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The relaxation dynamics of dipropylene glycol and tripropylene glycol (nPG—n=2,3) water solutions on the nPG-rich side has been studied by broadband dielectric spectroscopy and differential scanning calorimetry in the temperature range of 130–280K. Two relaxation processes are observed for all the hydration levels; the slower process (I) is related to the α relaxation of the solution whereas the faster one (II) is associated with the reorientation of water molecules in the mixture. Dielectric data for process (II) at temperatures between 150 and 200K indicate the existence of a critical water concentration (xc) below which water mobility is highly restricted. Below xc, nPG-water domains drive the dielectric signal whereas above xc, water-water domains dominate the dielectric response at low temperatures. The results also show that process (II) at low temperatures is due to local motions of water molecules in the glassy frozen matrix. Additionally, we will show that the glass transition temperatures (Tg) for aqueous PG, 2PG, and 3PG solutions do not extrapolate to ∼136K, regardless of the extrapolation method. Instead, we find that the extrapolated Tg value for water from these solutions lies in the neighborhood of 165K. ; Three of the authors (S.C., G.A.S., and A.A.) acknowledge the support of the University of Basque Country and the Basque Government: Project No. UPV/EHU, 00206.215 13568/2001 and the Spanish Ministry of Education Project No. MAT2004-01017. Another author (J.S.) is a Royal Swedish Academy of Sciences Research fellow supported by a grant from Kunt and Alice Wallenberg Foundation. The Swedish Research Council and the Swedish Foundation for Strategic Research are also acknowledged for financial support. REFERENCES ; Peer reviewed

Water dynamics in solutions with biological or non-biological solutes has been intensely studied when both components (solvent and solute) are amorphous. Here, we apply broadband dielectric spectroscopy combined with calorimetric measurements to analyze the dynamics of the aqueous solutions tri-propylene glycol (3PG) and ε-poly (lysine) (ε-PLL), after their water becomes semi-crystalline. Various crystallization levels were explored by conducting experiments with different annealing times at temperatures above the glass transition temperature (Tg). We find that the amount of ice depends on both the time and temperature of the annealing, and that this, in turn, affects Tg and dynamics of the amorphous part of the samples. However, it should be noted that the observed differences are relatively small for the degrees of crystallinity we have studied (up to about 26 wt% of the water). This also implies that the dynamic crossover of the water relaxation from a high temperature non-Arrhenius behavior to a low temperature Arrhenius dependence is unaffected by the partial crystallization and still occurs as a single crossover at the calorimetric Tg. Thus, we cannot detect two different crossovers, as commonly observed for other types of two-component systems, such as two glass formers. ; Financial support through the Grant Nos. PID2019-104650 GB-C21 (MICINN-Spain and FEDER-UE), LINKB20012 (CSIC), and IT1566-22 (Basque Government) are gratefully acknowledged, as well as the Grant No. 2019-04020 from the Swedish Research Council. ; We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). ; Peer reviewed

The dynamics of water confined in cement materials is still a matter of debate in spite of the fact that water has a major influence on properties such as durability and performance. In this study, we have investigated the dynamics of water confined in Portland cement (OPC) at different curing ages (3 weeks and 4 years after preparation) and at three water-to-cement ratios (w/c, 0.3, 0.4 and 0.5). Using broadband dielectric spectroscopy, we distinguish four different dynamics due to water molecules confined in the pores of different sizes of cements. Here we show how water dynamics is modified by the evolution in the microstructure (maturity) and the w/c ratio. The fastest dynamics (processes 1 and 2, representing very local water dynamics) are independent of water content and the degree of maturity whereas the slowest dynamics (processes 3 and 4) are dependent on the microstructure developed during curing. Additionally, we analyze the differences regarding the water dynamics when confined in synthetic C-S-H gel and in the C-S-H of Portland cement. ; Support from the Basque Government under the ELKARTEK Program is acknowledged (Super - KK2016/00060). S.C also acknowledges the Ministerio de Economia y Competitividad", code: MAT2015-63704-P (MINECO/FEDER, UE). H.J. acknowledges the Swedish research council FORMAS and the EU Climate KIC project Building Technologies Acceleration for financial support. ; Peer Reviewed

Characterizing the segmental dynamics of proteins, and intrinsically disordered proteins in particular, is a challenge in biophysics. In this study, by combining data from broadband dielectric spectroscopy (BDS) and both depolarized (DDLS) and polarized (PDLS) dynamic light scattering, we were able to determine the dynamics of a small peptide [ε-poly(lysine)] in water solutions in two different conformations (pure β-sheet at pH = 10 and a more disordered conformation at pH = 7). We found that the segmental (α-) relaxation, as probed by DDLS, is faster in the disordered state than in the folded conformation. The water dynamics, as detected by BDS, is also faster in the disordered state. In addition, the combination of BDS and DDLS results allows us to confirm the molecular origin of water-related processes observed by BDS. Finally, we discuss the origin of two slow processes (A and B processes) detected by DDLS and PDLS in both conformations and usually observed in other types of water solutions. For fully homogeneous ε-PLL solutions at pH = 10, the A-DLS process is assigned to the diffusion of individual β-sheets. The combination of both techniques opens a route for understanding the dynamics of peptides and other biological solutions. ; Financial support through the Grant No. PID2019-104650GB-C21 (Spanish Government "Ministerio de Ciencia, Innovacion y Universidades"), LINKB20012 (CSIC), Project No. IT-1175-19 (Basque Government) are gratefully acknowledged. ; Peer reviewed

The relaxation dynamic of ribose and deoxyribose water solutions at different concentrations has been studied by broadband dielectric spectroscopy and differential scanning calorimetry in the temperature range of 150–250 K. Two relaxation processes are observed for all the hydration levels; the slower (process I) is related to the relaxation of the whole solution whereas the faster one (process II) is associated with the reorientation of water molecules in the mixture. As for other polymeric water solutions, dielectric data for process II indicate the existence of a critical water concentration above which water mobility is less restricted. According to these results, attenuated total reflectance Fourier transform infrared spectroscopy measurements of the same sugar solutions showed an increment in the intensity of the OH stretching sub-band close to 3200 cm−1 as water content increases. ; The authors gratefully acknowledge the support of the Spanish Ministry of Education, project CSD2006–00053, the European Union, project 502235–2 and SOFTCOMP program and the Basque Government, project IT-436–07. ; Peer reviewed

In this study, the rotational dynamics of hydration water confined in calcium-silicate-hydrate (C-S-H) gel with a water content of 22 wt.% was studied by broadband dielectric spectroscopy in broad temperature (110-300 K) and frequency (10-1-108 Hz) ranges. The C-S-H gel was used as a 3D confining system for investigating the possible existence of a fragile-to-strong transition for water around 220 K. Such transition was observed at 220 K in a previous study [Y. Zhang, M. Lagi, F. Ridi, E. Fratini, P. Baglioni, E. Mamontov and S. H. Chen, J. Phys.: Condens. Matter 20, 502101 (2008)] on a similar system, and it was there associated with a hidden critical point of bulk water. However, based on the experimental results presented here, there is no sign of a fragile-to-strong transition for water confined in C-S-H gel. Instead, the fragile-to-strong transition can be explained by a merging of two different relaxation processes at about 220 K. © 2013 AIP Publishing LLC. ; The support from the Basque Government through the Nanoiker project (Grant No. E11-304) under the ETORTEK Program is acknowledged. S.C. also acknowledges the support of the Spanish Ministry of Education, project MAT2012-31088 and the Basque Government, and project IT-654-13 and Professor J. Colmenero for helpful discussions. H.J. acknowledges the Swedish Research Council Formas for financial support. ; Peer Reviewed

Supramolecular polymers possess versatile mechanical properties and a unique ability to respond to external stimuli. Understanding the rich dynamics of such associative polymers is essential for tailoring user-defined properties in many products. Linear copolymers of 2-methoxyethyl acrylate (MEA) and varying amounts of 2-ureido-4[1H]-pyrimidone (UPy) quadruple hydrogen-bonding side units were synthesized via free radical polymerization. Their linear viscoelastic response was studied via small amplitude oscillatory shear (SAOS). The measured linear viscoelastic envelope (LVE) resembles that of a well-entangled polymer melt with a distinct plateau modulus. Dielectric relaxation spectroscopy (DRS) was employed to independently examine the lifetime of hydrogen bond units. DRS reveals a high frequency α-relaxation associated with the dynamic glass transition, followed by a slower α*-relaxation attributed to the reversible UPy hydrogen bonds. This time scale is referred to as the bare lifetime of hydrogen bonding units. Using the sticky Rouse model and a renormalized lifetime, we predict satisfactorily the LVE response for varying amounts of UPy side groups. The deviation from the sticky Rouse prediction is attributed to polydispersity in the distribution of UPy groups along the chain backbone. We conclude that the response of associating polymers in linear viscoelasticity is general and does not depend on the chemistry of association, but rather on the polymer molecular weight (MW) and MW distribution, the number of stickers per chain, ns, and the distribution of stickers along the backbone. ; The work leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no. 607937 and the Danish National Advanced Technology Foundation (grant no. 55-2013-3). The ETORTEK Program and the Spanish Ministry of Education (MAT2015-63704-P) are also acknowledged. ; Peer reviewed

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. ; Peer Reviewed

9 páginas, 7 figuras, 1 tabla.-- Trabajo presentado a la "Gordon Research Conference: Water & Aqueous Solutions" celebrada en EE.UU. del 8 al 13 de agosto de 2010. ; The behavior of water dynamics confined in hydrated calcium silicate hydrate (C-S-H) gel has been investigated using broadband dielectric spectroscopy (BDS; 10−2–106 Hz) in the low-temperature range (110–250 K). Different water contents in C-S-H gel were explored (from 6 to 15 wt%) where water remains amorphous for all the studied temperatures. Three relaxation processes were found by BDS (labeled 1 to 3 from the fastest to the slowest), two of them reported here for the first time. We show that a strong change in the dielectric relaxation of C-S-H gel occurs with increasing hydration, especially at a hydration level in which a monolayer of water around the basic units of cement materials is predicted by different structural models. Below this hydration level both processes 2 and 3 have an Arrhenius temperature dependence. However, at higher hydration level, a non-Arrhenius behavior temperature dependence for process 3 over the whole accessible temperature range and, a crossover from low-temperature Arrhenius to high-temperature non-Arrhenius behavior for process 2 are observed. Characteristics of these processes will be discussed in this work. ; Authors gratefully acknowledge the support of Consolider (CSD2006-00053) and Etortek program. S.C. gratefully acknowledge the support of CSIC (200860I021) and S.C. S.A-I, A.A and J.C. gratefully acknowledge the support of the DYNACOP program and the Basque Government, and project IT-436-07 and the Spanish Ministry of Education, project MAT-22007-63681. ; Peer reviewed