Chiral Self-Assembly of Designed Amphiphiles: Optimization for Nanotube Formation

Thomas Barclay, Kristina Constantopoulos, Wei Zhang, Michiya Fujiki, Janis Matisons

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    13 Citations (Scopus)

    Abstract

    Four amphiphiles with l-aspartic acid headgroups (Asp) and a diphenyldiazenyl group (Azo) contained within the hydrophobic tails were designed and synthesized for self-assembly into helically based nanotubes. The amphiphiles of the form R'-{4-[(4-alkylphenyl)diazenyl]phenoxy}alkanoyl-l- aspartic acid (where R' is 10 or 11) varied only in alkyl chain lengths either side of the azo group, having 4, 7, or 10 carbon distal chains and 10 or 11 carbon proximal chains (R-Azo-R'-Asp, where R denotes the number of carbons in the distal chain and R' denotes the number of carbons in the proximal chain). Despite the molecular similarities, distinct differences were identified in the chiral order of the structures self-assembled from hot methanolic aqueous solutions using microscopy and spectroscopic analyses. This was reflected in dominant thermodynamic aggregate morphologies that ranged from amorphous material for 10-Azo-10-Asp, through twisted ribbons (196 ± 49 nm pitch) for 7-Azo-11-Asp, to the desired helically based nanotubes for 4- and 7-Azo-10-Asp (81 ± 11 and 76 ± 6 nm diameters, respectively). Another key variable in the self-assembly of the amphiphiles was the use of a second method to precipitate aggregates from solution at room temperature. This method enabled the isolation of thermodynamically unstable and key transitional structures. Helical ribbons were precursor structures to the nanotubes formed from 4- and 7-Azo-10-Asp as well as the wide, flattened nanotube structures (587 ± 85 nm width) found for 4-Azo-10-Asp. Overall, the results highlighted the interplay of influence of the headgroup and the hydrophobic tail on self-assembly, providing a basis for future rational design of self-assembling amphiphiles.

    Original languageEnglish
    Pages (from-to)14172-14179
    Number of pages8
    JournalLangmuir
    Volume28
    Issue number40
    DOIs
    Publication statusPublished - 2012

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    Barclay, T., Constantopoulos, K., Zhang, W., Fujiki, M., & Matisons, J. (2012). Chiral Self-Assembly of Designed Amphiphiles: Optimization for Nanotube Formation. Langmuir, 28(40), 14172-14179. https://doi.org/10.1021/la3030606