Vesicle structure and formation of AB/BC amphiphile mixture based on hydrogen bonding in a selective solvent: a Monte...

The effect of hydrogen bonding (H-bonding) on vesicle structure and its formation of the mixture of AB/BC amphiphilic molecules in a selective solvent for A and C blocks were studied using Monte Carlo simulation. For the purpose of comparison, H-bonding and covalent bonding were introduced via the two ends of two B blocks. The simulation results indicate that associative interaction of H-bonding (ε(hb)) and repulsive interaction between A and C blocks (ε(AC)) are the two key factors that determine vesicle structure. Four typical vesicles--symmetric, three-layer asymmetric, microphase-separated, and Janus vesicles--can be obtained through the adjustment of ε(hb) and ε(AC). This result is interesting for experimental researchers for controlling vesicle structure and its properties through the introduction of H-bonding. More interestingly, the pathway of vesicle formation also depends on H-bonding. For an H-bonded system, the vesicle is more likely to be formed via diffusion of hydrophilic blocks into the center of spherical micelles. This process is independent of ε(AC). However, for a covalently bonded system, the vesicle is more likely to be formed via oblate membrane-closing for higher ε(AC). In addition, the vesicle is more likely to be formed via diffusion of hydrophilic blocks into the center of spherical micelles for lower ε(AC). Conformational investigation reveals that this H-bonding dependence results from the reversibility of H-bonding.