Crystallization of Vanillin Isomers in Carboxymethyl Chitosan Gels

The medicinal value of vanillin and its isomers has not been well developed, so it is necessary to prepare crystals of vanillin and its isomers as well as to investigate their crystallization rules in detail using advanced crystallization techniques in polymer gel. Based on molecular simulation, the maximum number of hydrogen bonds between CMCS with Van, IsoVan and oVan were reached at molar ratios of 1:9 and 1:4 and 1:5, respectively. The gel hardness and apparent viscosity of CMCS/Van isomers were proportional to the mole ratio, while elongation at break and tensile strength decreased with an increase in molar concentration depending on the position of the side chain group of the Van isomer, exposure of the benzene ring, steric resistance and the number of hydrogen bonds formed. The crystallization of Van, IsoVan and oVan in CMCS gel unexceptionally follow classical supersaturation theory in the case that nVan mainly exhibits a unique growth pattern from needle to strip, IsoVan's growth style changes from plate to bulk and oVan adapts growth pattern from needle to branch bifurcating. It was also found that the Van crystal changed from II-type to I-type under long-term heating. Studies have further confirmed that the discrepancy of physicochemical characteristics of CMCS/Van blend gel can be attributed to differences in the number of hydrogen bonds compared to CMCS with given group positions of Van isomers. This study provides powerful technical support for the gel crystallization of van isomers.