posted on 2023-03-13, 20:30authored byRandall
A. Scanga, Ali Shahrokhinia, Jake Borges, Sean H. Sarault, Michael B. Ross, James F. Reuther
Polymerization-induced crystallization-driven
self-assembly
(PI-CDSA)
is combined, for the first time, with helical, rod-coil block copolymer
(BCP) self-assembly to enable scalable and controllable in
situ synthesis of chiral nanostructures of variable shape,
size, and dimensionality. Herein, we report newly developed asymmetric PI-CDSA (A-PI-CDSA) methodologies
in the synthesis and in situ self-assembly of chiral,
rod-coil BCPs composed of poly(aryl isocyanide) (PAIC) rigid-rod and
poly(ethylene glycol) (PEG) random-coil components. Using PEG-based
nickel(II) macroinitiators, the construction of PAIC-BCP nanostructures
with variable chiral morphologies is accomplished at solids contents
ranging 5.0–10 wt %. At low core-to-corona ratios for PAIC-BCPs,
we demonstrate the scalable formation of chiral one-dimensional (1D)
nanofibers via “living” A-PI-CDSA whose
contour lengths can be tuned through alterations to unimer-to-1D seed
particle ratio. At high core-to-corona ratios, A-PI-CDSA was implemented for the rapid fabrication of molecularly
thin, uniform hexagonal nanosheets via spontaneous nucleation and
growth aided by vortex agitation. Investigations into 2D seeded, living A-PI-CDSA revealed a brand-new paradigm in the context of
CDSA where hierarchically chiral, M helical spirangle
morphologies (i.e., hexagonal helicoids) are size-tuned in three dimensions
(i.e., heights and areas) via alterations to unimer-to-seed ratio.
These unique nanostructures are formed in situ at
scalable solids contents up to 10 wt % via rapid crystallization about
screw dislocation defect sites in an enantioselective fashion. The
liquid crystalline nature of PAIC blocks dictates the hierarchical
assembly of these BCPs, with chirality translated across length scales
and in multiple dimensions affording large amplifications in chiroptical
activity with g-factors reaching −0.030 for
spirangle nanostructures.