A series of semicrystalline-glassy (poly(amide11)–poly(lactide))
n
(PA11–PLA)
n
multiblock copolymers with >97% renewable carbon content
were
developed for tough PLA. The resulting copolymers exhibited superior
mechanical performance, comparable to those of commercial PA11 and
PLA. Amine-terminated PA11 with a M
n,NMR of 12 kg mol–1 was prepared by bulk self-condensation
and subsequently capped with only one LA molecule through mechanochemical
ball milling, to produce HO–LA–PA11–LA–OH.
After adding Sn(Oct)2, unreacted LA was propagated in one-pot
by ring-opening polymerization to make PLA–PA11–PLA
with a f
PLA of 0.5–0.8. The hydroxyl-telechelic
triblocks were also coupled with diisocyanate by ball milling to manufacture
(PA11–PLA)
n
multiblocks. The well-defined
molecular structures demonstrated controlled PA11 and PLA lengths.
Thermal analysis determined the phase separation of PA11 and PLA based
on T
g,PLA (48–56 °C) and T
m,PA11 (183–186 °C) and confirmed
the two transitions of thermal degradation (T
d). SAXS profiles of the multiblocks also verified their microphase-separated
morphologies. The temperature dependence of χ for the PA11–PLA
system, χPA11–PLA = (426.00 ± 4.81)/T – (0.90 ± 0.01), simply represented as 0.24
and 0.13 at 100 and 140 °C, was estimated using the T
ODT values obtained from the DMA of three symmetric PLA–PA11–PLA
triblocks with a f
PLA of 0.5. The resulting
semicrystalline-glassy multiblocks showed superior tensile characteristics,
merging PLA-originated initial modulus and yield stress (E = 758–903 MPa and σyield = 57–63
MPa), and a PA11-derived toughening even with strain hardening (εb = 380–500%, σb = 40–51 MPa,
and γ = 124–171 MJ m–3). These results
show promising potential for polymeric materials with sustainability
and strength-toughness balance.
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