Document Detail

Time-Resolved Observation of Chiral-Index-Selective Wrapping on Single-Walled Carbon Nanotube with Non-Aromatic Polysilane.
MedLine Citation:
PMID:  23320539     Owner:  NLM     Status:  Publisher    
In the present paper, we ascertain two novel findings on chiral-selective binding / separating of single-walled carbon nanotubes (SWNTs) with a non-aromatic polymer, poly(dialkylsilane)(PSi). PSi is a typical σ-conjugated polymer, composed of alkyl side chains attached to the silicon (Si)-catenated main chain. First, PSi with linear alkyl side chains showed significant diameter-selective wrapping for the SWNTs with ca. 0.9 nm in diameter, resulting in the selective separation of (7,6) and (9,4) SWNTs. Its driving force was demonstrated to be cooperative CH-π interactions among the alkyl side chains of PSi and the curved graphene of SWNTs. Second, the dynamic wrapping behavior of PSi onto SWNT was elucidated with time-resolved UV spectroscopy. Highly anisotropic UV absorption of PSi along the Si main chain was utilized as a "chromophoric indicator" to monitor the global / local conformations, which enabled us to track kinetic structural changes of PSi on SWNTs. Consequently, we concluded that upon wrapping, flexible / helical PSi with an average dihedral angle (ϕ) of 145 ° and Kuhn's segment length (λ-1) of 2.8 nm interconverted to the more planar / stiffer conformation with 170 ° and λ-1 of 7.4 nm. Furthermore, through kinetic analysis of the time-course UV spectra, we discovered the fact that PSis involve three distinct structural changes during wrapping. That is, (i) the very fast adsorption of several segments within dead time of mixing (< 30 ms), following (ii) the gradual adsorption of loosely-wrapped segments with the half maximum values (τ1) of 31.4 msec, and (iii) the slow rearrangement of the entire chains with τ2 of 123.1 msec, coupling with elongation of the segment lengths. The present results may be useful for rational design of polymers toward chiral-index selective binding / separating of desired (n,m) SWNTs.
Woojung Chung; Kazuyuki Nobusawa; Hironari Kamikubo; Mikio Kataoka; Michiya Fujiki; Masanobu Naito
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-16
Journal Detail:
Title:  Journal of the American Chemical Society     Volume:  -     ISSN:  1520-5126     ISO Abbreviation:  J. Am. Chem. Soc.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-16     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7503056     Medline TA:  J Am Chem Soc     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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