Microstructure and properties of poly(vinyl alcohol-co-vinyl acetate)-g-ε-caprolactone

Microstructural studies of Poly(vinyl alcohol-co-vinyl acetate)-g-polycaprolactone (PVA-Ac)-g-(PCL) were realized principally using NMR. Initial PVA-Ac has a rather blocky structure with an average sequence length of PVA units equal to 12.5. During the synthesis of the studied (PVA-Ac)-g-(PCL), alcoholysis and transesterification reactions led to PCL grafts with acetate end groups. These reactions typically concern 2-5.5% of the total acetate groups. The influence of the local tacticity on the alcohol triad reactivity was evidenced and explained the incomplete functionalization of the PVA-Ac hydroxyl groups. Alcoholysis reactions were also evidenced but with a very low rate in the tested conditions. Caprolactone homopolymerization was not observed. Other properties of the final synthesized copolymers were also presented. Crystallinity totally disappeared in the (PVA-Ac)-g-(PCL). The glass transition temperature was perfectly adjustable by the Fox law without significant modification of the viscoelastic properties characterized by dynamic rheology.