Determination of hydroxyl groups in biorefinery resources via quantitative 31P NMR spectroscopy

The analysis of chemical structural characteristics of biorefinery product streams (such as lignin and tannin) has advanced substantially over the past decade, with traditional wet-chemical techniques being replaced or supplemented by NMR methodologies. Quantitative 31P NMR spectroscopy is a promising technique for the analysis of hydroxyl groups because of its unique characterization capability and broad potential applicability across the biorefinery research community. This protocol describes procedures for (i) the preparation/solubilization of lignin and tannin, (ii) the phosphitylation of their hydroxyl groups, (iii) NMR acquisition details, and (iv) the ensuing data analyses and means to precisely calculate the content of the different types of hydroxyl groups. Compared with traditional wet-chemical techniques, the technique of quantitative 31P NMR spectroscopy offers unique advantages in measuring hydroxyl groups in a single spectrum with high signal resolution. The method provides complete quantitative information about the hydroxyl groups with small amounts of sample (~30 mg) within a relatively short experimental time (~30-120 min)

異方性コロイド粒子による階層構造の形成

九州工業大学博士学位論文 学位記番号: 工博甲第544号 学位授与年月日: 令和4年3月25日1. General introduction|2. Fabrication of CNC-polymer core-shell particles with CNC cores|3. Fabrication of CNC-polymer core-shell particles with CNC shells|4. Linear assembly of colloidal inorganic nanosheets: evaluation of the linearity|5. Electrically induced linear assembly of colloidal inorganic nanosheets: experimental conditions necessary for constructing the linear structures|6. Conclusions九州工業大学令和3年

Tailoring the Surface Charge of Cellulose Nanocrystals (CNC) Using a Polycation

Dans ce travail, la surface de nanocristaux de cellulose (CNC) a été modifiée en utilisant un polymère cationique, le polyéthylèneimine (PEI), pour améliorer leur compatibilité avec des milieux non polaires. La modification de surface, réalisée par un procédé simple et sans utiliser de solvants organiques, a été confirmée par différentes techniques analytiques : spectroscopie XPS, spectroscopie FT-IR et mesures de potentiel zêta. Une analyse thermogravimétrique (TGA) a été réalisée pour étudier la stabilité thermique des CNC séchés-modifiés (mCNC). La spectroscopie UV-Vis a également été réalisée pour étudier le taux de sédimentation des mCNC dans l'eau, ainsi que la stabilité du modificateur. Les charges de surface des mCNC ont été modifiées par les polycations, et les mCNC ont précipité dans l’eau ; ils pouvaient cependant être dispersés dans le toluène. On a également montré que les mCNC étaient stables sur une plage de températures adéquate (jusqu'à 200 °C), compatible avec la dispersion en polymère fondu. Être en contact avec un milieu neutre (l’eau et huile minérale) n'a pas affecté l'efficacité du modificateur de surface. De plus, une augmentation significative des propriétés viscoélastiques et du comportement gel est observée pour les suspensions aqueuses de mCNC, attribuée à l'effet électrovisqueux et à la formation d'une structure d’agglomérats du PEI/CNC en suspension aqueuse. Ces résultats indiquent que PEI a un grand potentiel pour être utilisé commercialement comme modificateur de surface des CNC grâce à un processus efficace, à faible coût et respectueux de l'environnement. Au-delà du traitement par PEI, la modification de surface de CNC a été préliminairement examinée utilisant deux grades de chitosanes. Les résultats obtenus ont démontré que le chitosane peut adsorber sur la CNC chargée négativement par interaction électrostatique et modifier ses propriétés de surface. Les CNC séchées-modifiées avec le chitosane (CHI-CNC) précipitent dans l'eau, mais se dispersent dans toluène. Les propriétés viscoélastiques de la suspension aqueuse CNC à une concentration de CNC de 1% massique augmentent de manière significative en ajoutant une faible quantité de chitosane (1% massique par rapport à la charge en CNC). Ceci est attribué à la structure du chitosane et une affinité élevée entre le chitosane et la CNC. En raison des propriétés bénéfiques du mélange CNC-chitosane, une étude plus approfondie de ce biopolymère en tant que modificateur de surface est proposée. ----------- In this work, the surface of cellulose nanocrystals (CNC) was modified using a cationic polymer, polyethyleneimine (PEI), to improve their compatibility with non-polar media through a simple process without using any organic solvents. The successful surface modification was confirmed through different analytical techniques: XPS, FT-IR spectroscopy and zeta potential measurements. Thermogravimetric analysis (TGA) was carried out to investigate the thermal stability of dried-modified CNC (mCNC). UV-Vis spectroscopy was also performed to study the precipitation rate of mCNC in water, as well as the stability of the modifier. The surface charge of mCNC was changed through this modification and mCNC precipitated in fresh water; they could however be dispersed in toluene. The mCNC were also shown to be stable in an adequate temperature range (up to 200 °C) for polymer melt processing. Being in contact with a neutral media (water and mineral oil) did not affect the efficiency of the surface modifier. In addition, a significant increase in viscoelastic properties and gel-like behavior were observed for PEI/CNC aqueous suspensions, ascribed to the electroviscous effect and to the formation of an agglomerates structure resulting from the hydrophobic nature of PEI/CNC aqueous suspension. These results indicate that PEI has a great potential to be used commercially as a CNC surface modifier through an efficient, low cost and eco-friendly process. In addition, the surface modification of CNC using two grades of chitosan was preliminary investigated. The obtained results showed that chitosan adsorbs on negatively charged CNC through electrostatic interaction and changes the surface properties of CNC. Dried-modified CNC with both chitosan grades (CHI-CNC) sedimented in water, however CHI-CNC dispersed in toluene. The viscoelastic properties of CNC aqueous suspension at CNC concentration of 1 wt.% significantly increased when adding a low amount of chitosan (1% wt.% respect to CNC) due to chitosan structure and high affinity between chitosan and CNC. Thanks to the beneficial properties of CNC and chitosan, the use of this biopolymer as a surface modifier of CNC is proposed for further investigation

Ultra-robust graphene based bio-nanocomposites and their electronic applications

This study is focused on the fundamental principles of fabricating polymer nanocomposite materials and optimizing their structural and functional properties. The status of the research on polymer nanocomposites has been critically reviewed and the motivation and challenges to develop ultra-robust, functional nanocomposite films are presented. Biopolymers, such as silk fibroin (SF) and cellulose nanocrystals (CNC), and graphene oxide (GO) are chosen as the model system to investigate the optimized interfacial interactions between biomacromolecules and the heterogeneous, most widely available graphene derivative. Two different aspects of the polymer nanocomposites were the focus of this study with multiple examples presented: 1) the mechanical enhancement by the synergistic reinforcement between the nanofiller and polymer matrix, and 2) the effective improvement of electrical properties of the graphene oxide component in the nanocomposite for electrical and functional applications. We suggest that the understanding of the integration of biopolymers and graphenes using versatile assembly techniques and the successive chemical modification of the electrical properties of the nanocomposite discussed in this study can be important for tackling the challenges faced by the employment of flexible and robust structural and bio-microelectronic materials.Ph.D

Cellulose Nanocrystal Microcapsules as Tunable Cages for Nano- and Microparticles

We demonstrate the fabrication of highly open spherical cages with large through pores using high aspect ratio cellulose nanocrystals with “haystack” shell morphology. In contrast to traditional ultrathin shell polymer microcapsules with random porous morphology and pore sizes below 10 nm with limited molecular permeability of individual macromolecules, the resilient cage-like microcapsules show a remarkable open network morphology that facilitates across-shell transport of large solid particles with a diameter from 30 to 100 nm. Moreover, the transport properties of solid nanoparticles through these shells can be pH-triggered without disassembly of these shells. Such behavior allows for the controlled loading and unloading of solid nanoparticles with much larger dimensions than molecular objects reported for conventional polymeric microcapsules