Search

We report a simple procedure to produce carboxylated cellulose nanocrystals (CNCs) from grassy biomass (Miscanthus X Giganteus) using a two-step approach consisting of biomass fractionation with a protic ionic liquid followed by oxidation of the resulting cellulose-rich pulps with H2O2. The impact of the fractionation severity on the composition, structure, size, thermal stability, crystallinity, and degree of polymerization of the CNCs was evaluated. It was found that fractionation severity had a large impact on the pulp purity and its reactivity during the oxidation stage. Nevertheless, the impact on the properties of the final CNCs was small. CNCs were recovered as suspensions of negatively charged, electrostatically stable, needle-like CNCs with a lower degree of crystallinity (58–61%) compared to the precursor pulps (65–69%). The presence of carboxyl groups on the surface of the CNCs facilitated the stability of the suspensions but also caused a slight decrease in the thermal stability of the CNCs. A milder oxidation process followed by ultrasonication allowed us to maximize the production of CNCs while better preserving the degree of crystallinity of the cellulose (63%). [ABSTRACT FROM AUTHOR]

Solid-state mechanoenzymatic approaches for the production of cellulose nanocrystals from cotton were examined using three commercially available cellulase systems from Trichoderma reesei, Aspergillus niger and a Cellic CTec2 cellulase blend. A rapid and sharp drop in the degree of polymerization, together with the proportional increase in cellulose crystallinity and generation of nanoscale particles, indicates that cotton is extensively transformed to cellulose nanocrystals with just 15 minutes of ball milling of cotton in the presence of the cellulase enzymes. Subsequent aging of the solid reaction mixture at 55 °C did not significantly affect the degree of polymerization, but resulted in higher material losses due to the increased production of glucose. These results reveal that the endo-activity of the commercial cellulase preparations on cellulose is particularly efficient in solid reaction mixtures (solid loading 50 wt%), allowing for a rapid acid-free generation of cellulose nanocrystals with as low as 0.085 wt% enzyme loading. [ABSTRACT FROM AUTHOR]

This study explores pre-service and in-service teachers' experiences in working as a learning community. Pre-service teachers (N = 60) and teacher educators (N = 9) from a Finnish university and in-service teachers (N = 27) from four local comprehensive schools worked together over six months. The teachers-as-learners continuous learning model was created and implemented in practice. The participants' written reflections were collected to explore what they learned, what challenges they experienced and how they would further develop the model. The results showed that the pre-service and the in-service teachers reflected on their work somewhat differently. The former experienced learning group working, self-regulation, and pedagogic and didactic skills. The latter learned group working skills and new teaching methods. Both groups of teachers experienced challenges, one of which was named role confusion. The pre-service teachers experienced role confusion in terms of guided versus independent work. The in-service teachers' role confusion led them to wonder whether they should provide the pre-service teachers with expert support or participate as equal group members. Both pre-service and in-service teachers reflected that the model would require active involvement of all teachers and teacher educators involved. The results provide implications for pre-service and in-service teacher education.

Oil-in-water emulsions stabilized using cellulose nanofibrils (CNF) form extremely stable and high-volume creaming layers which do not coalesce over extended periods of time. The stability is a result of the synergistic action of Pickering stabilization and the formation of a CNF percolation network in the continuous phase. The use of methyl cellulose (MC) as a co-emulsifier together with CNF further increases the viscosity of the system and is known to affect the droplet size distribution of the formed emulsion. Here, we utilize these highly stable creaming layer systems for in situ polymerization of styrene with the aim to prepare an emulsion-based dope for additive manufacturing. We show that the approach exploiting the creaming layer enables the effortless water removal yielding a paste-like material consisting of polystyrene beads decorated with CNF and MC. Further, we report comprehensive characterization that reveals the properties and the performance of the creaming layer. Solid-state NMR measurements confirmed the successful polymerization taking place inside the nanocellulosic network, and size exclusion chromatography revealed average molecular weight (Mw) of polystyrene as approximately 700,000 Da. Moreover, the amount of the leftover monomer was found to be less than 1% as detected by gas chromatography. The dry solids content of the paste was ∼20% which is a significant increase compared to the solids content of the original CNF dispersion (1.7 wt%). The shrinkage of the CNF, MC and polystyrene structures upon drying—an often-faced challenge—was found to be acceptable for this composite containing highly hygroscopic biobased materials. At best, the two dimensional shrinkage was no more than ca. 20% which is significantly lower than the shrinkage of pure CNF being as high as 50%. The paste, which is a composite of biobased materials and a synthetic polymer, was demonstrated in direct-ink-writing to print small objects. With further optimization of the formulation, we find the emulsion templating approach as a promising route to prepare composite materials.

This study explores fluctuation in students' emotional state and motivational goals during a learning project that requires self-regulation. The research asks the following questions: (1) How do students' emotional state and motivational goal fluctuate between the gStudy learning sessions during a two-month project? (2) How do students with different situational motivation describe their use of motivation regulation strategies? and (3) How is students' situational motivation associated with their learning outcomes? The students (N = 20) in one classroom evaluated their emotional state and motivational goals repeatedly with an emotion awareness tool during a two-month-long science project. At the end of the project, they completed a learning test and were interviewed about their regulation strategies. The results show that the students' situational motivation fluctuated in the course of the learning project. The students with a trend of a low situational motivation reported particularly the use of performance and mastery self-talk strategies, the students with moderate situational motivation emphasised environmental structuring and self-consequating, while the students with high situational motivation reported the use of self-consequating and interest enhancement strategies. The students typically reporting high or moderate situational motivation gained significantly more inquiry learning skills compared to their peers with low situational motivation.