Bacterial poly(3-hydroxybutyrate): An optical microscopy and microfocus X-ray diffraction study

Two-dimensional spatially resolved microfocus X-ray diffraction has been us ed to investigate spherulites of pure bacterial poly(3-hydroxybutyrate) (PH B) and of a blend of natural and synthetic atactic PHB (a-PHB) crystallized at a relatively high temperature (T-c = 140 degreesC). Both samples invest igated contained practically two-dimensional spherulites, characterized by wide extinction bands (band spacing > 80 mum). The X-ray diffraction patter ns confirmed that the unit cell a-axis is oriented along the spherulite rad ius in PHB and that the same is true for the a-PHB containing blend. Compar ison of the matrix of diffraction patterns with the polarized optical micro graph of the scanned sample area indicated a very clear correlation between pattern changes and banding, yielding a straightforward picture of the str uctural variations within the spherulite.