Unique Hierarchical Mesostructures Arising from Biobased Double-Crystalline PLLA-b-PHDO-b-PLLA ABA Triblock Copolymers.

The ability of block copolymers (BCPs) to self-assemble into microphases allows the creation of unique materials with enhanced tailored properties. In this study, we combined organocatalyzed polycondensation and ring-opening polymerization (ROP) to create fully biobased ABA triblock copolymers consisting of poly(1,6-hexanediol) (PHDO) and poly(l-lactide) (PLLA). Increasing the segregation strength (χN) from 4 to 11 causes the triblocks to shift from weak to intermediate segregation, with PHDO microphases dispersed within a PLLA-rich matrix. Long-range order appears when χN ≥ 6, resulting in a body-centered cubic (BCC) spherical morphology. Depending on thermal history, distinct hierarchical structures, including BCC spherical morphologies, BCC plus lamellar arrangements, and interdigitated double-lamellar structures, were obtained. Increasing the molar mass of the PLLA terminal blocks (MnPLLA = 18.5 kDa) enabled the formation of self-supporting films, for which preliminary mechanical and gas permeation properties were evaluated. Overall, this work establishes structure-morphology relationships of fully biobased double-crystalline triblock copolymers.