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-molecularweight thermoplastics. The number-average molecular weights (M n ) of the diamine celluloses, ranging from 60 to 82 kD, were investigated by gel permeation chromatography. The diamine celluloses exhibited glass transition temperatures (T g ) from 71 to 112 °C and were stable at high temperatures. Diamine cellulose generated from aniline and DAC showed the highest conversion, the highest T g (112 °C), and a narrow molecular weight distribution (D̵ of 1.30).

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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.

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By utilizing an expedient anion exchange protocol and starting with an improved synthesis of 2‐azido‐1,3‐dimethoxyimidazolium hexafluorophosphate, a series of six metathetical salts, including the energetic nitrate and perchlorate as well as the halides, was prepared. We focused on the crystallographic and thermal characterization of these compounds, representing intrinsically reactive hybrid organic / inorganic salts, and conducted a small comparative study with the related 2‐methyl‐1,3‐dimethoxyimidazolium salts. The latter compounds were expected to thermally disintegrate less sluggishly since the covalent azido‐group as intrinsic blasting initiator is missing. Both 2‐azido‐ and 2‐methylimidazolium nitrate exhibit a very sharp thermal onset of complete disintegration. In contrast, the respective perchlorates display a continuous thermogravimetric weight loss over a broad temperature range. Additionally, X‐ray single crystal structure determinations were performed for eight of the new compounds as well as for two 2‐azido‐1,3‐dimethoxyimidazolium salts with a mixed anion composition. Phase purity was also checked for five of the congeners using powder X‐ray diffraction (Pawley fitting). Notably, in the 2‐azido‐imidazolium cation, the intra‐ring bonds of the N1−C2 type were found to be significantly shorter than N1−C4 type bonds, and a characteristic asymmetry between the two N1−C2−N(azido) bond angles was observed. The experimental cation geometry was reproduced by DFT calculations on selected compounds.

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The title compound, C 21 H 12 Br 2 F 13 NOÁ2CH 3 OH, was obtained by condensation of 4-methyl-1-(1H,1H,2H,2H-perfluorooctyl)pyridinium iodide and 3,5-dibromo-4-hydroxybenzaldehyde, followed by deprotonation. It crystallizes as a methanol disolvate and exhibits short O-HÁ Á ÁO hydrogen bonds and a disordered perfluoroalkyl chain [occupancy ratio 0.538 (7):0.462 (7)]. Significant -stacking interactions are observed between the benzene and pyridine rings of neighbouring molecules along the b-axis direction. Chemical contextDyes with a fundamental type of conjugated system as in the title compound have long been known (Hü nig & Rosenthal, 1955). It was intended to combine the structural features of a delocalized -electron system with those of polyfluorinated compounds in order to derive a new material with advantageous properties such as altered solubility (Hoang & Mecozzi, 2004) and affinity (Wagner et al., 2016) profiles, given that the physical and chemical properties of organic compounds are strongly affected by the introduction of fluorinated substituents. Fluorosurfactants have a tendency towards micelle formation in biphasic or ternary solvent mixtures. Thus, the utilization of solvatochromic surfactants as self-indicating micelle reporters (Kedia et al., 2014) is an attractive analytical concept for fluorous-phase-related materials science. Structural commentaryThe title compound comprises a delocalized -electron system, involving either a zwitterionic benzoid or a non-polar ISSN 2056-9890 quinoid resonance structure. Inspection of bond lengths leads to the conclusion that it is not a typical cyclohexadienone system (Chandran et al., 2008;Chiverton et al., 1991) but rather a benzoid system similar to 2,6-dibromophenol predominant (Eriksson & Eriksson, 2001;Lu et al., 2011;Lehmler & Parkin, 2005). The heterocyclic ring also resembles a typical pyridinium system. Furthermore, the shortest C C bond in the bridge linking the two rings is between C6 and C7 with a length of 1.337 (6) Å , whereas the adjacent bonds are considerably longer. The framework thus is not quinoid but benzoid. The conjugated moieties of the dye molecule are almost planar and the mean planes of the benzene and pyridine rings form an angle of 2.97 (2) , whilst the fluorinated chains protrude from the plane.The carbon atoms C17-C21 and fluorine atoms F3-F13 of the polyfluorinated tail are disordered over sets of sites with an occupancy ratio for the two disorder fragments of 0.538 (7):0.462 (7). The chain adopts a slightly helical conformation (Fournier et al., 2010) with an average C-C-C-C twist angle (deviation from 180 ) of 3 . Typically, -electron donor-acceptor-substituted conjugated systems exhibit solvatochromism. Solutions of the title compound display absorption maxima at 610 nm (blue) in THF and 502 nm (red) in MeOH. Here, increased solvent polarity leads to higher transition energy (negative solvatochromism). A quinoid system based on 2,6-dibromophenol displaying positive solvatochromism has been reported previously (Laus et al....