Cyclic polymers

Semlyen, J.A.

doi:10.1351/pac198153091797

Cited by 182 publications

(277 citation statements)

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“…These reactions are not completely selective, and cyclic polymers with 10, 20, 30, 40 and 50 porphyrin units can be isolated by recycling gel permeation chromatography (GPC). There has been much previous work on the synthesis of cyclic polymers [28][29][30][31][32] , but to the best of our knowledge, nanorings c-P30, c-P40 and c-P50 are the largest monodisperse covalent carbocyclic macrocycles yet reported. The 50-porphyrin nanoring c-P50 contains an uninterrupted ring of 750 C-C bonds and has a diameter of 21 nm.…”

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confidence: 99%

Supramolecular nesting of cyclic polymers

et al. 2015

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Monodisperse cyclic porphyrin polymers, with diameters of up to 21 nm (750 C-C bonds), have been prepared using Vernier template-directed synthesis. The ratio of the intrinsic viscosities for cyclic and linear topologies is 0.72, indicating that these polymers behave as almost ideal flexible chains in solution. When deposited on gold surfaces, the cyclic polymers display a new mode of two-dimensional supramolecular organisation, combining encapsulation and nesting: one nanoring adopts a near-circular conformation thus allowing a second nanoring to be captured within its perimeter, in a tightly folded conformation. Scanning tunnelling microscopy reveals that nesting occurs in combination with stacking when nanorings are deposited under vacuum, whereas when they are deposited directly from solution under ambient conditions, there is stacking or nesting, but not a combination of both.The tertiary structures of biological macromolecules are achieved through folding, coiling and multiplex formation, driven by the cooperative effect of many weak interactions 1 . Synthetic monodisperse macromolecules with similar cooperative folding behaviour provide a viable approach to the programmed fabrication of 3D nanostructures [2][3][4][5] . Here we show that cyclic porphyrin polymers, with molecular weights of 30-60 kDa, self-assemble into nested structures on a gold surface. These nested assemblies are only observed when the cyclic polymer has 30 or more repeat units, in keeping with the predictions of a simple geometrical model.The importance of non-covalent self-assembly in biology has inspired many studies of supramolecular organisation on surfaces [6][7][8] , generating 2D assemblies with progressively escalating complexity, from early work on simple structures such as clusters 9 and rows 10,11 , to nanoporous arrays 12,13 , host-guest architectures [14][15][16] , hierarchical arrangements 17 , and multicomponent assemblies [17][18][19] . However, cooperative conformational control has proved difficult to achieve, and this remains a significant gulf between artificial and biological systems. One reason for this difference is that biological macromolecules are much more flexible than the component molecules studied in 2D supramolecular assemblies which are small and, with some exceptions 20,21 , are often treated as quasi-rigid building blocks. Here we illustrate how interactions between large flexible molecules can result in biomimetic cooperative conformational organisation.Studies of linear and cyclic butadiyne-linked zinc porphyrin oligomers (structures l-PN THS and c-PN, Fig. 1) have shown that the distance between the centres of the porphyrin units along the chain is a = 1.35 nm 5,22,23 . Thus the contour length of a linear oligomer, or the perimeter of a nanoring, is Na, where N is the number of porphyrin repeat units. Previously we have shown that nanorings adsorbed on Au(111) exhibit flexibility [24][25][26] , and also that they can act as nanoscale traps for other adsorbed species, such as C 60 guest molecules 2...

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Supramolecular nesting of cyclic polymers

et al. 2015

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“…Further, the pressure was increased up to 150 bar at room temperature (≈23°C). Under these conditions the pH of the water phase in the lower part of the reactor reached the values around 2.8, while the upper part of the reactor was occupied with liquid CO 2 (ρ ≈ 0.9 g/cm 3 ).…”

Section: Methodsmentioning

confidence: 99%

Synthesis of macrocyclic tris-cis-tris-trans- dodeca[(phenyl)(hydroxy)]cyclododecasiloxane in carbonic acid solution

Shchemelinina

Shchegolikhina

Molodtsova

et al. 2016

Green Chemistry Letters and Reviews

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“…[28][29][30] End-linking of telechelic precursors A direct end-to-end-linking reaction of an a-o-bifunctional linear polymer precursor with a bifunctional coupling reagent is a straightforward method to prepare ring polymers. 8 In practice, however, this bimolecular process has rarely been applied to produce high purity ring polymers in high yields. The rare use of the process has two main causes: first, the asymmetric telechelics formed as the product of the first step is prone to react again with the coupling reagent to form a symmetric telechelics, which cannot undergo cyclization: second, a high dilution condition is required to complete the intramolecular cyclization process and avoid concurrent intermolecular chain extension by using the strictly stoichiometric balance of the large polymer and the small coupling compound.…”

Section: Current Synthetic Challenges For Cyclic Polymersmentioning

confidence: 99%

“…However, in the last decade, a variety of precisely controlled topologies that include cyclic and multicyclic forms in addition to branched ones have been realized by the introduction of intriguing synthetic techniques based on living polymerization as well as selfassembly protocols. [6][7][8][9][10] In this review, recent progress in topological polymer chemistry [11][12][13][14] is discussed (with particular emphasis on cyclic and multicyclic polymers) to provide new perspectives for polymer science and polymer materials engineering.…”

Section: Introductionmentioning

confidence: 99%

Topological polymer chemistry for designing multicyclic macromolecular architectures

Tezuka

2012

Polym J

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The geometrical conception and current synthetic challenges of topological polymer chemistry have been reviewed. On the basis of the systematic classification and isomeric properties of polymer chain topologies, a variety of novel multicyclic macromolecular constructions have now been rationally designed and subsequently realized by intriguing synthetic protocols. In particular, cyclic and multicyclic polymer products are effectively produced by an electrostatic polymer self-assembly of telechelic precursors that contain cyclic ammonium salt groups accompanying polyfunctional carboxylate counteranions and the subsequent covalent conversion through the ring-opening or through the ring-emitting reaction of the cyclic ammonium salt groups by carboxylate counteranions (Electrostatic Self-assembly and Covalent Fixation (ESA-CF) process). Furthermore, the ESA-CF process, in conjunction with effective linking/cleaving chemistry (including the metathesis condensation (clip) and alkyne-azide addition (click) reactions), has been demonstrated as a new synthetic protocol for unprecedented multicyclic macromolecular topologies.

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Cyclic polymers

Cited by 182 publications

References 1 publication

Supramolecular nesting of cyclic polymers

Supramolecular nesting of cyclic polymers

Synthesis of macrocyclic tris-cis-tris-trans- dodeca[(phenyl)(hydroxy)]cyclododecasiloxane in carbonic acid solution

Topological polymer chemistry for designing multicyclic macromolecular architectures

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