Preparation and characterization of the layer-by-layer deposited ultrathin film based on the charge-transfer interaction in organic solvents

A layer-by-layer film could be fabricated on a substrate by the consecutive adsorption method based on the charge-transfer (CT) interaction between electron-donating carbazolyl groups and electron-accepting 3,5-dinitrobenzoyl groups in the side chains of two kinds of methacrylate polymers, poly[2-(9-carbazolyl)-ethyl methacrylate] (PCzEMA) and poly[2-[(3,5-dinitrobenzoyl)oxy]ethyl methacrylate] (PDNBMA), respectively. The film was characterized by surface plasmon (SP) and UV - vis absorption measurements. The thickness of each layer in the film could be determined by the SP measurements. In the UV - vis absorption measurements, the absorbance of the CT complex increased linearly with the increase in the number of adsorption cycles, indicating that the steady growth of the film took place by immersing the substrate alternatively in the 1,2-dichloroethane solutions of each polymer. Furthermore, the decrease in the absorbance of carbazolyl groups was observed on the immersion of the film with the PCzEMA surface in the solution of PDNBMA. This indicates the formation of the CT complex between adjacent polymer layers. The multilayered structure of the obtained film showed an excellent thermal stability up to 200 °C.