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When konjac glucomannan (KGM) molecules are deacetylated under alkaline conditions, the aqueous KGM solution is transformed into a thermally stable gel. In this study, series of Na 2 CO 3 -induced and K 2 CO 3 -induced KGM hydrogels were prepared by deacetylation using different concentrations (0.1, 0.2, 0.3, and 0.4 M) of alkali. The hydrogels were characterized using texture profile analysis, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy, X-ray diffraction, and rheological property analysis. The data showed that KGM hydrogel formation was facilitated at all the alkali concentrations used. The mechanisms of Na 2 CO 3 -induced and K 2 CO 3 –induced KGM hydrogels formation differed slightly. The hardness, springiness, chewiness, gumminess, and storage modulus G ′ of the Na 2 CO 3 -induced KGM hydrogels initially increased and then decreased with increasing alkali concentration. However, the values of the corresponding properties of the K 2 CO 3 -induced KGM hydrogels increased with increasing alkali concentration. All the data were consistent with the structures observed using SEM. The 0.3 M Na 2 CO 3 -induced KGM hydrogel had the highest hardness and storage modulus G ′, a well-proportioned network structure, and a dense architecture; 0.3 M Na 2 CO 3 was therefore the most suitable modifier for inducing KGM hydrogel formation. [ABSTRACT FROM AUTHOR]

• The Tröger base analogue coordinated with potassium iodide and containing crown ether CATB-KI was fabricated. • The acidified CATB-KIs shown high catalytic efficiency to cyclic carbonates. • The synergistic mechanism has been proved in terms of experimental results and calculation of dynamics. Tröger's bases (TB) containing two steric nitrogen atoms, are alternated as building block for constructing molecular acceptors to form covalent bonds with acids, making TB a promising catalyst. Herein, TB analogs fabricated with crown ethers were knitted by condensation reaction and combined with potassium iodide as a brand-new catalytic system (CATB-KIs), which were characterized using FT-IR, 13C CP MAS NMR, SEM, TGA, and XPS spectroscopy respectively. The generated CATB-KIs exhibited excellent performance for CO 2 fixation reaction with epoxides to produce cyclic carbonates under mild conditions, and the catalytic activity could be further improved by coordinating with acids beforehand, in which HBr performs fascinated activity. After 12 h, the corresponding cyclic carbonate from epichlorohydrin with 95.1% yield was detected at mild conditions with solvent-free in the presence of CATB-KI-2 and HBr. A series of terminal epoxides were converted into desired cyclic carbonates with desirable yields. The catalyst could be recovered successfully and reused six times without significant loss of activity. Finally, dynamics study on catalytic mechanism has been accomplished and the activated energy was calculated as 72.1 kJ/mol. A synergistic catalytic mechanism of hydrogen bonding and I anion has been proposed to account for the excellent catalytic activity of this catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]