Characterization of surface energetic heterogeneity of pure and poly (acrylic acid)-adsorbed carbon nanotubes by deconvoluting the nitrogen adsorption isotherm

The surface energetic heterogeneity of pure and poly (acrylic acid) (PAA)-adsorbed carbon nanotubes (CNTs) were studied by a nitrogen probe adsorption technique in a wide range of pressures. The adsorption energy distributions (AEDs) were calculated from the low-pressure data of isotherms by deconvoluting the low-pressure experimental nitrogen adsorption isotherms. The surface of pure CNTs is heterogeneous as its AED presents four peaks at 42, 52, 57 and 78 K. It is observed that the AED of CNTs can be evidently modified by PAA adsorption. While the PAA adsorption amount increases, the high-energy peaks at 52, 57 and 78 K gradually weaken and diminish at last, whereas the low ones such as at 42 K strengthen and new peaks arise at 27 and 32 K. It is proposed that PAA molecules prefer interacting with and screening the higher energetic sites to the lower ones. It will facilitate the understanding of the polymer adsorption on energetic heterogeneity surfaces. Copyright (C) 2006 John Wiley & Sons, Ltd.