Poly cyclic oligomers

The reported molar masses of polyesters obtained by enzymatic catalysis are relatively low, generally below 8000, except for polymers recovered by precipitation.336 This procedure results in the elimination of a soluble fraction consisting of low-molar-mass linear and cyclic oligomers.336 An Mw as high as 46,400 has thus been reported for a poly(tetramethylene decanedioate) obtained... 

Hydrolysis of end-labeled 3-hydroxybutyrate oligomers by purified A. faecalis T poly(3HB) depolymerase showed that the enzyme mainly cleaved the second and third ester linkage from the hydroxyl terminus [69]. However, since the enzyme also hydrolyzes cyclic oligomers, the A. faecalis depolymerase has endo-hydrolase activity in addition to exo-hydrolase activity [18, 70]. Results of... 

Bryant, J. J. L., and Semiyen, J. A., Cyclic polyesters 7. Preparation and characterization of cyclic oligomers from solution ring-chain reactions of poly(butylene terephthalate), Polymer, 38, 4531 (1997). 

Hodge, P Yang, Z Abderrazak, B.-H. A., and McGrail, C. S Cyclodepolymerization of poly(ethylene naphthalene-2,6-dicarboxylate) and ringopening polymerizations of the cyclic oligomers obtained, J. Mater. Chem., 10, 1533 (2000). 

Gollier, P.-A. and Bertrand, P. (2002). Cyclic oligomer segregation at the metallized poly(ethylene terephthalate) surface, J. Adhesion Sci. TechnoL, 16, 1, 1-13. 

Cyclic oligomers with x - 2-9 are found to be present in poly(1,3-dioxolane) samples prepared by monomer-polymer-equilibrations using boron trifluoride diethyl etherate as catalyst. The molecular cyclization equilibrium constants 7fx are measured and the values are in agreement with those calculated by the Jacobson-Stockmayer theory, using an RIS model to describe the statistical conformations of the corresponding chains and assuming that the chains obey Gaussian statistics. 

The above-mentioned examples belong to the captivating field of covalent reversible polymers. This field includes examples like reversible polymerization of cyclic oligomers from poly (ethylene terephthalate) [62], thermo-reversible polymers based on Diels-Alder and retro-Diels-Alder reaction (see, for example [63-69]), reversible photo-polymerization in the solid state of molecules... 

Goodman I, Nesbitt BF (1960) The structures and reversible polymerization of cyclic oligomers from poly (ethylene terephthalate). J Polym Sci 48 423 -33... 

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