Thin Films of Poly(isoprene‑<i>b</i>‑ethylene Oxide) Diblock Copolymers on Mica: An
Atomic Force
Microscopy Study
Michail Kalloudis
Emmanouil Glynos
Stergios Pispas
John Walker
Vasileios Koutsos
10.1021/la400041x.s001
https://acs.figshare.com/articles/journal_contribution/Thin_Films_of_Poly_isoprene_i_b_i_ethylene_Oxide_Diblock_Copolymers_on_Mica_An_Atomic_Force_Microscopy_Study/2442214
The structural behavior of three amphiphilic semicrystalline
poly(isoprene-<i>b</i>-ethylene oxide) block copolymers
(PI-<i>b</i>-PEO) with different PEO volume fraction (<i>f</i><sub>PEO</sub> = 0.32, 0.49, and 0.66), spin-coated on
freshly cleaved
mica surfaces from aqueous solutions, was investigated by atomic force
microscopy. We focus on the dependence of the resulting thin film
nanostructures on the molecular characteristics (<i>f</i><sub>PEO</sub> and molecular weight) and the adsorbed amount. The
nanostructures obtained immediately after spin-coating were robust
and remained unchanged after annealing and/or aging. The PEO affinity
for the highly hydrophilic mica and the tendency of the hydrophobic
and low surface energy PI to dewet and be at the free interface caused
the soft PI-<i>b</i>-PEO micelles to collapse leading to
the formation of 2D dendritic networks over mica. We show that, for
all three polymers, the dendritic monolayer thickness can be predicted
by a model consisting of a PEO crystallized layer (directly on top
of mica) of the same thickness in all cases and a PI brush layer on
top. In thicker areas, polymer material self-assembled into conelike
multilamellar bilayers on top of the monolayer and oriented parallel
to the substrate for both symmetric and asymmetric diblock copolymers
with the lowest <i>f</i><sub>PEO</sub>. We compare the lateral
morphology of the films and discuss the thickness heterogeneity, which
results from the coupling and competition of crystallization kinetics,
phase separation, and wetting/dewetting phenomena highlighting the
role of the two blocks to inhibit or enhance certain morphologies.
We show that the deviation of the <i>f</i><sub>PEO</sub> = 0.32 thin film from its bulk phase structure (cylinders in hexagonal
lattice) continues for several lamellar bilayers away from the substrate.
For the asymmetric PI-<i>b</i>-PEO polymer with the higher
PEO volume fraction (<i>f</i><sub>PEO</sub> = 0.66) and
higher APT, laterally extensive stacks of flat-on lamellar crystallites
formed on the surface demonstrating the crucial role of the PEO crystallization.
2016-02-19 22:21:35
PEO volume fraction
Diblock Copolymers
lamellar bilayers
block copolymers
crystallization kinetics
substrate
bulk phase structure
Thin Films
thickness heterogeneity
film nanostructures
PI brush layer
diblock copolymers
conelike multilamellar bilayers
Atomic Force Microscopy StudyThe
APT
surface energy PI
phase separation
2 D dendritic networks
PEO affinity
mica surfaces
dendritic monolayer thickness
PEO crystallization
fPEO
role
force microscopy