Silsesquioxanes cores

The reactions of POSS molecules fall into two categories, those involving the silsesquioxane core of the molecule and those involving reactions of the peripheral substituents. The silsesquioxane core in POSS compounds is fairly unreactive to many reaction conditions and this inertness has led to the successful application of POSS species in many materials (see Section V for further... 

Star-like PFs 236 with a silsesquioxane core have been prepared by Ni-mediated copolymerization of 2,7-dibromo-9,9-dioctylfluorene with octa(2-(4-bromophenyl)ethyl)octasilses-quioxane [333]. The polymer is thermally stable up to 424°C (TGA). In both chloroform solution and films, its absorption and PL spectra are very close to that for PFO 196, although a somewhat higher PL efficiency is observed in films (64 and 55%, respectively). The polymer 236, however, demonstrates a better PL color stability during thermal annealing. An ITO/PEDOT/236/Ca/Ag device can be turned on at 6.0 V, and shows a brightness of 5430 cd/m2 (at 8.8 V) with F] =0.44%, almost twice as high as that for the corresponding PFO device (Chart 2.60). 

Crivello, J. V. Malik, R. Synthesis and Photoinitiated Cationic Polymerization of Monomers Containing the Silsesquioxane Core. In Silicones and Silicone-Modified Materials-, Glarson, S. J., Fitzgerald, J. J., Owen, M. J., Smith, S. D., Eds. AGS Symposium Series 729 American Chemical Society Washington, DC, 2000 pp 284-295. 

This approach has also been employed for synthesis of highly enan-tiomerically enriched cychc silanes with sihcon-centered chirahty [141]. Zhang et al. [142] prepared second-generation dendrimers based on polyhedral silsesquioxane cores with up to 72 terminal groups at their surface (Scheme 13). 

Crivello, J.V. Malik, R. Synthesis and photoini-tiated cationic polymerization of monomers with the silsesquioxane core. J. Polym. Sci. Polym. Chem. 1997, 35, 407. 

Fig. 31 The structures of the hexa- and octa-silsesquioxanes cores for use as scaffolds...

Figure 10.6 Cole-Hamilton s dendrimer based on a polyhedral oligomeric silsesquioxanes core.

The PDMAEMA stars are weak cationic polyelectrolytes. But they can be easily transformed into strong cationic polyelectrolytes poly [2-(methacryloyloxy)ethyl] trimethylammonium iodide] (PMETAI) stars by quaternization with methyl iodide. Asymmetric field flow fractionation (AFFF) measurements showed that the silsesquioxane core remained intact. The PMETAI brushes were also subjected to... 

It is possible to observe the morphologies of the cationic PMETAI stars in solution by cryogenic transmission electron microscopy (cryo-TEM). Figure 1 clearly shows the distinct and well-separated structures in the vitrified solution. In some cases it is even possible to see the silsesquioxane core [28],... 

A carbosilane dendrimer decorated with Ru(bpy)3 units has been prepared and electrochemical studies reported. " " Newkome has reported first-generation stars with surface polyoxometallate decoration. " A silsesquioxane core has been functionalized and a series of dendritic systems bearing Frechet-type dendritic wedges and pendant Ru(tpy)(bpy)2 decoration has been described. Up to 32 of these units containing didentate tpy ligands have been attached to the surface. ... 

Costa, R. O. R. Vasconcelos, W. L. Tamaki, R. Laine, R. M., Organic/Inor-ganic Nanocomposite Star Polymers via Atom Transfer Radical Pol)uneriza-tion of Methyl Methacrylate Using Octafunctional Silsesquioxane Cores. Macromolecules 2001, 34, 5398-5407. 

The synthesis and properties of star polymers and dendrimers functionalized with ferrocene units has attracted a great deal of attention. The synthesis of high-generation dendrimers functionalized with chiral ferrocenyl units in their structures has been reported. The chiroptical properties of this class of dendrimer was dependent on the number of ferrocenyl groups and their chemical environment, but not on their position within the dendrimer. Deschenaux has reported the synthesis of hquid crystalline ferrocene-based polymers prossessing an enantiotropic smectic A phase. Ferrocene-functionahzed cyclic siloxane (29) and silsesquioxane branched polymers have also been reported. A hyperbranched polymer with a cubic silsesquioxane core was used to mediate the electrocatalytic oxidation of ascorbic acid. 

Synthesis and Photoinitiated Cationic Polymerization of Monomers Containing the Silsesquioxane Core... 

The present work focuses on the synthesis of novel multifunctional epoxy and vinyl ether monomers bearing the Tg silsesquioxane core and a study of their behaviour under photoinitiated cationic polymerization conditions. 

A series of octafunctional epoxy and 1-propenyl ether monomers bearing the Tg silsesquioxane core have been prepared and characterized. Despite the high functionality and reactivity of these monomers, the efficiency with which the monomers undergo crosslinking is considerably less than expected. Instead, due to steric inhibition effects and the proximity of the functional groups to one another, photoinduced cationic polymerization proceeds mainly by an intramolecular process. 

Polymers and Higher Order Structures with Cage Oligomeric Silsesquioxane Core. 208... 

Methacrylate and epoxy functionalized nanocomposites based on silsesquioxane cores for use in dental applications. European Polymer Journal,... 

There are several methods of introducing organic functional groups onto the cubic silsesquioxane core including both stoichiometric and catalytic procedures. The nucleophilic substitution is one of the most common, noncatalytic route and considers substitution of the halogen atom in w-haloalkyl derivatives of the silsesquioxane (Scheme 10.1) (2). 

Jaffres P-A, Morris RE (1998) Synthesis of highly functionalized dendrimers based on polyhedral silsesquioxane cores. J Chem Soc Dalton Trans 16 2767-2770... 

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