Homogenous carboxymethylation of starch using 1-butyl-3-methylimidazolium chloride ionic liquid medium as a solvent

Synthesis and properties of maleic anhydride-modified agar with reversibly controlled gel strength

Agar is modified by chemical methods to improve its functional properties and meet the increasing demand of the market. Some of the functional properties of agar are improved after chemical modification, while other properties are reduced, especially gel strength. This study aimed to comprehensively improve the functional properties of agar through acylation and crosslinking by reacting with maleic anhydride. ¹³C NMR indicated the maleylation reaction was preferred at the C2 hydroxyl group of D-galactose, and the crosslinking reactions occurred at the C2 and C6 hydroxyl groups of D-galactose in different agar chains. Interestingly, the maleylated agar monoester had higher gel transparency (1.5%, w/v) of up to 76% than the native agar (58%). However, it showed a significant decrease in gel strength from 783 g/cm² to 403 g/cm², while crosslinking endowed agar with higher gel strength (845 g/cm²) and gel transparency (78.4%). The high transparency of the modified agar plate made colony observation and colony counting easy. Maleylation of agar further enhanced the freeze-thaw stability of agar gel (24.8%, 7th freeze-thaw cycles). Overall, the maleylated agar possessed superior functional properties, and it could be used as food, bacteriological, and biotechnological agar.

The Importance of Ionic Liquids in the Modification of Starch and Processing of Starch-Based Materials

The main applications of ionic liquids in chemistry and material research on one of the most important natural polymers—starch—are presented in this review. A brief characterization of ionic liquids and the advantages and disadvantages of using them in the modification and processing of polysaccharides is presented. The latest reports on the use of various ionic liquids as solvents or co-solvents; as media for synthesizing starch derivatives in oxidation, etherification, esterification, and transesterification, with particular emphasis on biocatalyzed reactions; and as plasticizers or compatibilizers in the processing of starch-based polymers have been investigated. The current trends, possibilities, and limitations of using this type of compound for the production of functional starch-based materials are presented.

Catalyst-free esterification of high amylose starch with maleic anhydride in 1-butyl-3-methylimidazolium chloride: The effect of amylose content on the degree of MA substitution

The limited reactivity of starch towards maleic anhydride (MA) affords maleate with a low degree of MA substitutions (CC and COOH groups). In this study, we investigated the relationship between the starch structure, controlled by its amylose (AM)/amylopectin (AP) ratio, and the DS of starch maleates using C₄[mim]Cl as the recyclable media, and catalyst. The results indicated that starches with varying AM/AP ratio produced maleates with comparable CC groups (DS_NMR = 0.06-0.07). Following dissolution, the high amylose (DS_titration = 1.17, yield = 69.2 %) and regular starches (DS_titration = 1.17; yield = 59.3 %) produced high DS_titration maleates (COOH groups) at MA/AGU ratio of 12:1 (80 °C, 10 min). Comparatively, DS_titration value of waxy starch maleates (DS_titration = 0.88, yield = 59.3 %) was lower than AM-based starches, possibly due to the crosslinking tendency of AP branches consisting of carboxylic end-groups. Interestingly, DS_titration value for EHCS (1.17) ranged between its bulk (DS_NMR: 0.06) and surface distribution of MA (DSS_XPS 1.7); therefore, we considered it reliable for future reference.

Supramolecular Approach for Efficient Processing of Polylactide/Starch Nanocomposites

All-biobased and biodegradable nanocomposites consisting of poly(l-lactide) (PLLA) and starch nanoplatelets (SNPs) were prepared via a new strategy involving supramolecular chemistry, i.e., stereocomplexation and hydrogen-bonding interactions. For this purpose, a poly(d-lactide)-b-poly(glycidyl methacrylate) block copolymer (PDLA-b-PGMA) was first synthesized via the combination of ring-opening polymerization and atom-transfer radical polymerization. NMR spectroscopy and size-exclusion chromatography analysis confirmed a complete control over the copolymer synthesis. The SNPs were then mixed up with the copolymer for producing a PDLA-b-PGMA/SNPs masterbatch. The masterbatch was processed by solvent casting for which a particular attention was given to the solvent selection to preserve SNPs morphology as evidenced by transmission electron microscopy. Near-infrared spectroscopy was used to highlight the copolymer-SNPs supramolecular interactions mostly via hydrogen bonding. The prepared masterbatch was melt-blended with virgin PLLA and then thin films of PLLA/PDLA-b-PGMA/SNPs nanocomposites (ca. 600 μm) were melt-processed by compression molding. The resulting nanocomposite films were deeply characterized by thermogravimetric analysis and differential scanning calorimetry. Our findings suggest that supramolecular interactions based on stereocomplexation between the PLLA matrix and the PDLA block of the copolymer had a synergetic effect allowing the preservation of SNPs nanoplatelets and their morphology during melt processing. Quartz crystal microbalance and dynamic mechanical thermal analysis suggested a promising potential of the stereocomplex supramolecular approach in tuning PLLA/SNPs water vapor uptake and mechanical properties together with avoiding PLLA/SNPs degradation during melt processing.

Effect of carboxymethylation on physicochemical, micromeritics and release characteristics of Kyllinga nemoralis starch

Lesser usages of native starch has attracted attention in the modification of starch to incorporate its benefits for pharmaceutical application. A work has been carried out to study the influence of carboxymethylation on the morphological, physico-chemical, powder, spectroscopical and drug discharge characteristics of native starch. Various amount of monochloroacetic acid was used to study the influence of degree of substitution (DS) on the diverse characteristics of modified starch. Amylose content was found to be reduced with the increase in degree of substitution. An enhanced degree of structure deformation was observed with the increment in the DS by the help of scanning electron micrographs. The FT-IR spectra established the polysaccharide nature and the carboxymethylation of the chemically modified starch molecules through the new bands at 1602cm^-1, and 1418.69cm^-1. The stability of carboxymethyl starches pertaining to the temperature has been revealed by thermogravimetric analysis. Micromeritics of carboxymethylated starches shows their effectiveness as excipients in tablet formulation. The delayed % release of the drug, with the rise in degree of substitution from the tablets prepared marks that the carboxymethyl derivatives of Kyllinga nemoralis rhizomes starch may be used as a suitable source of excipient for sustained release formulations.

Corn starch-based graft copolymers prepared via ATRP at the molecular level

Starch-g-PS and Starch-g-PMMA with controlled graft chains and high graft ratio were prepared at the molecular level.

Thermal-sensitive Starch-g-PNIPAM prepared by Cu(0) catalyzed SET-LRP at molecular level

Starch-g-PNIPAM with controlled graft chains and its hydrogels with rapid shrinking rate were preparedviaSET-LRP at molecular level.