Effect of Steric Hindrance on Microphase-separated Structures of Block Copolymers Constructed by Hydrogen Bonding

There are plenty of studies on block copolymers constructed by hydrogen bonding in the literature. However, the number of reports on the effect of steric hindrance on the self-assembled strictures of these systems is very limited. In this work, supramolecular block copolymers PS-b-P4VP(Ben)(x) and PS-b-P2VP(Ben) x were constructed by hydrogen bonding between the pyridine-containing block copolymers PS-b-P4VP and PS-b-P2VP, having similar molecular weights and volume fractions and the synthesized small-molecule carboxylic acid Ben, where x is the molar ratio of the hydrogen-bonding donor Ben to the acceptor P4VP or P2VP. The microphase-separated structures of the hydrogen-bonding complexes were effectively controlled by adjusting the value of x. Fourier transform infrared spectroscopy (FTIR) was utilized to characterize the complexes obtained, confirming the formation of hydrogen bonding. Then differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) were used to investigate their phase behaviors. The glass transition temperatures of the supramolecular blocks were found to decrease with the increase of x. Neither P4VP(Ben)(x) nor P2VP(Ben) x exhibited liquid crystallinity. Finally, small-angle X-ray scattering (SAXS) was used to explore the microphase-separated structures of the two types of hydrogen-bonding complexes. And the effect of the steric hindrance during the formation of hydrogen bonding on the nanostructures of the hydrogen-bonding complexes was summarized by drawing the phase diagrams. This work provides the basis for effectively controlling the microphase-separated structures of supramolecular block copolymers. [GRAPHICS] .