Influence of Poly(ethylene glycol) Molecular Mass on Separation and Ordering in Solutions of CiEj Nonionic Surfactants: Depletion Interactions and Steric Effects

Ordered carbon nanotubes–n-dodecyl tetraethylene monoether liquid crystal composites through phase separation induced by poly(ethylene glycol)

We used a phase separation method to incorporate carbon nanotubes into the lamellar phase of a surfactant.

New one-pot technique to introduce charged nanoparticles into a lyotropic liquid crystal matrix

We present a new method to incorporate hydrophilic charged nanoparticles into the lyotropic liquid crystal (LLC) template. This method is based on the effect of the polymer-induced phase separation (PIPS) and consists of two steps. In the first step, the nanoparticles are mixed with a surfactant micellar solution. In the second step, upon addition of polymer, phase separation is induced and the LLC phase doped with the nanoparticles is formed. Columnar hexagonal and lamellar LLC templates are obtained with the PIPS method. The ordering of the LLC phase can be controlled by the amount of polymer added to induce phase separation. The method works both for the system of nonionic surfactants and polymers and ionic surfactants and polyelectrolytes. We demonstrate that the PIPS method enables the fabrication of the LLC templates doped with positively or negatively charged nanoparticles as well as with a mixture of oppositely charged nanoparticles in arbitrary proportions.

Single-walled carbon nanotube/lyotropic liquid crystal hybrid materials fabricated by a phase separation method in the presence of polyelectrolyte

We present a detailed study on the incorporation of single-walled carbon nanotubes (SWNTs) into lyotropic liquid crystals (LLC) by phase separation in the presence of polyelectrolytes. Two cases were studied in this work: (i) incorporation of SWNTs into the LLC phase formed by an anionic surfactant sodium dodecyl sulfate (SDS) in the presence of an anionic polyelectrolyte poly(sodium styrenesulfonate) (PSS); (ii) incorporation of SWNTs into the LLC phase formed by a cationic surfactant cetyltrimethylammonium bromide (CTAB) in the presence of a cationic polyelectrolyte poly(diallydimethylammonium chloride) (PDADMAC). The SWNTs/LLC composites were characterized by polarized optical microscopy (POM) observations and small-angle X-ray scattering (SAXS) measurements. In both systems, the surfactant phase was condensed into a hexagonal lattice by the polyelectrolyte within the investigated concentration range. Several factors that can influence the property of SWNTs/LLC composite were examined, including concentration of surfactants and polyelectrolytes and temperature. Aggregated SWNTs were not observed, indicating that SWNTs were well dispersed in the LLC phases. SAXS measurements showed the lattice parameter of the host LLC phase changed upon varying the mixing ratio of polyelectrolyte to ionic surfactant. The SWNTs/LLC hybrids showed considerable stability against temperature rise in both systems, and desorption of surfactant from SWNTs was not observed at higher temperature.

Incorporation of carbon nanotubes into a lyotropic liquid crystal by phase separation in the presence of a hydrophilic polymer

Single-walled carbon nanotubes (SWNTs) were incorporated into a lyotropic liquid crystal (LLC) matrix formed by n-dodecyl octaoxyethene monoether (C(12)E(6)) at room temperature through spontaneous phase separation induced by nonionic hydrophilic polymer poly(ethylene glycol) (PEG). The quality of SWNTs/LLC composite was evaluated by polarized microscopy observations and small-angle X-ray scattering (SAXS) measurements. The results obtained clearly indicated that SWNTs have been successfully incorporated into the LLC matrix up to a considerable high content without destroying the LLC matrix, although interesting changes of the LLC matrix were also induced by SWNTs incorporation. By varying the ratio of PEG to C(12)E(6), the type of LLC matrix can be controlled from hexagonal phase to lamellar phase. Temperature was found to have a significant influence on the quality of SWNTs/LLC composite, and tube aggregation can be induced at higher temperature. When SWNTs were changed to multiwalled carbon nanotubes (MWNTs), they became difficult to be incorporated into LLC matrix because of an increase in the average tube diameter.