Poly(acrylic acid) Template-guided Enzymatic Synthesis of Water-soluble Poly(o-toluidine)

It was recently reported that water-soluble conducting polyaniline may be prepared using a new template-guided enzymatic approach. It was found that the template provides a necessary type of local environment where the pH and charge density near the template molecules are different from that of the bulk solution. A strong acid polyelectrolyte, such as sulphonated polystyrene (SPS), is the most favourable because it provides a lower, local pH environment that serves to both charges and preferentially align the monomers through electrostatic and hydrophobic interactions to promote the desirable head-to-tail coupling. Poly(acrylic acid) (PAA) partial sodium salt is used as an acid polyelectrolyte in this work. Biocatalytic polymerization using a naturally occurring enzyme is advantageous because it is a simple, one-step and environmentally compatible method. The horseradish peroxidase (HRP) enzyme is used in polymerization of o-toluidine in the presence of poly(acrylic acid) partial salt as a template and camphor sulphonic acid as a dopant. The synthesis is simple and the conditions are mild. Best results are obtained in pH 4.3 phosphates buffered aqueous solutions with stoichiometric amount of monomer, template and oxidant and catalytic amount of enzyme. The synthesized polymers have been characterized by UV-vis and FTIR spectroscopy and cyclic voltammetry. These studies confirm that electroactive and conducting forms of poly(o-toluidine) (POT) are obtained in the presence of PAA.