Cellulose acetate butyrate (CAB) is a possible candidate, being a raw material derived from renewable resources, to replace fossil-based materials. This is due to its thermoplastic properties and the relative ease with which it could be implemented within the existing industry. With a significant amount of variation in CAB on the market today, a knowledge gap has been identified regarding the understanding of the polymer structural arrangement in films. This relates to the underlying mechanisms that regulate CAB film material properties, insights that are important in product development. In this study, commercially available CAB was investigated with XRD, SEM, AFM, and TOPEM DSC in order to obtain physicochemical information related to its micro-structural features in solvent-cast films. The film-forming ability relates mostly to the number of hydroxyl groups, and the semi-crystallinity of the films depends on the type and position of the side groups along the cellulose backbone. The appearance of signs of possible cholesteric ordering in the films could be connected to higher amounts of hydroxyl groups along the backbone that disturb the helix arrangement, while the overall order was primarily related to the butyrate substitution and secondarily related to the molecular weight of the particular CAB studied. Cold crystallization was also observed in one CAB sample.

Research interest in quaternization of cellulose fibres has increased considerably over the past decades. However, there is little or no consensus regarding how to characterize the material in terms of degree of substitution (DS), and the literature suggests a range of different methods focusing on charge determination as well as nitrogen content quantification. This work aims to fill the knowledge gap regarding how the different methods perform in relation to each other, and for what cellulosic systems each method has advantages, disadvantages and even potential pitfalls. FT-IR and NMR measurements are used to establish successful modification and determine the relative number of substituent groups. Another six methods are compared for the determination of the DS of cellulosic fibres and nanofibrils. The methods include Kjeldahl measurements, nitrogen determination by chemiluminescence, determination of molecular nitrogen by the Dumas method, colloidal titration, conductometric titration and polyelectrolyte adsorption. It can be concluded that most techniques investigated are reliable within certain ranges of DS and/or when using appropriate post-treatment of the quaternized material and suitable sample preparation techniques. The results from the present work hence provide recommendations to make an educated choice of method, and experimental protocol, based on the technique at hand.

Thanks to their high availability, renewability, and degradability, paper-based materials are promising candidates for partial replacement of less sustainable fossil-based products. A disadvantage of conventional paper is, however, its low strainability and restricted shapeability. Partial chemical modification of the fibers that constitute the paper, along with external plasticization, could alleviate this shortcoming. In this contribution, partial cationization of lignocellulosic fibers is employed to enhance the strength and strainability of handsheets; the extensibility is further improved by a moisture-induced plasticization. This combination of modification and hygroplasticization resulted in a strainability of 12%, allowing restraint-dried sheets to be formed into simple 3D structures. Dynamic vapor sorption, dynamic mechanical analysis, and small-angle X-ray scattering measurements are employed to gain deeper insight into the molecular and supramolecular mechanisms underlying the potential for 3D structuring of the papers. It can be concluded that cationization enhances the material’s moisture sorptivity. This is explained by increased accessibility of the fiber wall upon modification (as evidenced by decreased crystallinity and fibril separation) and by hydration of the functional groups. Moisture sorption is an enthalpically driven, highly exothermic process that results in softening of the material. It can be established that while cationization does not significantly affect the material’s temperature response, it does significantly affect its moisture response. Cationization lowers the onset for the fiber material to be softened by moisture, presumably explaining the extended strainability observed for the cationized, hygroplasticized material. Graphical abstract Graphical abstract showing, from left to right; the concept for cationization and hygroplasticization—the material’s response at a nanolevel—the material’s macroscopic response, mechanical properties and potential of 3D forming).

Paper is an attractive substrate for sustainable and scalable organic electronics; however, its intrinsically insulating nature, the absence of continuous electronic pathways, and the lack of control over mixed ionic-electronic transport have limited its use in electrochemical devices. Here, we nanoengineer cellulose fibers by introducing cationic charges to facilitate a high specific surface area accessible for the adsorption of functional components. We further speed up the diffusion-controlled adsorption through controlled partial fibrillation of the fibers. The combined cationic charge and high surface area enabled high adsorption of the conducting polymer PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrene sulfonate) throughout the internal nanostructure of the fiber wall. The modified fibers were then rapidly transformed to mechanically robust, electrically conductive papers using conventional papermaking methodology. Post-treatment of papers containing 30 wt% PEDOT:PSS resulted in excellent charge transport and a conductivity as high as 13 S cm^-1. Furthermore, electrochemical impedance spectroscopy of wet papers confirmed effective mixed ionic-electronic transport. Finally, to demonstrate the possibilities of the electroactive paper, we integrated the paper as channel materials in organic electrochemical transistors and evaluate them as enzyme-free hydrogen peroxide sensors, achieving a limit of detection of 0.79 µM and a sensitivity of 8.5% per decade, highlighting the potential of combining fiber-wall engineering with scalable processing and device integration.