Crystallization phenomena in bacterial poly[(R)-3-hydroxybutyrate]: 3. Toughening via texture changes

Poly[(R)-3-hydroxybutyrate] (I) is a bacterial storage polyester that is genuinely biodegradable, but its brittleness hampers its wide applicability as a biodegradable plastic. Most attempts to improve the mech. properties of I have focused on incorporating comonomers, but at the expense of prodn. costs. Strikingly, it appeared possible to toughen I using a simple annealing treatment. The present study attributes this remarkable phenomenon to a change in the lamellar morphol., which reduces the amorphous-cryst. interface area and thus the constraint imposed on the amorphous chains by the crystals. This elevates the relaxation strength of the amorphous regions, giving rise to the favorable fracture behavio