Nanostructured Silica-Based Organic-Inorganic Hybrid Materials—Evidence for Self-Organization of a Xerogel Prepared by Sol-Gel Polymerization

Abstract

A hydrolytic polycondensation reaction of a rigid, rodlike nonmesomorphous precursor leads to an isotropic sol and then an anisotropic birefringent xerogel (see scheme). Optical and X-ray structural analyses demonstrate a short-range order and the possibility of a crystalline order.

A More Efficient Catalyst for the Carbonylation of Chloroarenes

“…Other catalyst systems give less than satisfying yields (`40 %) and/or catalytic productivities (TON`40) in the carbonylation of unactivated chloroarenes. [8] Herein we describe a new palladium catalyst system that allows an efficient carbonylation of electron poor, neutral, and electron rich aryl chlorides in good to very good yields. With regard to catalytic productivity, all the results reported so far for the carbonylation of aryl chlorides are surpassed by at least an order of magnitude.…”

Bridged Silsesquioxanes with Organic Domains Self‐Assembled as Functionalized Molecular Channels

“…Self-assembly can occur previous to or during the polycondensation of terminal groups, induced by strong hydrogen bonds, aromatic p-stacking, or van der Waals interactions between (CH 2 ) n groups. [15][16][17][18][19][20][21][22][23][24][25][26] When the self-assembly and polycondensation processes take place simultaneously, the organization attained in the final material depends on their relative rates. [26] A variety of structures and properties has been reported for self-assembled bridged silsesquioxanes.…”

“…Weak interactions between aromatic units led to birefringent hybrids. [15] Helical morphologies, hollow tubes, and spheres were generated from chiral precursors capable of associating through strong hydrogen bonds between urea groups. [16,19,20] Highly crystalline hybrid materials were synthesized from a precursor with a diureabenzene group.…”

Formation of Ordered Silica-Organic Hybrids by Self-Assembly of Hydrolyzed Organoalkoxysilanes with Long Organic Chains

“…Because simple sol-gel reactions of alkoxysilanes usually result in the formation of amorphous materials [4], much efforts have been made in the structural control on a nanometer-length scale [5][6][7][8]. Such an attempt is of great interest from the possibility to produce novel hybrid materials with unique structures and properties.…”