Water‐soluble top coats for orientation control of liquid crystal‐containing block copolymer films

ABSTRACT An easily removable, water‐soluble top coat of polyvinylpyrrolidone (PVP) is used to control the orientation of microdomains in a liquid crystalline block copolymer (LC BCP, poly(ethylene oxide)‐block‐poly(6‐(4‐methoxy‐azobenzene‐4′‐butyl) hexyl methacrylate)). The corresponding LC homopolymer is also investigated for comparison. Atomic force microscopy is used to determine the orientation of the cylindrical microdomains of the LC BCP. UV–vis spectroscopy and grazing incidence wide‐angle X‐ray scattering are used to determine the orientation of the LC mesogens in the LC homopolymer and the LC BCP films annealed both with and without a top coat. Once the LC BCP morphology is self‐assembled, the PVP top coat layer can be easily removed with water or alcohol. The facile removal of the top coat improves the processability of BCPs in technological applications, and enables direct investigation of the BCP morphology in scientific studies. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1569–1574 An easily removable top coat layer of polyvinylpyrrolidone is used to control the orientation of microphase‐separated domains of liquid crystalline block copolymers (LC BCPs) by affecting the anchoring behavior of the liquid crystal mesogens in the matrix. Once the self‐assembly of the LC BCP is accomplished, the PVP top coat layer can be removed with water or alcohol. This makes it simpler to analyze the LC BCP morphology and improves the processability of LC BCPs in technological applications.