Other Grafted Supports

About 40% of this population express markers of oligodendrocytes, and a similar proportion have astrocytic markers. To test the potential of these cells in vitro, ES cells propagated in this fashion were transplanted into the spinal cord or cerebral ventricles of myelin-deficient rats. Two weeks after transplantation, ES derived cells were present in the dorsal columns of the spinal cord both at the implant and several millimeters in both directions from that site. The mouse origin of the ES cells transplanted into rat was confirmed by analysis of mouse satellite DNA in the grafts. Similarly, intraventricular transplanted cells formed myelin in multiple brain regions [29]. These and other results support the further study of stimulated ES cells for potential therapies in the nervous system. 

The grafting of PEG onto PS, aimed at a variety of interesting applications, was pioneered by Inman [36], Regen [37], War-shawsky and Patchornick [38] and Sherrington [39]. Independent of our work, the laboratories of both Mutter [40,41] and Bayer and Rapp [42-48] described alternative procedures for the preparation of PEG-PS, with a focus on their application to peptide synthesis. We concur with the conclusions of other workers about the value of graft supports, but are not in a position to provide a... 

To understand the activity of the [W(CH3)6] (26) with other oxide supports, the synthesis was extended from silica to silica-alumina. In a similar way, like in silica, [W(CH3)6l was grafted on silica-alumina partially dehydroxylated at 500°C. Grafting experiments of [W(CH3)6] carried out in pentane at -50 to -30°C resulted in a brown solid 28 (Scheme 16). 

Because such polyether spacer polymers are also of interest in other fields of polymer-supported immobilization, the first reports published on the synthesis of polystyrene graft copolymers date back to almost one decade agp [111,112]. In fact, these graft supports have been applied successfidly in f ds where insoluble polymers with homogeneous phase reacticais are advantageous, e.g., for phase-transfer reactions [113-116]. 

Abstract A review of the thermolytic molecular precursor (TMP) method for the generation of multi-component oxide materials is presented. Various adaptations of the TMP method that allow for the preparation of a wide range of materials are described. Further, the generation of isolated catalytic centers (via grafting techniques) and mesoporous materials (via use of organic templates) is simimarized. The implications for syntheses of new catalysts, catalyst supports, nanoparticles, mesoporous oxides, and other novel materials are discussed. 

While our discussion will mainly focus on sifica, other oxide materials can also be used, and they need to be characterized with the same rigorous approach. For example, in the case of meso- and microporous materials such as zeolites, SBA-15, or MCM materials, the pore size, pore distribution, surface composition, and the inner and outer surface areas need to be measured since they can affect the grafting step (and the chemistry thereafter) [5-7]. Some oxides such as alumina or silica-alumina contain Lewis acid centres/sites, which can also participate in the reactivity of the support and the grafted species. These sites need to be characterized and quantified this is typically carried out by using molecular probes (Lewis bases) such as pyridine [8,9],... 

A large variety of polymers has been considered. In the beginning, polystyrene and styrene/ divinylbenzene copolymers (Merrifield resins) were by far the most used.73 Then others were tested such as polyvinyls,47-50,61-64 polyacrylates,72 4,75 and cellulose.76,77 Most commonly, diphenylphos-phane groups were grafted on the polymeric support, either directly or via one CH2 group. 

To our knowledge, there have been no previous attempts to develop a broad class of molecular catalysts that have temperature-dependent solubilities. When molecular catalysts are covalently bound to polymeric supports, they generally assume the solubihty properties of the host polymer. In the above fluorous catalysts, we Hke to think that a short segment of polymer is being grafted onto a molecular catalyst, hi other words, the ponytails can be viewed as pieces of Teflon , which impart more and more of the solubility characteristics of the polymer as they are lengthened. 

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