Lipid Hydrocarbon Tail Structure Governs Interfacial Anchoring and Stripe Morphology in Cholesteric Liquid Crystals

Abstract

Liquid crystal-based biosensors exploit the sensitivity of interfacial anchoring to molecular adsorption. Cholesteric liquid crystals are especially useful because their helical structure supports multiple optically distinct textures that evolve with anchoring strength. Here, we compare saturated 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) and unsaturated 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) monolayers to determine how lipid acyl chain structure governs interfacial organization and director alignment. Mapping stripe spacing across lipid concentration, mixing ratio, cholesteric pitch, and confinement shows that the transition from fingerprint textures toward homeotropic alignment depends on both lipid structure and collective interfacial organization. DLPC produces comparatively regular textures and more readily promotes helix unwinding at high coverage, consistent with more spatially uniform collective anchoring. DOPC-containing interfaces show greater morphological heterogeneity, consistent with strong local anchoring from longer tails together with less uniform organization arising from cis-unsaturation. FRAP measurements provide complementary information on fluorescent-probe mobility, which becomes strongly restricted at high lipid concentration for both systems. Variations in pitch and film thickness further modulate the response, producing coexisting regular, distorted, and lipid-enriched textures. Together, these results show that lipid acyl chain structure regulates cholesteric anchoring through its effects on local interactions, collective interfacial organization, and mobility, providing design principles for responsive liquid-crystal interfaces.