Abstract
The use of cellulose nanocrystals (CNC) in high performance coatings is attractive for micro-scale structures or device fabrication due to the anisotropic geometry, however CNC are insulating materials. Carbon nanotubes (CNT) are also rod-shaped nanomaterials that display high mechanical strength and electrical conductivity. The hydrophobic regions of surface-modified CNC can interact with hydrophobic CNT and aid in association between the two anisotropic nanomaterials. The long-range electrostatic repulsion of CNC plays a role in forming a stable CNT and CNC mixture dispersion in water, which is integral to forming a uniform hybrid film. At concentrations favorable for film formation, the multiwalled nanotubes + CNC mixture dispersion shows cellular network formation, indicating local phase separation, while the single-walled nanotube + CNC mixture dispersion shows schlieren texture, indicating liquid crystal mixture formation. Conductive CNT + CNC hybrid films (5–20 μm thick) were cast on glass microscope slides with and without shear by blade coating. The CNT + CNC hybrid films electrical conductivity increased with increasing CNT loadings and some anisotropy was observed with the sheared hybrid films, although to a lesser extent than what was anticipated. Percolation models were applied to model the hybrid film conductivity and correlate with the hybrid film microstructure.
Highlights
With excellent mechanical, thermal and electrical properties, carbon nanotubes (CNT) have a plethora of potential applications [1,2]
The long-range electrostatic repulsion of CNC plays a role in forming a stable CNT and CNC mixture dispersion in water, which is integral to forming a uniform hybrid film
This phase behavior demonstrates that CNC play a critical role in the multiwall carbon nanotubes (MWNT) and single-wall carbon nanotubes (SWNT) dispersion stabilization
Summary
Thermal and electrical properties, carbon nanotubes (CNT) have a plethora of potential applications [1,2]. Of CNT and other anisotropic nanomaterials into ordered and oriented phases are highly desirable for many applications and are most achieved via colloidal processing [1], but polydispersity and poor colloidal dispersion in both aqueous and nonaqueous solvents make this a grand challenge. Methods to enhance CNT dispersion in aqueous solvents have relied on surface functionalization or modification of the dispersing medium. Lyotropic liquid crystal phase behavior of CNT and other nanoscale rigid rods has been observed in superacids [5], but the handling in superacids is hazardous and prohibitive for large scale applications. One example is the use of denatured DNA to promote a CNT lyotropic liquid crystal dispersion [9]. This work aims to investigate the use of benign, anisotropic colloidal nanorods for dispersion enhancement and the creation of conductive hybrid films
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