Octasubstituted phthalocyanine assemblies: Characterization, polymerization, and patterning

Abstract

This dissertation explores the characterization of new phthalocyanine materials, and the processability of these materials with regard to thin film structures envisioned for use in organic based electronic devices. Highly ordered, coherent molecular assemblies are formed by Cu centered benzyloxyethoxy-substituted phthalocyanines. The influence of molecular aggregate interactions with solid supports, based on phenyl-phenyl interactions, manifests itself in large changes in wettability, and also in molecular orientations within those molecular aggregates. Selective deposition of these Pc assemblies was achieved based on chemical interactions with a heterogeneous surface. A facile process of creating alternating hydrophobic/hydrophilic regions on a Au substrate surface through a combination of microcontact printing and electropolymerization techniques (μCP/EP) was demonstrated. Optimization of the hydrophobic channel bottom regions with a phenyl terminated dopant results in patterned phthalocyanine stripes up to 500 μm in length. The substitution of a Co metal center does not appreciably influence the properties of the benzyloxyethoxy-substituted phthalocyanine material, although the lone pair electron, in the d(z)² orbital perpendicular to the Pc macrocycle, appears to be responsible for differences in molecular orientation. The ability of the Co metal to coordinate ligands (i.e. O₂) is particularly evident in electrochemical data taken of this material. Two new photoreactive phthalocyanines, with styryl- and cinnamyl-terminations, result in the formation of new materials, whose preliminary characterization is presented. The photoexcited polymerization of the styryl-substituted material resulted in formation of a 1-dimensional rod-like polymer material, with a mean rod length of 72 nm. The conversion percentages for this material routinely reached 30%, and are expected to improve with purer monomeric materials. The photolysis of the cinnamyl-terminated material routinely reach 70% conversion, and resulted in an insoluble material, that allows for photopatterning. Conventional interdigitated microelectrode (IME) measurements made on these materials show conductivities as high as ca. 10⁻⁸Ω⁻¹·cm⁻¹, and mobility values as high as 10⁻³ cm²·V⁻¹s⁻¹. These charge carrier properties, combined with the selective deposition possibilities (i.e. using patterned substrates and/or photolysis techniques) make this class of materials desirable for further investigation and applications in organic based electronic devices.