Rotaxanes poly

Similar to those for rotaxanes, different approaches have been employed for poly-rotaxane syntheses these will be summarized in the next section. The most important parameter in polyrotaxanes, the min value, is often employed as a measure of the effectiveness of the preparation method. Because this value mainly depends on the strength of the attractive force between the cyclic and the backbone, this section is again divided into subsections according to the types of driving forces rather than the types of polyrotaxanes. 

Paraquat, an ionic molecule, is more rigid than polymeric crown ethers. In addition, die crown ether has to adopt a restricted conformation for complexation to occur. The total increase of the rigidity for derived polyrotaxanes 84 depended on the min value [118, 119]. The higher the value of min, the higher Tg of the poly-rotaxane. Paraquat is a crystalline material but the polyrotaxanes are amorphous. 

The aqueous solubility of CD also enables their potential application as poly-rotaxane-based drug carriers. Yui and coworkers incorporated CD onto PEO chains in polypseudorotaxanes and polyrotaxanes [92-94], The releasing kinetics of CD from the polymer chain were studied. The release was governed by the inclusion complexation equilibrium. Biodegradation to cleave the BG units was shown to cause the release of the CD from the polyrotaxanes. 

An alternative approach for the preparation of CD-based polyrotaxane using photoreactions is described (Scheme 9). The authors prepared a-CD-based polyrotaxanes by capping ends of a-CD-PPG complexes, in a pseudo-poly-rotaxane structure, with covalently bound stoppers. A polyrotaxane containing a number of /3-CD molecules was prepared by photoreactions of a precursor complex between /3-CD with PPG having a triphenyhnethyl group at... 

While the above studies are representative of the area, it should be noted that a considerable number of other [2]-pseudorotaxanes have been investigated. These include a system exhibiting enantioselective self-assembly during its formation as well as systems incorporating a new structural motif involving a l,2-bis(pyridini-um)ethane axle and a 24-crown-8 ether wheel .A number of poly-pseudoro-taxanes (and related poly-rotaxanes) as well as constitutionally asymmetric and chiral [2]-pseudorotaxanes have been reported. New, multiply-stranded and multiply-encircled systems have also been prepared. The solid state structure of... 

Since a very large number of rotaxanes and poly rotaxanes that contain cyclodextrins and cyclodextrin derivatives are known, discussion of only a representative selection of such compounds is presented in this section. 

One of the structural features seen in polyrotaxanes is the absence of any covalent binding between cyclic compounds and a linear polymeric chain capped with bulky end-groups at both terminals [1]. It looks like a necklace the cyclic compounds are mechanically locked by the linear polymeric chain. The cyclic compounds in a poly-rotaxane can slide and/or rotate along the axial polymeric chain if the polyrotaxane is soluble in a certain solvent. Furthermore, such mechanical locking between the cyclic compounds and the linear polymeric chain will be opened once one of the terminal bulky end-groups is cleaved by any external conditions. These characteristics are only observable in and specific to polyrotaxanes and are never seen in conventional polymeric architectures (Fig. 1). 

Scheme 4.20 Electropolymerization of rotaxane 93 gives poly(rotaxane) 94.

Pseudo)polyrotaxanes containing CB[6J threaded on organic polymers were also reported. Such (pseudo)poly-rotaxanes were synthesized by interfacial polymerization of CB[6]/polyamine pseudorotaxane with diacid chlorides such as 1,6-hexanedioyl chloride (adipoyl chloride). "" Steinke and coworkers recently reported a novel way to produce polyrotaxanes utilizing 1,3-dipolar cycloaddition between azide and alkyne inside the cavity of They also synthesized pseudopolyrotaxanes... 

Whang. D. Jeon. Y.-M. Heo, J. Kim. K. Self-assembly of a poly rotaxane contaning a cyclic bead" in every structural unit in the solid state Cucurbituril molecules threaded on a one-dimensional coordination polymer. J. Am. Chem. Soc. 1996, 118 (45). 11333-11334. 

Fraser. C.S.A. Jennings, M.C. Puddephatt, R.J. An organometallic poly rotaxane and a new type of poly rotaxane architecture. Chem. Commun. 2001. 1310-1311. 

Professor of Polymer Science, Osaka University, Japan Poly(rotaxane), example 1 Poly(rotaxane), example 2... 

Recently, a new class of CD-containing gene carriers based on poly-rotaxanes was developed. Polyrotaxanes are cytocleavable necklace-like... 

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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