Poly(3-hydroxybutyrate-co-10%3-hydroxyhexanoate)(PHBHHx) thin films were prepared by means of spin-coating PHBHHx/chloroform solutions on the silicon substrate. The crystalline morphologies of PHBHHx thin films were observed by atomic force microscopy(AFM) at room temperature. A novel crystalline morphology, that is like sunflower was found when the film is very thin and named as sunflower-like crystalline morphology. Compared with usual PHBHHx spherulites, there are obvious differences in aspects of nucleation, crystal growth process and crystalline morphology for the sunflowers. The PHBHHx/chloroform solution properties and the substrate have great effects on the formation of the sunflower. A circular boundary that may result from a liquid-liquid phase separation in PHBHHx solution first formed in the thin film during the spin-coating process, then it induced the formation of the sunflowers.
