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Formation of nematic liquid crystals of sterically stabilized layered double hydroxide platelets
- Source :
- The journal of physical chemistry. B. 112(33)
- Publication Year :
- 2008
-
Abstract
- Colloidal platelets of hydrotalcite, a layered double hydroxide, have been prepared by coprecipitation at pH 11-12 of magnesium nitrate and aluminum nitrate at two different magnesium to aluminum ratios. Changing the temperature and ionic strength during hydrothermal treatment, the platelets were tailored to different sizes and aspect ratios. Amino-modified polyisobutylene molecules were grafted onto the platelets following a convenient new route involving freeze-drying. Organic dispersions in toluene were prepared of the particles with the largest size and highest aspect ratio. The colloidal dispersions prepared in this way showed isotropic-nematic phase transitions above a limiting concentration in a matter of days. The number density at the transition and the width of the biphasic region were determined and compared to theory. The orientation of the platelets in nematic droplets (tactoids) and at the isotropic-nematic interface were analyzed by polarization microscopy. It was observed that sedimentation induces a nematic layer in samples that are below the limiting concentration for isotropic-nematic phase separation. No nematic phase was observed in the initial aqueous suspensions of the ungrafted particles.
- Subjects :
- Materials science
Hydrotalcite
Magnesium
Inorganic chemistry
chemistry.chemical_element
Surfaces, Coatings and Films
Magnesium nitrate
chemistry.chemical_compound
Colloid
chemistry
Chemical engineering
Liquid crystal
Ionic strength
Phase (matter)
Materials Chemistry
Hydroxide
Physical and Theoretical Chemistry
Subjects
Details
- ISSN :
- 15206106
- Volume :
- 112
- Issue :
- 33
- Database :
- OpenAIRE
- Journal :
- The journal of physical chemistry. B
- Accession number :
- edsair.doi.dedup.....2e40be1b587c25937b05e797a4051170