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. Can. J. Chem. 59,38 (1981).The solid state properties of poly-0-hydroxybutyrate (PHB) were investigated for samples with degrees of polymerization (m) from 4 to 994. The observed melting points ranged from 47°C to 18O0C. Electron diffractograms on carefully prepared single crystals of a high molecular weight sample provided data which confirmed the reported a and b parameters from X-ray fiber diffraction and provided clear justification for the P2,2,2, space group. The observed intensities in the electron diffractogram, corresponding to (hM) reflections, were compared with the predicted intensities for two proposed structures in the literature. The observed and calculated structure factors for both structures were in good agreement. Small angle X-ray diffraction ofthe meridional maximum for annealed "cold drawn" and "hot drawn" fibers showed a distinctly different dependence on temperature than the maximumm stacks of lamellar single crystals. For oligomers a long spacing was observed which was about twice the length of the sample DPn multiplied by the crystalline advance per monomer. Les points de fusion vont de 47°C a 180°C. Les absences systematiques observees en diffraction electronique sur monocristaux de forte masse confirment le groupe spatiale P2,2,2, propose a partir du diagramme a fibre (rayons-X). Les intensites observies des reflections (hkO) du cliche de diffraction tlectronique sont en accord avec celles predites a partir de deux structures crystallines proposies dans la literature et basies sur les donnees du diagramme a fibre. La diffusion meridionale des rayons-X aux petlts angles pour des fibres ttirtes "ifroid" et "achaud" a e t t enregistree et la variation des maximade diffusion, enfonction de la temperature, differe sensiblement de ce qui est observe pour la variation de l'kpaisseur de lamelles monocristallines. Pour des oligomtres cristallins I'observation d'une tache de diffraction dont I'espacement est deux fois la longueur de la chaine dans sa conformation crystalline mtne proposer une maille avec deux chaines bout bout selon I'axe c.

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Poly(/3-hydroxy butyrate) 735 lations seem to be fully justified. The average temperature coefficient d In (r^o/dT, in the range 0-90°, is also reported in Figure 9: it is always negative and rather small, being in the range from -0.1 to -0.4 X 10"3. It compares very well with viscosimetric measurements (-0.28 X 10"3 from 30 to 130°),27 and also with stresstemperature results on rubberlike samples (from -0.08 to -0.27 X 10"3 in the range 18-95°).28 ConclusionsWe wish to stress particularly a conclusion arising from the present study, concerning the effect of the (27) J.

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