Graft Ratio: Quantitative Measurement and Direct Evidence for its Blending Sequence Dependence during Reactive Compatibilization in PVDF/PLLA

Abstract The graft ratio during reactive compatibilization plays important roles in determining phase morphology and consequent performance. The quantitative measurement of it remains absent, which does hinder the basic understanding and applications of reactive compatibilization. In this work, co-continuous structures have been fabricated in PVDF/PLLA with reactive comb compatibilizers (RCC). Based on the co-continuous structures, acid hydrolysis has been employed to remove both reacted and free PLLA, producing acid hydrolysis ratio (AR). On the contrary, only free PLLA can be extracted by chloroform (its selective solvent), corresponding to the extraction ratio (ER). The difference between AR and ER represents the reacted weight percent of PLLA, which is a good parameter to describe the graft ratio (GR). According to the quantitative measurement of GR, the direct evidence for the blending sequence dependence of the extent of graft reaction has been provided. By optimizing the migration and localization of compatibilizers, 50nm co-continuous structures have been fabricated in (PLLA/RCC)/PVDF, in which GR exhibits the highest magnitude. This is the reason for the best mechanical and optical performances in the resultant specimen. Our results open a new avenue for understanding the reactive compatibilization in polymer blend.