Photo-conversion of self-assembled structures into continuous covalent structures via [2 + 2]-cycloaddition reactions.

In this study, the conversion of self-assembled structures into continuous polymeric structures by linking the self-assembled molecules using the [2 + 2]-cycloaddition reaction was investigated. Synthesized bio-inspired thymine-based bolaamphiphilic molecules were designed to force the interactions between two molecules to engage two thymines in their self-assembled structure to undergo a cycloaddition reaction. Thymine-based bolaamphiphilic molecules were designed and synthesized using different phenylene spacers based on aromatic substituents (ortho-) (meta-) (para-). The formed self-assembled structures from these molecules were characterized and compared using molecular mechanical simulations. Simulations were performed to discuss the relationship between the inter- and intramolecular cycloaddition sensitivity to different substituents. This study provides a strategy for creating higher molecular weight linear polymers by controlling the photocyclization sites within the self-assembly by spacers between thymines. An intermolecular [2 + 2] cycloaddition reaction of thymine-based bolaamphiphilic molecules proceeded within the self-assembled nano-ribbon-like structure to form the continuous covalent structure.