Morphogenesis of liquid crystal topological defects during the nematic-smectic A phase transition

• Published in: Nature communications Vol. 8; no. 1; p. 15453
• Main Authors: Gim, Min-Jun, Beller, Daniel A., Yoon, Dong Ki
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30.05.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/119/2795; 639/301/923/919; 639/301/923/966; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms15453

The liquid crystalline phases of matter each possess distinct types of defects that have drawn great interest in areas such as topology, self-assembly and material micropatterning. However, relatively little is known about how defects in one liquid crystalline phase arise from defects or deformations in another phase upon crossing a phase transition. Here, we directly examine defects in the in situ thermal phase transition from nematic to smectic A in hybrid-aligned liquid crystal droplets on water substrates, using experimental, theoretical and numerical analyses. The hybrid-aligned nematic droplet spontaneously generates boojum defects. During cooling, toric focal conic domains arise through a sequence of morphological transformations involving nematic stripes and locally aligned focal conic domains. This simple experiment reveals a surprisingly complex pathway by which very different types of defects may be related across the nematic–smectic A phase transition, and presents new possibilities for controlled deformation and patterning of liquid crystals. Defects in liquid crystals play a central role in determining their structural and dynamic properties, whilst it is challenging to characterize the defects at a molecule level. Here, Gim et al . trace the evolution pathway of defects during a phase transition from a nematic to a smectic state.