Multiple influences of hydrogen bonding interactions on PLLA crystallization behaviors in PLLA/TSOS hybrid blending systems

Abstract

The effects of hydrogen bonding, existing between hydroxyls of TSOS (trisilanolheptaphenyl POSS) molecules and carbonyls of PLLA chains, on the crystallization behaviors of PLLA have been detailedly investigated by DSC and temperature-programmed FTIR. The results of DSC scanning demonstrate that the recrystallization capability of quenched PLLA melts is remarkably enhanced in cold crystallization after introducing TSOS molecules due to the nucleating of TSOS molecules and hydrogen bonding interactins. In isothermal melt crystallization, TSOS molecules play a dual role of both inhibitors of crystallization because of hydrogen bonding interactions and nucleating agents resulting from aggregated TSOS molecules. Hydrogen bonding interaction between carbonyls of PLLA and hydroxyls of TSOS is determined by FTIR. Owing to the hydrogen bonding interaction in PLLA/TSOS nanocomposite, mobility and folding of PLLA chains are highly impeded, resulting in decrease of the overall crystallization rate in melt crystallization. The melt crystallization kinetics show that hydrogen bonding interaction plays a predominant role in determining the overall crystallization of PLLA. Besides, hydrogen bonding interactions in PLLA/TSOS blending system are further substantiated by a control experiment of PLLA/OVS blending system, where there is no existence of hydrogen bonding interaction. Because of high specific area of TSOS nano-filler, TSOS readily aggregates into POSS grains, which is detected by SEM and wide angle XRD.