Microphase separation in comblike liquid-crystalline diblock copolymers.
The interplay between liquid crystallinity and microphase separation in comblike liquid-crystalline diblock copolymers is examined via a Brazovskii-type phenomenological model using both analytical and numerical calculations. For symmetric diblock copolymers we determine a critical electric field that is required to tilt the orientation of the constituent liquid crystals of the polymer side chains in the microphase-separated lamellar state. Such electrically induced reorientation of the liquid-crystal molecules can lead to substantially large changes of lamellar periodicity. Our numerical results show that highly aligned polymer lamellar domains can self-assemble when the liquid-crystal ordering precedes microphase separation, and that weak electric fields can be used to direct the self-assembly process due to the dielectric anisotropy of the liquid-crystal side chains. We also find that phase separation of asymmetric diblock copolymers can coexist with a network of liquid-crystal nematic orientations, with domain morphology depending on the details of copolymer and liquid-crystal coupling.
Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48201, USA and Department of Physics, University of Swaziland, Private Bag 4, Kwaluseni M201, Swaziland.
S K
SK
Mkhonta
K R
KR
Elder
Zhi-Feng
ZF
Huang
Martin
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Grant