Bioinspired All-Polyester Diblock Copolymers Made from Poly(pentadecalactone) and Poly(3-hydroxycinnamate): Synthesis and Polymer Film Properties.

A bioinspired diblock copolymer was synthesized from pentadecalactone and 3-hydroxy cinnamic acid. Poly(pentadecalactone) (PPDL) with a molar mass of up to 43,000 g mol(-1) was obtained by ring-opening polymerization initiated propargyl alcohol. Poly(3-hydroxy cinnamate) (P3HCA) was obtained by polycondensation and end-functionalized with 3-azido propanol. The two functionalized homopolymers were connected via 1,3-dipolar Huisgen addition to yield the block copolymer PPDL-triazole-P3HCA. The structure the block copolymer was confirmed by proton NMR, FTIR spectroscopy and GPC. By analyzing the morphology of polymer films made from the homopolymers, from a 1:1 homopolymer blend, and from the PPDL-triazole-P3HCA block copolymer, clearly distinct micro- and nanostructures were revealed. Quantitative nanomechanical measurements revealed that the block copolymer PPDL-triazole-P3HCA had a DMT modulus of 22.3 ± 2.7 MPa, which was lower than that of the PPDL homopolymer (801 ± 42 MPa), yet significantly higher than that of the P3HCA homopolymer (1.77 ± 0.63 MPa). Thermal analytics showed that the melting point of PPDL-triazole-P3HCA was similar to PPDL (89-90 °C), while it had a glass transition was similar to P3HCA (123-124 °C). Thus, the semicrystalline, potentially degradable all-polyester block copolymer PPDL-triazole-P3HCA combines the thermal properties of either homopolymer, and has an intermediate elastic modulus.