Powerful tailoring effects of counterions of ammonium surfactants on the phase transitions of solvent-free DNA thermotropic liquid crystals

Abstract

Solvent-free DNA-surfactant thermotropic liquid crystals (TLCs) are new developed soft biomaterials in recent years. The phase transition behaviors of these DNA TLCs could be regulated by the chain lengths of used double chain surfactants. While, the impact of counterions of ammonium surfactants on the phase transitions of DNA TLCs is still not clear. Herein, a series of ammonium surfactants with different counterions were prepared and put into use of fabrication of DNA TLCs. With inorganic counterions, the resulted DNA materials exhibit distinct decrease on the thermodynamic stability of LC states along with the size increase of counterions, while, the use of planar p-toluenesulfonate as counterion leads to remarkable increased LC thermostability for the resulted DNA material, due to the different interaction between counterions and surfactant layers. These observations indicate that the LC property of DNA-surfactant complexes could be conveniently tailored by using surfactants with designed counterions, providing a new strategy for designing advanced solvent-free biomaterials.