Dendritic morphology composed of stacked single crystals in poly(ethylene succinate) melt-crystallized with poly(p-vinyl phenol)

Dendritic morphology with stacked single crystals of poly(ethylene succinate) (PESu) melt-crystallized in the presence of amorphous poly(p-vinyl phenol) (PVPh) were observed and analyzed using optical microscopy (OM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). At higher temperatures, the fluffy dendritic morphology was a transition in melt-crystallized PESu/PVPh from originally compact crystals at lower crystallization temperature. The addition of amorphous and strongly interacting PVPh polymer, confinement in thin films, and high crystallization temperature were considered as the main factors of the crystals transition from compact crystals to dendritic crystals. Single crystals of PESu were proven by AFM in the PESu/PVPh blend especially when confined in films of above 500 nm, melt-crystallized at T_c = 70 °C or above. The electron diffraction pattern of TEM result further confirmed the formation of PESu single crystals. The combination of thin film thickness, high crystallization temperature, and strong interaction between two polymers were believed to be the main factors for melt-crystallized PESu single crystals. In the single crystals with spiral arrays, the PESu chains, though achiral, tend to exhibit paired-up crystal entities resembling "identical twins" but with opposite helical directions. The single-layer thickness is almost equal between the paired-up lozenge lamellae screwing clockwise or counterclockwise. The PESu single crystals in PESu/PVPh blend were melt-grown, and electron diffraction patterns proven in this study are in agreement with the literature for neat PESu single crystals grown in dilute solutions.