The assembly of small molecular compounds, polymers, and nanoparticles in a confined 2D space – generally on flat surfaces – is often altered when compared to their behavior in bulk. From the materials perspective, the 2D assembly is interesting for sensors, transistors, or optoelectronic templates among many others. Here, we focus on understanding how 2D structures are formed from ordinary sulfated cellulose nanocrystals (CNCs) when deposited by spin coating on flat substrates. To understand the mechanisms behind the formation of the 2D structures, different parameters were probed: pH of the nanocellulose suspension, nature of the counter-ion, concentration of nanocrystals in the spin coating suspension and the nature of the substrates. The resulting morphologies showed that the decisive factor for the assembly of the nanocrystals during spin coating was the pH and concentration of the CNC dispersion. Under specific conditions, the formation of micron-sized cellular networks from the nanosized cellulose nanocrystals was detected. These cellulose networks were essentially 2D structures because their height corresponded to the height of single CNCs. (Not to be confused with molecular 2D structures such as graphene.) Such networks have been previously reported with, for example, spherical gold nanoparticles and their formation has been assigned to relatively complex hydrophobic forces during evaporation. The results in this work show that a robust spin coating method with straightforward control over electrostatic forces can be used to prepare cellular networks from biologically derived nanorods. Such structures can be interesting, for example, as templates for various micro- and nanostructures in 2D space.

Assembly of cellulose nanocrystals into 2D cellular networks during spin coating

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.