Process for preparing a polarized film or sheet containing β-form polyhydroxyalkanoate based copolymer

A process for preparing a polarized material comprising the steps of:

• a) forming a film or sheet of a polarizable polymeric composition, wherein the polarizable polymeric composition comprises at least one of:
• i. a polymer blend of two or more poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBHx) copolymers, each of the two or more PHBHx copolymers having a different comonomer content,
• ii. a PHA based copolymer with longer side chain selected from poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (PHBO) with pentyl side group, poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (PHBD) with heptyl side group, PHBO or PHBD with C15 side group chains, and medium-chain-length branched polyhydroxyalkanoates (mcl-PHA),
• iii. a polymer blend of a copolymer of PHBHx and one or more PHA based copolymer with longer side chain, and
• iv. a polymer blend comprising polyhydroxyalkanoate (PHA) based copolymer and one or more polymers selected from the group consisting of polyvinylchloride, polymethylacrylate, polymethylmethacrylate, poly(vinylidene cyanide/vinyl acetate) copolymers, vinylidene cyanide/vinyl benzoate copolymers, vinylidene cyanide/isobutylene copolymers, vinylidene cyanide/methyl methacrylate copolymers, vinylidene fluoride copolymer, polyvinylfluoride, polyacrylonitrile, polycarbonate, cellulose, proteins, synthetic polyesters and ethers of cellulose, poly(gamma-methyl-L-glutamate), vinylidene copolymers, Nylon-3, Nylon-5, Nylon-7, Nylon-9, Nylon-11 and blends thereof;
• and
• b) directionally perturbing the film or sheet to induce polarization to form a polarized polymeric composition by at least one of:
• (i) subjecting the film or sheet cast from solution to calendar rolling,
• (ii) subjecting the film or sheet cast from a solution to melt crystallization under shear or pressure,
• (iii) mechanically stretching the film or sheet formed from the polarizable polymeric composition in a gel state,
• (iv) freezing the polarizable polymeric composition in a gel state to induce shear by crystallization,
• (v) applying shear or pressure during molding of the film or sheet,
• (vi) applying electrical field during molding of the film or sheet from the polarizable polymeric composition in a melt state, or
• (vii) in situ polarization during step of forming a film or sheet by electrospinning a ribbon of fibers from a solution of the polarizable polymeric composition in one or more solvents, wherein each fiber of the electrospun ribbon of fibers comprises a shell formed of β-form and a core formed of α-form;
• c) optionally polarizing the polarizable polymeric composition of the directionally perturbed film or sheet by applying a high electric field which is of less intensity than that which would cause substantial dielectric breakdown of the PHA based copolymer;
• and
• d) optionally annealing the polarized polymeric composition of the film or sheet at a temperature less than a melting temperature of crystals of the polarized polymeric composition, whereby polarization is retained up to the melting temperature of crystals of the polarized polymeric composition, wherein the polarized polymeric composition comprises a β-form of the PHA based copolymer, present in an amount from 10% to 99%, as measured by x-ray diffraction.