Porphyrin-Based Polyesters Synthesized by Enzymatic Catalysis

The photochemical and photophysical properties of porphyrins and their derivatives make them useful materials in catalysis, photovoltaics, and biomedicine. The range of applications may be broadened through the synthesis of porphyrin-containing polymers. Polymers based on porphyrins may be prepared by radical polymerization and coupling reactions such as esterification, amidation, and click chemistry. In this work, we demonstrate the successful synthesis of polyesters containing porphyrin moieties in the backbone using Candida antarctica lipase B (CALB) as a catalyst in a two-step methodology comprising ring-closure and ring-opening reactions. The enzymatic reactions were facilitated by the addition of tri(ethylene glycol) spacers to circumvent the bulkiness of the prophyrinic structure in the substrates. A tetraphenylporphyrin-based macrocyclic lactone was first synthesized and characterized and then polymerized to yield polyesters with good thermal stability and optical properties similar to those of their porphyrinic precursors. Films may be cast from the polymers dissolved in organic solvents. The thermal and mechanical properties of the polyesters have been studied.