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 omega-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 degrees 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. Blockiness depends on reaction conditions: bio-based poly(pentadecalactone-co-oligoethylene furanoate) is obtained by ring-opening polymerization. Macroinitiation gives copolymers with varying degrees of blockiness, clicking the blocks together gives true block copolymers. image