Explicit Ion Effects on the Charge and Conformation of Weak Polyelectrolytes.

The titration behavior of weak polyelectrolytes is of high importance, due to their uses in new technologies including nanofiltration and drug delivery applications. A comprehensive picture of polyelectrolyte titration under relevant conditions is currently lacking, due to the complexity of systems involved in the process. One must contend with the inherent structural and solvation properties of the polymer, the presence of counterions, and local chemical equilibria enforced by background salt concentration and solution acidity.

Role of Associative Charging in the Entropy-Energy Balance of Polyelectrolyte Complexes.

Polyelectrolytes may be classified into two primary categories (strong and weak) depending on how their charge state responds to the local environment. Both of these find use in many applications, including drug delivery, gene therapy, layer-by-layer films, and fabrication of ion filtration membranes. The mechanism of polyelectrolyte complexation is, however, still not completely understood, though experimental investigations suggest that entropy gain due to release of counterions is the key driving force for strong polyelectrolyte complexation.

Computational structure determination of novel metal-organic frameworks.

A structure prediction tool has been developed to guide the discovery of MOF materials. This computational strategy has been trained over a series of existing MOFs and further successfully applied in tandem with an experimental effort to produce novel Zr MOFs based on naturally occurring carboxylic acids.

Weak polyelectrolyte complexation driven by associative charging.

Weak polyelectrolytes are relevant for a wide range of fields; in particular, they have been investigated as "smart" materials for chemical separations and drug delivery. The charges on weak polyelectrolytes are dynamic, causing polymer chains to adopt different equilibrium conformations even with relatively small changes to the surrounding environment. Currently, there exists no comprehensive picture of this behavior, particularly where polymer-polymer interactions have the potential to affect charging properties significantly.

SSAGES: Software Suite for Advanced General Ensemble Simulations.

Molecular simulation has emerged as an essential tool for modern-day research, but obtaining proper results and making reliable conclusions from simulations requires adequate sampling of the system under consideration. To this end, a variety of methods exist in the literature that can enhance sampling considerably, and increasingly sophisticated, effective algorithms continue to be developed at a rapid pace. Implementation of these techniques, however, can be challenging for experts and non-experts alike.

Highly selective carbon dioxide uptake by [Cu(bpy-n)2(SiF6)] (bpy-1 = 4,4'-bipyridine; bpy-2 = 1,2-bis(4-pyridyl)ethene).

A previously known class of porous coordination polymer (PCP) of formula [Cu(bpy-n)(2)(SiF(6))] (bpy-1 = 4,4'-bipyridine; bpy-2 = 1,2-bis(4-pyridyl)ethene) has been studied to assess its selectivity toward CO(2), CH(4), N(2), and H(2)O. Gas sorption measurements reveal that [Cu(bpy-1)(2)(SiF(6))] exhibits the highest uptake for CO(2) yet seen at 298 K and 1 atm by a PCP that does not contain open metal sites. Significantly, [Cu(bpy-1)(2)(SiF(6))] does not exhibit particularly high uptake under the same conditions for CH(4), N(2), and, H(2)O, presumably because of its lack of open metal sites.

Copolymerization of divinylsilyl-11-silicotungstic acid with butyl acrylate and hexanediol diacrylate: synthesis of a highly proton-conductive membrane for fuel-cell applications.

Highly conducive to high conductivity: Polyoxometalates were incorporated in the backbone of a hydrocarbon polymer to produce proton-conducting films. These first-generation materials contain large, dispersed clusters of polyoxometalates. Although the morphology of these films is not yet optimal, they already demonstrate practical proton conductivities and proton diffusion within the clusters appears to be very high.