Polylactic acid (PLA) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) nanofibers were prepared by melt extrusion of immiscible blends of PLA/polyvinyl alcohol (PVA) and P(3HB-co-4HB)/PVA via in situ formation of microfibrils during the melt extrusion process. The morphology of the blends and nanofibers after removal of PVA with water was studied using scanning electron microscopy. The intermolecular interactions in the blends were studied by Fourier-transform infrared spectroscopy. The compatibility of the components of the PVA/PLA blends was better than that of the PVA/P(3HB-co-4HB) blends. By varying the process conditions, the average diameter of the PLA nanofibers could be controlled in the range of 78–150 nm and that of the P(3HB-co-4HB) nanofibers could be controlled in the range of 274–424 nm.
