Step-growth polymers: metal polymer

Polymers in this category are synthesized by routes similar to the routes used to synthesize regular step-growth polymers. The difference, however, is that the monomer units contain a metal-metal bond. A sample step-growth polymerization reaction is shown in Eq. 7.1, which illustrates the reaction of a metal-metal bonded dialcohol with hexamethylene diisocyanate (HMDI) to form a polyurethane.4... 

Hvdroglycolysis The term hydroglycolysis refers to the combined use of polyols (diols, triols, etc.)/alcohols and water as the reagents to bring about chemical degradation of step-growth polymers. In one example PUR foam waste was dissolved in EG at 185-220°C under N2 water and alkali metal hydroxides (e.g. NaOH) were added to the... 

ABSTRACT. Polysilanes, (-SiRR -)n, represent a class of inorganic polymers that have unusual chemical properties and a number of potential applications. Currently the most practical synthesis is the Wurtz-type coupling of a dihalosilane with an alkali metal, which suffers from a number of limitations that discourage commercial development. A coordination polymerization route to polysilanes based on a transition metal catalyst offers a number of potential advantages. Both late and early metal dehydrogenative coupling catalysts have been reported, but the best to date appear to be based on titanocene and zirconocene derivatives. Our studies with transition metal silicon complexes have uncovered a number of observations that are relevant to this reaction chemistry, and hopefully important with respect to development of better catalysts. We have determined that many early transition metal silyl complexes are active catalysts for polysilane synthesis from monosilanes. A number of structure-reactivity correlations have been established, and reactivity studies have implicated a new metal-mediated polymerization mechanism. This mechanism, based on step growth of the polymer, has been tested in a number of ways. All proposed intermediates have now been observed in model reactions. 

The field of step-growth polymers encompasses many polymer structures and polymerization reaction types. This chapter attempts to cover topics in step-growth polymerization outside of the areas reviewed in the other introductory chapters in this book, i.e., poly(aryl ethers), dendritic polymers, high-temperature polymers and transition-metal catalyzed polymerizations. Polyamides, polyesters, polycarbonates, poly(phenylene sulfides) and other important polymer systems are addressed. The chapter is not a comprehensive review but rather an overview of some of the more interesting recent research results reported for these step-growth polymers, including new polymerization chemistries and mechanistic studies. 

Like other step-growth polymerization methods, factors such as the monomer purity, ratio of the monomers, conversion, temperature, and concentration will greatly influence the transition metal coupling polymerization. These factors have to be taken into account when higher molecular weight polymers need to be prepared.33... 

Hu, Q.-S., Nontraditional Step-Growth Polymerization—Transition Metal Coupling, in Synthetic Methods in Step-Growth Polymers, M. Rogers and T. Long, eds., Wiley, New York, 2003. 

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