Interaction of Polymers with Single-Wall Carbon Nanotubes

Abstract

Polymers\nare widely used for postsynthesis processing, purification,\nand individualization of single-wall carbon nanotubes (SWNTs) in aqueous\nor organic solvent environments. Here, the interaction of single-stranded\nDNA oligomers (ssDNA) and of a polyfluorene copolymer (F8T2) with\n(6,5) SWNTs was investigated from desorption kinetics and in the case\nof ssDNA also using adsorption isotherms. Eyring analysis of desorption\nrate constants reveals a linear increase of activation enthalpies\nwith ssDNA oligomer length until Δ_des<i>H</i>^‡ saturates at (155 ± 5) kJ·mol^–1 for oligomers exceeding the ssDNA Kuhn length of about 6 nm. The\nGibbs energy for desorption of Δ_des<i>G</i>^‡ = (96 ± 1) kJ·mol^–1 is length-independent because of entropy–enthalpy compensation.\nThe saturation of desorption energies at the high polymer coverages\nstudied here is attributed to incomplete adsorption with typically\nno more than a single Kuhn segment of a polymer attached to a SWNT.