Oligoesters, polycondensation

All-trans unsaturated ester oligomers have been synthesized by lipase-catalyzed polymerization of diesters of fumaric acid and 1,4-butanediol.217 No isomerization of the double bond was observed, as opposed to the extensive isomerization found during chemical polycondensations. Crystallinity was found in the enzymatically formed unsaturated oligoesters prepared in acetonitrile, whereas industrial unsaturated polyesters are amorphous. 

For example, it is reported in Ref. [186] on the synthesis of block-copolyesters and their properties in dependence on the composition and structure of oligoesters. The oligoesters used were oligoformals on the basis of diane with the degree of condensation 10 and oligosulfones on the basis of phenolphthalein with the degree of condensation 10. The synthesis has been performed in conditions of acceptor-catalyst polycondensation. 

Monomers n-oxybenzoic acid Polycondensation Polyesters oligoesters Synthesis... 

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. 

Rovkina et al. [222,280] reported on the synthesis of oligoesters having pendant carbazole groups. They were prepared by polycondensation of EPK (32a) or 3-(9-carbazolyl)propane-diol-l,2 (34a) with dicarboxylic acids (adipic, sebacic or phthalic). The carbazole-containing oligoesters had relative molecular masses from 640 to 2640 and exhibited photoconductivity and good film-forming properties. 

A third series of polycondensations was conducted with acetylated bisphe-nol-P (4) as a "chain-stopper", to obtain telechelic poly(Phla) with two identical functional endgroups (S in eq. 5). Bisphenol-P was selected as a chain-stopper, because its acetate is not volatile, and because die four methyl groups allow again an easy NMR spectroscopic detection of this builc g block in the isolated polyesters (Figure 3). Again both NMR spectra and inherent viscosities (Table 2) indicate the successful incorporation of the chain-stopper. In this case soluble oligoesters were obtained up to a M/I ratio of 80. 

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. 

The group of Kimura and Yamashita [70-72] focused on preparation and characterization of needle-like crystals (called whiskers) by polycondensation of 4-ABA in paraffin at 320 °C using a low monomer concentration. Based on EM pictures displaying shish-kebap -like crystals they postulated that oligoesters... 

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