Poly , side chain-type polyrotaxane

Poly(benzimidazole) can be used as the reactive polymer for the preparation of side chain-type polyrotaxane via the alkylation on nitrogen. Osakada et al. showed that deprotonation of poly(benzimidazole) followed by N-alkylation with alkyl bromide-terminated pseudorotaxane consisting of 2,3,6-trimethyl-/1-cyclodextrin gave a novel side chain-type polyrotaxane (Scheme 38) [206]. Poly(benzimidazole) having a long -hydroxyalkyl group as the side chain can form an inclusion complex with 2,3,6-trimethyl-/l-cy-... 

E and F). The essential difference in the main-chain structure between the two types of polyrotaxanes causes large differences in their physical or mechanical properties. Polyrotaxanes A-D are further divided into main- (A and B) and side-chain type (C and D). Meanwhile, the synthesis of poly[2]rotaxane (E) and poly[3]rotaxane (F) has been very recently achieved. Genuine poiyrotaxane seems to be one of the polyrotaxanes like the latter topological polyrotaxanes, which may reflect their truly unique structures to their properties. 

A side-chain polyrotaxane of Type 10 was also obtained by the reaction of de-protonated poly(benzimidazole) with a long-chain bromide bearing a BG at one end in the presence of / -CD [103], Because the CD was threaded onto the side chain before its reaction with backbone to form a hemirotaxane, the preparation is essentially Method 4. 

More recently, Harada et al. applied the complexation process to side-chain systems via Method 6 (Figure 10), in which the guest sites were introduced as pendant groups and thereafter the CD was threaded onto them [104, 105]. Different types of hydrocarbon chain as pendant groups were studied for their compatibility with different CDs. As the cyclic was not blocked, the products can be viewed as side-chain poly(pseudo rotaxane)s of Type 9. Probably because of the rapid exchange process between threaded and unthreaded forms, the isolation of the solid-state polyrotaxane was not reported. 

A rotaxane composed of many ring parts is referred to as a poly[ ]rotaxane [6] these, in turn, include mostly main-chain and side-chain polyrotaxanes (Figure 36.1). In main-chain polyrotaxanes, the ring components are threaded along a polymeric axle, to form a polymer of [2]rotaxanes. A variety of polymers can be used as the long axle molecules, ranging from polymethylene chains to aromatic polymers. Among the different types of side-chain polyrotaxane can be included pseudo-polyrotaxanes and poly(2]rotaxanes. 

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