Dependence of poly(3-hydroxybutyrate) crystal modifications on film thickness as revealed by reflection-absorption infrared spectroscopy

Key Words:PHB; Ultrathin-film; Infrared; beta-form; Biodegradable thermoplastic; Nanoscale

Abstract:Thickness-dependent ultrathin films of poly(3-hydroxybutyrate) (PHB) were investigated by using infrared reflection-absorption spectroscopy (IRRAS). It was first found that the autogenetic beta-form of PHB could be easily obtained through confining the film thickness under 20 nm at room temperature. Moreover, the interphase of PHB simultaneously exists with the beta-form of PHB in the films with a thickness less than 10 nm. With the film thickness increasing from several nanometers to about 30 nm, the PHB molecules gradually carry out an orientation shift at the b-axis of PHB crystallite; simultaneously, for the alpha-form of PHB a conformational rearrangement probably takes place for the growth of helical crystal unit cells in the ultrathin films. The molecular structures and crystal evolutions at sub-100 nm were explained in detail by analyzing the corresponding IRRAS features. (C) 2016 Elsevier B.V. All rights reserved.

Volume:86

Issue:

Translation or Not:no