Macromolecules, Vol.29, No.7, 2467-2471, 1996
Single-Crystals and Crystalline Morphology of Synthetic Racemic Poly(Beta-Hydroxybutyrate)
Single crystals of synthetic racemic poly(beta-hydroxybutyrate), PHB, of varying tacticities were grown in dilute chloroform/ethanol solutions. The single crystals of highly isotactic synthetic PHB were spear or lath shaped, like those of bacterial PHB; those from essentially atactic polymer were wrinkled but displayed the same electron diffractogram as isotactic PHB. Syndiotactic PHB gave a nondiffracting precipitate of two different morphologies; further examination suggests that these morphologies differ in tacticity. The average overall tacticities of the precipitated and soluble material were determined by C-13 NMR and found to be unchanged by the precipitation. This provides evidence that some cocrystallization of the R and S repeat units can occur and that the single crystals obtained can be correlated with original sample tacticities.
Keywords:RING-OPENING POLYMERIZATION;POLY-BETA-HYDROXYBUTYRATE;PREDOMINANTLY SYNDIOTACTIC POLY(BETA-HYDROXYBUTYRATE);PHYSICAL-PROPERTIES;BUTYROLACTONE;POLY(BETA-HYDROXYBUTYRATE-CO-BETA-HYDROXYVALERATE);STEREOREGULARITY;ISODIMORPHISM;POLYPROPYLENE;COPOLYESTERS