Exclusion and Trapping of Carbon Nanostructures in Nonisotropic Suspensions of Cellulose Nanostructures

Large-area, robust, transparent, and conductive ultrathin polymer nanocomposite membranes for flexible electronics

Ultrathin polymer nanocomposite membranes exhibit exceptional mechanical, electrical, and optical properties, making them increasingly important for flexible electronics and sensor devices. Here, we employ interfacial formation, assembly, and jamming of nanoparticle surfactants at liquid/liquid interfaces to fabricate large-area, robust, transparent, conductive, and freestanding ultrathin polymer nanocomposite membranes. Polystyrene (PS) dissolves in toluene and cellulose nanocrystal (CNC)-carbon nanotube (CNT) dispersed in water interact via electrostatic interactions and hydrogen bonding to form CNC-CNT surfactants rapidly at the oil/water interface. These surfactants assemble and jam to generate PS/CNC-CNT ultrathin nanocomposite membranes with exceptional mechanical properties. The freestanding membranes feature diameters up to 0.5 mm and are strong enough to support liquid masses at least 1000 times their own weight. We demonstrate that these ultrathin nanocomposite membranes exhibit tunable mechanical, electrical, and optical properties by simply varying the contents of PS and CNC-CNT, as well as the pH of the CNC-CNT aqueous dispersion, highlighting their great potential for applications in flexible electronics.

All-Aqueous Bicontinuous Structured Liquid Crystal Emulsion through Intraphase Trapping of Cellulose Nanoparticles

Here, we describe the all-aqueous bicontinuous emulsions with cholesteric liquid crystal domains through hierarchical colloidal self-assembly of nanoparticles. This is achieved by homogenization of a rod-like cellulose nanocrystal (CNC) with two immiscible, phase separating polyethylene glycol (PEG) and dextran polymer solutions. The dispersed CNCs exhibit unequal affinity for the binary polymer mixtures that depends on the balance of osmotic and chemical potential between the two phases. Once at the critical concentration, CNC particles are constrained within one component of the polymer phases and self-assemble into a cholesteric organization. The obtained liquid crystal emulsion demonstrates a confined three-dimensional percolating bicontinuous network with cholesteric self-assembly of CNC within the PEG phase; meanwhile, the nanoparticles in the dextran phase remain isotropic instead. Our results provide an alternative way to arrest bicontinuous structures through intraphase trapping and assembling of nanoparticles, which is a viable and flexible route to extend for a wide range of colloidal systems.

Surfactant-Mediated Co-Existence of Single-Walled Carbon Nanotube Networks and Cellulose Nanocrystal Mesophases

Hybrids comprising cellulose nanocrystals (CNCs) and percolated networks of single-walled carbon nanotubes (SWNTs) may serve for the casting of hybrid materials with improved optical, mechanical, electrical, and thermal properties. However, CNC-dispersed SWNTs are depleted from the chiral nematic (N*) phase and enrich the isotropic phase. Herein, we report that SWNTs dispersed by non-ionic surfactant or triblock copolymers are incorporated within the surfactant-mediated CNC mesophases. Small-angle X-ray measurements indicate that the nanostructure of the hybrid phases is only slightly modified by the presence of the surfactants, and the chiral nature of the N* phase is preserved. Cryo-TEM and Raman spectroscopy show that SWNTs networks with typical mesh size from hundreds of nanometers to microns are distributed equally between the two phases. We suggest that the adsorption of the surfactants or polymers mediates the interfacial interaction between the CNCs and SWNTs, enhancing the formation of co-existing meso-structures in the hybrid phases.