ma300820q_si_001.pdf (342.68 kB)
Hierarchical Structures in Lamellar Hydrogen Bonded LC Side Chain Diblock Copolymers
journal contribution
posted on 2012-09-11, 00:00 authored by Antti
J. Soininen, Ioanna Tanionou, Niels ten Brummelhuis, Helmut Schlaad, Nikos Hadjichristidis, Olli Ikkala, Janne Raula, Raffaele Mezzenga, Janne RuokolainenWe show that in a hydrogen bonded LC side chain diblock
copolymer
with lamellar morphology on the block copolymer level, two distinct
packing mechanisms of the side chain blocks are possible depending
on the amount of hydrogen bonded side chains. We mixed a hydrogen
bonding mesogen, cholesteryl hemisuccinate (CholHS), with poly(1,2-butadiene)-block-poly(2-vinylpyridine) (PBd-P2VP) and poly(styrene)-block-poly(4-vinylpyridine) (PS-P4VP), in which the poly(vinylpyridine)
act as host blocks, and we varied the CholHS to pyridine repeat unit
ratio (x). With all x, a lamellar
morphology on the block copolymer level was achieved. However, at
low binding of CholHS to the host block, the CholHS side chains microphase
separated into a single layer inside the poly(pyridine) lamellae resulting
in a novel microphase separated structure. This includes, for example,
the PS-P4VP sample with x = 0.25 and all the PBd-P2VP
based samples since hydrogen bonding of CholHS to P2VP was sterically
limited as revealed by infrared spectroscopy. No such limits were
present in the rest of the PS-P4VP samples which showed a gradual
shift from the single CholHS lamella morphology to exclusively liquid
crystalline smectic layers oriented perpendicular to the block domain
interfaces.