Investigation of the interaction of alkali ions with surfactant head groups for the formation of lyotropic biaxial nematic phase via optical birefringence measurements.

摘要

Lyotropic liquid crystals exhibiting nematic phases were obtained from the mixtures potassium laurate/alkali sulfate salts(M2SO4)/1-undecanol (UndeOH)/water and sodium dodecyl sulfate (SDS)/M2SO4/1-dodecanol (DDeOH)/water, whereM2SO4 represents the alkali sulfate salts being Li2SO4, Na2SO4, K2SO4, Rb2SO4 or Cs2SO4. The birefringencesmeasurements were performed via laser conoscopy. Our results indicated that cosmotropic and chaotropic behaviors ofboth ions and head groups are very important to obtain lyotropic biaxial nematic phase. To obtain the biaxial nematicphase, surfactant head group and ion present in lyotropic mixture have relatively opposite behavior, e.g. one morecosmotropic (more chaotropic) other less cosmotropic (less chaotropic) or vice versa.