Polyrotaxanes Structures

Polyquinoxalines, ladder structured conducting, 7 522 Polyrotaxane structures, 23 733 Polysaccharide extraction, 10 307... 

Swager and coworkers also applied the self-assembly process in side-chain systems [131, 132]. The bisphenylene crown ether was incorporated into a conjugated backbone, polyphenyleneacetylene 87. This polymer complexes with paraquat 88 to give a novel polyrotaxane structure (89). With a polythiophene backbone, a similar polyrotaxane was synthesized by the same approach. 

In this review, the recent progresses of functional macromolecules comprised with the dithiafulvene moiety, e.g., dithiafulvene/ -conjugated polymer hybrid systems, dendritic dithiafulvenes, polyrotaxane structures, and intramolecular CTs are highlighted. 

Ritter et al. [147-155] have been studying side chain poiyrotaxanes. They synthesized side chain poiyrotaxanes by amide coupling of polymer-carrying carboxylic acid moieties with various semirotaxanes of methylated /l-CD(s) and an axle bearing an amine group at one end [147-154]. These works have been reviewed in an excellent review by Raymo and Stoddard [78]. Ritter et al. [155] reported recently a new type of side chain polyrotaxane. They polymerized inclusion complexes of di(meth)acrylates of butan-l,4-diol and hexan-l,6-diol with a-CD and with methylated /1-CD using a redox initiator system in aqueous media, and characterized the polyrotaxane structure by IR and glass-transition temperature measurements. 

These findings suggest that the mechanically threaded structure of polyrotaxanes with controlled number of threading a-CD molecules can have favorable thermodynamic effects on multivalent interactions. Finally, we have established the concept that the combination of multiple copies of ligands and their supramolecular mobility along the mechanically threaded polyrotaxane structure should contribute to the novel design of polymeric architectures aiming at enhanced multivalent interactions. 

The finding as observed above is likely due to the mobile motion of a-CDs in the necklace-like structure of the polyrotaxane. The pDNA dissociation of the polyplex occurred through the SS cleavage in the polyrotaxane and the subsequent interexchange with polyanions. This is presumably due to a reduction on the potency of the multivalent interaction between the cationic polyrotaxane and the anionic pDNA through the supramolecular dissociation. A rapid endosomal escape and pDNA delivery to the nucleus using such cytocleavable polyrotaxanes can be achieved through systematic analyses of polyrotaxane structures. 

Polymers are normally classified into four main architectural types linear (which includes rigid rod, flexible coil, cyclic, and polyrotaxane structures) branched (including random, regular comb-like, and star shaped) cross-linked (which includes the interpenetrating networks (IPNs)) and fairly recently the dendritic or hyperbranched polymers. I shall cover in some detail the first three types, but as we went to press very little DM work has been performed yet on the hyperbranched ones, which show some interesting properties. (Compared to linear polymers, solutions show a much lower viscosity and appear to be Newtonian rather than shear thinning [134].) Johansson [135] compares DM properties of some hyperbranched acrylates, alkyds. and unsaturated polyesters and notes that the properties of his cured resins so far are rather similar to conventional polyester systems. 

A variety of polyrotaxane structures can be envisioned, as shown in Scheme 1 [1-3]. True rotaxanes polymers possess bulky groups at the ends of the linear species or along the backbone to prevent diffusive loss of the ring component. However, it has been shown that main chain polypseudo-rotaxanes dethread extremely slowly due to random coiling of the backbones [4,5], so that the distinction between pseu-dorotaxane and rotaxane polymers of the main chain type is somewhat blurred for these systems. Main chain polyrotaxanes are the most common type, although all of the other types shown in Fig. 43.1 have been synthesized. 

One conceptually easy way to access polyrotaxane structures is to prepare a rotaxane monomer which has reactive groups on (or as) its stoppers and/or on its macrocyclic component and then subsequently carry out a conventional polymerization reaction. This potentially opens up access to a wide range of interlocked polymeric architectures from simple main-chain polyrotaxanes to molecular necklaces, the daisy-chain systems and even dendritic interlocked species. 

The stability of the polyrotaxane structure can result from both the intermolecular interaction (of the type of hydrogen, donor-acceptor, and Van der Waals bonds) between the macrocydes and polymer and a conformation change due to mobility... 

Subjecting inclusion compounds, isolated beforehand, to y-irradiation, Maciejewski et al. 21.100.104) managed to obtain stable polymeric adducts with a polyrotaxane structure only when adducts of P-cyclodextrin with vinylidene chloride or allyl chloride served as initial adducts. Polymerization of the rest of the monomeric adducts resulted in unstable compounds, dissociating into a homopolymer and the initial P-cyclodextrin in hot water. 

Conducting the polymerization under such conditions allowed us to assume the following medianism of polyrotaxane formation. First the sweUing of cyclic urethanes in the monomer occurs, i.e. styrene penetrates into the bulk of cyclourethanes or their comfdexes also including their interiors. Polymerization of styrme v4iich is both in the interior and on the outside results in the formation of a polymer whose molecules pierce the cycles, i.e. the possibility of formation of compounds with a polyrotaxane structure arises. 

The X-ray diffraction of the product after PS extraction turned out to be similar to the X-ray scattering by the initial diurethane. These results prove an absence of a chemical interaction between urethane and PC. The identical nature of CU and their linear analog made it reasonable to suggest an absence of the chemical bonding also in the c e of PS and CU. It follows that a medianical en gement between cyclourethanes and PS molecute occurs in the samples, i.e. polyrotaxane-structure compounds are formed. 

Enhanced accessibility of peptide substrates toward membrane-bound metalloexopeptidase (aminopeptidase M) [16] using polyrotaxane structure was achieved. It is clarified that the polyrotaxanes form loosely packed association due to their rod-like structure [14] under physiological conditions, maintains enzymatic accessibility to terminal peptide moieties. A L-phenyl-alanlylglycylglycine (H-L-PheGlyGly)-terminated polyrotaxane in which many... 

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