Direction of the polymorphic form of entacapone using an electrochemical tuneable surface template

The ability to direct the surface crystallisation of different polymorphs of entacapone by tuning the electrochemical potential of Au(100) templates is demonstrated. Under quiescent conditions, without polarization (at open circuit potential), entacapone crystallises in its stable form A on the template surface and concomitantly in its metastable form D in the bulk solution. When Au(100) is negatively polarized (-150 mV), form D is still formed in the bulk solution but the metastable form α is found to crystallise at the edges of the template. Both crystals of form A and α were observed to grow epitaxially over the Au template surface. The electrochemical templating effect is consistent with the polarisation changing the structure of the initially adsorbed layers of supersaturated solution at the template surface which directs the nuclei formation and the subsequent crystal growth processes. This study demonstrates, for the first time, the direction of polymorphic form using a low field polarized nucleation template.