6 research outputs found
High Surface Area and Zā² in a Thermally Stable 8-fold Polycatenated Hydrogen-bonded Framework
1,3,5-Tris(4-carboxyphenyl)benzene assembles into an intricate 8-fold polycatenated assembly of (6,3) hexagonal nets formed through hydrogen bonds and Ļ-stacking. One polymorph features 56 independent molecules in the asymmetric unit, the largest Zā² reported to date. The framework is permanently porous, with a BET surface area of 1095 m2 gā1 and readily adsorbs N2, H2 and CO2
Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid
The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG) is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters) under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear magnetic resonance techniques were used to study the bulk phase acid-catalyzed aqueous reactions (Fischer esterification) of 2-MG. While the present results indicate that 2-MG oligoesters are formed in the bulk phase with similar water content equilibrium dependences as observed in atmospheric chamber SOA experiments, the acid-catalyzed rate of the Fischer esterification mechanism may be too slow to rationalize the 2-MG oligoester production timescales observed in the atmospheric chamber experiments. Furthermore, it appears that unrealistically high ambient SOA acidities would also be required for significant 2-MG oligoester content to arise via Fischer esterification. Therefore, the present results suggest that other, more kinetically facile, esterification mechanisms may be necessary to rationalize the existence of 2-MG oligomers in atmospheric chamber-generated and ambient SOA
Dynamic Coloration of Complex Emulsions by Localization of Gold Rings Near the Triphase Junction
Multiphase microscale emulsions are a material platform that can be tuned and dynamically configured by a variety of chemical and physical phenomena, rendering them inexpensive and broadly programmable optical transducers. Interface engineering underpins many of these sensing schemes but typically focuses on manipulating a single interface, while engineering of the multiphase junctions of complex emulsions remains underexplored. Herein, multiphilic triblock copolymer surfactants are synthesized and assembled at the triphase junction of a dynamically reconfigurable biphasic emulsion. Tailoring the linear structure and composition of the polymer surfactants provides affinity to each phase of the complex emulsion (hydrocarbon, fluorocarbon, and continuous water phase), yielding selective localization of polymers around the triphase junction. Conjugation of these polymers with gold nanoparticles, forming structured rings, affords a dynamic reflected isotropic structural color that tracks with emulsion morphology, demonstrating the uniquely enabling nature of a functionalized triphase interface. This color is the result of interference of light along the internal hydrocarbon/fluorocarbon interface, with the gold nanoparticles scattering and redirecting light into total internal reflection competent paths. Thus, the functionalization of the triphase junction renders complex emulsions colorimetric sensors, a powerful tool toward sensitive and simple sensing platforms
Supramolecular Assembly of Tris(4-carboxyphenyl)arenes: Relationship between Molecular Structure and Solid-State Catenation Motifs
The
crystal structures of seven 1,3,5-trisĀ(4-carboxyphenyl)Āarenes
with functionalized central arene rings are reported. The formation
of (6,3) <b>hcb</b> hexagonal sheets as a result of carboxylic
acid dimer formation was observed in most of the crystal structures,
with the exception of two compounds with functional groups capable
of forming hydrogen bonds, namely, 2,4,6-trisĀ(4-carboxyphenyl)-1,3-diaminobenzene
and 2,4,6-trisĀ(4-carboxyphenyl)-3-methylaniline. These structures
were found to incorporate THF solvent molecules in their hydrogen-bonding
motif, giving rise to distorted pseudohexagonal arrays. Functional
groups on the central ring were found to influence stacking distances,
stacking offsets, inclination angles, degree of catenation, and dimensions
of solvent-occupied channels. To better understand and appreciate
these complicated crystal structures, they were categorized into four
distinct stacking/catenation families: simple stacking, single-layer
offset catenation, double-layer offset catenation, and rotated-layer
catenation. The unique structure of the unfunctionalized parent compound
1,3,5-trisĀ(4-carboxyphenyl)Ābenzene is rationalized in light
of the structural behavior of its derivatives
High Surface Area and Zā² in a Thermally Stable 8-fold Polycatenated Hydrogen-bonded Framework
1,3,5-Tris(4-carboxyphenyl)benzene assembles into an intricate 8-fold polycatenated assembly of (6,3) hexagonal nets formed through hydrogen bonds and Ļ-stacking. One polymorph features 56 independent molecules in the asymmetric unit, the largest Zā² reported to date. The framework is permanently porous, with a BET surface area of 1095 m2 gā1 and readily adsorbs N2, H2 and CO2
High surface area and Zā² in a thermally stable 8-fold polycatenated hydrogen-bonded framework
1,3,5-Tris(4-carboxyphenyl) benzene assembles into an intricate 8-fold polycatenated assembly of (6,3) hexagonal nets formed through hydrogen bonds and pi-stacking. One polymorph features 56 independent molecules in the asymmetric unit, the largest Z\u27 reported to date. The framework is permanently porous, with a BET surface area of 1095 m(2) g(-1) and readily adsorbs N-2, H-2 and CO2