It will be shown that when polyether-b-amide (PEBA) is added to a PLA/PA11 blend, it tends toward the interface and results in a significant increase in the impact strength when all three phases are fully percolated. The addition of the elastomeric PEBA phase to the binary PLA/PA11 blend replaces a rigid PLA/PA11 interface with a much more deformable one. The further addition of PEO to PLA results in an ultratough material with an impact strength of ∼750 J/m, which is approximately 40 times greater than the original co-continuous PLA/PA11 blend. The tensile toughness and notched Izod impact strength are significantly influenced by the critical co-continuous composition region of the PLA/PA11 binary system and a minimum concentration to form a fully percolated PEBA layer at the co-continuous PLA/PA11 interface. The added PEO is also found to enhance the interfacial interactions and the chain mobility of PLA. The combined effects of co-continuity, strong interfacial interactions, a deformable interface, and sufficient PLA chain mobility are all essential to achieving ultratough behavior in PLA/PA11. Examination of the fracture surface of the ultratough material after impact indicates significant voiding. It is suggested that the stress-field overlap within the deformable PEBA phase in conjunction with suitable interfacial adhesion changes the failure mode from crazing to shear yielding. These results establish a strategy for the toughening of multiphase polymer blends, especially in the vicinity of the co-continuous region.

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A versatile approach to control the localization of cellulose nanocrystal (CNC) in PLA/PA11 blends is presented. A PEO/CNC mixture with a high level of CNC dispersion is prepared through a combination of high pressure homogenization and freeze-drying. The prepared PEO/CNC mixture is then incorporated into the PLA/PA11 blends using two different strategies. Typically for CNC/PLA/PA11, the CNCs selectively localize in PA11. However, PEO-coated CNC particles segregate into PLA irrespective of whether the PEO/CNC mixture is premixed with PLA or PA11. It is suggested that a strong interaction between PEO and CNC particles combined with the PLA/ PEO miscibility facilitates the localization of PEO-coated CNC in the PLA. The localization of PEO-coated CNC in the PLA has no effect on the morphology of the PLA-5PEO/PA11 with matrix/ dispersed phase form. However, 2 wt % PEO-coated CNC in the co-continuous (PLA-5PEO)/PA11 50/50 vol % blend diminishes the phase thickness from 11 6 1 to 46 1.5 lm. This is attributed to a retarded relaxation of the PLA phase. This work outlines a strategy to control the CNC localization into a given polymeric phase in a binary polymer-polymer mixture.

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