Solid-state modification of PBT with cyclic acetalized galactitol and D-mannitol: Influence of composition and chemical microstructure on thermal properties

Abstract

Two bicyclic carbohydrate-based diols, 2,3:4,5- di- O -methylene-galactitol (Galx) or 2,4:3,5-di- O -methylene- D - mannitol (Manx), were introduced into the backbone of poly(butylene terephthalate) using the solid-state modi fi cation technique (SSM). The resulting copolyesters had a unique block-like chemical microstructure that endows them with superior thermal properties when compared with their random counterparts obtained by melt copolymerization. The materials prepared by SSM displayed higher melting points, crystal- lization temperatures, and crystallinity due to the presence of long PBT sequences in the copolyester. The glass-transition temperatures also increased upon incorporation of the bicyclic comonomers, this e ff ect being more pronounced for Manx units. The melting points of these block-like copolyesters decreased after melting due to the occurrence of randomization, but they remained higher than those of copolyesters prepared from the melt. SSM was demonstrated to be a very suitable technique for the incorporation of rigid monomers into the amorphous phase of PBT, leading to bio-based non-random copolyesters with remarkable thermal properties