Abstract:

Block copolymers (BCPs) can assemble into various ordered nanostructures, making them ideal soft materials for constructing nanotemplates and nanoporous materials. The introduction of rod chains into BCPs would enhance incompatibility between blocks, rendering the possibility of obtaining small-sized ordered structures from rod-coil BCPs. However, it is difficult to the precise synthesis of narrowly dispersed BCPs from monomers with rigid structures. On the other hand, it is a facile method to construct rod-coil BCPs through non-covalent interactions such as hydrogen bonding using narrowly dispersed coil-coil BCP precursors. In this work, by using a small-molecule ligand 6TP that contains carboxylic acid and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) with different compositions and molecular weights as hydrogen bonding donors and acceptors, respectively, a series of supramolecular rod-coil BCPs PS-b-P4VP(6TP)_x were prepared. By controlling the molar complex ratio between 6TP and pyridine in P4VP, we were able to control the ordered nanostructures of the hydrogen-bonding complexes, and lamellar phase (LAM), bicontinuous double gyroid phase (GYR), hexagonally packed cylindrical phase (HEX), and body-centered cubic phase (BCC) were obtained. By exploring the effect of complex ratio on the self-assembled structure, we found that the molar ratio being close to 1 would be helpful in the formation of the GYR structure. Afterwards, ethanol was chosen as the etching solvent to remove 6TP to construct nanoporous materials with the bicontinuous GYR structure. However, although the GYR structure could be maintained after etching, its periodic size decreased, indicating that the dynamic self-assembled structure based on hydrogen bonding underwent collapsing to a certain degree. This work lays the foundation for the application of constructing small-sized porous networks using hydrogen-bonding complexes.

Key words: hydrogen bonding, rod-coil block copolymers, self-assembly, double gyroid phase