Fabrication and measurement of polypeptide-based piezoelectric composite polymer film

A new class of polymer composite piezoelectric materials based on piezoactive biopolymer, poly(-benzyl,L-glutamate) (PBLG), and a matrix polymer, poly(methylmethacrylate) (PMMA), is presented. The composite polymer offers the possibility of decoupling the electrical and mechanical properties, therefore improving the overall system efficiency. By simultaneously poling and curing (at ambient conditions) PBLG and methylmethacrylate (MMA) mixture solutions, we fabricated a flexible composite film with a significant portion of the PBLG molecules oriented normal to the film surface. This film exhibited moderate piezoelectricity (d33=20 pC/N), and its mechanical characteristics were similar to those of low molecular weight PMMA. Present samples are about 40 μm thick with tensile strength of 13 MPa and Young’s modules of 450 MPa. The frequency response is ± 3 dB from 0.1 to 7 kHz and at 1 kHz is linear with acceleration more than a 10 dB range.