Synthesis, characterization and stereocomplexation of polyamide 11/polylactide diblock copolymers

The present work deals with the building of novel, fully bio-based polyamide 11 (PA11)/polylactide (PLA) diblock copolymers (PA11xPLAy). The adopted two-step synthetic strategy involves first the preparation of an amino-terminated PA11 prepolymer (i.e., having the amino end-group available and the carboxylic one protected), to be employed subsequently as a macro-initiator in the ring-opening polymerization of D-lactide (or L-lactide). Upon tuning the lactide conversion, diblock copolymers with different PA11/PLA ratios are targeted and achieved, as demonstrated by1H NMR and TGA analysis. The thermal properties of these double-crystalline polymers are characterized by means of DSC. Finally, fast stereocomplexation is demonstrated upon mixing the enantiomeric PA11xPLAydiblock pairs. Indeed, the idea behind these systems is to conjugate the properties of PLA with those of the high-performance PA11, in a cumulative rather than intermediate fashion, as for widely reported random poly(ester amide)s, but without phase separation occurring, which is the case for PLA/PA11 immiscible blends. In addition, the presence of the stereocomplex, well-known for its improved chemical/thermal resistance over PLA homopolymer, could impart even further quality to the final materials.