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Cellulose, as a naturally abundant and biocompatible material, is still gaining interest due to its high potential for functionalization. This makes cellulose a promising candidate for replacing plastics. Understanding how cellulose interacts with various additives is crucial for creating composite materials with diverse properties, as it is the case for plastics. In addition, the mechanical properties of the composite materials are assumed to be related to the mobility of the additives against the cellulose. Using a well-defined cellulose model surface (CMS), we aim to understand the adsorption and desorption of two polymeric particles (core-shell particles and microgels) to/from the cellulose surface. The nanomechanics of particles and CMS are quantified by indentation measurements with an atomic force microscope (AFM). AFM topography measurements quantified particle adsorption and desorption on the CMS, while peak force AFM measurements determined the force needed to move individual particles. Both particles and the CMS exhibited pH-dependent charge behavior, allowing a tunable interaction between them. Particle adsorption was irreversible and driven by electrostatic forces. In contrast, desorption and particle mobility forces are dominated by structural morphology. In addition, we found that an annealing procedure consisting of swelling/drying cycles significantly increased the adhesion strength of both particles. Using the data, we achieve a deeper understanding of the interaction of cellulose with polymeric particles, with the potential to advance the development of functional materials and contribute to various fields, including smart packaging, sensors, and biomedical applications.

While thermal treatment of paper can lead to the formation of aromatic structures via hydrothermal treatment (low temperature) or pyrolysis (high temperature), neither of these approaches allow patterning the substrates. Somewhere in between these two extremes, a handful of research groups have used CO2 lasers to pattern paper and induce carbonization. However, none of the previously reported papers have focused on the possibility to form fluorescent derivatives via laser-thermal engraving. Exploring this possibility, this article describes the possibility of using a CO2 laser engraver to selectively treat paper, resulting in the formation of fluorescent compounds, similar to those present on the surface of carbon dots. To determine the most relevant variables controlling this process, 3 MM chromatography paper was treated using a standard 30 W CO2 laser engraver. Under selected experimental conditions, a blue fluorescent pattern was observed when the substrate was irradiated with UV light (365 nm). The effect of various experimental conditions (engraving speed, engraving power, and number of engraving steps) was investigated to maximize the fluorescence intensity. Through a comprehensive characterization effort, it was determined that 5-(hydroxymethyl)furfural and a handful of related compounds were formed (varying in amount) under all selected experimental conditions. To illustrate the potential advantages of this strategy, that could complement those applications traditionally developed from carbon dots (sensors, currency marking, etc.), a redox-based optical sensor for sodium hypochlorite was developed.

Grease, as used for lubrication of rolling bearings, is a two-phase organogel that slowly releases oil from its gelator matrix. Because the rate of release determines the operation time of the bearing, we study this release process by measuring the amount of extracted oil as a function of time, while we use absorbing paper to speed up the process. The oil concentration in the resulting stain is determined by measuring the attenuation of light transmitted through the paper, using a modified Lambert-Beer law. For grease, the timescale for paper imbibition is typically 2 orders of magnitude larger than for a bare drop of the same base oil. This difference results from the high affinity, i.e. wetting energy per unit volume, of the oil for the grease matrix. To quantify this affinity, we developed a Washburn-like model describing the oil flow from the porous grease into the paper pores. The stain radius versus time curves for greases at various levels of oil content collapse onto a single master curve, which allows us to extract a characteristic spreading time and the corresponding oil-matrix affinity. Lowering the oil content results in a small increase of the oil-matrix affinity yet also in a significant change in the spreading timescale. Even an affinity increase of a few per mill doubles the timescale.

Paper was impregnated with neat polyvinyl alcohol (PVOH) or cellulose nanocrystal (CNC) reinforced PVOH, and dried by infrared radiation. Complex phenomena involved during paper impregnation and drying have been rarely investigated in the scientific literature, although these steps are crucial for the properties of the ensuing paper. The drying kinetics was studied and it showed that CNC tends to reduce the skin effect classically observed during fast PVOH drying. Furthermore, the nanoparticles induced faster water removal at the end of the drying step, which can be explained by an increase of the absorbed heat flux density. In addition, PVOH crystallization mechanisms have been studied through classical equations (Avrami, and Arrhenius) and a model (the Hoffman-Weeks method) and it was proved that both the drying conditions and the presence of CNC act on the crystallization of the polymer.

Material failure is accompanied by important heat exchange, with extremely high temperature - thousands of degrees - reached at crack tips. Such a temperature may subsequently alter the mechanical properties of stressed solids, and finally facilitate their rupture. Thermal runaway weakening processes could indeed explain stick-slip motions and even be responsible for deep earthquakes. Therefore, to better understand catastrophic rupture events, it appears crucial to establish an accurate energy budget of fracture propagation from a clear measure of various energy dissipation sources. In this work, combining analytical calculations and numerical simulations, we directly relate the temperature field around a moving crack tip to the part α of mechanical energy converted into heat. By monitoring the slow crack growth in paper sheets using an infrared camera, we measure a significant fraction α = 12% ± 4%. Besides, we show that (self-generated) heat accumulation could weaken our samples by microfiber combustion, and lead to a fast crack/dynamic failure/regime.