Radical Coupling Allows a Fast and Tuned Synthesis of Densely Packed Polyrotaxanes Involving γ-Cyclodextrins and Polydimethylsiloxane

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.

Harnessing Polyisobutylene by Rotaxanation with γ‐Cyclodextrin: Opportunities for Making Smart Molecular Necklaces

“…For each population, ions resulting from the ionization of the PR with Li + , Na + , or K + cations were observed (Figure B and Figure S11B, Supporting Information). The results highlighted the presence of two main populations, Py(H)‐(CH2(CH3)2)n‐(H)Py + 1 γ‐CD(SO3)n + Li + and Py(Py)‐(CH2(CH3)2)n‐Py(Py) + 1 γ‐CD(SO3)n + K + corresponding to some previously reported species regarding the functionalization of α,ω‐dimethacrylate PEO and PDMS with PBS . A careful examination of the spectrum reveals the existence of the following ascribed ions: Py(H)‐(CH2(CH3)2)n‐(H)Py + 1 γ‐CD + Li + (), Py(H)‐(CH2(CH3)2)n‐(H)Py + 1 γ‐CDSO3 + Li + (), Py(H)‐(CH2(CH3)2)n‐(H)Py + 1 γ‐CD(SO3)2 + Li + (), Py(H)‐(CH2(CH3)2)n‐(H)Py + 1 γ‐CD + Na + (), Py(H)‐(CH2 (CH3)2)n‐(H)Py + 1 γ‐CDSO3 + Na + (), Py(H)‐(CH2(CH3)2)n‐(H)Py + 1 γ‐CD(SO3)2 + Na + (), Py(S)‐(CH2(CH3)2)n‐(S)Py + 1 γ‐CD + Na + (), Py(S)‐(CH2(CH3)2)n‐(S)Py + 1 γ‐CD(SO3) + Na + (), Py(Py)‐(CH2(CH3)2)n‐(H)Py + 1 γCD + Na + (), Py(Py)‐(CH2(CH3)2)n‐(Py)Py + 1 γCD(SO3) + K + (), Py(Py)‐(CH2(CH3)2)n‐(Py)Py + 1 γ‐CD + Na + (), Py(Py)‐(CH2(CH3)2)n‐(Py)Py + 1 γ‐CD(SO3) + Na + (), Py(Py)‐(CH2(CH3)2)n‐(S)Py + 1 γ‐CD(SO3) + Li + (), Py(S)‐(CH2(CH3)2)n‐(S)Py + 1 γCD(SO3)2 + K + ( ), Py(S)‐(CH2(CH3)2)n‐(S)Py + 1 γ‐CD + Li + (), and Py(Py)‐(CH2(CH3)2)n‐(Py)Py + 1 γ‐CD + K + ( ).…”

“…Pseudopolyrotaxane and polyrotaxane were sequentially made from threading of γ‐CD into diallyl polyisobutylene and then capped at the two extremities by pyrenyl group using our previous described radical coupling . Threading percentages can be usually controlled by varying the solvent composition during the rotaxanation.…”

“…Reaction was achieved in standard conditions for radical coupling use. DMSO/H 2 O 1/2 v/v with [PPR]/[PBS] (1/10, mol/mol) with initiator (Na 2 S 2 O 8 ) at 5% w/w stirred at room temperature for 24 h . Such settings led to a calculated conversion yield close to 100% (with a trapped part of solvent in the polyrotaxane structure) with a threading degree equal to 61% ( Table 2 , Sample 1).…”

“…A typical MALDI‐TOF mass spectrum exhibiting ions in the range of m / z 3000−19 600 with an average of 1300−1500 mass units shifts corresponding to the unmodified, mono‐, or disulfated γ‐CD molecular weights ( Figure A). The difficulty to desorb high‐molecular‐weight polyrotaxane is now well known . Taking into account the difficulties to get enough sensitivity for high‐molecular‐weight compounds, identification of species has been carried out on the first distribution corresponding to PR with one γ‐CD, and in reflector mode which offers better resolution and improved mass accuracies for m / z typically < 5000 g mol −1 (Figure B).…”

“…We have previously reported successful CD‐based PR synthesis involving α‐ and γ ‐CD with a hydrophilic polymer as polyethylene oxide (PEO) and a quite hydrophobic one as polydimethylsiloxane (PDMS), respectively, by adjusting solvent composition during synthesis . In this last case, it was also possible to finely control threading rate of γ ‐CD along PDMS by introducing a radical coupling strategy . Here, we report efforts to extend the aforementioned approach to achieve the successful synthesis of supramolecular complexes involving γ‐CDs and an undervalued highly hydrophobic polymer, PIB, which after rotaxanation can be solubilized in various (polar) solvents and easily handled for building new materials.…”