Galactose-Based Block Copolymers with Switchable ? Parameters for Tuning Phase Separated Morphology

Block copolymer (BCP) self-assembly has emerged over the past two decades as a promising method for generation of features for manufacture of integrated circuits and memory devices. Low-molecular-weight BCPs with blocks that are highly immiscible can generate features of dimensions below 10 nm. However, it is often challenging to select a common good solvent for high-x BCPs to allow spin coating. In addition, controlling the alignment of phase separated morphologies with respect to the wafer and at the air interface may be challenging. Here, we prepare a series BCPs of polystyrene (PS) and poly-6-O-methacryloyl-D- galactopyranose (PMAGal), where the polar galactose has been protected with more hydrophobic acetonides. The acetonide protecting groups could be deprotected with trifluoroacetic acid to yield the more polar galactose repeat units to increase the incompatibility of the sugar-containing block with the PS blocks. The bulk morphology of the protected and deprotected versions was studied using small-angle X-ray scattering, where the morphology could be switched from disordered for the protected BCP to either cylindrical or lamellar for the deprotected version or between two ordered phases. Finally, we demonstrate phase separation on the wafer via solvent vapor annealing with H2O/THF, resulting in lamellar patterning with domains as small as 14 nm.