Molecular mobility and morphology change of poly(vinyl alcohol) (PVA) film as induced by plasticizer glycerol

The addition of small molecular plasticizer is an efficient strategy to increase the process ability and macroscopic performance of poly(vinyl alcohol) (PVA). However, how the plasticizer influences the chain dynamics and morphology deserves further investigation. In this work, the PVA film with varying glycerol addition levels was used as the model system. The increasing glycerol addition-level results in the depression of the melting temperature and crystallization temperature, which in line with Flory's theory. The enhanced chain dynamics in the mobile domain was accessed by low-field NMR, whereas that in the crystalline region remains constant. The domain size as well as the morphology of the mobile phase are accessed by ¹H spin-diffusion NMR. The results indicate the increasing dimensionality of the plasticized PVA film with increasing the addition level of glycerol, where the addition level below 25 wt% leads to the dimensionality of 1D, and higher than 25 wt% results in the dimensionality of 2D. Current results elucidate the critical role of the plasticizer in modulating the dynamics heterogeneity of the plasticized polymer film, which is closely related to the macroscopic performance of the products.