Stimuli-Responsive Control over Self-Assembled Nanostructures in Sequence-Specific Functional Block Copolymers

The precise sequence of a protein's primary structure is essential in determining its folding pathways. To emulate the complexity of these biomolecules, functional block copolymers consisting of segmented triblocks with distinct functionalities positioned in a sequence-specific manner are designed to control the polymer chain compaction. Triblock polymers P-b-C-b-F and P-b-F-b-C and random diblock copolymer P-b-C-r-F consist of a hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic block with coumarin (C) and ferrocene (F) moieties that are grafted in a sequence-specific or random manner onto the hydrophilic block. External stimuli such as UVB light, redox, and chemical cues influence the functional hydrophobic block to alter the packing parameters that are monitored with spectroscopic and scattering techniques. Interestingly, the positioning of the stimuli-responsive moiety within the hydrophobic block of P-b-C-b-F, P-b-F-b-C, and P-b-C-r-F affects the extent of the hydrophobic–hydrophilic balance in block copolymers that renders orthogonal control in stimuli-responsive transformation of self-assembled vesicles to micelles.