1. Surface Chemistry of Diblock-Copolymer-Based Nanoporous Materials
Takashi Ito, Department of Chemistry, Kansas State University
Cylinder-forming diblock copolymers (e.g., PS-b-PMMA) provide a means for preparing membranes containing cylindrical nanoscale pores with uniform diameters. The resulting nanoporous membranes can be used to design novel membranes for efficient chemical catalysis and separations. For these future applications, in-depth understanding of the chemical properties of the nanopore surface is essential.
So far, using cyclic voltammetry (CV), we have shown:
These information cannot be obtained using spectroscopic and microscopic techniques.
(1) the presence of -COOH groups on the surface of PS-b-PMMA-derived nanopores (19-25 nm in diameter);
(2) chemical functionalization of the nanopore surface.
For native PS-b-PMMA-derived nanoporous films (left), the redox current of anionic Fe(CN)63- decreased with increasing solution pH due to the deprotonation of the surface -COOH groups, whereas that of cationic Ru(NH3)63+ was similar regardless of pH. In contrast, upon amidation of the nanopore surface with ethylenediamine (right), the redox current of Ru(NH3)63+ decreased with decreasing pH and that of Fe(CN)63- was independent of pH. The decrease in redox current of Ru(NH3)63+ at acidic pH was consistent with the presence of -NH2 groups on the nanopore surface as a result of the covalent immobilization of ethylenediamine.