Increasing the solubility range of polyesters by tuning their microstructure with co-monomers

ω-Pentadecalactone (PDL) is a biobased 16-membered macrolactone that can be derived from renewable resources. Its regular structure makes it highly crystalline and thus interesting as a biobased replacement for linear low density polyethylene. However, its solubility is very limited (chloroform) which hinders the use of PDL polymers in other applications requiring large solubility range. Co-polymerization with a branched lactone is one way to reduce crystallinity because it is expected to disrupt the co-polyesters’ microstructure. Nevertheless, it has been shown that the microstructure of PDL-based co-polyesters varies depending on the co-monomer structure. A block co-polyester is obtained with branched lactones while a random structure is obtained with unsubstituted lactones of various size.It was attempted to break the crystallinity of PDL-based co-polyesters with a view of increasing their solubility range. Therefore, PDL was copolymerized with the branched and biobased δ-undecalactone (UDL), whose homopolymer is amorphous. In order to obtain random microstructure rather than block-like, several monomer addition strategies were investigated. Monomer distribution within the PDL-co-UDL polyesters was assessed by 13C NMR. It was observed that crystallinity of the co-polyesters was decreased but not suppressed as measured by DSC, partially because they did not display a fully random monomer order. Hansen solubility parameters determination however showed that the solubility range of the co-polyesters was improved compared to PDL homopolymers.