High molecular weight polyrotaxanes are usually characterized by nuclear magnetic resonance and size exclusion chromatography but rarely by mass spectrometry. This article reports effort to detect high molecular weight structures of cyclodextrin based polyrotaxanes (CD based PRs) by matrix-assisted laser desorption ionization mass spectrometry (MALDI−TOF MS). A particular attention was paid to verify the composition of the polyrotaxanes by determination of the number of macrocycles borne by the polyrotaxane and the polyrotaxanes synthetic route. Various matrices including crystalline or ionic liquid ones were screened to optimize the detection. Dimethylformamide as solvent widely used in supramolecular chemistry, but unusual in mass spectrometry, was successfully employed during all analyses. To prove the ability of the optimized MALDI−TOF MS conditions, three different polyrotaxane structures varying by polymer nature, i.e., poly(ethylene oxide) or polydimethylsiloxane and cyclodextrins type i.e. α or γ with or without modifications were evaluated. Finally, we have concluded that 1,1,3,3-tetramethylguanidinium salts of both 2-(4-hydroxyphenylazo)benzoic acid and 2′,4′,6′-trihydroxyacetophenone, are the most reliable and efficient matrices. These ones afforded the possibility to detect masses of 24804 and 26447 g·mol−1, corresponding to poly[17]- and poly[18]rotaxanes, respectively.

No abstract

The first radical end-coupling synthesis of polydimethylsiloxane (PDMS)−γ-cyclodextrins (γ-CDs) based polyrotaxane is reported. Conversely to usual chemical way, the radical process leads to fast both controlled size and structure with minimal side reaction while exhibiting very high conversion rate (w/w, 80%). Pure PDMS−γ-CDs molecular necklaces were successfully isolated by preparative size exclusion chromatography and finely characterized both by 1D/2D/STD 1H and 13C NMR and MALDI-TOF mass spectrometry. The observations give clear evidence of the supramolecular assembly synthesis where the filling ratio (γ-CD/monomer unit) of PDMS chains is as high as 40% of γ-CDs. Combination of such radical-based coupling supported by detailed analytical characterizations appears at the forefront of a fast, suitable, and easily amenable scaling-up CDs-based polyrotaxane synthesis process.

No abstract