Spontaneous formation of narrowly‐distributed self‐assembly from polyamidoamine dendron‐poly( L ‐lysine) block copolymers through helix‐coil transition of poly( L ‐lysine) block

The self‐assembly of head‐tail type block copolymers composed of polyamidoamine dendron head block and poly(L‐lysine) (PLL) tail block was studied using a light scattering technique and transmission electron microscopy. A PLL tail block in a head‐tail type block copolymer exhibits a coil‐to‐helix transition as a result of the change in solvent quality from water to methanol. When the PLL tail block takes a helical conformation in high methanol content, the resulting head‐tail type block copolymer has a defined three‐dimensional structure like that of a protein molecule. Self‐assemblies of such block copolymers having a totally fixed molecular shape spontaneously form polymersome‐like self‐assemblies with an extremely narrow size distribution through converging to a thermodynamically stable assembling state.