Microscopic and macroscopic evaluations of piezoelectric properties of PHBH fiber and film

Abstract This study evaluates the microscopic and macroscopic piezoelectric properties of PHBH fibers, focusing on the effects of annealing temperature. PHBH, a chiral polymer with asymmetric carbons, forms helical molecular chains oriented during fiber drawing. Piezoresponse force microscopy reveals that the fibers’ microscopic shear deformation is influenced by annealing, with temperatures between 70 °C and 90 °C showing significant piezoelectric responses. As the annealing temperature increases, smaller particles coalesce into larger ones, but at 100 °C and above, small holes appear on the fibers’ surface. Macroscopic evaluations include the crystallinity observed using polarizing microscopy and thermal behavior measured by differential scanning calorimetry. PHBH fibers exhibit distinct thermal properties with two melting peaks, indicating different crystalline structures. Dynamic piezoelectric measurements confirm that PHBH films show shear piezoelectricity when cut at 45° to the fiber direction, with responses comparable to other biopolymer fibers like PLLA. This study demonstrates PHBH’s potential as a biodegradable piezoelectric material for sensor applications.