Temperature-responsive self-assembled nanostructures from lysine-based surfactants with high chain length asymmetry: from tubules and helical ribbons to micelles and vesicles

Stimuli-sensitive self-assembled nanostructures are of great relevance for the templating of nanomaterials and the design of efficient systems for the controlled delivery of molecules. Amino acid-based surfactants often display such fascinating self-assembly due to a combination of molecular feature...

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Bibliographic Details
Published inSoft matter Vol. 15; no. 18; pp. 3700 - 3711
Main Authors Oliveira, Isabel S, Lo, Mikail, Araújo, Maria J, Marques, Eduardo F
Format Journal Article
LanguageEnglish
Published England Royal Society of Chemistry 08.05.2019
Subjects
Amino acids
Asymmetry
Atomic force microscopy
Atomic properties
Chains
Chirality
Hydrogels
Interfacial properties
Light microscopy
Lysine
Micelles
Morphology
Nanomaterials
Nanostructure
Nanotechnology
Phase transitions
Pollutants
Self-assembly
Solubilization
Surface tension
Surfactants
Temperature
Thermodynamic properties
Tubules
Vesicles
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Summary:Stimuli-sensitive self-assembled nanostructures are of great relevance for the templating of nanomaterials and the design of efficient systems for the controlled delivery of molecules. Amino acid-based surfactants often display such fascinating self-assembly due to a combination of molecular features such as critical packing parameter, chirality and H-bonding interactions. Herein, we focus on a family of newly synthesized double-chained alkylcarboxylates derived from l-lysine, and designated by 8Lysn, mLys8, with n, m = 12, 14 and 16, and 12Lys16 and 16Lys12, where the numbers represent the number of C atoms in each hydrocarbon chain. The effects of the chain length asymmetry and structural isomerism of the surfactants on their interfacial properties, thermal behavior and self-assembly in water were investigated by a comprehensive toolbox, including surface tension, DSC, imaging (light microscopy, SEM, TEM and AFM) and SAXS. All the surfactants below their Krafft temperature self-organize into tubular structures of various morphologies (flat structures, twisted and coiled ribbons and hollow tubes), forming hydrogels at low surfactant concentration. Upon the solubilization phase transition, micelles or vesicles are formed depending on the surfactant structure, and the tubule-micelle or tubule-vesicle transition is thermoreversible. A molecular-level rationalization of the observed self-assembly and phase transition features is put forth.
ISSN:1744-683X
1744-6848
DOI:10.1039/c9sm00399a