Vibrational spectra of ferrocene, ferrocene-containing polymers and their oxidized compounds

Ferrocene-containing polymers are an important member in the class of redox- responsive polymers, changing e.g. their solubility or conformation upon external stimuli. We present a study of their vibrational spectra using inelastic neutron scattering, focusing on the central building block of these polymers, the organometallic ferrocene complex. The vibrational modes of a bulk ferrocene sample are compared to those of poly(vinylferrocene), poly(ferrocenyldimethylsilane) and poly(ferrocenylmethylsilane). In the former polymer, the ferrocene complex is laterally attached to the polymer chain and the vibrational spectrum shows a slight shift and broadening of the fingerprint modes in the range of 100-800 cm⁻¹ except for the ring-metal-ring stretching mode which was not detectable anymore. The latter two polymers, where the ferrocene complex is part of the polymer backbone, exhibit larger differences to the vibrational spectrum of bulk ferrocene. Moreover, several contributions to the spectra caused by methyl groups in these polymers could be identified. In order to study the influence of oxidation on ferrocene and redox-responsive polymers, we investigated the ionic compound ferrocenium triiodide and oxidized poly(vinylferrocene). It is observed that the weakening of the η⁵-complex bond by a missing electron leads to a significant shift of the fingerprint modes to lower frequencies

Water Dynamics In Soft Confinement - Neutron Scattering Investigations On Reverse Micelles

In the present experimental study we investigate the dynamical behaviour of water in soft confinement. As a model system we choose the AOT (sodium bis[ethylhexyl] sulfosuccinate) based water-in-oil droplet microemulsion which we precharacterize in detail. Using small angle neutron scattering we determine the microemulsion structure as a function of composition. Spherical water droplets (reverse micelles) coated by a monomolecular layer of the surfactant are dispersed in the continuous oil matrix. By variation of the molar ratio of water to surfactant one may control the droplet size between a few Angström and several nanometers. We extend the phase diagram to temperatures far below the freezing point of bulk water to determine the range of structural stability of the droplets as a function of water loading. The supercooling of the confined water is investigated by means of elastic fixed window scans on neutron backscattering. The freezing point of the confined water as well as the lower stability temperature decrease with decreasing droplet size. Moreover we use neutron- spin-echo spectroscopy to measure droplet diffusion and form fluctuations, whereof we deduce the temperature dependency of the bending modulus of the surfactant shell. The influence of confinement on the water mobility is then studied using two systems with different droplet sizes. We access the water dynamics over three orders of magnitude from pico- to nanoseconds by the combination of neutron backscattering and time-of-flight spectroscopy. We analyze the data taking into account rotation and jump diffusion. We find the water diffusion inside the droplets on average to be considerably slowed down with respect to bulk water. The translational mobility further decreases with decreasing droplet size. We extract values for rotational and translational diffusion coefficients. Dependent on water loading, two dynamically separated water fractions inside the droplets are resolved, one probably corresponding to surfactant bound water and the other one corresponding to less hindered water in the middle of the droplet core. We determine the absolute number of tightly bound water molecules per AOT molecule

Vibrational spectra of ferrocene, ferrocene-containing polymers and their oxidized compounds

Ferrocene-containing polymers are an important member in the class of redox- responsive polymers, changing e.g. their solubility or conformation upon external stimuli. We present a study of their vibrational spectra using inelastic neutron scattering, focusing on the central building block of these polymers, the organometallic ferrocene complex. The vibrational modes of a bulk ferrocene sample are compared to those of poly(vinylferrocene), poly(ferrocenyldimethylsilane) and poly(ferrocenylmethylsilane). In the former polymer, the ferrocene complex is laterally attached to the polymer chain and the vibrational spectrum shows a slight shift and broadening of the fingerprint modes in the range of 100-800 cm −1 except for the ring-metal-ring stretching mode which was not detectable anymore. The latter two polymers, where the ferrocene complex is part of the polymer backbone, exhibit larger differences to the vibrational spectrum of bulk ferrocene. Moreover, several contributions to the spectra caused by methyl groups in these polymers could be identified. In order to study the influence of oxidation on ferrocene and redox-responsive polymers, we investigated the ionic compound ferrocenium triiodide and oxidized poly(vinylferrocene). It is observed that the weakening of the η 5 -complex bond by a missing electron leads to a significant shift of the fingerprint modes to lower frequencies