A Study On Melting Recrystallization Behavior Of Poly (β-Hydroxybutyrate) Ultrathin Film On The Amorphous Polymer Sublayer

The layered composite film material was becoming an important research direction with the research direction developing to high performance and special function. The condensed state structure of polymer interface layer had an important influence on the performance of layered composite film materials, therefore, this experiment used double layers coating of the polymer materials. This experiment revealed the Factors of effect on the crystallization behavior according to regulate the interaction parameters between polymer and polymer interface layer.1. The double layers were prepared by spin coating. The upper layer film was the poly (β-hydroxybutyrate) (PHB). It is a crystalline biodegradable material. The lower layer film was the amorphous Poly (vinyl phenol) (PVPh). According to control the thickness of the PHB thin film at 120 nm, the crystallization ability of the PHB layer was weakening with the increase of the PVPh layer thickness from the polarizing optical microscope (POM).The number of the intermolecular hydrogen bonds between PHB and PVPh molecules was increased with the increase of the PVPh layer thickness from the fourier transform infrared spectroscopy (FTIR). So the the activity of the PHB molecular chain will be weaker, this making the crystallization ability of PHB layer was weakening and the crystallization rate was slow. With the increasing in the thermal annealing temperate, the lamellae orientation changed from the b-axis being perpendicular to the film surface (edge-on) to the c-axis becoming perpendicular to the film surface (flat-on). We attributed the high temperature was beneficial to the heterogeneous nucleation forming the flat-on crystal orientation, the low temperature was beneficial to the Homogeneous nucleation forming the edge-on crystal orientation. The temperature of edge-on crystal orientation to flat-on crystal orientation will be different with the changing of the PVPh layer thickness.2. The dendritic crystal was forming in 120 nm thickness PHB on thicker PVPh films (65 nm and 100 nm) from the atomic force microscope (AFM). It can be attributed that the activity of the PHB molecular chain was limited, the thickness of dendritic crystal was only about 6 nm, the growth of the crystal was controlled by diffusion limited aggregation (DLA). Then the unstable growth of the crystal caused the forming of the dendritic crystal.3. In order to research the dependence on the thickness of the morphology of dendritic crystal, according to control the thickness of PVPh thin film at 65 nm, it could find that the crystallization ability of PHB was gradually improved with increasing of the PHB thickness by itself. So the crystallization ability of PHB was jointly decided by the thickness of PHB and PVPh.