Hydrogenation reactions, star-block

Figure 10. Hydrogenation and sulfonation reactions of star-block copolymers.

Stars have been made with various functional groups. These include hydroxyl, acid, amine, epoxy, and reactive double bonds. The functional group can be incorporated randomly in the arm, in blocks, in the core, or at the end of the arms. The easiest way to functionalize the ends of the arms is to use a functional Initiator. Of course functional groups that contain active hydrogens, such as hydroxyl and acid, need to be protected during the GTP reaction. The blocking groups can be removed after polymerization is complete. 

With the exception of a few commercial polymers such as polyisobutylene, polybutadiene and styrene-butadiene block copolymers, living polymers are prepared in small quantities under stringent conditions. Larger amounts can only be prepared by repeating the synthesis many times, and this is a costly and time-consuming process. In the case of hydrogenated polybutadiene, to prepare samples that resemble polyethylene, the need for a secondary reaction step renders the preparation even more costly. This has so far limited the extent to which it has been possible to use these materials to test models. Cell et al. [ 18] prepared asymmetric stars with structures similar to ethylene-propylene copolymers by hydrogenation of star-branched polyisoprene. The reactions to produce these materials took up to three weeks, and... 

The TMS protective group was quantitatively deprotected by treatment with (C4H9)4NF in THF at room temperature (Scheme 7). SEC profiles of the resulting poly(12) and poly (13) exhibited narrow monomodal distributions similar to those of the original poly(12a) and poly(13a), respectively. Thus, TMS group is capable of protecting the active ethynyl hydrogen of 12 in addition to hydroxyl and amine functions. Since ethynyl and the related C=C bonds have been recently used in click reaction with azides to prepare block copolymers, star-branched polymers, and even hyperbranched... 

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