ma7b01567_si_001.pdf (7.89 MB)
Semicrystalline Block Copolymers in Rigid Confining Nanopores
journal contribution
posted on 2017-10-18, 19:07 authored by Man Yan
Eric Yau, Ilja Gunkel, Brigitte Hartmann-Azanza, Wajiha Akram, Yong Wang, Thomas Thurn-Albrecht, Martin SteinhartWe have investigated PLLA crystallization
in lamellae-forming PS-b-PLLA confined to straight
cylindrical nanopores under
weak confinement (nanopore diameter D/equilibrium
PS-b-PLLA period L0 ≥
4.8). Molten PS-b-PLLA predominantly forms concentric
lamellae along the nanopores, but intertwined helices occur even for D/L0 ≈ 7.3. Quenching
PS-b-PLLA melts below TG(PS) results in PLLA cold crystallization strictly confined by the
vitrified PS domains. Above TG(PS), PLLA
crystallization is templated by the PS-b-PLLA melt
domain structure in the nanopore centers, while adsorption on the
nanopore walls stabilizes the outermost cylindrical PS-b-PLLA shell. In between, the nanoscopic PS-b-PLLA
melt domain structure apparently ripens to reduce frustrations transmitted
from the outermost immobilized PS-b-PLLA layer. The
onset of PLLA crystallization catalyzes the ripening while transient
ripening states are arrested by advancing PLLA crystallization. Certain
helical structure motifs persist PLLA crystallization even if PS is
soft. The direction of fastest PLLA crystal growth is preferentially
aligned with the nanopore axes to the same degree as for PLLA homopolymer,
independent of whether PS is vitreous or soft.