Supramolecular Copolyesters with Tunable Properties

The effect of chain structure (supramolecular random copolymer vs supramolecular segmented copolymer) on material properties of supramolecular polymers was studied, using polyesters, end-functionalized with quadruple hydrogen-bonding ureidopyrimidinone (UPy) units. Mixing of miscible UPy homopolymers led to supramolecular segmented copolymers while functionalized random copolymer diols resulted in supramolecular random copolymers. The (co)polymers were prepared by (co)polymerization of ε-CL and δ-VL using Novozym 435, followed by end functionalization with UPy. Thermal analysis of the functionalized (co)polymers showed two melting transitions. With variable temperature IR, the lower transition was attributed to the melting of the polyester part, while the higher transition corresponded to melting of UPy moieties. The materials can therefore be considered as supramolecular thermoplastic elastomers with a hard phase of microphase separated UPy dimers, giving mechanical strength to the material. Mixing of UPy functionalized homopolymers gave better control over the mechanical properties than UPy functionalized copolymers as a correlation was found between the Young modulus and the fraction of δ-VL polymer in the material.