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An artificial molecular chaperone: poly-pseudo-rotaxane with an extensible axle
Motofumi Osaki1, Yoshinori Takashima, Hiroyasu Yamaguchi
1Department of Macromolecular Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
Journal of the American Chemical Society
|November 2, 2007
Summary
Cyclodextrins (CDs) threaded onto poly(delta-valerolactone) chains initiate solid-state polymerization of delta-valerolactone (delta-VL). This poly-pseudo-rotaxane formation is crucial for polymerization, acting like an artificial chaperone.
Area of Science:
- Polymer Chemistry
- Supramolecular Chemistry
- Materials Science
Background:
- Poly-pseudo-rotaxanes are supramolecular structures formed by threading cyclic molecules onto polymer chains.
- Cyclodextrins (CDs) are known for their ability to form inclusion complexes and act as hosts.
- Solid-state polymerization offers controlled synthesis and unique material properties.
Purpose of the Study:
- To investigate the role of cyclodextrins (CDs) in initiating the solid-state polymerization of delta-valerolactone (delta-VL).
- To explore the formation and function of poly-pseudo-rotaxanes in polymerization.
- To understand the mechanism of polymerization initiation mediated by CDs.
Main Methods:
- Synthesis of poly(delta-valerolactone) chains with a beta-cyclodextrin (beta-CD) end-group (denoted as 1).
- Threading of various CDs (alpha-CD, beta-CD, 2,6-di-O-methyl-beta-CD) onto polymer chains.
- Solid-state polymerization experiments of delta-VL.
- Characterization using powder X-ray diffraction and solid-state NMR spectroscopy.
- Inhibition studies using adamantane (Ad) to probe beta-CD cavity accessibility.
Main Results:
- CDs threaded onto poly(delta-valerolactone) initiated delta-VL polymerization in the solid state, forming poly-pseudo-rotaxanes.
- Polymer chains without threaded CDs showed no polymerization ability.
- Adamantane blocked the beta-CD cavity, inhibiting polymerization, confirming the beta-CD's role in initiation.
- The formation of poly-pseudo-rotaxanes was essential for initiating delta-VL polymerization.
- Threaded CDs acted as artificial chaperones, folding the polymer chain for polymerization.
Conclusions:
- The formation of poly-pseudo-rotaxanes, where CDs are threaded onto polymer chains, is a key requirement for initiating solid-state delta-VL polymerization.
- The beta-CD cavity plays a critical role in the polymerization process, acting as a template and initiator.
- CDs function as artificial chaperones, guiding polymer chain conformation for efficient polymerization.
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