Cyclic alkyl ketene oligomers

摘要

Two alkyl ketene oligomers (AKOs) with almost 100% purities were prepared in high yields of 80-90% from palmitic acid chloride and alkyl ketene dimer (prepared from palmitic acid chloride) in the presence of amine promoters. Two AKOs thus obtained had quite similar molecular weights (1000-10,000), carbon/hydrogen contents, X-ray diffraction patterns, solution-state ~(13)C-NMR spectra, and water-contact angles. However, two AKOs had different size-exclusion chromatograms, differential scanning calorimetric curves, FTIR spectra, and solution-state ~(13)C-NMR spectra for ~(13)C-labeled AKOs. Based on the ~(13)C-NMR spectra of ~(13)C-unlabeled AKOs, AKOs are likely to have cyclic structures, thus having the limited molecular weights of <10,000. The results of FTIR spectra and ~(13)C-NMR spectra of ~(13)C-labeled AKOs indicated that three different repeating units were linked with various molar ratios and various connection patterns and combinations, constituting the cyclic AKOs. As a result, ~(13)C-NMR spectra of ~(13)C-labeled AKOs showed quite a number of carbon signals due to various ~(13)C?￡O and ~(13)C?￡C structures present in AKOs.