Microscopic molecular mobility of high-performance polymers of intrinsic microporosity revealed by neutron scattering - bend fluctuations and signature of methyl group rotation.

Polymers of intrinsic microporosity exhibit a combination of high gas permeability and reasonable permselectivity, which makes them attractive candidates for gas separation membrane materials. The diffusional selective gas transport properties are connected to the molecular mobility of these polymers in the condensed state. Incoherent quasielastic neutron scattering was carried out on two polymers of intrinsic microporosity, PIM-EA-TB(CH) and its demethylated counterpart PIM-EA-TB(H), which have high Brunauer-Emmett-Teller surface area values of 1030 m g and 836 m g, respectively.

Determination of Cooperativity Length in a Glass-Forming Polymer.

To describe the properties of glass-forming liquids, the concepts of a cooperativity length or the size of cooperatively rearranging regions are widely employed. Their knowledge is of outstanding importance for the understanding of both thermodynamic and kinetic properties of the systems under consideration and the mechanisms of crystallization processes. By this reason, methods of experimental determination of this quantity are of outstanding importance.

Inelastic neutron scattering analysis with time-dependent Gaussian-field models.

Converting neutron scattering data to real-space time-dependent structures can only be achieved through suitable models, which is particularly challenging for geometrically disordered structures. We address this problem by introducing time-dependent clipped Gaussian field models. General expressions are derived for all space- and time-correlation functions relevant to coherent inelastic neutron scattering for multiphase systems and arbitrary scattering contrasts.

Low frequency vibrational density of state of highly permeable super glassy polynorbornenes - the Boson peak.

Inelastic incoherent neutron time-of-flight scattering was employed to measure the low frequency density of states for a series of addition polynorbornenes with bulky side groups. The rigid main chain in combination with the bulky side groups give rise to a microporosity of these polymers in the solid state. The microporosity characterized by the BET surfaces area varies systematically in the considered series.

Complex molecular dynamics of a symmetric model discotic liquid crystal revealed by broadband dielectric, thermal and neutron spectroscopy.

The molecular dynamics of the triphenylene-based discotic liquid crystal HAT6 is investigated by broadband dielectric spectroscopy, advanced dynamical calorimetry and neutron scattering. Differential scanning calorimetry in combination with X-ray scattering reveals that HAT6 has a plastic crystalline phase at low temperatures, a hexagonally ordered liquid crystalline phase at higher temperatures and undergoes a clearing transition at even higher temperatures. The dielectric spectra show several relaxation processes: a localized γ-relaxation at lower temperatures and a so called α2-relaxation at higher temperatures.

Proton diffusion in the catalytic layer for high temperature polymer electrolyte fuel cells.

The present study focuses on quasielastic neutron scattering (QENS) of the proton dynamics in phosphoric acid (PA) inside the catalytic layer of high-temperature polymer electrolyte fuel cells (HT-PEFCs). The nanosecond proton dynamics is investigated on the local length scale around operating temperatures (300 K-430 K) using neutron backscattering spectroscopy. We have investigated the catalyst doped with different amounts of PA in order to understand the distribution of PA inside the layer.

Accelerated Local Dynamics in Matrix-Free Polymer Grafted Nanoparticles.

The tracer diffusion coefficient of six different permanent gases in polymer-grafted nanoparticle (GNP) membranes, i.e., neat GNP constructs with no solvent, show a maximum as a function of the grafted chain length at fixed grafting density.

Fractal diffusion in high temperature polymer electrolyte fuel cell membranes.

The performance of fuel cells depends largely on the proton diffusion in the proton conducting membrane, the core of a fuel cell. High temperature polymer electrolyte fuel cells are based on a polymer membrane swollen with phosphoric acid as the electrolyte, where proton conduction takes place. We studied the proton diffusion in such membranes with neutron scattering techniques which are especially sensitive to the proton contribution.

Anomalies in the low frequency vibrational density of states for a polymer with intrinsic microporosity - the Boson peak of PIM-1.

Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. Here, the vibrational density of states (VDOS) for PIM-1, the prototypical polymer with intrinsic microporosity, is investigated by means of inelastic neutron scattering. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid).

Description of poly(ethylenepropylene) confined in nanopores by a modified Rouse model.

A recent model for unentangled polymer chains in confinement [M. Dolgushev and M. Krutyeva, Macromol.

Temperature fluctuations and the thermodynamic determination of the cooperativity length in glass forming liquids.

The aim of this paper is to decide which of the two possible thermodynamic expressions for the cooperativity length in glass forming liquids is the correct one. In the derivation of these two expressions, the occurrence of temperature fluctuations in the considered nanoscale subsystems is either included or neglected. Consequently, our analysis gives also an answer to the widely discussed problem whether temperature fluctuations have to be generally accounted for in thermodynamics or not.

Probing cooperative liquid dynamics with the mean square displacement.

Literature data for picosecond mean square displacements show that the anharmonicity explains only about half of the fragility (with different fractions for different glass formers). The other half must be ascribed to the Adam-Gibbs mechanism of a growing cooperatively rearranging region. One can measure both influences separately by a simultaneous measurement of liquid and crystal in the coexistence region.

Vibrational density of states of triphenylene based discotic liquid crystals: dependence on the length of the alkyl chain.

The vibrational density of states of a series of homologous triphenylene-based discotic liquid crystals HATn (n = 5, 6, 8, 10, 12) depending on the length of the aliphatic side chain is investigated by means of inelastic neutron scattering. All studied materials have a plastic crystalline phase at low temperatures, followed by a hexagonally ordered liquid crystalline phase at higher temperatures and a quasi isotropic phase at the highest temperatures. The X-ray scattering pattern for the plastic crystalline phase of all materials shows a sharp Bragg reflection corresponding to the intercolumnar distance in the lower q-range and a peak at circa 17 nm(-1) related to intracolumnar distances between the cores perpendicular to the columns as well as a broad amorphous halo related to the disordered structure of the methylene groups in the side chains in the higher q-range.

Molecular dynamics of n-hexane: a quasi-elastic neutron scattering study on the bulk and spatially nanochannel-confined liquid.

We present incoherent quasi-elastic neutron scattering measurements in a wave vector transfer range from 0.4 Å(-1) to 1.6Å (-1) on liquid n-hexane confined in cylindrical, parallel-aligned nanochannels of 6 nm mean diameter and 260 μm length in monolithic, mesoporous silicon.

Inelastic neutron scattering study of a glass-forming liquid in soft confinement.

We have studied the microscopic dynamics of a glass-forming liquid in the soft confinement formed by microemulsion droplets using inelastic neutron scattering. The confined liquid was propylene glycol, the outer, hydrophobic phase was decalin, and the surfactant sodium dioctylsulfosuccinate (AOT) with the same composition used before with other spectroscopic methods [L.-M.

Endothelin receptor B in trabecular meshwork.

Endothelin-1 (ET-1), the most potent vasoconstrictor known to date, seems to be involved in the pathogenesis of primary open angle glaucoma. ET-1 was found in different tissues of the eye and in high concentrations in the aqueous humour. The effects of ET-1 are mediated by two receptors, ET-A receptor (ET-AR) and ET-B receptor (ET-BR), which are both expressed in bovine trabecular meshwork (TM).

Plasticizer effect on the dynamics of polyvinylchloride studied by dielectric spectroscopy and quasielastic neutron scattering.

We have studied the influence of plasticization on the microscopic dynamics of a glass-forming polymer. For this purpose we studied polyvinylchloride (PVC) with and without the commercially used plasticizer dioctylphthalate (DOP). We used dielectric spectroscopy and inelastic neutron scattering employing the neutron spin echo (NSE) technique.

Glassy dynamics of polymers confined to nanoporous glasses revealed by relaxational and scattering experiments.

The glassy dynamics of poly(propylene glycol) (PPG) and poly(dimethyl siloxane) (PDMS) confined to a nanoporous host system revealed by dielectric spectroscopy, temperature-modulated DSC and neutron scattering is compared. For both systems the relaxation rates estimated from dielectric spectroscopy and temperature-modulated DSC agree quantitatively indicating that both experiments sense the glass transition. For PPG the segmental dynamics is determined by a counterbalance of adsorption and confinement effect.

Electrochemical remediation of copper contaminated kaolinite by conditioning anolyte and catholyte pH simultaneously.

This report examined electrochemical remediation of copper contaminated kaolinite by controlling electrolytes' pH for both of anolyte and catholyte simultaneously. Results showed that electrokinetic process and remediation efficiency varied obviously when different buffer systems, including citric acid (test 1 ) nitric acid + EDTA (test 2) and nitric acid (test 3), were used to control catholyte pH and Na2CO3 was used at the same time to control all anolyte one. It was found that under such pH condition soil's pH in soil column kept at 3.

Anisotropic motion of cholesterol in oriented DPPC bilayers studied by quasielastic neutron scattering: the liquid-ordered phase.

Quasielastic neutron scattering (QENS) at two energy resolutions (1 and 14 microeV) was employed to study high-frequency cholesterol motion in the liquid ordered phase (lo-phase) of oriented multilayers of dipalmitoylphosphatidylcholine at three temperatures: T = 20 degrees C, T = 36 degrees C, and T = 50 degrees C. We studied two orientations of the bilayer stack with respect to the incident neutron beam. This and the two energy resolutions for each orientation allowed us to determine the cholesterol dynamics parallel to the normal of the membrane stack and in the plane of the membrane separately at two different time scales in the GHz range.

How to move things around a hospital: transport logistics at St. Michael's.

Ongoing fiscal restraint challenges hospitals to focus their resources primarily on core services. Support services receive much less attention. This article describes the experience of Toronto's St.

Best laid plans: effective implementation of re-engineering recommendations.

Continuing pressures on health care funding have led most hospitals to undertake re-engineering and restructuring projects to reduce operating expenses. Unfortunately, savings often turn out to be less than anticipated, as the projects falter in the implementation stage. As part of a two-year process improvement and expense reduction project, Toronto's St.