Emergent hybrid mesophases in ternary mixtures of cellulose nanocrystals - pluronic micelles -water
2The Center for Nanoscience and Nanotechnology, and the Institute of Life Sciences, The Hebrew University of Jerusalem, Israel
3The Ilse Katz Institute for Nanoscience and Technology, Ben-Gurion University of the Negev, Israel
Liquid suspensions comprising mixtures of spherical and cylindrical nanoparticles are complex fluids that may modify the phase diagram of each of the components forming hybrid materials with new functionalities and are commonly used in various applications. The ternary rod-sphere-solvent systems are expected to exhibit isotropic-nematic liquid-liquid phase separation with marked partitioning of the rods and spheres between the isotropic and nematic phase, where the spheres are almost totally excluded from the nematic phase thus enriched by the rods.
Motivated by this rationale, we investigated the co-assembly of Cellulose Nanocrystals, CNCs, that self-assembles into a chiral nematic liquid crystalline phase in aqueous phases and an amphiphilic block copolymer Poly(ethylene oxide)-poly(propylene oxide)-poly(ethyleneoxide) PEO100-PPO70-PEO100 F127 Pluronic (BASF) that form core-shell micelles above its critical micellization concentration, CMC at room temperature, and.
The combined system was characterized via several methods; structural characterization via small angle x-ray scattering (SAXS)and cryo-TEM, optical properties using polarized light microscopy (POM), surface properties via zeta potential and surface tension measurements. Our results indicate a very different behavior where hybrid liquid crystalline phase emerge from the co-assembly of F127 micelles and the suspended CNCs. The polymeric micelles are observed to modulate the interaction among the CNCs in the emergent phases: weak modulation is observed in CNCs-F127 mixtures of up to 10% (w/v) F127, where the mixed phases preserve the nematic order of the native CNCs phase, but the dimensions of the individual nanoparticles and the interparticle distance are modified due to adsorption of the F127 micelles onto the CNCs. Strong modulation and modification of the nematic phase is observed at higher F127 concentrations where competing interactions among the free micelles and the CNCs-micelle hybrid shape the nanostructure and length-scale of the emergent mesophase.
Improved understanding of the assembly and phase behavior of multi-component systems comprising functional nanomaterials is expected to be beneficial for the development of new hybrid materials.
Powered by Eventact EMS