Effect of adding nanometre-sized heterogeneities on the structural dynamics and the excess wing of a molecular glass former

Abstract

We present the relaxation dynamics of glass-forming glycerol mixed with 1.1 nm sized polyhedral oligomeric silsesquioxane (POSS) molecules using dielectric spectroscopy (DS) and two different neutron scattering (NS) techniques. Both, the reorientational dynamics as measured by DS and the density fluctuations detected by NS reveal a broadening of the α relaxation when POSS molecules are added. Moreover, we find a significant slowing down of the α-relaxation time. These effects are in accord with the heterogeneity scenario considered for the dynamics of glasses and supercooled liquids. The addition of POSS also affects the excess wing in glycerol arising from a secondary relaxation process, which seems to exhibit a dramatic increase in relative strength compared to the α relaxation.

Metabasin transitions are Johari-Goldstein relaxation events

“…We also believe that this is the first time β JG relaxation has been identified from neutron scattering data, although Sperl previously proposed a Cole-Cole form for susceptibilities that accounted for dynamics observed over a similar lengthscale and time scale in optical Kerr effect data. 61 We note also that, very shortly after the first posting of a portion of this work, 62 Gupta et al 63 also showed that β JG relaxation could be obtained from EINS.…”

Study of the Segmental Dynamics and Ion Transport of Solid Polymer Electrolytes in the Semi-crystalline State

“…To capture the dynamics of the PEO chains in this confinement, we used Cole-Cole function (Equation 2) to fit S(Q, E) in the energy space. Cole-Cole distribution function has been successfully used to capture the dynamics in various confined systems (Cole and Cole, 1941;Gupta et al, 2016;Mamontov and O'Neill, 2017;Dyatkin et al, 2018). In Cole-Cole function, two parameters are fitted independently: E 0 (Q), the half width at half maximum of S(Q, E), and α(Q), the stretched exponential.…”

Investigations of structural and dynamical mechanisms of ice formation regulated by graphene oxide nanosheets

“…To further investigate the dynamical mechanisms behind ice nucleation in GO aqueous dispersions, we performed QENS experiments on GOs in H 2 O and D 2 O, as well as pure water, above and approaching the ice formation temperature. QENS has proved to be a prevailing tool to study the dynamics of water molecules on the timescale of pico- to nano-seconds, 27 since the hydrogen atoms have much larger incoherent scattering cross section compared to other atoms present in the GO aqueous dispersions. The normalized QENS spectra from IRIS are shown in Figs.…”

“…The stretch exponent β can be considered as Q-independent in the Q range of measurements and can be obtained by fitting curves at all 10 Q values together. 27 …”