Phase Behaviors of Dialkyldimethylammonium Bromide Bilayers

Dialkyldimethylammonium bromide (2C( n )Br) surfactants in bilayer exhibit polymorphic phases and richself-assemblybehaviors. However, the effects of alkyl chain length on the phasebehavior of the 2C( n )Br bilayer are stillnot completely understood. Herein, we investigate the 2C( n )Br bilayers by performing all-atom molecular dynamicssimulations, taking into consideration the influence of temperatureand initial interdigitated degree. Our findings indicate that DOAB(2C(8)Br) is challenging to remain in a bilayer structure,while DDAB (2C(12)Br) and DPAB (2C(16)Br) maintainbilayers in different phases. DDAB bilayers exhibit an interdigitatedgel phase, and this phase structure enhances the stability and rigidityof the bilayer membrane. In contrast, DPAB bilayers show a ripplegel phase, which has better softness and ductility. The differencesin phase behaviors can be attributed to a competition between therigidity of the 2C( n )Br surfactants andthe hydrophobic interaction of the alkyl tails. The results revealthe crucial role of the bilayer phase in determining the rigidityof bilayer membranes.