Journal article
Effects of Optical Purity and Finite System Size on Self-Assembly of 12-Hydroxystearic Acid in Hexane: Molecular Dynamics Simulations
The journal of physical chemistry. B, v 121(39), pp 9223-9233
05 Oct 2017
PMID: 28876930
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
12-Hydroxystearic acid (12HSA) and its derivatives are well-known organogelators, and they play critical roles in a variety of applications. The overall aggregate structure of 12HSA is sensitive to the chirality at the 12th carbon, but a fundamental understanding of this dependence is lacking. In this study, molecular dynamics simulations were conducted on microsecond long time scales for (1) (R)-12HSA, (2) (S)-12HSA, and (3) a 50/50 racemic mixture, each solvated at 12.5 wt % in explicit hexane. Self-assembly was accelerated by turning off alkyl chain dihedral gauche states and forcing the molecules to adopt an all-trans conformation. The stability of the resulting aggregates was tested by quenching them with access to gauche states restored. Ordered aggregates produced from optically pure (R)- and (S)-12HSA remained stable for at least 1 μs. The characteristic ordered structure observed is termed a “ring-of-rings” motif, and it contains two twisted six-membered ringlike bundles connected through acetic acid dimerization and surrounded by six satellite bundles. The chirality at the 12th carbon dictates the overall twist of the rings and thereby the handedness of the aggregates. Racemic mixtures did not produce stable ordered aggregates likely due to insufficient enantiomerically pure ring formation. The most prevalent finite-size effect observed was the stochastic formation of percolating aggregates, which were later avoided by using solvent-permeable, solute-impermeable, confining walls. The resulting ordered aggregates were in all important ways identical to those produced in unconfined systems. The combination of cycling off and on gauche states and the semipermeable walls may be an important new way to study the self-assembly underlying aggregation at industrially relevant concentrations of surfactants in organic solvents.
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Details
- Title
- Effects of Optical Purity and Finite System Size on Self-Assembly of 12-Hydroxystearic Acid in Hexane: Molecular Dynamics Simulations
- Creators
- Ryan Gordon - Drexel UniversitySpencer T Stober - ExxonMobil Research and EngineeringCameron F Abrams - Drexel University
- Publication Details
- The journal of physical chemistry. B, v 121(39), pp 9223-9233
- Publisher
- American Chemical Society; Washington, DC
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Chemical and Biological Engineering
- Web of Science ID
- WOS:000412718600015
- Scopus ID
- 2-s2.0-85060167175
- Other Identifier
- 991014969867904721
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- Collaboration types
- Industry collaboration
- Domestic collaboration
- Web of Science research areas
- Biophysics
- Chemistry, Physical