PVDF thin film having a bimodal molecular weight and high piezoelectric response

A polymer thin film, comprising:

• a crystalline polymer;
• and
• an additive, wherein the crystalline polymer has a weight average molecular weight of at least approximately 100,000 g/mol, the additive has a weight average molecular weight of less than approximately 25,000 g/mol and comprises a moiety derived from a monomer selected from the group consisting of vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and vinyl fluoride, and the polymer thin film has a piezoelectric coefficient (d31) of at least approximately 5 pC/N.

A method comprising:

• forming a polymer thin film by mixing a high molecular weight crystallizable polymer having a weight average molecular weight of at least approximately 100,000 g/mol and a low molecular weight additive having a weight average molecular weight of less than approximately 25,000 g/mol;
• and
• producing an in-plane strain in the polymer thin film along a first direction in an amount sufficient to re-orient crystals or align polymer chains within the polymer thin film and form a mechanically and piezoelectrically anisotropic polymer thin film, wherein the low molecular weight additive comprises a moiety derived from a monomer selected from the group consisting of vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, vinyl fluoride, homopolymers thereof, co-polymers thereof, and tri-polymers thereof and the polymer thin film is characterized by a piezoelectric coefficient (d31) of at least approximately 5 pC/N or an electromechanical coupling factor (k31) of at least approximately 0.1.