Synthesis and characterization of high molecular weight polyrotaxanes:: towards the control over a wide range of threaded α-cyclodextrins

This work focuses on the synthesis of polyrotaxanes with high molecular weight template poly(ethylene glycol) PEG (20 kg mol(-1)) having various and well-defined amounts of alpha-cyclodextrins (alpha-CD) per chain N from 3 up to 125. N is the complexation degree of the polyrotaxane defined to be the average number of cyclodextrin molecules per template chain, The usual route has been used for high values of N, while sparsely complexed polyrotaxanes have been synthesized with an original one pot synthesis in water. Furthermore, it systernatic study wits carried out to understand and control the complexation degree N of the polyrotaxane as it function of the complexation time, the temperature and the initial ratio of alpha-CD to template polymer. It has been shown that a high temperature thermal plateau leads to the formation of very sparsely complexed (low N) pseudo-polyrotaxanes for which, the threaded alpha-CD act like nuclei and generate a favourable driving force for the final complexation at lower temperature.