Self-assembled structures with liquid-crystalline order in aqueous solution by patterning poly(phenylene ethynylene)s

Facially amphiphilic (FA) phenylene ethynylene (PE) polymers that self-assemble in aqueous solution were studied by small-angle X-ray diffraction (SAXD) and found to self-assemble into bilayers with a fully extended backbone. The resulting bilayers have long-range liquid-crystalline order. This self-assembly is programmed into the molecule by placing polar and nonpolar groups at precise locations so that they segregate onto opposite sides of the molecular structure. The absence of FA patterning generated an amorphous sample confirming the importance of this programmed amphiphilicity in the self-assembly process. Facially amphiphilic patterning represents a new design criterion for supramolecular chemistry, illustrated here in the observation of molecular ordering into bilayers reminiscent of self-assembled structures commonly found in biology, including amphiphilic beta-sheet polypeptides and phospholipid bilayers.