Poly(amide11)-Incorporated Block Copolymers as Compatibilizers to Toughen a Poly(lactide)/Polyamide 11 Blend

We added a block copolymer compatibilizer to a thermodynamically immiscible blend of poly(lactide) (PLA) and poly(amide11) (PA11) and achieved a maximum strain at break (εb) and toughness (γ) of 467% and 157 MJ m–3, respectively, which were about 30 times higher than those of the neat PLA/PA11 blend system, while maintaining a yield stress (σyield) of 87% that of the neat PLA homopolymer. The PLA and PA11 based di-, tri-, and multiblock copolymer compatibilizers were synthesized via bulk polycondensation reactions of 11-aminoundecanoic acid (11-AUDA) and hexamethylene diamine (HMDA) or decylamine without the use of solvents. This was followed by a mechanochemical ball milling reaction between the resulting polyamide 11 containing di- or mono terminated amine end-groups and d,l-lactide through ring-opening polymerization (ROP) and urethane linkage reaction. The morphology of the prepared PLA/PA11/compatibilizer blend was investigated by O-PTIR and AFM analyses. As the content of the multiblock compatibilizer increased from 0 to 0.2, 0.5, and 1 wt %, the size of the domain droplets dramatically decreased, from 2.4 to 1.4 μm, and the interfacial thickness increased from 17.0 to 25.5, 55.2, and 76.9 Å, thereby supporting increased adhesion at the PLA/PA11 interface. Mechanical property analyses demonstrated that the mechanical properties improved as the amount of compatibilizer was increased from 0 to 0.2, 0.5, and 1 wt %, as the molecular weight (MW) of the blocks increased beyond the critical molecular weight (Mc) and the MW for cocrystallization, and as the number of blocks increased. The findings of this study demonstrate the potential of enhancing the mechanical properties of biobased polymer blends by incorporating block copolymer compatibilizers. This could help expand the broad range of applications for biobased polymers suitable for various fields.