Oligoesters, cyclic

The polymerization of cyclic low-molar-mass polycarbonates, polyarylates, and PBT to high-molar-mass thermoplastics has been extensively studied by the General Electric Company during the last decade.57,58 Due to very low viscosity, cyclic oligoesters can be processed like thermosetting resins but retain thermoplastic properties in the final state, after polymerization in the presence of suitable... 

Cyclic esters, ring-opening polymerization of, 85-87 Cyclic lactams, 174 Cyclic oligoesters, 31 Cyclic oligomers, 63, 542 formation of, 39... 

In connection with studies on the ring-opening polymerization of cyclic acetals, we have undertaken investigations on the polymerization of bicyclic acetals, bicyclic oxalactone, and bicyclic oxalactam, which yield polysaccharide analogs, macrocyclic oligoesters, and a hydrophilic polyamide, respectively, some of which can be expected to be useful as novel speciality polymers. The monomers employed in the studies were prepared via synthetic routes presented in Scheme 1, starting from 3,4-dihydro-2H-pyran-2-carbaldehyde (acrolein dimer) I. 

Ruddick, C. L., Hodge, P., Zhuo, Y., Beddoes, R. L., and Helliwell, M., Cyclo-depolymerization of polyundecanoate and related polyesters characterisation of cyclic oligoundecanoates and related cyclic oligoesters, J. Mater. Chem., 9, 2399 (1999). 

Burch, R. R., Lustig, S. R. and Spinu, M., Synthesis of cyclic oligoesters and their rapid polymerization to high molecular weight, Macromolecules, 33, 5053 (2000). 

Bachmann and Seebach [159] have reported the preparation and characterization of cyclic lactones (MeCHCH2C(0)0)n, where n = 4 and 8. The reaction product between butyl lithium in benzene and the solid polystyrene support PS-C6H4CH2NH2 leads to a lithiated species that can be represented as PS-Cfd bCI 12N11 Li(BuI i)x, where x 4 is active in the ring-opening of the cyclic esters L-lactide, rac-lactide, and 2,5-morpholinediones, leading to their respective cyclic oligoesters and cyclodepsipeptides (Fig. 49) [160]. The... 

Linear and cyclic polyamines [13], as well as linear oligoesters [14], are also efficient chelators for zinc ions, used especially for zinc imaging in cultured cells. Depending on the target cell and/or intercellular structure, various sensor architectures are applied. 

The product mercaptoacetic acid will self-esterify on storage or heating. The self-esterification products are primarily the linear dimer (x = 1), along with some cyclic dimer, oligoesters (x = 2-I-), and solid orthothioester. These self-esterification reactions, with the exception of the formation of the orthothioesters, can be readily reversed in water with dilute acid or base catalyst. 

Okumara et al. [10] were the first to attempt the enzyme-catalyzed synthesis of oligoesters from a reaction between dicarboxylic acids and diols. Gutman et al. [11] reported the first study on polyester synthesis by enzyme-catalyzed polymerization of A-B type monomers. Two independent groups in 1993 [12, 13] were first to report enzyme-catalyzed ring-opening polymerization (ROP). Their studies focused on 7- and 6-membered unsubstituted cyclic esters, e-caprolactone (e-CL) and 8-valerolactone (8-VL), respectively. 

Maleic acid and phthalic acid are used as oligoester components together with bivalent alcohols (e.g., ethylene glycol, 1,4-butanediol) as co-condensation partners. Crosslinking is achieved by copolymerization of styrene, vinyl acetate, diallyl phthalate, acrylonitrile or acrylic ester. Cyclic structures impart a higher glass transition temperature. The aliphatic glycols in the... 

Ring opening polymerization (ROP) of cyclic oligoesters is an emerging method of polymerization that has some advantages compared to melt phase polycondensation (71). In this method, the polyester is prepared from low-viscosity precursors by an entropi-cally driven process that evolves without releasing of volatiles and emission of heat. 

THF calibrated with cyclic oligoesters of known molecular weight. 

The predominance of diol terminated linear chains reduces the influence of end-biting , but the formation of cyclics by back-biting cannot be suppressed. The role of ring-chain equilibria and the extraction and characterization of cyclic oligoesters is discussed in Chap. 5. However, it was also demonstrated by means of MALDI-TOF mass spectrometry that high molar mass PBT contains cyclic polymers with masses at least up to 12 kDa and not only cyclic oligomers [8]. 

Finally, RO-PCs of the aromatic silacycle (e) (Formual 9.5) with various dicarboxylic acid dichlorides were studied [39]. These polycondensations were again performed in bulk using chloride ions as catalysts. The H NMR spectra indicated almost complete conversion, but the solution viscosities were so low that the Mns certainly did not exceed 2 kDa. The Fast-Atom-Bombardment mass spectra exclusively displayed peaks of cyclic oligoesters, suggesting that the chain growth was mainly limited by cyclization. 

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