Organic Cyclic Polymers

Roovers, Jacques

doi:10.1007/0-306-47117-5_10

Cited by 50 publications

(83 citation statements)

References 90 publications

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“…The apparent M n,SEC decreased from 29.0 10 3 to 24.0 10 3 upon cross-linking, merely because of the successful conversion of linear into cyclic macromolecules. [6] This is an essential observation that confirms that the ring-shape of the copolyester 8 is maintained after hydrolysis of the endocyclic tin alkoxides of 7. The SEC trace was symmetrical and unimodal after hydrolysis, and the cyclization reaction did not change the molar mass distribution (M w /M n = 1.45), which is evidence for the well-controlled Scheme 5.…”

Section: Resultsmentioning

confidence: 58%

“…[2,6] The limitation of this method is that, whenever the molecular weight of the precursor is too high, the direct coupling is quite a problem because of coupling is then much less probable than the undesired chain extension. [6] Very recently, an original process was reported for the synthesis of high molecular weight (20 000) cyclic PCL. The synthetic strategy relies on the sequential polymerization of eCL and a few units of 1-(2-oxooxepan-3-yl)ethyl acrylate (aAeCL) (15)(16)(17)(18)(19)(20) initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP) with formation of tin-containing Abstract: Spirocyclic tin dialkoxides are unique initiators for the ring-expansion polymerization of lactones leading to complex, but well-defined macromolecular architectures.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of Eight‐ and Star‐Shaped Poly(ε‐caprolactone)s and Their Amphiphilic Derivatives

Riva

Kricheldorf

et al. 2007

Chemistry A European J

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Spirocyclic tin dialkoxides are unique initiators for the ring-expansion polymerization of lactones leading to complex, but well-defined macromolecular architectures. In a first example, epsilon-caprolactone (epsilon CL) was polymerized, followed by the resumption of polymerization of a mixture of epsilon CL and epsilon CL alpha-substituted by a chloride (alpha Cl epsilon CL), so leading to "living" eight-shaped chains. Upon hydrolysis of the alkoxides, a four-arm star-shaped copolyester was formed, whose each arm was grafted by conversion of the chloride units into azides, followed by the Huisgen's [3+2] cycloaddition of alkyne end-capped poly(ethylene oxide) (PEO) onto the azide substituents. The complexity of this novel amphiphilic architecture was increased further by substituting the four-arm interconnecting PCL by an eight-shaped PCL. In a preliminary step, epsilon CL was polymerized followed by a few units of epsilon CL alpha-substituted by an acrylate. The intramolecular photo-crosslinking of the acrylates adjacent to the tin dialkoxides was effective in stabilizing the eight-shaped polyester while preserving the chain growth sites. This quite unusual tetrafunctional macroinitiator was used to copolymerize epsilon CL and alpha Cl epsilon CL, followed by hydrolysis of the alkoxides, conversion of the chloride units into azides and grafting of the four arms by PEO (see above). This architecture reported for the very first time is nothing but a symmetrical four-tail eight-shaped copolyester macromolecule.

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Section: Resultsmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Synthesis of Eight‐ and Star‐Shaped Poly(ε‐caprolactone)s and Their Amphiphilic Derivatives

Riva

Kricheldorf

et al. 2007

Chemistry A European J

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“…Therefore, not all conclusions and interpretations are in good agreement with each other. 16 However, all authors agreed in that the temperature dependence of the zero-shear viscosity is the same for cyclic and linear PS. More complicated proved measurement and interpretation of the molecular weight dependence of the zeroshear melt viscosity.…”

Section: Bulk Propertiesmentioning

confidence: 90%

“…Meanwhile, several review articles dealing with syntheses and properties of circular polymers have appeared, but these articles do not clearly distinguish between synthetic methods and synthetic strategies. [14][15][16][17][18][19] Therefore, this differentiation should be presented at this point before any discussion of new theories and experimental results.…”

Section: P 149)mentioning

confidence: 99%

Cyclic polymers: Synthetic strategies and physical properties

Kricheldorf

2009

J. Polym. Sci. A Polym. Chem.

401

442

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Syntheses of cyclic polymers including cyclic homopolymers, cyclic block copolymers, sun-shaped polymers, and tadpole polymers are discussed on the basis of a differentiation between synthetic methods and synthetic strategies (e.g., polycondensation, ring-ring equilibration, or ring-expansion polymerization). Furthermore, all synthetic methods are classified as kinetically or thermodynamically controlled reactions. Characteristic properties of cyclic polymers such as smaller hydrodynamic volume, lower melt viscosities, and higher thermostabilities are compared to the properties of their linear counterparts. Furthermore, the nanophase separation of cyclic diblock copolymers is discussed.

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“…Several reviews containing further details on the preparation methods of macrocycles can be found in the literature [24][25][26].…”

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confidence: 99%

Naturally occurring and synthetic cyclic macromolecules

Deffieux

Schappacher

2009

Cell. Mol. Life Sci.

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Macrocyclic polymers are fascinating molecules that have triggered the curiosity of biologists, chemists and theoreticians since the discovery of cyclic DNA in living cells, more than 50 years ago [1,2]. The topological restriction imposed by the cyclic architecture and the absence of chain ends in ring polymers result in original properties, some of which have yet to be completely elucidated. For example, it has been shown that cyclic polymers have smaller hydrodynamic volumes and radii and are less viscous than their linear analogues. Other specific properties such as diffusion and viscoelastic behaviors, which should also be strongly influenced by the cyclic topology, have been only marginally explored due to the limited availability of the corresponding high molar mass macrocycles.Much less is known about more complex ring topologies such as knotted and catenated macromolecular rings (Scheme 1) that are also found in nature. Their mechanism of formation and their function are still unclear, and increasing efforts are being conducted to tentatively prepare and investigate their specific characteristics and properties.Various examples of cyclized and pluri-cyclized DNA macromolecules have been reported in the literature since the pioneer work of Clayton [3] who identified circular forms of mitochondrial DNA in extracts of human leukemic leucocytes, both in the form of circular dimers and as catenanes made up of interlocked rings.The winding of DNA in higher-order forms such as knots and catenanes was also shown on electron micrographs of DNA molecules coated with Echerichia coli RecA protein. It was found that DNA topoisomerase I of E. coli generates an equal mixture of (?) and (-) duplex DNA knots, as well as catenanes [4]. Together, RecQ helicase and topoisomerase III (Topo III) of E. coli comprise a potent DNA strand passage activity that can catenate covalently closed DNA [5]. The structure of the catenated DNA species formed by RecQ helicase and Topo III was directly assessed using atomic force microscopy (AFM) [6] (Fig. 1).The mechanism by which topoisomerase mediates knotting of supercoiled DNA was investigated by Wasserman [7]. Knotting was explained by DNA contacts stabilized by enzyme molecules.DNA catenanes and large circular DNA have also been prepared by the reaction of T4 DNA ligase with linear DNA in the presence of nicked DNA [8,9].In addition to naturally occurring macrocycles and the investigation of their formation mechanisms, the preparation and the study of well-defined synthetic ring polymers as models of natural rings, has been implemented. Preliminary studies were first oriented towards polymer systems bearing reactive functions on the backbone chain, such as polydimethylsiloxanes [10], polyethers [11], polyesters [12], and so forth.The synthesis of cyclic polymers by end-to-end coupling of chains, first proposed by Casassa [13], was experimentally performed in 1980 [14,15] by the ring closure of living a, x-difunctional polymer chains in the presence of a difunctional coupling agent, u...

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Organic Cyclic Polymers

Cited by 50 publications

References 90 publications

Synthesis of Eight‐ and Star‐Shaped Poly(ε‐caprolactone)s and Their Amphiphilic Derivatives

Synthesis of Eight‐ and Star‐Shaped Poly(ε‐caprolactone)s and Their Amphiphilic Derivatives

Cyclic polymers: Synthetic strategies and physical properties

Naturally occurring and synthetic cyclic macromolecules

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