Quantitative investigation of surface functionalization of cylindrical nanopores derived from polystyrene-poly(methylmethacrylate) diblock copolymers

Abstract

This paper reports quantitative measurements of surface modification efficiency on nanoporous films (20–35 nm in thickness; 14, 20 and 30 nm in pore diameter) derived from cylinder-forming polystyrene-poly(methylmethacrylate) diblock copolymers. The density of free –COOH groups on the nanopore surface was determined by measuring their probe counter cations released via cation exchange using spectrofluorometry and inductively coupled plasma mass spectrometry. The yields of aqueous-phase amidation mediated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide in phosphate buffer (pH 6) were 20–30%. In contrast, organic-phase amidation and esterification using oxalyl chloride offered much higher yields (87–89%), providing efficient means for functionalizing the nanopore surface. Quantitative information on the surface modification will provide a basis for assessing the influences of the surface functionality on the efficiency of chemical separations with the nanoporous films.