Neutron reflectometry (NR) measurements were carried out to probe the structure and stability of two model biomembranes consisting of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) phospholipid bilayers hydrated by water solutions of two prototypical room-temperature ionic liquids (RTILs), namely, 1-butyl-3-methyl-imidazolium chloride ([bmim][Cl]) and choline chloride ([Chol][Cl]) at concentrations of 0.1 M and 0.5 M, respectively. The raw data were analyzed by fitting a distribution of scattering length densities arising from the different chemical species in the system. The results of this analysis show that (a) for all systems and concentrations that we considered, the thickness of the bilayers shrinks by ∼1 Å upon dissolving the ionic liquid into water and that (b) the RTIL ions enter the bilayer, finding their way to a preferred location in the lipid range that is nearly independent of the lipid and of the [bimim](+) or [Chol](+) choice. The volume fraction of RTIL sorbed in/on the bilayer, however, does depend on the lipid, but, again, is the same for [bmim][Cl] and for [Chol][Cl]. Thus, the RTIL occupies ∼5% of the bilayer volume in POPC, rising to ∼10% in DMPC. Repeating the measurements and data analysis after rinsing in pure water shows that the changes in the bilayer due to the RTIL sorption are irreversible and that a measurable amount of IL remains in the lipid fraction, that is, ∼2.5% of the bilayer volume in POPC and ∼8% in DMPC.

A detailed study of the dynamical and structural aspects of the cold crystallization behavior of highly flexible poly(dimethylsiloxane)(PDMS) is presented. In order to understand the complete behavior, before, under and after crystallization, a wide range of experimental techniques have been employed. A particular emphasis is made on the interplay between dynamical and structural effects and how the properties of the amorphous phase evolve during the crystallization. This is highlighted by combining mobility sensitive techniques, involving broadband dielectric spectroscopy (BDS) and differential scanning calorimetry, with neutron scattering: wide and small-angle neutron scattering (WANS/SANS) which are sensitive to the relative ordering of the atoms. In this way, we are able to compare the structure associated with crystal formation with the evolution and modification of the amorphous phase. The kinetics deduced from WANS points toward a classical nucleation and growth behavior closely following a Avrami-like growth with an exponent of about n ) 3 which is expected for athermal nucleation from fixed centers followed by three-dimensional crystal growth. Furthermore, the amorphous phase (deduced from BDS) decays in parallel with the emergence of the crystalline phase (from WANS/SANS) without any shift in the characteristic relaxation time. However a careful comparison of the crystallization at short times indicates that the amorphous phase seems to be affected before any measurable crystallization is detected by WANS. Although this might be compatible with the existence of mesomorphic phase, it may also be attributed to more simple precursors as initial crystalline "baby-like" nuclei. In this picture, these crystalline nuclei may be formed homogeneously in the system which in turn causes a constraint on the surrounding chains connected to these crystalline nuclei. This is manifested as a distinct relaxation contribution that is drastically slower and heterogeneous than the conventional amorphous R-relaxation of the melt. It would also explain a signal in SANS before any accompanying crystallization signal in WANS. Once the crystal starts developing, the fraction of the slower amorphous phase (constrained amorphous phase, CAP) grows and the conventional amorphous phase gradually disappears. At the very end the growing crystalline fronts start to overlap and some of the remaining CAP becomes even more constrained due to cross-link strongly manifested in both the dielectric response and the heat capacity.

A detailed investigation on the nature of the relaxation processes occurring in a typical room temperature ionic liquid (RTIL), namely, 1-butyl-3-methyl imidazolium hexafluorophosphate ([bmim][PF(6)]), is reported. The study was conducted using both elastic and inelastic neutron scattering over a wide temperature range from 10 to 400 K, accessing the dynamic features of both the liquid and glassy amorphous states. In this study, the inelastic fixed energy scan technique has been applied for the first time to this class of materials. Using this technique, the existence of two relaxation processes below the glass transition and a further diffusive process occurring above the glass-liquid transition are observed. The low temperature processes are associated with methyl group rotation and butyl chain relaxation in the glassy state and have been modeled in terms of two Debye-like, Arrhenius activated processes. The high temperature process has been modeled in terms of a Kohlraush-Williams-Watts relaxation, with a distinct Vogel-Fulcher-Tamman temperature dependence. These results provide novel information that will be useful in rationalizing the observed structural and dynamical behavior of RTILs in the amorphous state.