Why would a bilayer containing only gangliosides be unstable?

The cell membrane is abiological membrane that protects all cells by separating their interiors from the outside environment.

The gangliosides are known to have a more complicated structure and to show a lot of structural diversity. Because of the large oligosaccharide head groups found in gangliosides, a bilayer consisting only of gangliosides is unstable. These oligosaccharides impede tight packing of the lipid bilayer. The polar membrane is made up of two layers of lipid molecules, which are very thin.

Thus, gangliosides have big head groups, a bilayer made entirely of them would not pack well, leaving wide gaps between them. Because huge gaps aren't allowed in a regular lipid bilayer, this ganglioside-only bilayer would be unstable.