Bimodal Latex Effect on Spin-Coated Thin Conductive Polymer–Single-Walled Carbon Nanotube Layers

Abstract

We synthesize two differently sized poly(methyl methacrylate-co-tert-butyl acrylate) latexes by emulsion polymerization and mix these with a sonicated single-walled carbon nanotube (SWCNT) dispersion, in order to prepare 3% SWCNT composite mixtures. We spin-coat these mixtures at various spin-speed rates and spin times over a glass substrate, producing a thin, transparent, solid, conductive layer. Keeping the amount of SWCNTs constant, we vary the weight fraction of our smaller 30-nm latex particles relative to the larger 70-nm-sized ones. We find a maximum in the electrical conductivity up to 370 S/m as a function of the weight fraction of smaller particles, depending on the overall solid content, the spin speed, and the spin time. This maximum occurs at 3-5% of the smaller latex particles. We also find a more than 2-fold increase in conductivity parallel to the radius of spin-coating than perpendicular to it. Atomic force microscopy points at the existence of lanes of latex particles in the spin-coated thin layer, while large-area transmission electron microscopy demonstrates that the SWCNTs are aligned over a grid fixed on the glass substrate during the spin-coating process. We extract the conductivity distribution on the surface of the thin film and translate this into the direction of the SWCNTs in it.

Unusual geometric percolation of hard nanorods in the uniaxial nematic liquid crystalline phase

“…[3][4][5][6] The underlying assumption in many of these studies is that the filler particles are oriented isotropically, which in practice need not be the case due to, e.g., processing or confinement in a thin film. [1, 17,18] In fact, we expect the percolation threshold to be close to the critical concentration at which long rod-like particles spontaneously form a nematic liquid crystal in an isotropic host fluid. [19,20] At high enough packing fraction, the particles in the isotropic phase run out of space due to excluded volume interactions and align along a common axis, i.e., the uniaxial nematic phase becomes the stable phase.…”

Geometric percolation of hard nanorods: The interplay of spontaneous and externally induced uniaxial particle alignment

“…If the liquid is not allowed to relax before solidification, the aligned structure is then frozen in in the final composite. [11,66,67] An often undesired effect of particle alignment is that it typically raises the percolation threshold by decreasing the contact volume of particle pairs and increasing the average surface-to-surface distance. [11,19,23,30,62,[68][69][70][71][72] In a recent study, we have theoretically shown that percolation becomes very unusual if nanoparticles align by transitioning into the uniaxial nematic phase.…”

Chemically Enhanced Polymer-Coated Carbon Nanotube Electronic Gas Sensor for Isopropyl Alcohol Detection

“…Therefore, film homogeneity and film thickness need to be controlled to produce conductive polymer films. 19 To test the impact of film thickness and composition, we deposited various films using both dip coating and tested how the composition of the polymer, as well as the film thickness impacted deposition properties, and eventually sensor performance. As indicated in Supporting Information (SI) Table S2, 0.25 and 0.55 wt % poly(1-vinylpyrrolidone- co -vinyl-acetate) dip-coated samples resulted in film thickness of 35 and 53 nm, respectively.…”