Kinetics and Mechanism Studies on Dispersion of CNT in SDS Aqueous Solutions

Abstract

AbstractThe objects of this research are to study the dispersion of CNT (carbon nanotube) in SDS (sodium dodecyl sulfate) aqueous solutions with kinetics approach and to obtain some information about mechanism for this dispersion. Firstly, I measured the UV‐visible absorption at 260 nm of CNT in SDS aqueous solutions after different time of dispersion for different concentrations of CNT and SDS. Then, curves of the time‐dependent absorbance were analyzed by various mathematical models and were found to fit well with equation of A = A∞ exp(‐kobs t), where A∞ is the absorbance at infinite time and kobs is the observed rate constant. The values of A∞, kobs, and, minimum time for dispersion can be obtained. From the effects of concentrations of SDS and CNT on A∞ and kobs, the dissociation constant for CNT‐SDS complex and the optimum ratio of [CNT]/[SDS] can be estimated. Finally, the mechanism for this dispersion may be proposed as”$\rm{b-CNT \xrightleftharpoons[\rm{k_{-1} \left[CNT\right]} ]{\rm{k_{1}}} CNT \xrightharpoon[]{\rm{k_{2} \left[SDS\right]}} CNT-SDS}$where b‐CNT, CNT, CNT‐SDS, and, ki s are bounded CNT, exfoliated CNT, CNT‐SDS complex, and, the rate constants, respectively. In this mechanism, b‐CNT is firstly unbounded by supersonic energy to form CNT intermediate with rate constant of k1, which is proportional to the supersonic energy per time. The CNT intermediate then recombines to form b‐CNT with rate constant k−1[CNT] or reacts with SDS to form CNT‐SDS complex, which has absorbance at 260 nm in UV‐visible spectrum, with rate constant of k2 [SDS]. Details of kinetics and mechanism will be discussed in this paper.