Biobased Thin Films via Self‐Assembled Carbohydrate Block Copolymers and Nanocellulose

Marie Gestranius, Issei Otsuka, Sami Halila, Daniel Hermida‐Merino, Eduardo Solano, Redouane Borsali, Tekla Tammelin

Advanced Materials Interfaces, 2020, 7, 1901737

Abstract: 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.

Keywords: carbohydrate-based block copolymers, cellulose nanofibrils, green materials, self-assembly, thin films

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