Ring opening polymerization metal catalyzed

Ring-Opening Polymerization. As with most other inorganic polymers, ring-opening polymerization of cyclotetrasilanes has been used to make polysilanes (109,110). This method, however, has so far only been used for polymethylphenylsilane (eq. 12). Molecular weights (up to 100,000) are higher than from transition-metal catalyzed polymerization of primary silanes. 

This scheme is remarkably close to the coordination insertion mechanism believed to operate in the metal alkoxide-catalyzed ring-opening polymerization of cyclic esters (see Section 2.3.6). It shares many features with the mechanism proposed above for the metal alkoxide-catalyzed direct polyesterification (Scheme 2.18), including the difficulty of defining reaction orders. 

Co/Zn double metal cyanide catalyzed ring-opening polymerization of propylene oxide effect of cocataiysts on polymerization behavior... 

Ring opening polymerization can also be catalyzed by transition metals as shown in reaction (13) (12,30). The process appears to involve hydrogenolysis of the Si-N bond, given that reaction (13)... 

None of the above described ring opening polymerization methods has, as yet, proved useful for the formation of polysilazane preceramic polymers. However, Si-N bond cleavage and reformation, as it occurs in reaction (13), is probably responsible in part for the curing or thermoset step in transition metal catalyzed dehydrocoupling polymerization of hydridosilazanes (31), as described below. 

Recent Developments in Metal-Catalyzed Ring-Opening Polymerization of Lactides and Glycolides Preparation of Poly lactides, Polyglycolide, and Poly(lactide-co-glycolide)... 

Recent Developments in Metal-Catalyzed Ring-Opening Polymerization... 

Conventional ring-opening polymerization of cyclic anhydrides, carbonates, lactones, and lactides require extremely pure monomers and anhydrous conditions as well as metallic catalysts, which must be completely removed before use, particularly for medical applications. To avoid these difficult restrictions, an enzymatic polymerization may be one of the more feasible methods to obtain the polyesters. This method was first reported by two independent groups (Kobayashi [152] and Gutman [153]) who showed that lipases, enzymes capable of catalyzing the hydrolysis of fatty acid esters, can polymerize various medium-sized lactones. 

SCBs and disilacyclobutanes are known to undergo ring-opening polymerization catalyzed by transition metal complexes including those of platinum, palladium, and rhodium <1965JOC2618>. Lappert and co-workers suggested that... 

It is applied to macromolecules in the ring-opening polymerization of cycloalkenes and bicycloalkenes. Polypenlenamer is obtained by the polymerization of cy-clopentene catalyzed by transition metal compounds. 

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