Browsing by Author "Kondor, Anett"

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Dispersion of bacterial cellulose bundles in organic solvents and their assembly as ultra-low grammage coating on woven fabric
(2025-04-15) Li, Joanne; Cham, Yee Shuen; Kondor, Anett; Kontturi, Eero; Stone, Corinne; Dennis, Mike; Lee, Koon Yang
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Water is commonly considered as the optimal dispersing medium for nanocellulose given its hydrophilic nature. However, studies have also proven otherwise that alternative organic solvents may give better dispersion quality. Herein, a thermodynamic approach is used to estimate the Hansen solubility parameters of bacterial cellulose (BC) and understand the dispersion of BC bundles in selected organic solvents (i.e. ethyl acetate, acetone and ethanol-water mixtures). The correlation between the BC dispersion in different solvents and the aerosol particulate filtration performance of the resultant BC coated woven fabric is also presented. It is discovered that the best dispersion was achieved in a 60 % ethanol-water mixture, resulting in enhanced aerosol particulate filtration performance. At a BC coating grammage of 0.5 g m−2, the filtration efficiency exceeded 80 %, outperforming the BC coating produced from a water dispersion. These findings highlight the potential of understanding nanocellulose dispersion from a solubility parameter approach.
Regioselective and water-assisted surface esterification of never-dried cellulose: nanofibers with adjustable surface energy
(2021-09-21) Beaumont, Marco; Otoni, Caio G.; Mattos, Bruno D.; Koso, Tetyana V.; Abidnejad, Roozbeh; Zhao, Bin; Kondor, Anett; King, Alistair W. T.; Rojas, Orlando J.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
A new regioselective route is introduced for surface modification of biological colloids in the presence of water. Taking the case of cellulose nanofibers (CNFs), we demonstrate a site-specific (93% selective) reaction between the primary surface hydroxyl groups (C6-OH) of cellulose and acyl imidazoles. CNFs bearing C6-acetyl and C6-isobutyryl groups, with a degree of substitution of up to 1 mmol g(-1) are obtained upon surface esterification, affording CNFs of adjustable surface energy. The morphological and structural features of the nanofibers remain largely unaffected, but the regioselective surface reactions enable tailoring of their interfacial interactions, as demonstrated in oil/water Pickering emulsions. Our method precludes the need for drying or exchange with organic solvents for surface esterification, otherwise needed in the synthesis of esterified colloids and polysaccharides. Moreover, the method is well suited for application at high-solid content, opening the possibility for implementation in reactive extrusion and compounding. The proposed acylation is introduced as a sustainable approach that benefits from the presence of water and affords a high chemical substitution selectivity.
Surface energy properties of lignin particles studied by inverse gas chromatography and interfacial adhesion in polyester composites with electromagnetic transparency
(2022-03) Suzuki, Mayu; Kondor, Anett; Sakuraba, Yuma; Rojas, Orlando J.; Ago, Mariko
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We introduce a simple spray drying method for the scaleup production of spherical organic (lignin) particles with sizes between 0.85 and 1.57 µm. We assess the surface energy of the lignin particles by inverse gas chromatography to reveal their role in composites synthesized with unsaturated polyester. Such nanocomposites are shown to be transparent to electromagnetic irradiation (millimeter wave bands). The permittivity and tanδ of the composite material reached values 3.01 and 0.01 at 28 GHz with 10% lignin content. Vinyl groups were introduced on the surface of the particles to achieve enhanced interfacial adhesion, and resulted in a reduced relative permittivity (2.75). Together with wave interactions, the mechanical and thermal properties of the composites are put in perspective, opening new opportunities in the development of bio-based devices for 5G high-speed communication.