Application of Polymer Solubility Theory to Solution Phase Dispersion of Single-Walled Carbon Nanotubes

PT: J; TC: 20; UT: WOS:000266447600018

Single-walled carbon nanotubes below 1.5 mu m in length are effectively rigid rod-like polymers, but polymer solubility theory has not yet been applied to their solution phase dispersion despite its success in modeling other polymer systems. In this work, we experimentally determine the solubility of arc discharge single-walled carbon nanotubes (SWNT) covalently functionalized with aryl carboxylic acid or aryl hydroxyl groups in aqueous solution using UV-vis-nIR photoabsorption spectroscopy. Empirically, stable suspension is observed when the optical density at 632 nm is above 0.05. The critical level of functionalization required for surfactant-free aqueous suspension is found to be > 1.5 and > 5.1 functional groups per 100 carbons for the carboxylic acid and hydroxyl aryl groups, respectively. Solubility parameters are estimated by using established polymer solubility theory (Fedors and Refined Solubility Parameter group additivity models), molecular simulations (Maiti Dissipative Particle Dynamics), or a combination of both (Maiti-RSP and Maiti-Fedors). Flory-Huggins interaction parameters are calculated for suspensions of both chemistries in water and dimethyl formamide (DMF). Comparison of experiment and model indicates that the combined Maiti-RSP model best describes increasing solubility with increasing functionalization.