Sugar Alcohol-Based Deep Eutectic Solvents as Potato Starch Plasticizers.

The aim of this work was to prepare sugar alcohol-based deep eutectic solvents (DES) and test them as starch plasticizers. Thermoplastic starch (TPS) films were obtained via a simple and convenient thermocompression method. Influence of starch/DES premixtures conditioning (preheating, storage time) on TPS properties was investigated. TPS/sorbitol (S)-based DES exhibited similar tensile strength (TS) (8.6 MPa) but twice higher elongation at the break (ε) (33%) when compared with TPS plasticized only with S. Extra treatment, i.e., heating or prolonged storage time, facilitated starch/DES plasticizing. Starch with selected DES was also extruded and the influence of preconditioning and extrusion rotational speed were subsequently studied on thermocompressed films. Extrusion at 100 rpm led to films with TS up to ca. 10 MPa and ε up to 52%. Some differences in film samples morphology obtained via two processing methods were observed. X-ray diffractograms revealed that extruded samples exhibited a V-type peak at 18.2°, with intensity depending on plasticizer total molecular size. Applied techniques (mechanical tests, XRD, Dynamic Mechanical Analysis (DMA), FTIR-Attenuated Total Reflection (ATR), and moisture sorption) indicated that S-based DES forms stronger interactions with starch than glycerol (G) only used as conventional plasticizer, thus leading to better mechanical properties and inhibited tendency to starch recrystallization (studied up to one year).

Deep eutectic solvents for polysaccharides processing. A review.

In the review a new class of green solvents - Deep Eutectic Solvents (DES) as media for polysaccharides treatment has been presented. They are an alternative for ionic liquids, non- or low toxic, biodegradable multipurpose agents obtained via simple and convenient way. Moreover, a large number of composition possibilities allow to tailor their properties. Because of selective solubilization of polysaccharides DES can be used for lignocellulosic biomass delignification, cellulose extraction as well as cellulose nanofibrillation or nanocrystalization. DES have been applied in extraction, separation or purification of some specific biopolymers like chitin, carrageenans and xylans, but also as components of polysaccharide based materials, e.g. plasticizers (mainly for starch, but also for cellulose derivatives, chitosan, agar and agarose), compatibilizers or modifiers. An interest in applying DES as green solvents increased rapidly within last years and it may be expected that their applications in polysaccharides treatment would be developed also on industrial scale.

Effect of microwave treatment on structure of binders based on sodium carboxymethyl starch: FT-IR, FT-Raman and XRD investigations.

The paper deals with the influence of the microwave treatment on sodium carboxymethyl starch (CMS-Na) applied as a binder for moulding sands. The Fourier transformation infrared spectrometry (FT-IR), Raman spectroscopy (FT-Raman) and XRD analysis data of native potato starch and three different carboxymethyl starches (CMS-Na) with various degree of substitution (DS) before and after exposition to microwave radiation have been compared. FT-IR studies showed that polar groups present in CMS-Na structure take part in the formation of new hydrogen bonds network after water evaporation. However, these changes depend on DS value of the modified starch. The FT-Raman study confirmed that due to the impact on the samples by microwave, the changes of intensity in the characteristic bands associated with the crystalline regions in the sample were noticed. The X-ray diffraction data for microwave treated CMS-Na samples have been compared with the diffractograms of initial materials and analysis of XRD patterns confirmed that microwave-treated samples exhibit completely amorphous structure. Analysis of structural changes allows to state that the binding of sand grains in moulding sand with CMS-Na polymeric binder consists in the formation of hydrogen bonds networks (physical cross-linking).

Imidazole-based deep eutectic solvents for starch dissolution and plasticization.

Potato starch and high-amylose starch were treated with imidazole-based deep eutectic solvents (DESs) as dissolution and plasticization media. Beside imidazole (IM) for two-component DESs preparation choline chloride (CC), glycerol (G) or carboxylic acids (citric or malic) were used. An influence of water content in starch (as well as an extra water in the starch/DES system) on polymer dissolution and plasticization processes was investigated. Dissolution and gelatinization of starch in DESs were followed via DSC and laser scanning microscopy. A rheometric characteristics revealed an influence of starch/DES system storage time on the plasticization process. The tendency to recrystallization of compression-molded-starch films was evaluated using XRD technique. High dissolution and plasticization effectiveness of CC/IM and G/IM and a low tendency to film retrogradation of thermoplasticized starch were noted.

Carboxymethyl starch/montmorillonite composite microparticles: Properties and controlled release of isoproturon.

Preparation of novel high substituted carboxymethyl starch-based microparticles containing sodium montmorillonite (MMT) by crosslinking with Al(3+) was described. For preparing nanocomposite granules carboxymethyl starch (CMS) from native potato starch as well as CMS from amylopectin has been used. The hydrophilic CMS/MMT composite systems were used for herbicide, i.e. isoproturon encapsulation (ca. 75% encapsulation efficiency). The herbicide release rate from CMS/MMT composites in water was significantly reduced when compared to commercial isoproturon: 95% released after ca. 700 h and ca. 24h, respectively. Leaching in soil from composite systems was relatively slower than release in water. After a series of eight irrigations leached about 10% of isoproturon loaded. The CMS/MMT carriers could reduce the potential leaching of herbicide and beneficially reduce pollution of the environment.

Novel hydrophilic carboxymethyl starch/montmorillonite nanocomposite films.

Preparation of novel carboxymethyl starch (CMS)-based biodegradable films with calcium montmorillonite has been described. The biocomposites were obtained by casting method, glycerol and citric acid were used as plasticizer and crosslinking agent, respectively. The effect of calcium montmorillonite (MMT-Ca) on hydrophilicity (moisture absorption, solubility in water as well as contact angle measurements) was evaluated. Moreover, thermomechanical and mechanical properties of nanocomposites were determined. For all the systems tested intercalated structure of MMT-Ca was revealed, however the most efficient clay platelets dispersion was noted for film containing 5 wt.% MMT-Ca. Such biodegradable CMS/MMT-Ca films exhibiting relatively good mechanical properties could find application in controlled delivery systems as well as in agriculture for seed tapes production where hydrophilicity of polymer carrier is strongly advantageous.

Crosslinked carboxymethyl starch: one step synthesis and sorption characteristics.

Crosslinked carboxymethyl starch (cCMS) hydrogels were synthesized in a simple one step process using various crosslinking agent content - dichloroacetic acid (DCA) with the constant monochloroacetic acid and DCA/anhydroglucosidic unit (AGU) 1.75:1 molar ratio whereas DCA/AGU was changed in a range 0.15-1.0mol/AGU. The degree of substitution (DS=0.4-0.9), and reaction efficiency were evaluated. Moreover, swellability in water and aqueous solutions was determined. Adsorption tests for Fe(II) cation as a function of cCMS crosslinking degree, sorbent dose and time were performed in autogenic pH (ca. 7.0). For comparison four other divalent metal cations were tested. Adsorption efficiency was up to 98% for Fe(II), 96% for Ca(II) and above 99.7% for Cu(II), Cd(II) and Pb(II).