Template nonionic

N°I°, where both the template, nonionic polyethylene oxide (N°) and inorganic species (1°) are neutral. The organic-inorganic interaction is due to hydrogen bonding. 

Nonionic template synthesis of amide-linked catenanes and rotaxanes with macroheterocyclic fragments 97AG(E)930. 

R. Jager, F. Vogtle, A New Synthetic Strategy towards Molecules with Mechanical Bonds Nonionic Template Synthesis of Amide-Linked Catenanes and Rotaxanes , Angew. Chem Int. Ed. Engl. 1997,36,930-944. 

Since this initial work there has been a plethora of literature on mesoporous molecular sieves. In addition to the silica and aluminosilicate frameworks similar mesoporous structures of metal oxides now include the oxides of Fe, Ti, V, Sb, Zr, Mn, W and others. Templates have been expanded to include nonionic, neutral surfactants and block copolymers. Pore sizes have broadened to the macroscopic size, in excess of 40 nm in diameter. A recent detailed review of the mesoporous molecular sieves is given in ref [73]. Vartuli and Degnan have reported a Mobil M41S mesoporous-based catalyst in commercial use, but to date the application has not been publicly identified.[74]. 

The reaction of fumaryl dichloride (59a) with 52 in the presence of macro-ring 32 resulted indeed in 26% [2]rotaxane 60a and 26% of the pure thread 61a [19]. The remarkably high yield of 60a indicates that arene units are not needed for this nonionic template-assisted reaction. When, however, the 2,4-hexadiene diacid dichloride (59b) was used for rotaxane synthesis the [2]rotaxane 60b, even though detected by mass spectrometry, could not be isolated, either at room tem-... 

Amide-linked catenanes and rotaxanes, readily accessible via nonionic template synthesis, are molecules with fascinating topology, but their final breakthrough was only achieved when they became substrates for further chemical derivatiza-tion. A potential reaction site in the catenanes and rotaxanes presented so far is the sulfonamide group, because the proton can be selectively abstracted in the presence of carbon amide groups. Subsequent alkylation offers numerous possibilities of catenane and rotaxane chemistry. 

The nonionic template strategy based on hydrogen bonds and to a certain extent on n-n interactions has made catenanes and rotaxanes readily available. The molecular recognition and self-organization process which is responsible for the formation of intertwined and interlocked structures is founded upon the same weak interactions that govern many biological processes. Amide-based catenanes and rotaxanes can thus serve as valuable models for complex molecular recognition patterns in nature. 

Spherical particles in the micrometric size range of mesoporous MSU-X silica were obtained with nonionic PEO-based surfactant by a new, easy and highly reproducible synthesis pathway leading to Micelle Templated Structures (MTS) with large surface area and narrow pore size distribution. First results on their adsorption properties show that they could be used for HPLC applications. 

The typical procedure (42) involved mixing 4 g of nonionic triblock copolymer L123 (BASF), 20 g of water, and 80 g of 2M HC1. To this solution, 8 g of tetraethylorthosilicate was added at room temperature. The mixture was then stirred at room temperature for 24 h. The solid product was recovered by filtration. The polymer template was removed by calcination at 500°C for 5 h. 

Furthermore, aggregates of nonionic surfactants like polyoxyethylene alkyl/aryl ethers of the Tergitol, Triton, and Brij series were used as templates for the formation of mesoporous silica materials in neutral or acidic media. The pore diameters of the materials that can be obtained with these surfactants are restricted to around 5.5 nm. The advantages of these surfactants over triblock copolymers are that they are cheap, nontoxic, and biodegradable. An overview of the most commonly used SDAs is compiled in Table 3.1. 

Bagshaw, S. A., Prouzet, E. and Pinnavaia, T. J. Templating of mesoporous molecular sieves by nonionic polyethylene oxide surfactants, Science, 1995, 269, 1242-1244. 

Catalysts and catalytic supports are often formulated from aluminas owing to their low cost, and their thermal, chemical and mechanical stability [27], To this end, nonionic surfactant templating with polyethylene oxide surfactants was used to synthesize mesoporous alumina [28], Partially ordered mesoporous materials with wormhole channels were obtained - this seems to be a characteristic of templating with nonionic surfactants. Cationic surfactants have recently been found to template mesoporous aluminum oxide with pore sizes that could be fine-tuned by varying the molar ratio of the reactants [29]. The material obtained was thermally stable to 900 °C and exhibited a narrow pore size distribution. 

Recently, surface-functionalized particles with covalently bound carboxyl groups were prepared using an ionic as well as a nonionic surfactant as templates to perform crystallization on the surface of the particles [101]. This approach of crystallization outside of the particle (Fig. 9a) is in contrast to a previous report [27], where the... 

In a detailed study, mesostructured zirconia has been prepared by using various amphiphilic surfactants with different headgroups (anionic and nonionic) and different tail lengths (1-18 carbons) as templates. Removal of snrfactants leads to the loss of structural order and a decrease ofthe siuface area. However, the presence of phosphates and snlfates in the walls may improve the stability. 

This paper describes a novel process for the preparation of spherical mesoporous silica spheres in the submicrometer and micrometer size range. Tetra-n-alkoxysilanes are hydrolysed and condensed in the presence of n-alkylamine as nonionic template and ammonia as catalyst. The porosity and the morphology parameters can be independently adjusted in wide ranges. These materials are promising adsorbents in separations techniques and valuable catalyst supports. 

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