Preparation of the Layer-by-Layer Deposited Ultrathin Film Based on the Charge-Transfer Interaction

Abstract

This paper is concerned with a novel layer-by-layer adsorption method for preparing multilayer assemblies of polymeric materials. We employed two kinds polymers, poly[2-(9-carbazolyl)ethyl methacrylate] and poly[2-[(3,5-dinitrobenzoyl)oxy]ethyl methacrylate], both bearing nonionic pendant groups in the side chains which have electron-donating character and electron-accepting character, respectively. These polymers were alternatively adsorbed onto the gold surface and the quartz substrates from the solutions in methylene chloride. The formation of this multilayer assembly is based on the charge-transfer (CT) interaction between these groups at the solid−liquid interface and the films obtained have periodic layers of CT complexes. The successive increase of the thickness could be easily monitored by surface plasmon measurements. The thickness increment increased with the increase in the number of layers, and the increment became constant around the 10th layer, indicating that the total thickness of the film increases linearly by the alternating adsorption of the counter polymer.