Piezoelectric ultrathin polymer films synthesized by electrostatic self-assembly processing

Ultrathin piezoelectric composite films composed of poly(sodium 4-styrenesolfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDDA) were synthesized using the electrostatic self-assembly (ESA) process. The ESA-processed PSS/PDDA films have a layer-by-layer laminated structure, and exhibit a piezoelectric response directly without electric field poling. The measured piezoelectric coefficient d(33) = 6.0 PC N-1. The molecular self-assembly process plays a very important role in molecular alignment, resulting in a net macroscopic polarization of the layer-by-layer structured ultrathin film, although the process is quite different from that used to form conventional piezoelectric materials. Further study concerning the principles governing the novel ESA processing of piezoelectric and other functional films is on-going.