Aaltodoc Repository :: Browsing by Author "Simon, Jonas"

Browsing by Author "Simon, Jonas"

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Debugging periodate oxidation of cellulose: Why following the common protocol of quenching excess periodate with glycol is a bad idea
(Elsevier Science Ltd., 2023-06-15) Simon, Jonas; Fliri, Lukas; Drexler, Felix; Bacher, Markus; Sapkota, Janak; Ristolainen, Matti; Hummel, Michael; Potthast, Antje; Rosenau, Thomas; Department of Bioproducts and Biosystems; Biopolymer Chemistry and Engineering; University of Natural Resources and Life Sciences, Vienna; UPM Research Center
Periodate oxidation of cellulose to produce “dialdehyde cellulose” (DAC) has lately received increasing attention in sustainable materials development. Despite the longstanding research interest and numerous reported studies, there is still an enormous variation in the proposed preparation and work-up protocols. This apparently reduces comparability and causes reproducibility problems in DAC research. Two simple but prevalent work-up protocols, namely glycol quenching and filtration/washing, were critically examined and compared, resulting in this cautionary note. Various analytical techniques were applied to quantify residual iodine species and organic contaminations from quenching side reactions. The commonly practiced glycol addition cannot remove all oxidising iodine compounds. Both glycol and the formed formaldehyde are incorporated into DAC's polymeric structure. Quenching of excess periodate with glycol can thus clearly be discouraged. Instead, simple washing protocols are recommended which do not bear the risk of side reactions with organic contaminants. While simple washing was sufficient for mildly oxidised celluloses, higher oxidised samples were more likely to trap residual (per)iodate, as determined by thiosulfate titration. For work-up, simple washing with water is proposed while determining potential iodine contaminations after washing with a simple colorimetric test and, if needed, removal of residual periodate by washing with an aqueous sodium thiosulfate solution.
Indirect determination of partial depolymerization reactions in dialdehyde celluloses (DAC) by gel permeation chromatography of their oxime derivatives
(Springer, 2023-09) Fliri, Lukas; Simon, Jonas; Sulaeva, Irina; Rosenau, Thomas; Potthast, Antje; Hummel, Michael; Department of Bioproducts and Biosystems; Biopolymer Chemistry and Engineering; University of Natural Resources and Life Sciences, Vienna
Owing to a supposed quantitative transformation, oximation of dialdehyde cellulose (DAC) with hydroxylamine hydrochloride is commonly employed in chemical DAC analysis, e.g., for the determination of the degree of oxidation (DO) by titration or elemental analysis. In this study, this modification was utilized for the indirect determination of molecular weight distributions (MWD) by gel permeation chromatography (GPC). The presumably quantitative conversion of aldehyde groups in DAC to the corresponding oxime also breaks up the intermolecular and intramolecular hemiacetal crosslinks, which were associated with solubility issues in the DMAc/LiCl solvent system in previous studies. The limits of the procedure and the material's stability during oximation were investigated. For samples with a DO up to approximately 9% a good applicability was observed, before at higher DO values residual crosslinks led to solubility problems. The oximation/GPC protocol was used to examine the development of the MWD in the early stages of DAC formation under different reaction conditions. The time-dependent partial depolymerization of the polymer backbone was observed. Furthermore, the stability of DAC towards different pH conditions ranging from strongly acidic to strongly alkaline was tested. The depolymerization of DAC in alkaline media occurred with concomitant degradation of aldehyde moieties. In turn, DAC proved to be remarkably stable in acidic and neutral solutions up to a pH of 7.
Insights into the borohydride reduction of dialdehyde cellulose: the dilemma of competing reduction and β-elimination reactions
(Springer, 2023-09) Simon, Jonas; Fliri, Lukas; Fröhlich, Flavia; Sapkota, Janak; Ristolainen, Matti; Hummel, Michael; Rosenau, Thomas; Potthast, Antje; Department of Bioproducts and Biosystems; Biopolymer Chemistry and Engineering; University of Natural Resources and Life Sciences, Vienna; UPM Research Center
Borohydride reduction of dialdehyde cellulose (DAC) is a promising strategy to generate dialcohol cellulose as bio-based alternative to petroleum-based materials. However, the degradation of the polymer backbone according to β-elimination mechanisms limits the practical applications of the reaction. Therefore, we aimed at optimizing the process to suppress degradation reactions by varying reaction time, pH, and reagent stoichiometry. The degree of oxidation (DO) of the DAC intermediates significantly impacts the yields and molecular weights of the isolated dialcohol celluloses, with a “leveling-off” effect at higher DO values. Increasing the amount of sodium borohydride can minimize—but not entirely prevent—chain scissions. Lowering the pH value during reduction slows down the degradation but results in incomplete conversion of the aldehyde functionalities. Our study provides valuable insights into the consequences of side reactions during borohydride reduction of DAC as well as into chemistry and analysis of the dialdehyde cellulose/dialcohol cellulose system. Graphical abstract: About a dilemma in cellulose chemistry: Dialcohol cellulose derived by periodate oxidation and subsequent borohydride reduction of cellulose has received increasing attention in the development of sustainable thermoplastic materials. The present study highlights the challenge of suppressing β-elimination and favoring the reduction pathway to optimize reaction conditions and minimize chain degradation.
Reductive Amination of Dialdehyde Cellulose: Access to Renewable Thermoplastics
(AMERICAN CHEMICAL SOCIETY, 2023-01-09) Simon, Jonas; Fliri, Lukas; Sapkota, Janak; Ristolainen, Matti; Miller, Stephen A.; Hummel, Michael; Rosenau, Thomas; Potthast, Antje; Department of Bioproducts and Biosystems; Biopolymer Chemistry and Engineering; University of Natural Resources and Life Sciences, Vienna; UPM Research Center; University of Florida
The reductive amination of dialdehyde cellulose (DAC) with 2-picoline borane was investigated for its applicability in the generation of bioderived thermoplastics. Five primary amines, both aliphatic and aromatic, were introduced to the cellulose backbone. The influences of the side chains on the course of the reaction were examined by various analytical techniques with microcrystalline cellulose as a model compound. The obtained insights were transferred to a 39%-oxidized softwood kraft pulp to study the thermal properties of thereby generated high-molecular-weight thermoplastics. The number-average molecular weights (Mn) of the diamine celluloses, ranging from 60 to 82 kD, were investigated by gel permeation chromatography. The diamine celluloses exhibited glass transition temperatures (Tg) from 71 to 112 °C and were stable at high temperatures. Diamine cellulose generated from aniline and DAC showed the highest conversion, the highest Tg (112 °C), and a narrow molecular weight distribution (Døµ of 1.30).
Towards Tailored Dialdehyde Cellulose Derivatives: A Strategy for Tuning the Glass Transition Temperature
(Wiley-VCH Verlag, 2024-03-08) Simon, Jonas; Schlapp-Hackl, Inge; Sapkota, Janak; Ristolainen, Matti; Rosenau, Thomas; Potthast, Antje; Department of Bioproducts and Biosystems; Biopolymer Chemistry and Engineering; UPM Research Center; University of Natural Resources and Life Sciences, Vienna
The derivatization of dialdehyde cellulose (DAC) has received increasing attention in the development of sustainable thermoplastics. In this study, a series of dialcohol celluloses were generated by borohydride reduction, which exhibited glass transition temperature (Tg) values ranging from 23 to 109 °C, depending on the initial degree of oxidation (DO) of the DAC intermediate. However, the DAC derivatives did not exhibit thermoplastic behavior when the DO of the modified DAC was below 26 %. The influence of introduced side chains was highlighted by comparing DAC-based thermoplastic materials obtained by either oximation or borohydride reduction. Our results provide insights into the generation of DAC-based thermoplastics and highlight a strategy for tailoring the Tg by adjusting the DO during the periodate oxidation step and selecting appropriate substituents in subsequent modifications.

Browsing by Author "Simon, Jonas"

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