Structural Transition in a Nematic LC Block Copolymer Induced by the Transition to the LC Phase

Abstract

The morphology of a liquid-crystalline ABA triblock copolymer with polystyrene (PS) blocks (12 vol %) and a side chain nematic liquid crystalline B block has been studied by TEM and temperature dependent SAXS measurements. Above the clearing temperature (T c = 122 °C) the morphology is characterized by a body-centered cubic (bcc) lattice of polystyrene spheres. The transition to the nematic phase induces a reversible transition to a morphology of hexagonally packed cylinders by coalescence of the PS spheres along the [1,1,1] direction of the bcc lattice.

Understanding and controlling the morphology of styrene–isoprene side-group liquid crystalline diblock copolymers

“…A very strong preferred anchoring condition could destabilize and thus eliminate microdomain structures in which satisfaction of the IMDS boundary condition for the mesophase would result in the production of significant defect energy (a high enough number and density of defects produced by the preferred anchoring). Strong evidence for this effect is given by the reversible structural transition from spheres to cylinders on passage through T I-N reported by Gronski and coworkers [31]. Alternatively, the mesophase may change, such that some other, perhaps even less ordered, mesophase is produced, but the boundary condition is satisfied and a stable microdomain structure is realized, as suggested by the data of Fischer et al [12] which shows a change of mesophase from smectic A in lamellar microdomains to nematic in spherical ones.…”

Influence of liquid crystalline formation on the phase behavior of side-chain liquid crystalline block copolymers

“…The OOT corresponds to a thermotropic phase change in microphase morphology induced simply by the change in annealing temperatures. S€ anger et al reported an OOT in the morphology of a block copolymer accompanied by the loss of the anisotropic phase structure above the isotropization temperature of the LC block [19]. In this study, the OOT of LCBCPs triggered by LC blocks is investigated.…”

Hierarchical self-assembly, photo-responsive phase behavior and variable tensile property of azobenzene-containing ABA triblock copolymers

“…32 Moreover, the LC clearing transition can alter the interfacial curvature in the LC BCPs, resulting in an OOT of the microphase-separated morphology. 18,31,34 When the LC block is ordered, i.e. smetic or nematic, the microphaseseparated structure prefers to be LAM or HEX rather than BCC with a highly curvatured interface, even though the composition of BCP is quite asymmetric.…”