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Nanometer Confinement-Driven Promotion and Stabilization of a Hexatic Phase Intervening between Ordered Rotator
Sujeet Dutta1, Sowmya Srikantamurthy1, Prabir Kumar Mukherjee2
1Centre for Nano and Soft Matter Sciences , Bengaluru 560013 , India.
The Journal of Physical Chemistry. B
|November 14, 2018
Summary
Confinement in nanopores extends the hexatic phase of alkane mixtures and increases molecular ordering. This study explains the hexatic phase emergence and confinement effects using X-ray diffraction and theoretical models.
Area of Science:
- Materials Science
- Physical Chemistry
- Soft Matter Physics
Background:
- Binary mixtures of n-tricosane (C23H48) and n-octacosane (C28H58) exhibit rotator phases (RII, RI, RIII, RIV).
- A hexatic mesophase, characterized by loss of long-range positional order but retention of hexagonal geometry, exists between rotator phases in bulk mixtures.
- Confinement within 200 nm alumina pores alters the hexatic phase's temperature range and molecular ordering.
Purpose of the Study:
- To elucidate the mechanism behind the hexatic phase formation in alkane binary mixtures.
- To investigate the dual effects of nanopore confinement on the hexatic phase: extended temperature range and enhanced molecular ordering.
- To theoretically explain confinement-induced modifications using Landau and Flory-Huggins theories.
Main Methods:
- Temperature-dependent X-ray diffraction studies were performed on confined and bulk alkane mixtures.
- Theoretical modeling combined Landau and Flory-Huggins theories to analyze phase behavior.
- Analysis focused on finite-size effects and interfacial interactions between alkanes and alumina pore walls.
Main Results:
- The hexatic phase in confined alkane mixtures showed an extended temperature range compared to the bulk phase.
- Increased molecular ordering was observed in the confined hexatic phase, contrasting with bulk behavior.
- The study identified counter-reacting behaviors of the hexatic phase under confinement.
Conclusions:
- Confinement in nanopores significantly influences the stability and structure of the hexatic phase in alkane binary mixtures.
- The interplay between finite-size effects and interfacial interactions governs the observed phenomena.
- The combined theoretical and experimental approach provides a comprehensive understanding of confined soft matter systems.
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