Polymerization, elastomer synthesis reactions

With the development of DESs, they have been applied on some polymerization reactions that are carried out at relatively high temperatures. In these synthetic processes, the eutectic mixtures can act as true solvent-template reactant systems, and thus the DES is at the same time the precursor, the template, and the reactant medium for the fabrication of the desired polymeric material with a defined morphology or chemical composition. Monte and co-workers have reported i) the frontal polymerizations carried out in the eutectic mixtures ChCl/Acrylic acid and ChCl/Mac, " ii) the synthesis of poly(octane-diol-co-citrate) elastomers using eutectic mixtures of 1,8-octanediol and lidocaine at temperatures below 100 C (see Figure 20.3.4), " and iii) the synthesis of poly(acrylic acid)-carbon nanotube composites in the eutectic mixture ChCl/Aciylic acid. " ... 

ADMET is quite possibly the most flexible transition-metal-catalyzed polymerization route known to date. With the introduction of new, functionality-tolerant robust catalysts, the primary limitation of this chemistry involves the synthesis and cost of the diene monomer that is used. ADMET gives the chemist a powerful tool for the synthesis of polymers not easily accessible via other means, and in this chapter, we designate the key elements of ADMET. We detail the synthetic techniques required to perform this reaction and discuss the wide range of properties observed from the variety of polymers that can be synthesized. For example, branched and functionalized polymers produced by this route provide excellent models (after quantitative hydrogenation) for the study of many large-volume commercial copolymers, and the synthesis of reactive carbosilane polymers provides a flexible route to solvent-resistant elastomers with variable properties. Telechelic oligomers can also be made which offer an excellent means for polymer modification or incorporation into block copolymers. All of these examples illustrate the versatility of ADMET. 

The synthesis of elastomers by step, chain, and ring-opening polymerizations is reviewed. These reactions are characterized as to the process variables which must be controlled to achieve the synthesis and crosslinking of an elastomer of the required structure. Both radical and ionic chain polymerizations are discussed as well as the structural variations possible through copolymerization and s tereoregularity. 

Gheneim R, Perez-Beramen C, Gandini A. Diels-Alder reactions with novel polymeric dienes and dienophiles synthesis of reversibly cross-linked elastomers. Macromolecules 2002 35 7246-7253. 

AO containing various phenolic moieties were prepared by transesterification in the presence of tetraalkyl titanates. Randomly distributed -active moieties are characteristic of 140 (only the hard polyester segment is given) prepared from dimethyl terephthalate, 1,4-butanediol, poly(tetramethylene oxide)diol and dimethyl 5-(3,5-di-tm-butyl-4-hydroxybenzenepropaneamido)isophthalate [181]. The mentioned polymeric AO was used for stabilization of polyether-polyester elastomers. A partial attachement of tetrakis[methylene 3(3,5-di-tert-butyl-4-hydroxy-phenyl)propionate]methane (3) via transesterification reaction was expected in the synthesis of another polyether-polyester elastomer by [182]. A reversible redox polyester was formed from 2,5-bis(2-hydroxyethyl)hydroquinone and dichlorides of aliphatic dicarboxylic acids [137],... 

A thermopolastic elastomer based on sulfonated-EPDM, S-EPDM, was developed in the 1970 s by Exxon and more recently by Uniroyal. Unlike the synthesis of the carboxylate ionomers described above, S-EPDM is prepared by a post-polymerization sulfonatlon reaction(28). Compared to the metal neutralized S-EPDM, the sulfonic acid derivative is not highly associated. The free acid materials possess low strengths and are less thermally stable. The metal salts of S-EPDM have properties comparable to crosslInked elastomers, but they do exhibit viscous flow at elevated temperatures. In the absence of a polar cosolvent, such as methanol, hydrocarbon solutions of the metal salts of S-EPDM are solid gels at polymer concentrations above several percent(31). With the addition of 1 to 5% alcohol the polymer solution becomes fluid with solution viscosities of the order of 10 to 100 poise. 

ADMET polymerization represents a versatile technique for the synthesis of unique, complex, and functional polymer stractures. ADMET is a step-growth polycondensation reaction that proceeds under mild conditions, whereby any molecule that can be functionalized with two terminal olefin groups has the potential to become an ADMET monomer. This, in turn, allows an almost Hmitless possibility to create interesting and useful polymer structures. Recently, ADMET has been used to synthesize functionalized PEs, silicon-containing elastomers, conductive polymers, and many other exotic and interesting macromolecules. Yet, this area of research is by no means exhausted rather, this simple and elegant reaction will continue to provide the means to explore the basic stracture-property relationships of complex functional materials. 

The sol-gel synthesis of hybrid materials involves the occurrence of hydrolysis and condensation reactions in the presence of an organic polymer. Obviously, the selection of suitable polymer is of fundamental importance for the synthesis of the hybrid materials, as it should exhibit good miscibility with typical sol-gel precursors. The presence of suitable functional groups can facilitate the linkage between the polymer and the inorganic component. Also, the nature of the polymeric matrix is important because different properties of the matrix and, consequently, of the resulting nanohybrid material can be addressed for instance, the polymeric marix can be an elastomer (as in the case of polydimethylsiloxane) or thermoplastic (e.g., polytetrahydrofuran), amorphous, or (partially) crystalline [81]. 

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