Oligomer telechelic

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. 

Figure 8.17 Copolymerization of telechelic oligomer 30 with a rigid aromatic diene.

This strategy is used for the synthesis of three different exact-mass telechelic oligomers. GPC, NMR, and GC/MS evidence indicates that clean depolymerization chemistry occurs for all three samples. Poly( 1,4-butadiene) (38) is broken down into oligomeric units with two, three, and four repeat units using catalyst 23. Catalyst 14 is more efficient and produces even lower molecular weight oligomers, primarily one and two repeat units. When allylchlorodimethylsilane is used instead of ethylene with 14, telechelic dimers are the only product. 

Figure 8.20 Metathesis depolymerization produces exact-mass telechelic oligomers.

Figure 8.21 Synthesis of various difunctional telechelic oligomers via ADMET depolymerization.

In order to prove that intramolecular cyclization occurs before telechelic oligomer formation, an experiment similar to previous work by Calderonlf is performed using 14 in place of Calderon s classical catalyst system. Macrocyclic species are formed when a toluene solution of polybutadiene is exposed to this catalyst, supported by both NMR and GC data. The vinylic resonances are clearly shifted upfield from polybutadiene. GC analysis shows macrocyclic trimers and tetramer regioisomers. 

TDI isomers, 210 Tear strength tests, 242-243 TEDA. See Triethylene diamine (TEDA) Telechelic oligomers, 456, 457 copolymerization of, 453-454 Telechelics, from polybutadiene, 456-459 TEM technique, 163-164 Temperature, polyamide shear modulus and, 138. See also /3-transition temperature (7)>) Brill temperature Deblocking temperatures //-transition temperature (Ty) Glass transition temperature (7) ) Heat deflection temperature (HDT) Heat distortion temperature (HDT) High-temperature entries Low-temperature entries Melting temperature (Fm) Modulu s - temperature relationship Thermal entries Tensile strength, 3, 242 TEOS. See Tetraethoxysilane (TEOS)... 

Fig. 3. a,ro-Dienyl telechelic oligomers used for producing segmented copolymers by ADMET... 

Bismaleimide (BMI) polymers are produced by reaction of a diamine and a bismaleimide (Eq. 2-211) [de Abajo, 1988, 1999 Mison and Sillion, 1999]. Polymerization is carried out with the bismaleimide in excess to produce maleimide end-capped telechelic oligomers (XLVI). Heating at temperatures of 180°C and higher results in crosslinking via radical chain... 

HYDROGEN BOND FUNCTIONALIZED BLOCK COPOLYMERS AND TELECHELIC OLIGOMERS... 

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