Abstract
In this study, we investigated the self-assembled structures of a cationic diblock copolymer PS-b-P4VP(CH3I) complexed with DNA. The nanostructure of the complex prepared in H2O is nanostructure lacked obvious long-range order due to poor solvent for PS chain. However, SAXS profiles and TEM images of the complex prepared using H2O/THF mixed solvent revealed the formation of a long-range ordered lamellar structure with the interlamellar distance of 32nm. In this case, the complexation with DNA induced a structural transition of the copolymer domains from P4VP(CH3I) cylinder to lamellae. In addition to this structural order at the length scale of tens of nm, a smaller-scale structure characterized by the length scale of 2.56nm was found due to the ordered packing of DNA within the polar layers. Using the electronic density profile analysis, a model for the internal nanostructure of the complexes was proposed. The self-assembled structure is governed by the electrostatic interaction between P4VP(CH3+) block and DNA as well the conformational entropy of the PS block covalently linked with P4VP(CH3+) block.