Polymers, addition organosilicon

Poly(dimethylsiloxane) (PDMS) is the simplest of organosilicone elastomers. PDMS was commercially developed by Dow Coming in the 1960 s. It possesses inertness and usefiil mechanical properties, and can also be readily made into various desired shapes for medical items including prostheses of different bone and soft tissue elements (in surgery), and ancillary components such as tubes, catheters, shunts and dmg carriers. In addition, PDMS has shown good compatibility in clinical research.(7) So it has been a very usefiil synthetic polymer in medicine. In fact, silicone polymers are often employed in checking the biocompatibility of new polymers. Furthermore, organosilicones comprise an important class of compounds used in resins, and room temperature and heat-cured robber industrial and consumer products. 

In 1957 (2) platinic, ruthenium, and iridium chlorides were shown to be catalysts leading to very rapid additions, sometimes below room temperature, of many kinds of SiH compounds. These findings initiated much activity, chiefly in industrial research laboratories, in several countries, because they indicated that the manufacture of new organosilicon monomers and many new silicone polymers and copolymers would become commercially practicable for the first time. 

In conclusion, we would like to mention that, in addition to this new direction, a large consumer of metal alkoxides (initially aluminium and titanium) is by tradition the technology of materials, where the alkoxides are used for hy-drophobization and for cross-linking of the polyhydroxocompounds, epoxides and polyester resins, and organosilicon polymers. The products of the partial hydrolysis and pyrolysis of alkoxides — polyorganometalloxanes — are applied as components of the thermally stable coatings [48J. 

Muzafarov, Golly and Moller 646 have prepared similar poly(alkoxysilanes) that are easily hydrolyzed under acidic conditions and are thus biodegradable. Additional branched organosilicon polymers of interest include those of Ishikawa et al. fi4c ... 

Marosfoi, B., Szabo, A., Kiss, K., and Marosi, G. 2009. Use of organosilicone composites as flame retardant additives and coating for polypropylene. In Fire Retardancy of Polymers, eds. Kandola, K. and Hull, R. Cambridge, U.K. Royal Society of Chemistry, pp. 49-58. 

Especially the latter subject is a strongly developing field of research, trying to find answers to such important questions as, e.g., the stereo- and enantioselective synthesis of organosilicon polymer precursors and the use of Si-M compounds for the production of new polymers. In addition, even in widely used industrial processes as, e.g. the hydrosilylation reaction, the respective mechanism is still under discussion and research is focused on the development of more active and less expensive catalysts (compared to the today used nobel metal complexes). 

In addition to new resists, future generations of devices will require improved dielectrics that can be deposited at low temperatures and provide process flexibility. Again, organosilicon polymers have promise for this application. In this chapter, the chemistry and processes for both of these areas will be reviewed. 

Hydrosilylation of unsaturated organosilicon compounds has also found several applications in molecular and polymer organosilicon chemistry. In particular, the addition of polyfunctional silicon hydrides to poly(vinyl)organosiloxane, catalyzed exclusively by Pt compounds and providing an activated cure for silicon rubber [10], has been of great practical importance. Hydrosilylation of the vinyl group at silicon seems to be effective synthetic method for preparation of oligomers and polymers with a linear or cyclolinear stmcture (polyhydrosilylation), and can occur either via the addition of dihydro-carbosilanes and -siloxanes to divinyl-silanes and -siloxanes [25, 26] or by intermolecular hydrosilylation [4] (eq. (1)). 

The reaction is a sequential Michael addition of an organosilicon compound to a,P-unsaturated esters, ketones, rritriles, and carboxamides. Chain propagation proceeds by transfer of the silyl group from the silyl ketene acetal catalyst to the monomer with the generation of a new ketene acetal, and if inadvertent termirration is avoided, repeated addition of the monomer leads to a living polymer. The typical reaction shown as follows rrses the catalyst l-methoxy-l-trimethylsiloxy-2-methyl prop-l-ene, but a cocatalyst is required, and this is either an anionic species or a Lewis acid. 

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