Dielectric Study of Tetraalkylammonium and Tetraalkylphosphonium Levulinate Ionic Liquids

Broadband dielectric spectroscopy in a broad temperature range was employed to study ionic conductivity and dynamics in tetraalkylammonium- and tetraalkylphosphonium-based ionic liquids (ILs) having levulinate as a common anion. Combining data for ionic conductivity with data obtained for viscosity in a Walden plot, we show that ionic conductivity is controlled by viscosity while a strong association of ions takes place. Higher values for ionic conductivities in a broad temperature range were found for the tetraalkylphosphonium-based IL compared to its ammonium homolog in accordance with its lower viscosity. Levulinate used in the present study as anion was found to interact and associate stronger with the cations forming ion-pairs or other complexes compared to the NTf2 anion studied in literature. In order to analyze dielectric data, different fitting approaches were employed. The original random barrier model cannot well describe the conductivity especially at the higher frequencies region. In electric modulus representation, two overlapping mechanisms contribute to the broad low frequencies peak. The slower process is related to the conduction mechanism and the faster to the main polarization process of the complex dielectric permittivity representation. The correlation of the characteristic time scales of the previous relaxation processes was discussed in terms of ionic interactions

Water dynamics and thermal properties of tyramine-modified hyaluronic acid - Gelatin hydrogels

[EN] A new family of injectable hydrogels, enzymatically crosslinked from mixtures of tyramine conjugates of hyaluronic acid (HA) and gelatin (Gel) are characterized in terms of their molecular morphology, miscibility and water sorption ability by employing Field Emission Scanning Electron Microscopy, water sorption/desorption measurements and differential scanning calorimetry technique. The hydrogels were chemically crosslinked by reaction of the phenol groups of the tyramine in the presence of the enzyme horseradish peroxidase and a small amount of hydrogen peroxide. The water fraction in the microporous hydrogels, h(w), was up to 0.68 being achieved by equilibration in environment of saturated water vapor. Our measurements reveal good miscibility between HA and Gel components in the whole hydration range studied and that the HA/Gel mixtures exhibit glass transition characteristics, water diffusion dynamics and equilibrium water contents that are independent of the composition. The intermolecular interactions have been found to be dependent on the hydration level and the mixtures behave like the Gel component for h(w) 0.40) show that they become partially crystallized at subzero temperatures and reveal that absorbed water molecules form, at least, two discrete forms of ice crystals. In the phase separated hydrogels, next to ice phase, a second phase of polymer/water homogeneous mixture with constant water fraction about 0.25 has been identified.The Spanish Ministry support through the MAT2016-76039-C4-1-R project (including the FEDER funds) is acknowledged. The CIBER-BBN initiative is funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. We thank Dr. P. Klonos for his assistance in preparing Scheme 1.Kripotou, S.; Stefanopoulou, E.; Culebras-Martínez, M.; Morales-Román, RM.; Ferrer, G.; Kyritsis, A. (2019). Water dynamics and thermal properties of tyramine-modified hyaluronic acid - Gelatin hydrogels. Polymer. 178:1-13. https://doi.org/10.1016/j.polymer.2019.121598S11317

Dielectric Study of Tetraalkylammonium and Tetraalkylphosphonium Levulinate Ionic Liquids

Broadband dielectric spectroscopy in a broad temperature range was employed to study ionic conductivity and dynamics in tetraalkylammonium- and tetraalkylphosphonium-based ionic liquids (ILs) having levulinate as a common anion. Combining data for ionic conductivity with data obtained for viscosity in a Walden plot, we show that ionic conductivity is controlled by viscosity while a strong association of ions takes place. Higher values for ionic conductivities in a broad temperature range were found for the tetraalkylphosphonium-based IL compared to its ammonium homolog in accordance with its lower viscosity. Levulinate used in the present study as anion was found to interact and associate stronger with the cations forming ion-pairs or other complexes compared to the NTf2 anion studied in literature. In order to analyze dielectric data, different fitting approaches were employed. The original random barrier model cannot well describe the conductivity especially at the higher frequencies region. In electric modulus representation, two overlapping mechanisms contribute to the broad low frequencies peak. The slower process is related to the conduction mechanism and the faster to the main polarization process of the complex dielectric permittivity representation. The correlation of the characteristic time scales of the previous relaxation processes was discussed in terms of ionic interactions

Structure and Crystallization Behavior of Poly(ethylene oxide) (PEO) Chains in Core–Shell Brush Copolymers with Poly(propylene oxide)-<i>block</i>-poly(ethylene oxide) Side Chains

Core–shell brush copolymers featuring a poly­(<i>p</i>-hydroxystyrene) (PHOS) backbone and PPO-<i>b</i>-PEO (PPO and PEO stand for poly­(propylene oxide) and poly­(ethylene oxide)) side chains with different molecular compositions and exhibiting two inverse molecular architectures in regard to the side chains were investigated. Differential scanning calorimetry (DSC) and temperature-resolved wide- and small-angle X-ray scattering (WAXS/SAXS) were used to characterize the thermal and structural behavior. For the sample with the crystallizable PEO block linked directly to the backbone and a high PEO fraction (84.9 wt %), our results reveal a PEO crystallization/melting behavior similar to the one of bulk PEO. Surprisingly, the crystalline order, as determined by WAXS, persists up to 30 K above the melting point determined by DSC (<i>T</i>_m = 54 °C). For the samples where the PPO block is directly linked to PHOS backbone and the PEO chains are dangling, our results indicate that the side arm architecture has remarkable effects on the thermal and structural behavior. With decreasing PEO fraction in the side arms, the calorimetric crystallization temperature, <i>T</i>_c, and the melting point, <i>T</i>_m, of the PEO domains are strongly suppressed, reaching values as low as −45 °C and −8 °C, respectively. Furthermore, PEO crystallizes in an asymmetric lamellar phase with a distorted PEO crystalline phase. Above <i>T</i>_m the morphology changes from microphase-separated symmetric lamellae to hexagonally perforated lamellae with PEO domains immersed within a PHOS/PPO matrix with decreasing PEO fraction. Our results suggest that this specific brush copolymer architecture allows for tuning the ability of PEO blocks to crystallize

Dynamics of hydration water in gelatin and hyaluronic acid hydrogels

[EN] We employed broadband dielectric spectroscopy (BDS), for the investigation of the water dynamics in partially hydrated hyaluronic acid (HA), and gelatin (Gel), enzymatically crosslinked hydrogels, in the water fraction ranges [Formula: see text]. Our results indicate that at low hydrations ([Formula: see text]), where the dielectric response of the hydrogels is identical during cooling and heating, water plasticizes strongly the polymeric matrix and is organized in clusters giving rise to [Formula: see text]-process, secondary water relaxation and to an additional slower relaxation process. This later process has been found to be related with the dc charge conductivity and can be described in terms of the conduction current relaxation mechanism. At slightly higher hydrations, however, always below the hydration level where ice is formed during cooling, we have recorded in HA hydrogel a strong water dielectric relaxation process, [Formula: see text], which has Arrhenius-like temperature dependence and large time scale resembling relaxation processes recorded in bulk low density amorphous solid water structures. This relaxation process shows a strong-to-fragile transition at [Formula: see text]C and our data suggest that the VTF-like process recorded at [Formula: see text]C is controlled by the same molecular process like long range charge transport. In addition, our data imply that the crossover temperature is related with the onset of structural rearrangements (increase in configurational entropy) of the macromolecules. In partially crystallized hydrogels ([Formula: see text]) HA exhibits at low temperatures the ice dielectric process consistent with the bulk hexagonal ice, whereas Gel hydrogel exhibits as main low temperature process a slow relaxation process that refers to open tetrahedral structures of water similar to low density amorphous ice structures and to bulk cubic ice. Regarding the water secondary relaxation processes, we have shown that the [Formula: see text]-process and the [Formula: see text] process are activated in water hydrogen bond networks with different structures.The support from Ministerio de Economia, Industria y Competitividad (MINECO) through the MAT2016-76039-C4-1-R project (including the FEDER funds) is acknowledged. The CIBER-BBN initiative is funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. We thank Dr. P. Klonos for his assistance in preparing scheme 1.Kripotou, S.; Zafeiris, K.; Culebras-Martinez, M.; Ferrer, G.; Kyritsis, A. (2019). Dynamics of hydration water in gelatin and hyaluronic acid hydrogels. The European Physical Journal E. 42(8):1-18. https://doi.org/10.1140/epje/i2019-11871-2S118428M. Heyden, J. Chem. Phys. 141, 22D509 (2014)D. Laage, T. Elsaesser, J.T. Hynes, Chem. Rev. 117, 10694 (2017)R. Biswas, B. Bagchi, J. Phys.: Condens. Matter 30, 013001 (2018)A.S. Hoffman, Adv. Drug Deliv. Rev. 43, 3 (2002)B.V. Slaughter, S.S. Khurshid, O.Z. Fisher, A. Khademhosseini, N.A. Peppas, Adv. Mater. 21, 3307 (2009)S. Khodadadi, A.P. Sokolov, Soft Matter 11, 4984 (2015)S. Cerveny, I. Combarro-Palacios, J. Swenson, Phys. Chem. Lett. 7, 4093 (2016)F. Mallamace, C. Corsaro, P. Baglioni, E. Fratini, S.-H. Chen, J. Phys.: Condens. Matter 24, 064103 (2012)P.W. Fenimore et al., Chem. Phys. 424, 2 (2013)W.G. Liu, K.D. Yao, Polymer 42, 3943 (2001)E. Mamontov, Y. Yue, J. Bahadur, J. Guo, C.I. Contescu, N.C. Gallego, Y.B. Melnichenko, Carbon 111, 705 (2017)J. Swenson, Phys. Chem. Chem. Phys. 20, 30095 (2018)J.L. Finney, Philos. Trans. R. Soc. Lond. B 359, 1145 (2004)P.G. Debenedetti, J. Phys.: Condens. Matter 15, R1669 (2003)M. Kobayashi, H. Tanaka, J. Phys. Chem. B 115, 14077 (2011)G. Bullock, V. Molinero, Faraday Discuss. 167, 371 (2013)K. Amann-Winkel, R. Böhmer, C. Gainaru, F. Fujara, B. Geil, T. Loerting, Rev. Mod. Phys. 88, 011002 (2016)N. Kastelowitz, V. Molinero, ACS Nano 12, 8234 (2018)U. Kaatze, J. Mol. Liq. 162, 105 (2011)G. Franzese, V. Bianco, S. Iskrov, Food Biophys. 6, 186 (2011)M.D. Fayer, Acc. Chem. Res. 45, 3 (2012)D. Russo, J. Teixeira, J. Non-Cryst. Solids 407, 459 (2015)L. Zhao, K. Ma, Z. Yang, Int. J. Mol. Sci. 16, 8454 (2015)I. Brovchenko, A. Oleinikova, Chem. Phys. Chem. 9, 2695 (2008)M. Rosenstihl, K. Kämpf, F. Klameth, M. Sattig, M. Vogel, J. Non-Cryst. Solids 407, 449 (2015)J. Wolfe, G. Bryant, K.L. Koster, CryoLetters 23, 157 (2002)L. Lupi, A. Hudait, V. Molinero, J. Am. Chem. Soc. 136, 3156 (2014)P. Gallo et al., Chem. Rev. 116, 7463 (2016)O. Mishima, H.E. Stanley, Nature 396, 329 (1998)H.E. Stanley et al., J. Non-Cryst. Solids 357, 629 (2011)F. Bruni, R. Mancinelli, M.A. Ricci, J. Mol. Liq. 176, 39 (2012)F. Caupin, J. Non-Cryst. Solids 407, 441 (2015)N. Shinyashiki, M. Shimomura, T. Ushiyama, T. Miyagawa, S. Yagihara, J. Phys. Chem. B 111, 10079 (2007)S. Gekle, R.R. Netz, J. Chem. Phys. 137, 104704 (2012)P. Ben Ishai, S.R. Tripathi, K. Kawase, A. Puzenko, Y. Feldman, Phys. Chem. Chem. Phys. 17, 15428 (2015)U. Kaatze, J. Chem. Phys. 147, 024502 (2017)D.R. Martin, J.E. Forsmo, D.V. Matyushov, J. Phys. Chem. B 122, 3418 (2018)D.E. Stillman, J.A. MacGregor, R.E. Grimm, J. Geophys. Res. 118, 1 (2013)I. Popov, A. Puzenko, A. Khamzin, Y. Feldman, Phys. Chem. Chem. Phys. 17, 1489 (2015)K. Sasaki, R. Kita, N. Shinyashiki, S. Yagihara, J. Phys. Chem. B 120, 3950 (2016)T. Yasuda, K. Sasaki, R. Kita, N. Shinyashiki, S. Yagihara, J. Phys. Chem. B 121, 2896 (2017)P. Pissis, A. Kyritsis, J. Polym. Sci. Part B: Polym. Phys. 51, 159 (2013)J. Swenson, S. Cerveny, J. Phys.: Condens. Matter 27, 033102 (2015)S. Cerveny, F. Mallamace, J. Swenson, M. Vogel, L. Xu, Chem. Rev. 116, 7608 (2016)N. Shinyashiki, S. Sudo, S. Yagihara, A. Spanoudaki, A. Kyritsis, P. Pissis, J. Phys. C: Condens. Matter 19, 205113 (2007)S. Capaccioli, K.L. Ngai, N. Shinyashiki, J. Phys. Chem. B 111, 8197 (2007)S. Cerveny, Á. Alegría, J. Colmenero, Phys. Rev. E 77, 031803 (2008)C. Gainaru, A. Fillmer, R. Böhmer, J. Phys. Chem. B 113, 12628 (2009)A. Kyritsis, A. Panagopoulou, P. Pissis, R.S.i. Serra, J.L. Gomez Ribelles, N. Shinyashiki, IEEE Trans. Dielectr. Electr. Insul. 19, 1239 (2012)A. Panagopoulou, A. Kyritsis, N. Shinyashiki, P. Pissis, J. Phys. Chem. B 116, 4593 (2012)A. Panagopoulou, A. Kyritsis, M. Vodina, P. Pissis, Biochim. Biophys. Acta 1834, 977 (2013)K.L. Ngai, S. Capaccioli, S. Ancherbak, N. Shinyashiki, Philos. Mag. 91, 1809 (2011)K.L. Ngai, S. Capaccioli, A. Paciaroni, Biochim. Biophys. Acta 1861, 3553 (2017)S. Cerveny, G.A. Schwartz, R. Bergman, J. Swenson, Phys. Rev. Lett. 93, 245702 (2004)J. Swenson, J. Phys.: Condens. Matter 16, S5317 (2004)S. Capaccioli, K.L. Ngai, S. Ancherbak, P.A. Rolla, N. Shinyashiki, J. Non-Cryst. Solids 357, 641 (2011)S. Capaccioli, K.L. Ngai, J. Chem. Phys. 135, 104504 (2011)J.E. Scott, F. Heatley, Biomacromolecules 3, 547 (2002)C. Alber, J. Engblom, P. Falkman, V. Kocherbitov, J. Phys. Chem. B 119, 4211 (2015)T. Hatakeyama, M. Tanaka, A. Kishi, H. Hatakeyama, Thermochim. Acta 532, 159 (2012)A. Pruŝová, F.J. Vergeldt, J. Kucerík, Carbohydr. Polym. 95, 515 (2013)S. Kawabe, M. Seki, H. Tabata, J. Appl. Phys. 115, 125 (2014)O. Miyawaki, C. Omote, K. Matsuhira, Biopolymers 103, 685 (2015)S. Thakur, P.P. Govender, M.A. Mamo, S. Tamulevicius, K. Kumar, V. Thakur, Vacuum 146, 396 (2017)A. Panagopoulou, J. Vázquez Molina, A. Kyritsis, M. Monleón Pradas, A. Valles Lluch, G. Gallego Ferrer, P. Pissis, Food Biophys. 8, 192 (2013)K. Sasaki, R. Kita, N. Shinyashiki, S. Yagihara, J. Chem. Phys. 140, 124506 (2014)K. Sasaki, A. Panagopoulou, R. Kita, N. Shinyashiki, S. Yagihara, A. Kyritsis, P. Pissis, J. Phys. Chem. B 121, 265 (2017)S. Poveda-Reyes, V. Moulisova, E. Sanmartín-Masiá, L. Quintanilla-Sierra, M. Salmerón-Sánchez, G. Gallego Ferrer, Macromol. Biosci. 16, 1311 (2016)V. Moulisova, S. Poveda-Reyes, E. Sanmartín-Masiá, L. Quintanilla-Sierra, M. Salmerón-Sánchez, G. Gallego Ferrer, ACS Omega 2, 7609 (2017)E. Sanmartín-Masiá, S. Poveda-Reyes, G. Gallego Ferrer, Int. J. Polym. Mater. Polym. Biomater. 66, 280 (2017)L. Greenspan, J. Res. Natl. Bur. Stand. A Phys. Chem. 81A, 89 (1977)F. Kremer, A. Schönhals, Broadband Dielectric Spectroscopy (Springer, Berlin, 2002)M. Wübbenhorst, J. van Turnhout, J. Non-Cryst. Solids 305, 40 (2002)R. Pelster, A. Kops, G. Nimtz, A. Enders, H. Kietzmann, P. Pissis, A. Kyritsis, D. Woermann, Ber. Bunsenges. Phys. Chem. 97, 666 (1993)K. Pathmanathan, G.P. Johari, J. Chem. Soc., Faraday Trans. 90, 1143 (1994)Y. Suzuki, M. Steinhart, R. Graf, H.-J. Butt, G. Floudas, J. Phys. Chem. B 119, 14814 (2015)G.P. Johari, E. Whalley, J. Chem. Phys. 75, 1333 (1981)P.M. Suherman, P. Taylor, G. Smith, J. Non-Cryst. Solids 305, 317 (2002)K.-D. Kreuer, Chem. Mater. 8, 610 (1996)M.G. Mazza et al., Proc. Natl. Acad. Sci. U.S.A. 108, 19873 (2011)E. Brini, C.J. Fennell, M. Fernandez-Serra, B. Hribar-Lee, M. Luksic, K.A. Dill, Chem. Rev. 117, 12385 (2017)O. Andersson, J. Phys.: Condens. Matter 20, 244115 (2008)C. Gainaru et al., Proc. Natl. Acad. Sci. U.S.A. 111, 17402 (2014)G.P. Johari, O. Andersson, Thermochim. Acta 461, 14 (2007)E.B. Moore, E. de la Lave, K. Welke, D.A. Scherlis, V. Molinero, Phys. Chem. Chem. Phys. 12, 4124 (2010)N. Shinyashiki et al., J. Phys. Chem. B 113, 14448 (2009)E.B. Moore, J.T. Allen, V. Molinero, J. Phys. Chem. C 116, 7507 (2012)S.R. Gough, D.W. Davidson, J. Chem. Phys. 52, 5442 (1970)T. Loerting et al., J. Non-Cryst. Solids 407, 423 (2015)K. Yamamoto, H. Namikawa, Jpn. J. Appl. Phys. 27, 1845 (1988)K. Yamamoto, H. Namikawa, Jpn. J. Appl. Phys. 28, 2523 (1989)P. Pissis, A. Kyritsis, V.V. Shilov, Solid State Ion. 125, 203 (1999)J.C. Dyre, T.B. Schrøder, Rev. Mod. Phys. 72, 873 (2000)J.C. Dyre, P. Maass, B. Roling, D.L. Sidebottom, Rep. Prog. Phys. 72, 046501 (2009)C. Gainaru et al., J. Phys. Chem. B 120, 11074 (2016)M. Nakanishi, A.P. Sokolov, J. Non-Cryst. Solids 407, 478 (2015