Copolymer catenane

With the exception of DNA catenanes and protein catenanes, and despite various synthetic attempts, only one polymeric catenane structure, i.e. the catenated block copolymer 72, is known [31]. Evidently, the fact that the two constitutive cyclic polymers have two different chemical structures greatly facilitates the syn-... 

Bria et al. synthesized a tetracationic cyclophane-aromatic crown ether-type side-chain poly[2]catenane 59 by employing click chemistry, via route iii (Scheme 17.18) [111]. First, the template-directed coupling reaction between bis(bipyridinium) salt 28 and the alkyne-substituted p-xylylene dibromide 55, in the presence of dinaphtho crown ether 54, afforded an alkyne-functionalized [2]catenane 56 [112], Substitution of the chloro group on styrene-vinylbenzyl chloride copolymer 57 (M = 3.7 kDa, M , = 6.3 kDa) with sodium azide gave the azide-functionalized polymer 58 [83,113-115]. By employing CuS04/ascorbic acid as catalyst [116-120], click chemistry between azide-functionaUzed polymer 58 and alkyne-functionalized [2]catenane 56 afforded the side-chain poly[2]catenane 59, the successful formation of which was confirmed with Fourier transform infrared (FTIR) and NMR analyses. Unfortunately, both of these techniques revealed that the reaction of the azide groups was incomplete, and the observation was ascribed to a Coulombic repulsion of the cyclophane units and steric hindrance caused by the bulky catenane units[121]. 

The synthesis of catenated polystyrene-cat-polyvinylpyridine with a molar mass of lODOOgmol was also reported. Polyvinylpyridine was synthesized by the lithium naphthalide-initiated sequential polymerization of 2-vinylpyridine. The catenane copolymer was obtained by end-to-end coupling of the P2VP dianion lithium salt with l,4-bis(bromomethylbenzene) in THF in the presence of a PS maaocyde (Mp = 4500gmoU ). The catenane was isolated by predpitation-extraction procedmes. 

Solid-state properties of the catenane copolymer were determined using DSC and dynamic mechanical analysis (DMA) and were compared with pure PC. DSC revealed a glass transition temperature of ca. 150°C for all the catenane copolymers 22 to 24, which is essentially the same as the pure PC sample of the same molecular weight. This insensitivity of the Jg to the presence of the catenane repeat unit is possibly on account of the considerable flexibility/mobiUty of these catenanes. DMA of the copolymer containing 20% (w/w) catenane showed three transitions at —100, —6, and - -80°C. The first and third transitions are observed in PC films while the —6°C was linked to the catenane ring/chain movements. 

Another type of polymeric catenane architecture that has recently been reported is that of a polymeric [2]catenane in which the two macrocycles that constitute the catenane are themselves polymers [24]. A polystyrene (PS)-poly(2-vinylpyridine) (P2VP) catenane copolymer with a molecular weight around 10,000, Mw/Mn = 1.3 has been isolated and characterized by SEC, H-NMR, and fluorescence spectroscopy. The synthesis of this interesting material was achieved by the end-to-end coupling of a linear P2VP dianion lithium salt with l,4-bis(bromomethyl... 

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