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.
Herein, high-performance sustainable ternary blends were prepared via a melt blending method from completely biodegradable polyesters, namely commercial polylactide (PLA), poly(propylene carbonate) (PPC) and a series of poly(hydroxyalkanoate)s (PHAs), including poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydoxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and two types of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P 34 HB) having different 3HB molar ratios. The miscibility, phase structure, mechanical and thermal properties of the blends were investigated to deeply understand the influence of the blend compositions and species of PHAs on the structure and physical performance of the multiphase blends. Thermal and morphological analysis revealed that the PLA, PPC and PHAs components showed partial miscibility with each other, especially the blend with P 34 HB of a low 3HB ratio. Remarkable enhancement in the ductility and toughness of PLA was gained by the addition of PPC and P 34 HB. An optimum tensile strain of 171% was achieved for the PLA/PPC/P 34 HB (60/30/10) blend, while PLA/PPC/P 34 HB (60/10/30) blend showed the highest impact strength with a value of 45 kJ m À2 , which is 14 times higher than that of PLA. Synergistic toughening from the flexible PPC and P 34 HB phase with a degree of interfacial compatibilization played an effective role in enhancing the mechanical performance of the ternary blends.
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