Positron/positronium annihilation as a probe for chemical environments of free volume holes in fluoropolymers

Type 3 porous liquids based on non-ionic liquid phases - a broad and tailorable platform of selective, fluid gas sorbents

We describe a series of Type 3 porous liquids, denoted "T3PLs", based on a wide range of microporous solids including MOFs, zeolites and a porous organic polymer (PAF-1). These solids are dispersed in various non-ionic liquid phases (including silicone oils, triglyceride oils, and polyethylene glycols) which have a range of structures and properties, and that are in many cases sterically excluded from the pores of the solids. Several stable dispersions with high gas uptakes are obtained. We show how these dispersions can be tailored toward important gas separation processes (CO2/CH4, C2H4/C2H6) and applications that require biocompatibility.

Amino-diol borate complexation for controlling transport phenomena of penetrant molecules into polymeric matrices

A new type of epoxy-amine-borate (EAB) hybrid material is reported for control of penetrant solvent molecules into cross-linked polymer networks.

The ability of the Coincidence Doppler Broadening Spectroscopy to characterize polymers containing different chemical elements

Hydrocarbon polymers, O-containing, F-containing and Cl-containing polymers are comprehensively studied by Coincidence Doppler Broadening Spectroscopy (CDBS). It is shown that for polymers with different chemical structure, CDBS results can effectively distinguish polar groups CO, CCl, and CF. For polymers with similar chemical structure, the intensity of the element-specific peak in the CDBS ratio curve is dependent not only on the fraction of free positrons, but also on the content of characteristic atom in polymer repeated unit, and the polarity of the polymer molecule. For polymers containing several different polar groups, such as PCTFE (CF & CCl) and PFA (CF & CO), whether the element-specific peak appears or not depends on the amount of the polar groups and its positron capture ability. This work may provide insights into potential applications of CDBS for studying complex polymer systems.

Positron annihilation characteristics, water uptake and proton conductivity of composite Nafion membranes

The connection between microstructure evolution, in terms of o-Ps lifetime, and proton conductivity in Nafion membranes with different water uptakes.

Molecular-level insight of hindered phenol AO-70/nitrile-butadiene rubber damping composites through a combination of a molecular dynamics simulation and experimental method

The damping properties of AO-70/NBR composites get a noteworthy increase with the introduction of AO-70—max tan δincreased by 66.9%.

Towards new proton exchange membrane materials with enhanced performance via RAFT polymerization

This study focuses on the synthesis of well-defined proton exchange membranes (PEM) for fuel cell applications using reversible addition–fragmentation chain transfer (RAFT) polymerization in the radiation-induced grafting part of the overall process.

Experimental study and molecular dynamics simulation of dynamic properties and interfacial bonding characteristics of graphene/solution-polymerized styrene-butadiene rubber composites

The effect of the vinyl content on microstructure, thermodynamics and dynamics properties of graphene/SSBR composites was investigated. SSBR with the highest vinyl content has the highest interfacial shear stress by pullout simulation.

Element specificity of ortho-positronium annihilation for alkali-metal loaded SiO2 glasses

Momentum distributions associated with ortho-positronium (o-Ps) pick-off annihilation photon are often influenced by light elements, as, e.g., carbon, oxygen, and fluorine. This phenomenon, so-called element specificity of o-Ps pick-off annihilation, has been utilized for studying the elemental environment around the open spaces. To gain an insight into the element specificity of o-Ps pick-off annihilation, the chemical shift of oxygen 1s binding energy and the momentum distributions associated with o-Ps pick-off annihilation were systematically investigated for alkali-metal loaded SiO2 glasses by means of X-ray photoelectron spectroscopy and positron-age-momentum correlation spectroscopy, respectively. Alkali metals introduced into the open spaces surrounded by oxygen atoms cause charge transfer from alkali metals to oxygen atoms, leading to the lower chemical shift for the oxygen 1s binding energy. The momentum distribution of o-Ps localized into the open spaces is found to be closely correlated with the oxygen 1s chemical shift. This correlation with the deepest 1s energy level evidences that the element specificity of o-Ps originates from pick-off annihilation with orbital electrons, i.e., dominantly with oxygen 2p valence electrons and s electrons with lower probability.