SINGLE-CRYSTALS OF BACTERIAL AND SYNTHETIC POLY(3-HYDROXYVALERATE)

Lamellar, folded-chain single crystals of bacterial homopolymer, of sy nthetic racemic poly(beta-hydroxyvalerate) (PHV), and of bacterial pol y(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (P(HB-co-HV)), with hi gh KV content (superior to 77 mol%) were obtained from dilute ethanoli c solutions. They all exhibited the same square shape as opposed to th e characteristic lath shape of poly(beta-hydroxybutyrate) single cryst als and P(HB-co-HV) single crystals with low HV content. The electron diffraction patterns recorded from selected areas of these single crys tals were identical and allowed the comparison of our observed basal u nit cell parameters with those derived from X-ray fibre diffraction. T he results provided a visual and quantitative confirmation of the isod imorphism phenomenon and confirmed the P2(1)2(1)2(1) orthorhombic symm etry. The lower perfection in the morphology of the single crystals fr om the synthetic PHV homopolymer than in those from the bacterial samp les is attributable to a stereoblock segregation during the crystalliz ation according to block chirality.