Polymer composites with photo-responsive phthalocyanine for patterning in color and fluorescence

Abstract

Polymer composites containing stimuli responsive small molecules have been explored for various applications, including patterning and data storage. Phthalocyanines (Pc) have been widely synthesized and used as dyes, catalysts, and optical limiting materials, as well as active components in modern organic electronic devices. The solubility of Pcs and miscibility with a polymer matrix require the use of covalently attached alkyl side chains that rarely serve any other purpose than solubility. Herein we report a polymer composite with a novel cobalt (II) Pc dye with alkyl chains connected through a photolabile linker. The materials are synthesized using standard reactions and characterized by FTIR, MALDI, and absorption and emission spectroscopies. Upon UV irradiation in solution or in the polymer films, the alkyl groups are cleaved rendering the Pc core insoluble and turning on fluorescence of the small molecule byproduct. This observation is in direct contrast to treatment of similar Pc molecules that lack the photoresponsive group. PMMA and PDMS films are patterned with resolution down to 250μm using only 0.1wt% of our tailored Pc molecule. This work presents a fundamental method for patterning in polymer films by tuning the solubility, color, and fluorescence of a Pc based system and could ultimately be used for sensing, data storage, or pigmentation.