Water-Induced Structural Rearrangements on the Nanoscale in Ultrathin Nanocellulose Films

Abstract

Many nanoscale biopolymer building blocks with defectfree molecular structure and exceptional mechanical properties have the potential to surpass the performance of existing fossil-based materials with respect to barrier properties, load-bearing substrates for advanced functionalities, as well as light-weight construction. Comprehension and control of performance variations of macroscopic biopolymer materials caused by humidity-driven structural changes at the nanoscale are imperative and challenging. A long-lasting challenge is the interaction with water molecules causing reversible changes in the intrinsic molecular structures that adversely affects the macroscale performance. Using in situ advanced X-ray and neutron scattering techniques, we reveal the structural rearrangements at the nanoscale in ultrathin nanocellulose films with humidity variations. These reversible rearrangements are then correlated with wettability that can be tuned. The results and methodology have general implications not only on the performance of cellulosebased materials but also for hierarchical materials fabricated with other organic and inorganic moisture-sensitive building blocks.

Key Factors for Template‐Oriented Porous Titania Synthesis: Solvents and Catalysts

“…Solvent effects on surfactant templated mesoporous sol–gel silica systems were, e.g., studied by Kruk and co‐workers . However, to the best of our knowledge, a similar study about the block copolymer assisted sol–gel titania synthesis has been rarely studied, which is also of great importance to the final thin morphologies . In the microphase‐separated sol–gel system, the swelling degree of the polymer chains in each domain is significantly influenced by the solvent nature.…”

Core–Shell Nanoparticle Interface and Wetting Properties

“…The cleaned substrates were then kept in MilliQ‐water until use and dried just minutes prior the spray deposition by applying a flow of nitrogen. 35,39…”

“…Latex dispersions were left in sonication bath for 10 min prior to spraying. Spray deposition was performed with an airbrush device (D55500, Spray Systems, Germany) using single spray pulses of 50 ms and 1 mL min −1 flow rate 35. The nozzle‐to‐substrate distance was 200 mm in the very dilute spray regime where the droplet size is very homogeneous and about 4.5 µm in diameter (as stated by manufacturer).…”

“…In order to do so, thin films with individual NPs must be fabricated. Among other thin film methods available as dip‐coating28–31 and spin‐coating,32,33 airbrush spray deposition34,35 is a widely applied, rapid and easily scalable technique. Spray deposition is a very versatile method for nanostructuring due to tuneable homo‐ or heterogeneous droplets or deposition on 3D shapes as in car manufacturing 36,37.…”

“…Spray deposition is a very versatile method for nanostructuring due to tuneable homo‐ or heterogeneous droplets or deposition on 3D shapes as in car manufacturing 36,37. Nowadays, spray deposition is also well established for thin films in combination with in situ X‐ray scattering techniques to study the nanoscale self‐assembly of particles 35,38–40. Different spray‐coating devices have been applied in both industry and academia for a long time depositing conventional colloids, however more recently focused on more advanced colloidal systems and NPs including gold,41 silica,42 Cu 2 FeSnS 4 ,43 polymeric,44 and titianium dioxide 45.…”