Immiscible Polymer Blends Compatibilized through Noncovalent Forces: Construction of a "Quasi-Block/Graft Copolymer" by Interfacial Stereocomplex Crystallites

Interfacial compatibilization is acknowledged to be the most effective approach to improve interfacial strength between the thermodynamically immiscible components of polymer blends. However, the compatibilizer, mainly achieved by graft or block copolymers, necessarily connected by covalent bonds, can rarely be satisfied presently. Herein, we propose a concept of "quasi-block/graft copolymer" to compatibilize the immiscible polyolefin elastomer (POE) and graft copolymer was achieved by the stereocomplex crystals (SC) of poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) moieties that reactively grafted on the main chains of the components. By taking advantage of the interfacial compatibilization through noncovalent forces, the microphase morphology of the blend can be adjusted and the mechanical properties can be improved: firstly, the curvature of the phase interface decreases significantly, facilitating co-continuous morphology on account of the "rigid" interfacial layers; secondly, the tensile strength and modulus of the blend are obviously improved; thirdly, the original phase structure of the blend can be well maintained during long-term annealing due to the high melting point of the interfacial SC. This strategy of compatibilizing immiscible blends by using the hydrogen bonding force of the stereocomplex opens up an idea for interfacial compatibilization.