New Lyotropic Mixtures with Non-Chiral N-Acylamino Acid Surfactants Presenting the Biaxial Nematic Phase Investigated by Laser Conoscopy, Polarized Optical Microscopy and X-ray Diffraction

Materials

Erol Akpinar²  Dennys Reis¹  Muhammet Yildirim² 

[1] Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, São Paulo, SP 05314-970, Brazil; E-Mails:;Department of Chemistry, Arts and Sciences Faculty, Abant Izzet Baysal University, Bolu 14280, Turkey; E-Mail:

关键词: biaxial nematic;    phase transitions;    birefringence;    laser conoscopy;    structure;    hydrogen bonding;    X-ray diffraction;   

DOI  :  10.3390/ma7064132

来源: mdpi

【 摘 要 】

Amino acid-based surfactants were used as the main surfactants to prepare new lyotropic mixtures presenting three nematic phases. One of them is biaxial (N_B), and the two others are uniaxial, discotic (N_D) and calamitic (N_C). These surfactants were the non-chiral molecules, potassium N-dodecanoyl-dl-alaninate (dl-KDDA), potassium N-dodecanoyl-dl-serinate (dl-KDDS), disodium N-dodecanoyl-dl-aspartate (dl-NaDDAs) and potassium N-dodecanoyl-glycinate (KDDGly). Measurements of the optical birefringences and X-ray diffraction analysis were used to characterize the nematic phases and phase transitions. Mixtures with dl-KDDS exhibited the largest biaxial phase domain (~9 °C) with respect to the other mixtures in this study. The results obtained with the KDDGly mixture showed that the existence of hydrogen bonding between the head groups of the surfactant molecules seems to hinder the orientation of the micelles under the action of an external magnetic field.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.