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Gravity-induced liquid crystal phase transitions of colloidal platelets
David van der Beek1, Tanja Schilling, Henk N W Lekkerkerker
1Van't Hoff Laboratory for Physical and Colloid Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
The Journal of Chemical Physics
|September 9, 2004
Summary
Gravity causes colloidal gibbsite platelets to form a columnar phase over time. An osmotic compression model accurately describes this three-phase equilibrium, validated by simulations and literature data.
Area of Science:
- Colloid science
- Materials science
- Physics
Background:
- Sterically stabilized colloidal suspensions can exhibit complex phase behavior.
- Gravity can influence the sedimentation and ordering of anisotropic particles.
- Gibbsite platelets are a model system for studying colloidal self-assembly.
Purpose of the Study:
- To investigate the influence of gravity on a suspension of sterically stabilized colloidal gibbsite platelets.
- To describe the formation of a columnar phase in such suspensions.
- To validate a theoretical model using simulations and experimental data.
Main Methods:
- Performed Monte Carlo simulations of cut spheres with an aspect ratio of 1/15.
- Utilized literature data for equations of state.
- Applied a simple osmotic compression model to describe the observed phenomena.
Main Results:
- An initially isotropic-nematic biphasic suspension developed a columnar phase at the bottom upon prolonged standing.
- The osmotic compression model successfully described the observed three-phase equilibrium.
- Simulations and literature data supported the model's predictions.
Conclusions:
- Gravity-induced sedimentation drives the formation of ordered phases in colloidal suspensions.
- Osmotic compression is a viable model for explaining phase transitions in colloidal systems.
- The study provides insights into the self-assembly of anisotropic particles under gravitational influence.