Polymer macrocyclic

In poly(ether sulfone)s that are prepared by polycondensation of silyl-ated 4-terf-butylcatechol and 4,4 -difluorodiphenyl sulfone, macrocyclic polymers were obtained to some extent. The cyclic polymers were detected by means of matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. 

Under the conditions of a kinetically controlled polycondensation reaction, cyclization reactions compete with propagation steps. The extent of cyclization depends on the flexibility of the polymer chain and on the concentration of the active species. Blends of PES with its homologous macrocyclic oligomers show greatly lowered melt viscosities in comparison to the corresponding original PES. 

This may facilitate the production and fabrication of such materials. The macrocycles can undergo a ring-opening polymerization in situ. The ring-opening is governed by entropy.  

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A second possibility is that the metal center remains intact, but the macrocycle ligands react with each other. In macrocycles treated in the absence of a support there is evidence that polymerization of the macrocycles occurs.76,111 Likewise, in the presence of a carbon black support, such polymerization could occur during pyrolysis and could possibly affect activity and stability for similar reasons to the ones mentioned in the previous paragraph.76,92 However, for a treatment above 400 °C (which produces a more active material) the macrocycle polymer is thought to decompose.92 Another possibility is that the heat treatment helps disperse the macrocycles on the support surface and leads to strong chemisorption rather than physisorption.110... 

Macrocyclic lattice hosts, 14 111 Macrocyclic mercuracarboranes, 4 216-217 Macrocyclic oligoesters, 25 125 Macrocyclic polymers, 14 252 Macrocyclic polythioethers, 23 707 Macrocylic ligands, 7 576 Macroemulsions, 10 113 16 433-434 Macrofouling organisms, in industrial water treatment, 26 149-150 Macrolide antibiotics, 15 271-320. See also Macrolides... 

R. Grubbs, C. Bielawski, and D. Benitez, Synthesis of macrocyclic polymers by ring insertion polymerization of cyclic olefin monomers, US Patent 6946533, assigned to California Institute of Technology (Pasadena, CA), September 20,2005. 

A bimolecular process was reported by two independent groups, i.e., Hocker [19] and Rempp [20] in 1980. Macrocyclic polymers have been successfully prepared by the coupling reaction of a two-ended living polystyryl anion with a difunctional electrophile such as a, a -dibromo-p-xylcnc under high dilution to yield cyclic and linear mixtures. The cyclic polymer was isolated by a fractional precipitation. This bimolecular end-to-end reaction process has been used for synthesizing cyclic polystyrene by many researchers [21-25]. 

Deffieux et al. proposed a new approach to the synthesis of macrocyclic polymers with unimolecular end-to-end coupling reaction using a/o-hclero-difunctional linear polymer precursor [26]. In the method, which involves... 

Under such chromatographic conditions it is possible to determine the heterogeneities of the polymer chain selectively and without any influence of the polymer chain length. LC-CC has been successfully used for the determination of the functionality type distribution of telechelics and macromonomers [104-109], for the analysis of block copolymers [111-114], macrocyclic polymers [115], and polymer blends [116-118]. 

Noting the clear difference in reactivity between the vinyl ether and the styrenic double bonds, Deffieux and his co-workers synthesized macrocyclic polymers via living cationic polymerization [123,162,226], Thus, the French group started the synthesis from an asymmetrically hexafunctional monomer, with three vinyl ether and three p-alkoxystyrenic groups (27, Fig. 11) [162]. Addition of three equivalents of hydrogen iodide selectively... 

These developments in cationic polymerization of 1,3,5-trioxane are discussed in more detail, because in this system the problems related to the mechanism of cyclization are now well understood. Cyclic oligomers were identified, isolated, their molecular weight distribution was determined, and the plausible explanation for observed distribution was given. From the synthetic point of view, the cationic polymerization of 1,3,5-trioxane offers the possibility of preparing macrocyclic polymers with relatively narrow molecular weight distribution and predictable (within discussed limits) molecular weights. The cyclic polymers can be prepared easily in relatively large quantities and conveniently separated from linear polymer by alkaline hydrolysis of the latter. 

Laurent, B. A. and Grayson, S. M. (2006) An efficient route to well-defined Macrocyclic polymers via Click cyclization. J. Amer. Chem. Soc., 128, 4238 -239. 

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