Basque Government.

QENS/WINS 2022 – 15th Edition of the QENS Series and 10th of the WINS Workshops., We investigate by neutron scattering and calorimetry a mixture of styrene-butadiene rubber (SBR) and a commercial resin. The neat materials present a large dynamic contrast, having SBR a much lower glass-transition temperature than the resin. The focus is to exploit neutron scattering selectivity in an isotopically labelled sample where deuterated SBR is the majority component. This direct insight into the resin atomic motions within the mixture allows determining the ‘microscopic’ glass transition of the resin in the presence of the a priori much more mobile SBR. This transition takes place in the vicinity of the initial calorimetric glass transition temperature, mainly dictated by the majority component., We acknowledge the Grant PID2021-123438NB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. We also acknowledge financial support of Eusko Jaurlaritza, code: and IT1566-22, as well as from the IKUR Strategy under the collaboration agreement between Ikerbasque Foundation and the Materials Physics Center on behalf of the Department of Education of the Basque Government.

The origin of the QENS conferences series dates back to 1992, when its first edition—organized by Barbara Gabrys, Spencer Howells, Colin Carlile and Phil Salmon—was celebrated in Windsor, UK. Accor...

The diffusion of polymer chains in miscible polymer blends with large dynamic asymmetry—those where the two blend components display very different segmental mobility—is not well understood yet. In the extreme case of the blend system of poly(ethylene oxide) (PEO) and poly(methyl methacrylate)(PMMA), the diffusion coefficient of PEO chains in the blend can change by more than five orders of magnitude while the segmental time scale hardly changes with respect to that of pure PEO. This behavior is not observed in blend systems with small or moderate dynamic asymmetry as, for instance, polyisoprene/poly(vinyl ethylene) blends. These two very different behaviors can be understood and quantitatively explained in a unified way in the framework of a memory function formalism, which takes into account the effect of the collective dynamics on the chain dynamics of a tagged chain., The author gratefully acknowledges the financial support of the Basque Government, project code: IT-654-13 and the Ministerio de Economía y Competitividad, project code: MAT2015-63704-P (MINECO/FEDER, UE).

This article belongs to the Section Polymer Physics and Theory., We present fully atomistic molecular dynamics simulations on polyisobutylene (PIB) in a wide temperature range above the glass transition. The cell is validated by direct comparison of magnitudes computed from the simulation and measured by neutron scattering on protonated samples reported in previous works. Once the reliability of the simulation is assured, we exploit the information in the atomic trajectories to characterize the dynamics of the different kinds of atoms in PIB. All of them, including main-chain carbons, show a crossover from Gaussian to non-Gaussian behavior in the intermediate scattering function that can be described in terms of the anomalous jump diffusion model. The full characterization of the methyl-group hydrogen motions requires accounting for rotational motions. We show that the usually assumed statistically independence of rotational and segmental motions fails in this case. We apply the rotational rate distribution model to correlation functions calculated for the relative positions of methyl-group hydrogens with respect to the carbon atom at which they are linked. The contributions to the vibrational density of states are also discussed. We conclude that methyl-group rotations are coupled with the main-chain dynamics. Finally, we revise in the light of the simulations the hypothesis and conclusions made in previously reported neutron scattering investigations on protonated samples trying to address the origin of the dielectric β-process., This research was funded by the Basque Government, code: IT-1175-19 and the Ministerio de Economía y Competitividad code: PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE).

This article belongs to the Special Issue Single-Chain Polymer Nanotechnology., The folding of certain proteins (e.g., enzymes) into perfectly defined 3D conformations via multi-orthogonal interactions is critical to their function. Concerning synthetic polymers chains, the “folding” of individual polymer chains at high dilution via intra-chain interactions leads to so-called single-chain nanoparticles (SCNPs). This review article describes the advances carried out in recent years in the folding of single polymer chains into discrete SCNPs via multi-orthogonal interactions using different reactive chemical species where intra-chain bonding only occurs between groups of the same species. First, we summarize results from computer simulations of multi-orthogonally folded SCNPs. Next, we comprehensively review multi-orthogonally folded SCNPs synthesized via either non-covalent bonds or covalent interactions. Finally, we conclude by summarizing recent research about multi-orthogonally folded SCNPs prepared through both reversible (dynamic) and permanent bonds., This research was funded by Gipuzkoako Foru Aldundia -Programa Red Gipuzkoana de Ciencia, Tecnología e Innovación 2019-, grant number 2019-CIEN-000050-01; Basque Government, grant number IT-1175-19; and MCIU/AEI/FEDER, UE, grant number PGC2018-094548-B-I00.

We present an investigation by molecular dynamics (MD)-simulations of the coherent dynamic structure factor, S(Q, t) (Q: momentum transfer), of liquid water at the mesoscale (0.1 Å−1 ≤ Q ≤ Qmax) [Qmax ≈ 2 Å−1: Q-value of the first maximum of the static structure factor, S(Q), of water]. The simulation cell—large enough to address the collective properties at the mesoscale—is validated by direct comparison with recent results on the dynamic structure factor in the frequency domain obtained by neutron spectroscopy with polarization analysis [Arbe et al., Phys. Rev. Res. 2, 022015 (2020)]. We have not only focused on the acoustic excitations but also on the relaxational contributions to S(Q, t). The analysis of the MD-simulation results—including the self- and distinct contributions to the diffusive part of S(Q, t)—nicely explains why the relaxation process hardly depends on Q in the low Q-range (Q ≤ 0.4 Å−1) and how it crosses over to a diffusion-driven process at Q ≈ Qmax. Our simulations also give support to the main assumptions of the model used to fit the experimental data in the above mentioned paper. The application of such a model to the simulation S(Q, t) data delivers (i) results for the relaxation component of S(Q, t) in agreement with those obtained from neutron experiments and (ii) longitudinal and transverse hydrodynamic-like components with similar features than those identified in previous simulations of the longitudinal and transverse current spectra directly. On the other hand, in general, our MD-simulations results of S(Q, t) qualitatively agree with the viscoelastic transition framework habitually used to describe inelastic x-ray scattering results., We acknowledge the grant PGC2018-094548-B-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe,” as well as Grant Code IT-1175-19 funded by Eusko Jaurlaritza (Basque Government).

This article belongs to the Special Issue Polymers and Soft Matter: From Synthesis to Structure & Dynamics., We present a combined study by quasielastic neutron scattering (QENS), dielectric and mechanical spectroscopy, calorimetry and wide-angle X-ray diffraction on single-chain nano-particles (SCNPs), using the corresponding linear precursor chains as reference, to elucidate the impact of internal bonds involving bulky cross-links on the properties of polymer melts. Internal cross-links do not appreciably alter local properties and fast dynamics. This is the case of the average inter-molecular distances, the β-relaxation and the extent of the atomic displacements at timescales faster than some picoseconds. Contrarily, the α-relaxation is slowed down with respect to the linear precursor, as detected by DSC, dielectric spectroscopy and QENS. QENS has also resolved broader response functions and stronger deviations from Gaussian behavior in the SCNPs melt, hinting at additional heterogeneities. The rheological properties are also clearly affected by internal cross-links. We discuss these results together with those previously reported on the deuterated counterpart samples and on SCNPs obtained through a different synthesis route to discern the effect of the nature of the cross-links on the modification of the diverse properties of the melts., This research was funded by the Basque Government, code: IT-1175-19 and the Ministerio de Economía y Competitividad code: PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE).

Meeting Reports.

The recent measurement of what could be interpreted as the signature of hydrogen bond switching in 2-ethyl-1-hexanol monoalcohol [J. Mol. Liq 312(2020)113441] has open again the question about the impact of hydrogen bonds dynamics on the dielectric response of hydrogen bonded liquids. A systematic study of the shear and dielectric response on a series of diverse glass forming systems shows that when comparing the timescales of the dielectric α relaxation and the shear structural relaxation, the dielectric relaxation of 2-ethyl-1,3-hexanediol and glycerol polyalcohols (PA) do not conform to the general trend. Instead, the observed dielectric relaxation for these PAs correlates with a low frequency mode (slower than structural relaxation) emerging in the shear response. We interpret this finding as a signature of the contribution of hydrogen bonds to the relaxation of the polarization. The dielectric response of PAs would then contain overlapped and non-resolved contributions from structural (alpha) relaxation and hydrogen bond dynamics, causing the slowing down of the overall signal relative to the structural relaxation observed by shear measurements., We acknowledge financial support from the projects: PGC2018- 094548-B-I00 by the Spanish Ministry “Ministerio de Ciencia, Innovación y Universidades” (MICINN-Spain) and FEDER-UE; and IT-1175-19 by the Basque Government.

In this short review we summarize the outcome of the large amount of effort made during the past decade from both the experimental and the theoretical point of view in order to understand the effect of blending on the segmental dynamics in polymers. Each of the two families of models proposed—one based on thermally activated concentration fluctuations, the other on chain connectivity effects—account for each of the two main experimental observations: the broadening of the component response with respect to that of the homopolymer and the dynamic heterogeneity, respectively. The complementarity of these approaches, their main achievements and failures, are critically revised. We also include recent results on blends of components with very different mobilities. In the neighbourhood of the glass-transition of the slow polymer, the dynamics of the other component seem to be confined within the frozen chains. We suggest possible ingredients and new routes to be considered in order to elaborate more predictive theoretical frameworks for all these phenomena., Support from the European Commission NoE SoftComp, Contract NMP3-CT-2004-502235, the projects MAT2004-01017 and 9/UPV00206.215-13568/2001, the Spanish Ministerio de Educacion y Ciencia (Grant No. CSD2006-53) and ‘Donostia International Physics Center’ is also acknowledged.

The existence of an ideal glass and the resolution to the Kauzmann paradox is a long-standing open question in materials science. To address this problem, we exploit the ability of glasses with large interfacial area to access low energy states. We submit aggregates of spheres of a polymeric glass former to aging well below their glass transition temperature, Tg; and characterize their thermodynamic state by calorimetry, and the vibrational density of state (VDOS) by inelastic neutron scattering (INS). We show that, when aged at appropriate temperatures, glassy spheres attain a thermodynamic state corresponding to an ideal glass in time scales of about one day. In this state, the boson peak, underlying the deviation from the Debye level of the VDOS, is essentially suppressed. Our results are discussed in the framework of the link between the macroscopic thermodynamic state of glasses and their vibrational properties., D. C. and J. C. acknowledge financial support from the Project No. PGC2018-094548-B-I00 (MICINN-Spain and FEDER-UE) and the Project No. IT-1175-19 (Basque Government).

We address the dynamics of isofrictional bimodal polyisoprene (PI) blends and emphasize the effect of concentration and topology of the short component on the dynamics of the long-chain component. The experiments were performed on blends of long well-entangled linear chains with shorter linear and star-branched chains varying systematically the concentration of the short component (additive). Small-angle neutron scattering showed that the conformation of the long chains does not change either with concentration or with the additive topology. Applying different spectroscopic techniques, we studied the terminal times of both the long chain and the additives. Thereby, the dielectric and viscoelastic terminal times for the long-chain dynamics, as well as the diffusion times deduced from pulsed-field-gradient (PFG)-NMR measurements, follow the same scaling behavior as a function of the volume fraction of the long chains (φL). For the case of the linear additive, the scaling τL ∼φL is observed in the full concentration range covered (0.1 ≤ φL ≤ 1). In the case of the star additives, deviations from this scaling law are evident at φL ≲ 0.4. The zero-shear viscosity scales as η0 ∼φL3 for φL ≳ 0.4. Deviations are observed at lower values of φL for both additive topologies. On the other hand, the terminal relaxation time of the short chain or the arm retraction time for the stars obtained from dielectric spectroscopy (DS) is only weakly affected by blending and stays nearly constant over the full concentration range. However, the diffusion times of both types of additives depend significantly on φL. Finally, measuring the dynamic structure factor by neutron spin echo (NSE), we directly observe the process of constraint removal at the molecular scale. These results are discussed in terms of the different theoretical approaches available. Thereby, the nearly quantitative agreement of the rheological results with the Read extension of the Viovy theory for long-chain volume fractions φL ≥ 0.5 is emphasized. On the other hand, the low φL results cannot be accounted for. Also, predictions of the tension equilibration mechanism leading to an enhanced φL-dependence are not supported by our data., Authors from the Materials Physics Center (San Sebastian)́ gratefully acknowledge the financial support of the Basque Government, code IT-1175-19, and the Ministerio de Ciencia, Innovacion y Universidades, code PGC2018-094548-B-I00 ́ (MCIU/AEI/FEDER, UE). P.M.d.M. gratefully acknowledges the financial support provided by the SoftComp Consortium for a research visit at Forschungszentrum Jülich, Germany

By means of the recent implementation of neutron polarization analysis on a wide-angle time-of-flight spectrometer, we have been able to separately measure coherent and incoherent dynamic structure factors of heavy water with sub-meV resolution in a wide scattering vector (Q) range. The observed decorrelation of collective fluctuations at mesoscales hardly depends on Q. In the crossover towards intermolecular scales, the coherent dynamics is nicely described by the convolution of a Q-independent mode and diffusion, in addition to collective excitations., Authors from the Materials Physics Center (San Sebastián) gratefully acknowledge the financial support of the Eusko Jaurlaritza, code IT-1175-19, and the Ministerio de Economía y Competitividad code PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE).

Applying small-angle neutron scattering (SANS) on isotopically labeled samples, we have characterized the thermally driven concentration fluctuations (TCFs), one of the main factors in the phenomenology of blend dynamics, in mixtures of styrene–butadiene rubber (SBR) and oligomers of polystyrene (PS) with different compositions. This system displays a large dynamic asymmetry and is thus a good model to explore the tunability of properties of interest in the rubber industry. The SANS experiments, complemented with neutron diffraction with polarization analysis, have allowed one to determine the UCST behavior of the blend and establish its phase diagram. We find a close vicinity of the spinodal and vitrification lines for intermediate concentrations and samples rich in PS. This induces the freezing of the correlation length for TCF when decreasing the temperature and also has an impact on the reported dielectric response of these mixtures. Furthermore, we have deduced the relevant length scale for segmental relaxation from the comparison of SANS and dielectric results. The values found (≈1.5–2 nm) are close to the Kuhn lengths of the components. The relevance of nanometric length scales in this system could also be tentatively attributed to an underlying nanodomain structure associated with the segregation of phenyl rings and main chains, supported by complementary X-ray diffraction experiments., The authors gratefully acknowledge the financial support of the Basque Government, code: IT-1175-19, and the Ministerio de Economı́a y Competitividad, code: PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE). This work was based on experiments performed at KWS-2 and DNS (Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany) and was supported by the European Commission under the 7th Framework Programme through the “Research Infrastructures” action of the “Capacities” Programme, NMI3-II Grant Number 283883.

This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Spain (2020,2021)., Combining neutron scattering and fully atomistic molecular dynamics simulations allows unraveling structural and dynamical features of polymer melts at different length scales, mainly in the intermolecular and monomeric range. Here we present the methodology developed by us and the results of its application during the last years in a variety of polymers. This methodology is based on two pillars: (i) both techniques cover approximately the same length and time scales and (ii) the classical van Hove formalism allows easily calculating the magnitudes measured by neutron scattering from the simulated atomic trajectories. By direct comparison with experimental results, the simulated cell is validated. Thereafter, the information of the simulations can be exploited, calculating magnitudes that are experimentally inaccessible or extending the parameters range beyond the experimental capabilities. We show how detailed microscopic insight on structural features and dynamical processes of various kinds has been gained in polymeric systems with different degrees of complexity, and how intriguing questions as the collective behavior at intermediate length scales have been faced., This research was funded by the Basque Government, code: IT-1175-19 and the Ministerio de Economía y Competitividad code: PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE).

The impact of purely intramolecular cross-linking on the properties of a polymer melt is studied by neutron diffraction and quasielastic incoherent and coherent neutron scattering on a system composed exclusively of single-chain nanoparticles. As a reference, a parallel study is presented on the melt of the linear precursor chains’ counterpart. Associated with structural heterogeneities provoked by the internal compartmentalization due to cross-links, a dramatic slowing down of the relaxation of density fluctuations is observed at intermediate length scales., We acknowledge the financial support of the Basque Government (Code No. IT-1175-19) and the Ministerio de Economía y Competitividad [Code No. PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE)]. This work was based on experiments performed at the FOCUS instrument operated by the Swiss spallation neutron source SINQ (Paul Scherrer Institute, Villigen, Switzerland) and SPHERES [Heinz–Maier–Leibnitz Zentrum (MLZ), Garching, Germany] and was supported by the European Commission under the 7th Framework Programme through the “Research Infrastructures” action of the “Capacities” Programme, NMI3-II (Grant No. 283883).

More than 100 years after Debye proposed his model for the dielectric relaxation of monoalcohols (MA), some fundamental questions about their dynamics and its relation with the supramolecular structures created by hydrogen bonding remain not fully understood. The recent detection of the dynamics of hydrogen bonded aggregates by techniques other than dielectric spectroscopy is leading to novel insights and opening new questions. In particular it was recently reported that the shear response of some MA present three relaxation components, at variance with their apparent bimodal dielectric response. We show by mixing an archetype MA with LiCl that both shear and dielectric measurements are consistent with the presence of three separated contributions. Results are discussed in the more general context of MAs with non-exponential slow dielectric relaxations. In particular, we propose the recently reported third process as the origin of the unusual broadening of the Debye-like dielectric relaxation of some MAs., We acknowledge financial support from the projects: PGC2018-094548-B-I00 by the Spanish Ministry “Ministerio de Ciencia, Innovación y Universidades” (MICINN-Spain) and FEDER-UE; and IT-1175-19 by the Basque Government.

This article belongs to the Special Issue Single-Chain Polymer Nanotechnology., We investigate the effect of intra-molecular cross-links on the properties of polymer bulks. To do this, we apply a combination of thermal, rheological, diffraction, and neutron spin echo experiments covering the inter-molecular as well as the intermediate length scales to melts of single-chain nano-particles (SCNPs) obtained through ‘click’ chemistry. The comparison with the results obtained in a bulk of the corresponding linear precursor chains (prior to intra-molecular reaction) and in a bulk of SCNPs obtained through azide photodecomposition process shows that internal cross-links do not influence the average inter-molecular distances in the melt, but have a profound impact at intermediate length scales. This manifests in the structure, through the emergence of heterogeneities at nanometric scale, and also in the dynamics, leading to a more complex relaxation behavior including processes that allow relaxation of the internal domains. The influence of the nature of the internal bonds is reflected in the structural relaxation that is slowed down if bulky cross-linking agents are used. We also found that any residual amount of cross-links is critical for the rheological behavior, which can vary from an almost entanglement-free polymer bulk to a gel. The presence of such inter-molecular cross-links additionally hinders the decay of density fluctuations at intermediate length scales., This research was funded by the Basque Government, code: IT-1175-19 and the Ministerio de Economía y Competitividad code: PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE).

Single-chain polymer nanoparticles (SCNPs) are soft nano-objects consisting of uni-macromolecular chains collapsed to a certain degree by intramolecular crosslinking. The similarities between the behaviour of SCNPs and that of intrinsically disordered proteins suggest that SCNPs in concentrated solutions can be used as models to design artificial micro-environments, which mimic many of the general aspects of cellular environments. In this work, the self-assembly into SCNPs of an amphiphilic random copolymer, composed by oligo(ethylene glycol)methyl ether methacrylate (OEGMA) and 2-acetoacetoxy ethyl methacrylate (AEMA), has been investigated by means of the dielectric relaxation of water. Direct evidence of segregation of the AEMA repeating units is provided by comparison with the dielectric relaxation of water in similar solutions of the linear hydrophilic polymer, P(OEGMA). Furthermore, the results of comparative studies with similar water solutions of an amphiphilic block copolymer forming multi-chain micelles support the single-chain character of the self-assembly of the random copolymer. The overall obtained results highlight the suitability of the dielectric spectroscopy to confirm the self-assembly of the amphiphilic random copolymers into globular like core–shell single-chain nanoparticles at a concentration well above the overlap concentration., The authors thank the financial support of the Basque Government, project: IT-1175-19, and the Ministerio de Ciencia, Innovación y Universidades, project: PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE).

We present a small-angle neutron scattering (SANS) and neutron spin echo investigation on the structure and dynamics of irreversible single-chain nanoparticles (SCNPs) in dilute solution. SCNPs are ultra-small soft nano-objects obtained by intramolecular folding/collapse of individual linear polymer chains (precursors). SANS has demonstrated the compaction of macromolecules upon creation of internal cross-links, although their conformation is far from a globular topology. To describe the dynamic structure factor of the SCNPs in solution, we have taken into account their dual polymer/nanoparticle character and applied theoretical approximations based on the Zimm model. The study reveals relaxation of internal degrees of freedom but clearly slowed down with respect to the precursor counterparts. This effect is attributed to the internal friction associated to the compartmentation in domains within the macromolecule. We discuss the structural and dynamical similarities of SCNPs with disordered proteins, in particular with intrinsically disordered proteins. The high internal friction in both cases seems to be associated to the existence of internal domains., The authors gratefully acknowledge the financial support of the Basque Government, code: IT-1175-19 and the Ministerio de Economı́a y Competitividad code: PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE). This work is based on experiments performed at KWS-2 and J-NSE (Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany) and has been supported by the European Commission under the 7th Framework Programme through the “Research Infrastructures” action of the “Capacities” Programme, NMI3-II grant number 283883.

The supramolecular self-assembly of monocarboxydecyl-terminated dimethylsiloxane oligomer is investigated and characterized by combining different experimental methods. Thermodynamic properties were accessed by temperature-modulated differential scanning calorimetry, and two subambient phase transitions were identified. Fourier transform infrared spectroscopy gave access to the main molecular entities involved in these phase transitions. Diffraction experiments using small-angle X-ray scattering and wide-angle X-ray scattering evidenced the development of two distinct well-ordered sub-10 nm structures, each associated with one of the thermal transitions, without any indication of long-range atomic order. All the results point to the self-assembly of the oligomeric dimers below 230 K, giving rise to supramolecular structures involving new H-bonding interactions. A further structure is developed below 205 K by the assembly of the alkane part of the molecules in an arrangement of hexagonally packed cylinders. Dielectric relaxation experiments evidenced both the pronounced effect of the lowest temperature transition on the H-bond network fluctuations and the very effective segregation of dimethylsiloxane at lower temperatures. Moreover, we found that the structured liquid presents a rubber-like mechanical behavior in the temperature range 150-200 K, where dimethylsiloxane phase remains amorphous, and at lower temperatures a glassy nanostructured material is found., The authors gratefully acknowledge the financial support of the Basque Government code: IT-654-13 and the Ministerio de Economia y Competitividad code: MAT2015-63704-P (MINECO/FEDER, UE).

Searching for the ideal glass transition, we exploit the ability of glassy polymer films to explore low energy states in remarkably short time scales. We use 30 nm thick polystyrene (PS) films, which in the supercooled state basically display the bulk polymer equilibrium thermodynamics and dynamics. We show that in the glassy state, this system exhibits two mechanisms of equilibrium recovery. The faster one, active well below the kinetic glass transition temperature (Tg), allows massive enthalpy recovery. This implies that the ‘fictive’ temperature (Tf) reaches values as low as the predicted Kauzmann temperature (TK) for PS. Once the thermodynamic state corresponding to Tf = TK is reached, no further decrease of enthalpy is observed. This is interpreted as a signature of the ideal glass transition., The authors acknowledge the University of the Basque Country and Basque Country Government (Ref. No. IT-654-13 (GV)), Depto. Educacion, Universidades e investigacion; and Spanish Government (Grant No. MAT2015-63704-P, (MINECO/FEDER, UE)) for their financial support.

We report a microscopic observation of the time-dependent dynamic tube dilation process on isofrictional bidisperse melts. By applying neutron spin echo (NSE) and dielectric techniques on blends of long polyisoprene (PI) chains with short PI additives with different topology, we access the dynamics of the tube dilation process on a molecular scale. The time-dependent tube dilation is directly revealed by NSE as an additional time dependence of the dynamic structure factor in the local reptation regime. We identify the characteristic time of tube dilation as the terminal time of the additive., Authors from the Materials Physics Center (San Sebastián) gratefully acknowledge the financial support of the Basque Government, code IT-1175-19, and the Ministerio de Economía y Competitividad, code PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE). P. M. M. gratefully acknowledges the financial support provided by the SoftComp Consortium for a research visit at Forschungszentrum Jülich, Germany.

One of the key areas in nanomedicine is the use of nanometer-sized materials as nanocarriers for therapeutic and diagnostic (theranostic) purposes. In particular, nanoparticles (NPs) have attracted a considerable attention due to their small size that confers the ability to be transported more easily through the body. Ideally, nanocarriers would be biocompatible and biodegradable so the involvement of soft matter-based NPs is an interesting approach. Folding individual polymer chains to single-chain nanoparticles (SCNPs) endows the resulting soft nano-objects with promising prospects for drug encapsulation and subsequent controlled delivery. In this work, we report on the preparation and preliminary (in vitro) evaluation of Povidone SCNPs as potential drug delivery nanocarriers. We select Povidone (polyvinylpyrrolidone) as a water-soluble polymer with a large commercial use in medicine, which is biocompatible and non-antigenic as well as safe for oral and topical applications. For evaluation of Povidone SCNPs as drug delivery nanocarriers, we select two drugs with reported anti-cancer activity: (i) Cisplatin, a widely used hydrophilic anticancer agent for treatment of a variety of cancer cells; and (ii) Lovastatin, a lipophilic compound with in vitro anti-proliferative, pro-apoptotic and anti-invasive effects in different cancer cell lines. After showing release of these drugs from Povidone SCNPs, we demonstrate that these nanoparticles can be rendered fluorescent in combination with functional aggregation-induced emission (AIE) fluorophore molecules paving the way to the potential development of theranostic Povidone SCNPs.

Single-chain polymer nanoparticles (SCNPs) are individual intrachain cross-linked polymer chains -typically with a size < 20 nm-which can be considered as emerging building blocks for bionanotechnology. Very recently, surfaces displaying molecular recognition motifs have been decorated with brushes of responsive SCNPs and transformed into a cross-linked polymeric monolayer, thus paving the way to controlled nanofilm formation around bioactive surfaces (e.g., virus capsids). In this work, the structural properties of brushes formed by topologically complex SCNPs on flat surfaces are investigated as a function of SCNP size and intrachain cross-linking degree. A detailed comparison is performed to the structural features displayed by brushes of other macromolecular architectures, thus revealing the tunable, unique properties of brushes comprising elastic SCNPs. Remarkably, this work paves the way to the potential design of brushes of SCNPs with drug delivery characteristics based on stimulus-mediated rupture of intrachain cross-links., Financial support by the Spanish Ministry “Ministerio de Economia y Competitividad” MAT2015-63704-P, (MINECO / FEDER, UE) and the Basque Government, IT-654-13, is acknowledged.

The conformation of single-chain nanoparticles (SCNPs) in the presence of linear polystyrene crowding molecules has been studied by small-angle neutron scattering under contrast-matching of the crowders. A model describing the scattering of aggregating polydisperse SCNPs has been developed, resulting in the determination of the potentially squeezed size of the individual SCNPs within aggregates, their local chain statistics, and the average aggregation number, as a function of crowding. Two different crowders, of low and high molecular weights, are shown to have a different effect: while long chains tend to impede their aggregation above their overlap concentration, short ones are found to mediate depletion interactions leading to aggregation. Self-imposed crowding within the aggregates has a similar impact on chain conformation independently of the crowding of the surrounding medium. Our results are compared to recent simulations and shall contribute to the microscopic understanding of the phase behavior of soft intrinsically disordered nano-objects and in particular the effect of crowding on biomacromolecules., Funding by DIPC, the European Network of Excellence Softcomp, the Basque Government (code: IT1175-19), and the Ministerio de Ciencia, Innovación y Universidades [code: PGC2018-094548-B-I00 (MICINN/ FEDER, UE)] is gratefully acknowledged. This work is based on experiments performed at KWS-2 [Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany] and has been supported by the European Commission under the 7th Framework Programme through the “Research Infrastructures” action of the “Capacities” Programme, NMI3-II Grant Number 283883.

Access to completely deuterated single-chain nanoparticles (dSCNPs) has remained an unresolved issue. Herein, the first facile and efficient procedure to produce dSCNPs is reported, which comprises: i) the use of commercially available perdeuterated cyclic ether monomers as starting reagents, ii) a ring-opening copolymerization process performed in bulk to produce a neat dSCNP precursor, iii) a standard azidation reaction to decorate this precursor with azide moieties, and iv) a facile intramolecular azide photodecomposition step carried out under UV irradiation at high dilution providing with highly valuable, completely deuterated soft nano-objects from the precursor. dSCNPs are used to investigate by means of neutron-scattering measurements the form factor (radius of gyration, scaling exponent) of polyethylene oxide (PEO) chains in nanocomposites with different amounts of dSCNPs. Moreover, to illustrate the possibilities offered by the synthetic route disclosed in this communication for potential applications, the significant reduction in viscosity observed in a pure melt of polyether-based single-chain nanoparticles when compared to a melt of the corresponding linear polymer chains is shown., Financial support by the Spanish Ministry “Ministerio de Economia y Competitividad,” MAT2015‐63704‐P (MINECO/FEDER, UE), the Basque Government, IT‐654‐13, and the Gipuzkoako Foru Aldundia, Programa Red Guipuzcoana de Ciencia, and Tecnología e Innovación 2017 (RED 101/17) is acknowledged.

Single-chain polymer nanoparticles (SCNPs) obtained through chain collapse by intramolecular cross-linking are attracting increasing interest as components of all-polymer nanocomposites, among other applications. We present a dielectric relaxation study on the dynamics of mixtures of poly(vinyl methyl ether) (PVME) and polystyrene (PS)-based SCNPs with various compositions. Analogous dielectric measurements on a miscible blend of PVME with the linear precursor chains of the SCNPs are taken as reference for this study. Both systems present completely different behaviors: While the blend with the linear precursor presents dynamics very similar to that reported for PVME/PS miscible blends, in the PVME/SCNP mixtures there are an appreciable amount of PVME segments that are barely affected by the presence of SCNPs, which nearly vanishes only for mixtures with high SCNP content. Interestingly, in the frame of a simple two-phase system, our findings point towards the existence of a SCNP-rich phase with a constant PVME fraction, regardless of the overall concentration of the mixture. Moreover, the dynamics of the PVME segments in this SCNP-rich phase display an extreme dynamic heterogeneity, a signature of constraint effects., This research was funded by Eusko Jaurlaritza project code: IT-654-13 and the Ministerio de Economía y Competitividad project code: MAT2015-63704-P (MINECO/FEDER, UE).

By means of intramolecular folding/collapse of individual polymer chains (precursors), ultra-small soft nano-objects called single-chain nano-particles (SCNPs) can be synthesized. Here we present a combination of scattering techniques [small angle X-Ray and neutron scattering (SAXS and SANS), neutron spin echo (NSE) and dynamic light scattering (DLS)] to investigate the structure and dynamics of SCNPs in solution and their linear precursors as reference. Coarse-grained molecular dynamics (MD) simulations have also been carried out to complement this study. The application of SANS and SAXS has proved the compaction of the macromolecules upon creation of internal cross-links. However, the SCNPs obtained by different routes exhibit a far from globular topology in good solvent. Regarding the dynamics, we report on the first experimental investigation of the dynamic structure factor of SCNPs in solution. It reveals a clear impact of internal cross-links through (i) a reduction of the translational diffusion coefficient and (ii) an important slowing down of the internal modes. The data have been analyzed in terms of theoretical approximations based on the Zimm model. Both, structurally and dynamically, SCNPs show striking resemblances with intrinsically disordered proteins: similar scaling properties reflecting sparse morphologies and an extremely high internal friction.

The incorporation of high-molecular-weight poly(ethylene oxide) (PEO) in the nanopores of resorcinol–formaldehyde resin nanoparticles (RNPs) leads to the suppression of polymer crystallization, changes in the chain conformation, and a noticeable slowdown of the two dielectric relaxations that reflect the segmental and local PEO dynamics. Both relaxations are significantly slower than those corresponding to bulk PEO. These results are independent of the pore characteristics of the different RNP materials. The segmental relaxation shows a crossover at ca. 220 K in its temperature dependence from non-Arrhenius to Arrhenius-like behavior on cooling. These results suggest the occurrence of limited cooperativity at low temperatures due to the enhancement of long-living hydrogen bonding between PEO and RNP pore walls., The authors gratefully acknowledge the support of the Spanish Ministry “Ministerio de Economıa y Competitividad ́ ”, code: MAT2015-63704-P (MINECO/FEDER, UE), the Basque Government (IT-654-13), and the UK Science and Technology Facilities Council for the provision of beam time on the TOSCA spectrometer. P.P. acknowledges a PhD research contract from UCM (BE45/10). F.F.A. and S.R. acknowledge financial support from the UK Science and Technology Facilities Council.

Nowadays there are clear evidences from both experiments and MD-simulations proving that the chain Rouse modes correlation functions are non-exponential in unentangled polymer blends and also in pure polymers at low temperature (with respect to that of the glass transition Tg) even for the long wavelengths modes where local potentials and chain stiffness should not play any role. In a recent paper [S. Arrese-Igor et al, Phys. Rev. Lett. 113, 078302 (2014)] it has been proposed that this non-exponential behavior depends on the ratio between the so-called Rouse time - i.e., the characteristic time of the slowest chain mode relaxation - and the time scale of the α-relaxation. This parameter is in some way ‘universal’ in the meaning that it can encode many different experimental situations. In this paper, we show that this behavior can be quantitatively explained in the framework of a theoretical approach based on: (i) a generalized Langevin equation (GLE) formalism and (ii) a memory function which takes into account the effect of collective dynamics on the chain dynamics of a tagged chain and which was constructed taking inspirations from the original ideas of the reptation model proposed by de Gennes.

The mechanical characterization of rubber materials at the frequencies relevant for the tire function during braking (about 1 MHz) is extremely challenging. On the other hand, dielectric relaxation experiments provide a suitable tool for the analysis of relaxation phenomena over a broad frequency range with high sensitivity. Here we show that by analyzing dielectric relaxation experiments in the framework of a simple model the mechanical relaxation of simplified industrial systems based on mixtures of a styrene butadiene rubber (SBR) with a polystyrene oligomer can be anticipated, at least for the SBR rich mixtures that are more relevant for development of tire polymers. The model needs the description of the dielectric and mechanical relaxation processes of the single components of the mixture and uses concepts and ideas introduced in the past for describing the segmental dynamics of athermal polymer blends. The model description of dielectric relaxation experiments on the mixtures provides a quantification of the thermal fluctuations of concentration in the blends. With this input, the mechanical relaxation of the mixtures are calculated using well established equations for the mechanical properties of composite materials. The present approach should be helpful in a rational design of the rubber material depending on the specific requirements., The authors gratefully acknowledge the financial support of the Basque Government project: IT-1175-19 and the Ministerio de Ciencia, Innovación y Universidades, project: PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE).

The impact of supramolecular aggregate formation on the shear viscosity response of hydrogen bonded liquids was investigated. In particular, we study the shear mechanical response of several monoalcohols showing exponential and non-exponential shape dielectric Debye-like relaxation. In addition to the structural relaxation, distinctive of the glass transition, and the terminal crossover to pure viscous flow, characteristic of simple liquid flow, systematic analysis of complex viscosity curves evidences the presence of an additional intermediate process between those two. While the recovery of pure viscous flow would reflect the complete relaxation of the hydrogen bonded aggregates the intermediate process correlates with the rotational dynamics of hydroxyl groups, potentially caused by the breaking of individual hydrogen bonds., We acknowledge the support of the following research projects MAT2015-63704-P (MINECO/FEDER, UE) supported by the Spanish Ministry “Ministerio de Economía y Competitividad” and IT-654-13 Supported by the Basque Government.

We apply the methodology and concepts developed over the past years for the study of segmental dynamics on miscible polymer blends to the investigation of a blend made of styrene-butadiene rubber (SBR) and an oligomer of polystyrene (PS) as an example of a simplified industrial system. In this way we obtain detailed information about the segmental dynamics of both components within the blend. To this end, a judicious combination of broad-band dielectric spectroscopy (BDS) and quasi-elastic neutron scattering (QENS) results on deuterium-labeled blends was required. Difficulties on the comparison between isotopically different samples arose due to changes in polymer microstructure associated with the obtention of deuterated polymers. Nevertheless, the strategy for data analysis developed in this work made it possible to readily resolve the components' segmental dynamics of the investigated mixtures. It was found that Gaussian distributions of the components' effective glass-transition temperatures provide a very good description of all the experimental data collected in the SBR/PS (50/50 wt %) mixtures over the whole accessible temperature range, not only by BDS and QENS but also those obtained by differential scanning calorimetry and by neutron elastic fixed window scan experiments., The authors gratefully acknowledge the financial support of the Basque Government code: IT-654-13 and the Ministerio de Economía y Competitividad code: MAT2015-63704-P (MINECO/FEDER, UE). This work is based on experiments performed at DNS(41,42) operated at Jülich Centre for Neutron Science (JCNS), TOFTOF,(43) operated by the Technische Universität München, and SPHERES (Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany) and has been supported by the European Commission under the seventh Framework Programme through the “Research Infrastructures” action of the “Capacities” Programme, NMI3-II Grant 283883.

In this chapter, we first introduce the main concepts related to quasielastic neutron scattering (QENS) techniques and the way they can be connected to dielectric spectroscopy (DS). This is not obvious, because they access different correlation functions. The dielectric permittivity measured by DS reflects the orientational dynamics of the molecular dipoles in a very broad temperature/frequency range, while, thanks to the transfer of energy (\(\hbar \omega \)) and momentum (\(\hbar Q\)) dependence of the measured intensities, QENS provides information about nuclear positions with space/time resolution. In particular, QENS on protonated samples follows the self-correlation function of the hydrogens. Next, we describe the general findings from both techniques relative to the \(\alpha \)-relaxation in glass-forming systems. From the comparison of the results, we define a Q-value (\(Q^\star \)) at which the timescale of the \(\alpha \)-process measured by QENS and DS become similar and compile its values from the literature for diverse systems ranging from polymers and low-molecular weight glass-forming systems to water and water solutions. The results are discussed in a phenomenological way in terms of structural and dynamic parameters. Thereafter, we show that in the case of a simple diffusive process, a simple approach based on molecular hydrodynamics and a molecular treatment of DS allows expressing \(Q^\star \) in terms of a many-body magnitude—a generalized Kirkwood parameter —and a single-molecule magnitude—the hydrodynamic radius. The application of these ideas to liquid water and water solutions is presented. Finally, we explore the possibility of extending this kind of treatment to the more complex subdiffusive case.