POISEUILLE-MEDAL-AWARD-LECTURE - PIEZOELECTRICITY OF BIOPOLYMERS

The piezoelectricity of semicrystalline biopolymers was first discover ed for wood and bone in the 1950's. piezoelectric properties have sinc e been investigated for a number of biological substances, including p olysaccharides, proteins and deoxyribonucleates. The shear piezoelectr ic constants -d(14) = d(25) were determined for their oriented structu res with a uniaxial symmetry D-infinity. From studies of synthetic pol ypeptides and optically active polymers, it was concluded that the ori gin of piezoelectricity lies in the internal rotation of dipoles such as CONH, Values of d(14) = -10 pC/N were determined for highly elongat ed films of poly-L-lactic acid, optically active and biodegradable, Th e implantation of this polymer induced the growth of bone, possibly be cause ionic current caused by piezoelectric polarization stimulated th e activity of bone cells. Submicron-thick polyurea films were prepared by evaporating diisocyanate and diamine monomers in vacuum, After pol ing, the films exhibited pyro- and piezoelectric effects. The tensile piezoelectric constant d(31) = 10 pC/N persisting up to 200 degrees C was also observed for aliphatic polyurea films.