Rod-Like Amphiphile of Diblock Polyisocyanate Leading to Cylindrical Micelle and Spherical Vesicle in Water

The self-assembling property of an amphiphilic rod–rod diblock copolymer has been demonstrated using poly( n -hexyl isocyanate)- block -poly(2,5,8,11-tetraoxatridecyl isocyanate) ( PHIC- b -PEOIC ) with different degrees of polymerization for the PHIC and PEOIC segments. The critical aggregation concentrations (CAC) of PHIC- b -PEOIC decreased with the increasing fraction of the hydrophobic PHIC segment. The relation between the hydrodynamic radius ( R h ) and the PHIC / PEOIC ratio differed from that for the radius of gyration ( R g ). The self-assembled PHIC- b -PEOIC was stable in various polymer concentrations. The ρ parameter ( R g / R h ) strongly suggested that the macromolecular architecture was a cylindrical micelle for PHIC 13 - b -PEOIC 41 (ρ = 1.63) and a spherical vesicle for PHIC 22 - b -PEOIC 36 (ρ = 1.09) and PHIC 31 - b -PEOIC 31 (ρ = 1.09). Transmission electron microscope (TEM) images closely agreed with the structures of the cylindrical micelle and spherical vesicle, which were expected based on the ρ parameter.