ELECTROMECHANICAL PROPERTIES OF AN ULTRATHIN-LAYER OF DIRECTIONALLY ALIGNED HELICAL POLYPEPTIDES

The electromechanical properties of a monomolecular film of poly-gamma -benzyl-L-glutamate (PBLG) 15 nanometers thick grafted at the carboxyl -terminal end to a flat aluminum surface were measured. The field-indu ced change in film thickness, dominated by a large inverse-piezoelectr ic effect, demonstrates that the ''grafting-from'' technique forces th e chains into a parallel arrangement. The mechanical plate modulus of the film as determined by electrostriction agrees with the theoretical prediction for a single PBLG molecule along the chain axis. The exper iments show that ultrathin polypeptide layers with large persistent po larization can be fabricated by the grafting approach.