Preparation of urea-poly(tetrahydrofuran) complexes and their application for fractionation of oligomers

The synthesis of the urea channel inclusion complexes of poly(tetrahydrofuran)) (PTHF) is described. These complexes could be obtained in the form of single crystals forM _n 1700 g/mol of PTHF as the guest, and they exhibit a hexagonal unit cell (a=8.20(2) Å,c=11.05(3) Å) very similar to the wellknown urea-n-alkane complexes. X-ray investigations, elemental analysis and density measurements suggest an all trans zig-zag conformation of the polymer chain.The formation of the complexes was exploited for the purpose of fractionation of PTHF, making use of the correlation between temperature of crystallization andM _n of the included polyether chain.The distribution and the molecular weights of the fractions, obtained by extractive crystallization, were determined by reversed phase HPLC analysis and vapour pressure osmometry (VPO). Narrow fractions with M_w/M_n=1.02 were obtained from commercial PTHF samples.Successive fractionation was applied also on product mixtures from oligomer synthesis, as demonstrated for the separation of the dodecamer H-(o-(CH₂)₄-)₁₂OH.Herrn Prof. Dr. R. Bonart mit den besten Wünschen zum 60. Geburtstag gewidment