Soft-template electropolymerization of 3,4-(2,3-naphtylenedioxy)thiophene-2-acetic acid esters favoring dimers: Controlling the surface nanostructure by side ester groups

Abstract

A series of the esters of 3,4-(2,3-naphtylenedioxy)thiophene-2-acetic acid (NaphDOT-R) have been synthesized, with varying the structure of the ester fragments in the molecules (fluoroalkyl groups and different aromatic moieties: benzene, naphthalene, carbazole and pyrene). Their anodic oxidation by cyclic voltammetry scanning between –1 and +2.0 V led to electrochemical deposition of the films on the electrode surface which show different surface morphology. NaphDOT-R derivatives can be divided into two groups: (1) the monomers with fluoroalkyl and benzyl ester groups can only dimerize with depositing insoluble dimers on the electrode surface, whereas (2) monomers with condensed aromatic moieties (naphthalene, carbazole and pyrene) in the ester fragment undergo further electropolymerization involving these groups. The surfaces of the deposited films were studied by scanning electron microscopy toward their roughness and wettability. The influence of water on the electropolymerization process and the surface nanostructures is discussed through TEM observations of the micellar template in the electropolymerization solutions. No template was nevertheless detected for NaphDOT-Pyr in dichloromethane, which electropolymerization leads to the formation of aggregated spherical nanoparticles or tree-like surface nanostructures (3D), whereas in dichloromethane saturated with water, unidirectional (1D) growth of vertically aligned nanotubes was observed. The wettability studies on electrodeposited films with three probe liquids (water diiodomethane and hexadecane) showed that they are generally slightly hydrophobic and oleophilic, while the structure of the side ester group and the deposition conditions effect on the quantitative parameters of the surface roughness and wettability.