Aliphatic cyclic carbonates and spiroorthocarbonates as monomers

The room-temperature reactions of excess Ti(OiPr)4 with the hydroxyl groups of a nonporous silica yield dinuclear surface complexes regardless of the degree of partial dehydroxylation of the silica. The surface reactions were studied by in situ IR transmission spectroscopy, 13C CP/MAS NMR, GC/MS, and elemental analysis. The spontaneous stoichiometric formation of both 2-propanol and propene during grafting indicates that interaction of Ti(OiPr)4 with the silica surface induces disproportionation of alkoxide ligands with concomitant formation of Ti−O−Ti bridges. A synthetic route to mononuclear silica-supported Ti alkoxide complexes was developed by reaction of grafted amide complexes (⋮SiO)nTi(NEt2)4-n (n = 1 or 2) with alcohols. Subsequent reactions of the mononuclear surface alkoxide complexes with Ti(OiPr)4 yield dinuclear species identical to those prepared by the direct reaction of Ti(OiPr)4 with silica. Both mono- and dinuclear supported alkoxide complexes undergo ligand-exchange reactions with tert...

Mono- and Dinuclear Silica-Supported Titanium(IV) Complexes and the Effect of TiOTi Connectivity on Reactivity

Nanolimes are alcohol dispersions of Ca(OH)2 nanoparticles used in the conservation of cultural heritage. Although it was believed that Ca(OH)2 particles were inert when dispersed in short-chain alcohols, it has been recently shown that they can undergo transformation into calcium alkoxides. Little is known, however, about the mechanism and kinetics of such a phase transformation as well as its effect on the performance of nanolimes. Here we show that Ca(OH)2 particles formed after lime slaking react with ethanol and isopropanol and partially transform (fractional conversion, α up to 0.08) into calcium ethoxide and isopropoxide, respectively. The transformation shows Arrhenius behavior, with apparent activation energy Ea of 29 ± 4 and 37 ± 6 kJ mol–1 for Ca-ethoxide and Ca-isopropoxide conversion, respectively. High resolution transmission electron microscopy analyses of reactant and product phases show that the alkoxides replace the crystalline structure of Ca(OH)2 along specific [hkl] directions, preser...

Kinetics and Mechanism of Calcium Hydroxide Conversion into Calcium Alkoxides: Implications in Heritage Conservation Using Nanolimes.

The combination of organic polymers with the sol–gel process represents one major route for the preparation of inorganic–organic hybrid materials. One challenge in this kind of materials is to overcome macroscopic phase separation. This review gives an overview of concepts that lead to homogeneously dispersed materials by tailoring the inorganic–organic interface.

The search of a homogeneously dispersed material—the art of handling the organic polymer/metal oxide interface

Low temperature methods have been applied to the synthesis of many advanced materials. Non-hydrolytic sol-gel (NHSG) processes offer an elegant route to stable and metastable phases at low temperatures. Excellent atomic level homogeneity gives access to polymorphs that are difficult or impossible to obtain by other methods. The NHSG approach is most commonly applied to the preparation of metal oxides, but can be easily extended to metal sulfides. Exploration of experimental variables allows control over product stoichiometry and crystal structure. This paper reviews the application of NHSG chemistry to the synthesis of negative thermal expansion oxides and selected metal sulfides.

https://www.mdpi.com/1996-1944/3/4/2567/pdf

D.E. Tcheboukov

Papers

Physicochemical approach to the studies of metal alkoxides