High-Resolution Patterned Biobased Thin Films via Self-Assembled Carbohydrate Block Copolymers and Nanocellulose

The exploitation of the effortless self-assembly behavior of biomass-based bricks can be seen as a promising route toward the innovative architectures. Here, a straightforward approach is presented where carbohydrate-based diblock copolymer, polystyrene-block-maltoheptaose (PS-b-MH), is organized either on a rigid ultrathin film or on a flexible self-standing film of wood-derived cellulose nanofibrils (CNFs). During solvent annealing PS-b-MH deposited on relatively rough CNF film undergoes spontaneous rearrangement into high-resolution patterns with a diblock domain spacing of 10-15 nm. The ideal conditions the self-assembly require weak interactions between block copolymer and the substrate to increase the chain mobility and enable rearrangements. This is exactly how the system behaves. Adsorption studies of PS-b-MH on CNF surfaces reveal weak interactions, and the formed PS-b-MH layer is soft and mobile. Even the appearance of more challenging vertical orientation formed on smooth CNF substrates is tentatively evidenced by grazing-incidence small-angle X-ray scattering and atomic force microscope indicating favorable surface interactions between CNF and PS-b-MH.