Thermotropic phase behavior of cationic gemini surfactants and their equicharge mixtures with sodium dodecyl sulfate

• Type: Article in International Scientific Journal
• Date: 2006

Authors

Wang, YJ (Author) FCUP; Marques, EF (Author) FCUP

Journal

Title: Journal of Physical Chemistry B

Vol. 110

Pages: 1151-1157

ISSN: 1520-6106

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 39 Citations

Scopus - 36 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-004-NMX

DOI: 10.1021/jp0552729

Abstract (EN): The lyotropic phase behavior for the neat cationic gemini surfactants alkanediyl-alpha,omega-bis(alkyldimethylammonium bromide), designated here as in-s-m, has been investigated previously in several works, but the thermotropic behavior has not been well characterized. Only for 15-s-15 and 14-s- 12 have thermotropic liquid crystals (Lc) been reported. In this work, for the first time and in contrast to previous reports, we observe thermotropic Lc formation for m-2-m geminis with in = 12, 14, 16, and 18, by means of polarizing microscopy and differential scanning calorimetry (DSC). Furthermore, we investigate mixtures of m-2-m and SDS, m-2-m Br(2)center dot 2SDS, which exhibit crystal-to-crystal phase transitions at lower temperature and, at high temperature, smectic Lc phases. The transition temperatures and enthalpies for Lc phases, obtained by DSC, present clear trends upon increase of the chain lengths. Combining Langmuir film experiments, possible lamellar arrangements for the different phases are tentatively discussed.

Language: English

Type (Professor's evaluation): Scientific