Bioinspired all‐polyester diblock copolymers made from poly(pentadecalactone) and poly(3,4‐ethylene furanoate): synthesis and polymer film properties

Bio-based, fully degradable aliphatic-aromatic block copolymers are synthesized from ω-pentadecalatone and cyclic oligo(3,4-ethylene furanoate). In the first approach, the ring-opening polymerization of the cyclic oligo(3,4-ethylene furanoate) is initiated by a poly(pentadecalactone) macroinitiator with a terminal hydroxy group. The reaction temperatures of the melt polymerization are 210–230 °C due to the high melting points of the oligo(3,4-ethylene furanoate). Under these conditions, transesterification is observed. The blockiness of the reaction products depends on the reaction temperature and on the ratio of pentadecalactone to 3,4-ethylene furanoate repeat units, which is 50:50, 80:20, and 90:10. At lower temperatures and more pentadecalactone content, the blockiness is larger. The number average molar mass of the block copolymers remains smaller than 20 000 g mol−1. In the second approach, poly(pentadecalactone) is functionalized with an alkyne group, and the OH group of the oligo(3,4-ethylene furanoate) (molar mass 1900 g mol−1) is converted into an azide group. Connecting the two polymers in a copper-catalyzed 1,3-dipolar addition reaction (“click reaction”) yields block copolymers with a number average molar mass of 12 400 g mol−1. The mechanical properties of the polymer films are intermediate between those of the parent homopolymers.