Smectic and Cubic Mesophases of Alkylammonium Poly(vinylsulfonate)s

Mesomorphism of a new series of catanionic 4-(1-pentylheptyl)benzenesulfonates

The effect of cationic chemical structure on the mesophase behavior, and self-assembly of catanionic compounds is studied through a systematic structure variation of six cationic surfactants with anionic sodium 4-(1-pentylheptyl)benzenesulfonate surfactant. A series of cationic surfactants are selected with an increasing number of n-dodecyl chains on the same ammonium headgroup (from one to three), and with an increasing number of ammonium headgroups (from two to four). Thermal and phase behavior of the synthesized products were examined by thermogravimetry, polarizing microscopy, differential scanning calorimetry, powder and grazing incidence X-ray diffraction, and molecular simulation. The compounds are complexes of high thermal stability. Most of the thermotropic mesophases are smectic, although the hexagonal mesophase is also observed. Introduction of the third dodecyl chain into the cationic part leads to pronounced lower melting temperatures and eradicates mesomorphism, while the addition of a fourth ammonium headgroup leads to a catanionic benzenesulfonate that decomposes simultaneously under melting. Melting and crystallization temperatures show nonlinear dependence on the total number of alkyl chains, and on the number of headgroups in the molecule. Molecular dynamics simulation of the smectic phase points to separated hydrophilic and hydrophobic layers, favoring head-to-head packing of antiparallel molecules. On the other hand, there are two ion pairs in the column cross-section of the hexagonal LC phase of didodecyldimethylammonium-4-(1-pentylheptyl)benzenesulfonate.

3D continuous water nanosheet as a gyroid minimal surface formed by bicontinuous cubic liquid-crystalline zwitterions

Co-organization of amphiphilic zwitterions and bis(trifluoromethanesulfonyl)imide led to the formation of bicontinuous cubic liquid-crystalline structures having 3D continuous hydrophilic gyroid minimal surface. The gyroid surface, incorporating a small amount of water, provided extremely thin but macroscopically continuous water nanosheet with a thickness of approximately 5 Å. The water nanosheet functioned as alignment free proton conduction pathway.

Mesomorphic imidazolium salts: new vectors for efficient siRNA transfection

The preparation of chloride (1(n)) and bromide (2(n)) derivatives of 1-methyl-3-[3,4-bis(alkoxy)benzyl]-4H-imidazolium with n = 6, 12, 16, 18 is described. The two series of salts possess a rich thermotropic mesomorphism, chain-length dependent. Thus, a lamellar smectic A phase, a bicontinuous cubic Ia3d phase, and a columnar hexagonal liquid crystalline mesophase are induced as a function of increasing chain length. The mesomorphic properties were studied by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction, and with the support of dilatometry and molecular dynamics, models for the various supramolecular arrangements of the salts are proposed. Such cationic amphiphiles were expected to be candidate molecules to design a new delivery reagent for nucleic acid transfection, particularly for short interfering RNA (siRNA). The use of an RNA interference mechanism, by introduction into cells by transfection of chemically synthesized siRNAs, is a powerful method for gene silencing studies. To exploit the potential of these amphilic imidazolium salts, these molecules were formulated with cohelper lipids and tested for their efficacy to deliver active siRNAs. Our results show high transfection efficacy of our formulated compounds and high silencing efficiency with more than 80% inhibition of the targeted gene at 10 nM siRNA concentration. Taken together our results show the potency of amphiphilic imidazolium salts as a new generation of transfection reagents for RNA interference.