A series of poly­(L-lactic acid) (PLLA)-b-poly­(methyl methacrylate) (PMMA) block copolymers with well-defined chemical structures were synthesized by ring-opening polymerization followed by atom-transfer radical polymerization. These copolymers were investigated as effective A-b-C-type compatibilizers for poly­(lactic acid) (PLA) and renewable poly­(epichlorohydrin-co-ethylene oxide) (ECO) elastomer blends. Compared to the neat binary PLA/ECO blend, the PLLA-b-PMMA copolymers significantly improved the compatibility of the PLA and ECO phases, leading to enhanced interfacial adhesion and mechanical performance. Interestingly, by tuning the chain structure and adding different amounts of the copolymer, two different phase structures were achieved in the blends: a typical sea-island morphology of the blends with a low content of PLLA-b-PMMA block copolymers (<15%) and a unique tricontinuous phase morphology with a percolated PLLA-b-PMMA copolymer zone of the blend with the addition of 20 wt % asymmetric A181M868 block copolymer. Both the morphological structures endowed the blends with excellent toughness, including a high elongation at break (>260%) and non-broken behavior with an optimum impact strength above 63 kJ/m2. Accordingly, two different toughening mechanisms were proposed for the blends with different phase structures. The PLLA-b-PMMA block copolymers provide highly efficient and versatile A-b-C-type compatibilizers to fabricate high-performance sustainable PLA-based materials for wide application prospects.

A series of elastomeric ionomers functionalized with different imidazolium-based cations were synthesized by a facile and efficient quaternization reaction from commercial bromobutyl rubber (BIIR) and different functionalized imidazoles, including 1-ethylimidazole, N-(2-hydroxyethyl)­imidazole, newly designed 1-(11′-hydroxyundecyl)­imidazole, and N-[3-(1H-imidazol-1-yl)­propyl]-hexanamide. These BIIR-based elastomeric ionomers (i-BIIRs) with a balanced mechanical performance, interfacial polar interactions, and a suitable processability were employed as novel modifying agents for poly­(lactic acid) (PLA) to achieve highly toughened sustainable blends. The influence of the cationic structure of these ionomers and blend ratio on the compatibility and mechanical performance of the blends was thoroughly investigated. The introduction of polar hydroxyl groups with varied alkyl lengths or an amide group into the imidazolium cation of the i-BIIRs markedly improved the compatibility and impact toughness of the PLA/i-BIIR blends, relative to those of the pure BIIR and the i-BIIR ionomers without functional polar groups. These PLA/i-BIIR ionomer blends exhibited an excellent flexibility–stiffness balance, in which the highest elongation at break up to 300% was achieved with a small loss in stiffness. An impressively high impact strength of 17.1 kJ/m2 was achieved for the PLA and i-BIIR-11-OH (80/20) blends, and this impact strength is almost 6 times that of the neat PLA. The interfacial adhesion between the evenly dispersed small ionomer and PLA matrix was improved because the synergistic multiple intermolecular interaction is the native mechanism for enhancing the toughness and flexibility of the blends.

Optimizing interfacial compatibility is one of the core issues for constructing high-performance green poly­(lactic acid) (PLA) blends. Herein, we prepared a poly­(epichlorohydrin)-b-poly­(d-lactic acid) (PECH-b-PDLA) diblock copolymer as an efficient compatibilizer for poly­(l-lactic acid)/poly­(epichlorohydrin) (PLLA/CHR) blends. The PECH-b-PDLA enabled the blends to form unique interlocks among the chains through combining the strong dipolar interaction and PLLA/PDLA stereocomplexation (SC). This strategy endows the PLLA/CHR blend with a unique “co-continuous” structure composed of CHR particles as the core and a bilayer shell formed by the PECH entanglement layer with strong dipolar interaction and a rigid SC thin layer. Physical properties of the blends were remarkably improved by a co-continuous structure with enhanced interfacial adhesion between phases. The optimum formulation showed unprecedented balanced mechanical properties: a nonbroken sample with an impact strength of 106.7 kJ/m2 and a high elongation at break of up to 467.2%; both were about 40 times those of pure PLLA. The interlocking mechanism through strong dipolar interaction and SC provides a broadly applicable and facile strategy to achieve PLA materials with superior properties for expanded industrial application.

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