DETHREADING DURING THE PREPARATION OF POLYROTAXANES

Using a diol blocking group, bis(p-tert-butylphenyl)bis [p-(2-(2-hydro xyethoxy)ethoxy)phenyl]methane (diol BG 1), a diol with a sterically l arge core, copoIysebacate 30-crown-10 (30C10) rotaxanes 8, 9 and 10 we re synthesized by incorporating different amounts of 1,10-decanediol. These copolymeric rotaxanes were characterized by different techniques , including proton NMR spectra, hydrolytic recovery of 30C10 and 2D NO ESY. It was found that threaded 30C10 displayed a range of chemical sh ifts corresponding to the various sequence structures in which it was constrained. In addition, it was proved that the threading efficiency (min value, the average number of cyclic molecules per repeating unit) increased with feed ratio of diol BG 1 vs. 1,10-decanediol. A linear relationship of threading or dethreading degree vs. the percentage of diol BG in the total diol feed was revealed; more BG, less dethreading . The results demonstrate that dethreading occurs during the polyconde nsation in the absence of BGs.