Modified inorganic materials

An alternative strategy to obtain silica immobilised catalysts, pioneered by Panster [23], is via the polycondensation or co-condensation of ligand functionalised alkoxysilanes. This co-condensation, later also referred to as the sol-gel process [24], appeared to be a very mild technique to immobilise catalysts and is also used for enzyme immobilisation. Several novel functional polymeric materials have been reported that enable transition metal complexation. 3-Chloropropyltrialkoxysilanes were converted into functionalised propyltrialkoxysilanes such as diphenylphosphine propyltrialkoxysilane. These compounds can be used to prepare surface modified inorganic materials. Two different routes towards these functional polymers can be envisioned (Figure 3.4). One can first prepare the metal complex and then proceed with the co-condensation reaction (route I), or one can prepare the metal complex after the... 

Two types of membranes may eontains fillers hydrophobie membranes (usually polydimelhoxysiloxane filled with zoelites) and heterogeneous ion-exchange membranes which may contain various surface modified inorganic materials. 

Although, in the context of electrode surface modifiers, inorganic materials are sometimes perceived to lack some of the synthetic fiexibiKty associated with polymeric materials (see Sect. 2.7.3.7), they commonly possess greater stability and robustness to physicochemical manipulation. This has provided the motivation to study the interfacial properties of a number of electroactive inorganic materials using the EQCM. 

FIGURE 4.1 Schematic approach used in the modification of biopolymers (a) blends, (b) chemical linkages, (c) cross-linking, (d) grafting, and (e) biocomposite formation (i, biopolymer matrix ii, biopolymer fillers iii, surface modified inorganic materials). (See insert for color representation of the figure.)... 

This includes inorganic materials such as mica, glass fibre and asbestos etc., impregnated or glued together with varnishes or compositions comprising ordinary organic substances for heat resistance such as oil-modified synthetic resins, bitumen, shellac and Bakelite. 

Woolfson and Mahmoud have classified the routes to preparation of decorated self-assembling peptide materials [53] as (1) co-assembly, where the functional part is already attached to a self-assembling component prior to assembly, and (2) postassembly, where a non-functionahsed self-assembled structure is modified by covalent or non-covalent means. This discussion adheres to this classification. A third route, beyond the scope of this review, is the use of structured peptides as templates for inorganic materials. Section 4.1 discusses functionalised self-assemblies formed from co-assembly-type approaches, while post-assembly modifications of self-assembled structures are considered in Sect. 4.2. 

The use of ordered supramolecular assemblies, such as micelles, monolayers, vesicles, inverted micelles, and lyotropic liquid crystalline systems, allows for the controlled nucleation of inorganic materials on molecular templates with well-defined structure and surface chemistry. Poly(propyleneimine) dendrimers modified with long aliphatic chains are a new class of amphiphiles which display a variety of aggregation states due to their conformational flexibility [38]. In the presence of octadecylamine, poly(propyleneimine) dendrimers modified with long alkyl chains self-assemble to form remarkably rigid and well-defined aggregates. When the aggregate dispersion was injected into a supersaturated... 

Phosphors are inorganic materials which convert incident radiant energy to visible light within a device. The device chosen can be a cathode-ray tube, i.e.- a television tube, or a fluorescent lamp. A phosphor consists of a matrix modified by an additive chosen so that it becomes optically active within the matrix, or compound. This is an example of a substitutional impurity in a lattice wherein the additive, usualty Ccdled an "activator", introduces a lattice defect that is optically active. However, the added impurity still follows all of the rules found for defects in a lattice, as shown by the following example. 

Voltron (DuPont) is a wire enamel in which nanoparticles of silicates or other inorganic materials are chemically linked to the enamel polymer backbone. Voltron provides a much better corona resistance than enamels merely filled with inorganic ingredients. One of the first ignition coils to use Voltron is for road-course and circle-track racing of modified stock cars. 

Organic polymers are widely used in modified electrodes [220], but inorganic materials such as zeoHtes, clays or microporous solids are attractive as replacements since they have much better stability, tolerance to high temperatures and oxidizing conditions, and chemical inertness. Due to the capability of clays to exchange intercalated ions, clay modified electrodes have been extensively studied. 

Transesterification Reactions. The heterogeneous acid-catalyzed transesterification of TGs has not been investigated as much as its counterpart, the base-catalyzed reaction. Various solids are available with sufficient acid strength to be effective catalysts for the named reaction. Among the solid acids available are functionalized polymers, such as the acid forms of some resins, as well as inorganic materials, such as zeolites, modified oxides, clays, and others. Some of these solids have already been found to be effective in transesterification reactions of simple esters and (3-ketoesters. 

The surface of polymer particles is characterized by ionogenecity, hydrophilicity, softness, roughness, etc. The most prominent feature of the organic polymer particle, compared with inorganic materials, is that these characteristics can be easily modified. Various modifications were reviewed in this chapter to give a guide to those who intend to prepare functional polymer particles. 

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