Syndio-rich P3HB (sr-P3HB), readily synthesized from the eight-membered meso-dimethyl diolide, has a unique set of stereomicrostructures comprising enriched syndiotactic [rr] and no isotactic [mm] triads but abundant stereo-defects randomly distributed along the chain. This sr-P3HB material is characterized by high toughness (UT=96 MJ/m3), as a result of its high elongation at break (>400%) and tensile strength (34 MPa), crystallinity (Tm=114° C.), and optical clarity (due to its sub-micron spherulites), and good barrier properties, while it still biodegrades in freshwater and soil. On the other hand, iso-rich P3HB (ir-P3HB) can be synthesized from the eight-membered rac-dimethyl diolide. While sr-P3HB exhibits excellent adhesion strength toward a variety of substrates, both sr-P3HB and ir-P3HB can substantially toughen brittle stereoperfect biological or synthetic P3HB. Both sr-P3HB and ir-P3HB can also be obtained from the four-membered rac-beta-butyrolactone with appropriate catalysts.