6 th International Discussion Meeting on Relaxations in Complex Systems , ROME 2009

1. Collaborators: University of Silesia,Poland: Marian Paluch Andrzej Grzybowski Sebastian Pawlus Universitàdi Pisa,Italy: Simone Capaccioli Daniele Prevosto SergiyAncherbak Katarzyna Grzybowska Institute of Physics University of Silesia in Katowice POLAND Relaxation dynamics of water in the aqueous mixtures of propylene glycol oligomersat ambient and elevated pressure 6th International Discussion Meeting on Relaxations in Complex Systems, ROME 2009

2. To prepare water mixtures we used polypropylene glycols (PPG) (=diols) of different chain lengths p-1

3. Water mixtures of propylene glycol oligomers At atmospheric pressure it has been studied over 20 water mixtures of polypropylene glycols (DPG, TPG,and PPG400) with different content of water For the mixture PPG 400 + 26%H2O it has been performed dielectric measurements at elevated pressure: P = 360 MPa P = 500 MPa P = 1800 MPa 26 0.89

4. Dielectric measurements of water mixtures of PPG at P=0.1 MPa Water significantly changes the relaxation dynamics of PPG: 1) Appearing of a new additional - relaxation process TPG+H2O (glassy state) DPG+H2O (liquid state) ν-relaxation α-relaxation ν-relaxation -process The spectacular increase in dielectric strenght Δεν with increasing of water content in solution ν-process reflects mainly the water dynamics in the mixture

5. 2) Even a small amount of water added to pure PPG results in a slowdown of the -relaxation observed in anhydrous PPG and the drop of Δε PPG 400+H2O (glassy state) ν-process -process Hindering of the reorientations of PPGOH groups by H-bonds formed between water molecules and OH groups of PPG -processoriginatesfromsomereorientations of terminal parts of PPG moleculescontaining OH groups K. Grzybowska, et al.J. Chem. Phys. 128 134904 (2008); K. Grzybowska, et al. J. Phys.: Condens. Matter19, 376105 (2007)

6. Temeperature dependences of dielectric relaxation times forwater mixtures of PPG at P=0.1 MPa VFT eq. Arrhenius law

7. Activation enery Ea of ν and -processes obtained at T<Tg from Arrhenius eq. vs mole fraction of water at P=0.1 MPa I. Takei, Physics and Chemistry of Ice, Cambiridge (2007) R.P. Auty, R.H. Cole, J. Chem. Phys. 20, 1309 (1952) S. Cerveny, et al., Phys. Rev. Lett. 93, 245702 (2004)

8. Dielectric spectra of the mixturePPG+26%H2O at high pressure ν-process α -process α –process (α-peak is hidden due to a high contribution of dc-conductivity to ε”) ν-process P=0.1 MPa ν-process α -process P=1.8 GPa P=500 MPa

9. Near the glass transition, the ν- relaxation is less sensitive to changes of pressure and temperature than α- process P=500MPa T=-41oC P=0.1 MPa T=-75oC PPG 400 + 26% H2O Property typical for JG-process decade the separation between α and  processes is one decade greater in the case of measurement at 500 MPa than that for ambient pressure  process has the same sensitivity to pressure and temperature like typical JG secondary relaxation in many glass forming-liquids In this respect the ν-relaxation can be considered as a secondary relaxation reflecting some local dynamics of water component in the aqueous mixture

10. Relaxation map for PPG 400+26%H2O at high pressures Tg of the water mixture increase with increasing P α-processes Tg =267 K (P=1.8 GPa) Tg(τα=100s) =Tcross Tg=267 K 1.8GPa Tg(P=0)=193K,Π=298MPa, β=0,17 τ cross τν cross(P→∞)=3s VFT equation at T>Tg for medium P Arrhenius equation at T<Tg for all P pressure considerably influences the nature of -process dynamic crossover ν relaxation time (τν cross) at the dynamic crossover decreases exponentially with compression

11. Unusual pressure dependences of -process activation energies and fragility of the mixture PPG400+26%H2O Ea of -process in the liquid state of the mixture evaluated from Arrhenius eq. (for P=0.1 MPa and 1.8GPa at T>Tg) and VFT eq. (for P=360 and 500 MPa at Tg=Tcross) Non-associated liquids Ea of -process in the glassy state of the mixture evaluated from Arrhenius eq. Initially the increase in pressure can facilitate the hydrogen bonds forming, whereas P>1 GPa may significant reducing of H-bonds in the water clusters in mixture R. Casalini, C. M. Roland, Phys. Rev. B 71, 014210 (2005)

12. SUMMARY PPG 400 + 26% H2O Ithasbeenfound that pressure considerably affects the relaxation dynamics of water mixture of PPG 400. • In the whole pressure range (0.1MPa-1.8GPa) we observed the dynamic crossover of -relaxationtimes) • At medium pressures (360 and 500 MPa),-relaxationtimesrevealfragile-to-strongdynamiccrossover LDL In contrary to confined water the dependence Tcross(P) for water mixture has an increasing character and we cannot relate it to the liquid-liquid phase transition line in a T-P plane. HDL Confinedwaterinporoussilicamaterial Protein hydrationwater X-Q. Chu et al., http://shibayama.issp.utokyo.ac.jp/nagao/NSE2006/Abstracts/NSE2006_yoshida.pdf. (2008); L. Liu et al., Phys. Rev. Lett. 95 117802 (2005).

13. For PPG400+26%H2O, the crossover relaxation time τν cross decreases exponentially with increasing P , whereas for confined waterτcross(P)const. PPG 400 + 26% H2O 2-D confined protein hydration water For watermixture, Ea(P) for the -relaxation is nonmonotonic and reveals a maximum, while the Arrhenius activation energy for the confined water process decreases with increasing P at T<Tcross. PPG 400 + 26% H2O Supercooled water in the mixture of PPG have different properties than pure supercooled confined water. Our findings indicate that  process should be rather considered as a secondary relaxation reflecting some local dynamics of water component in the aqueous mixture