Telechelic synthesis pathways

Figure 3.1 Schematic overview of synthesis pathways to telechelic metathesis polymers.

An interesting pathway to telechelics is the synthesis of polymers containing heat- or light-sensitive groups in the main chain, for example, azo groups (432, 433,463). Thus, polycondensation of AIBN with diols yields polyesters (Fig. 17). 

Synthetic procedures are in place today that allow the polymer end-functionalization for all commonly used carbene complexes based on ruthenium, tungsten, and molybdenum. From a practical and applications point of view, both ends of a polymer chain are equally useful. From a mechanistic point of view, the functionalization of the polymer chain end using the reactivity of the propagating carbene complex is much more readily achieved than functionalization of the focal group. Nonetheless, functional initiation is an attractive way to ensure complete end (start) functionalization, which has received comparatively little attention so far. Reliable methods for the functional derivatization of commercially available carbene catalysts will allow not only the synthesis of mono-telechelic polymers with high degrees of end-functionalization but also polymerization from surfaces or solid supports and open up more synthetic pathways to hetero-telechelic polymers. 

PIB-toughened poly(methyl methacrylate) (PMMA) networks have been reported in which the PIB domains are covalently bound to a PMMA matrix [26]. The synthesis involved a macromonomer approach where a combination of radical and cationic polymerization techniques were used. Methacrylate tri-telechelic PIBs were prepared by living cationic polymerization followed by end functionalization and used in free-radical solution copol)mierization with various amounts of MMA. Scheme 14 represents the general reaction pathways for the synthesis of network. 

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