Nonuniformity of starch/nanosilica composites and interfacial behaviour of water and organic compounds

Hydrated starch alone and in composition with nanosilica A-300 and quercetin (natural antioxidant) was studied in the form of powders (mechanical mixture) and gels using ¹H NMR (at 200-280 K), FTIR (293 K), TG (293-573 K), TSDC (90-265 K) and quantum chemistry methods. Influence of weakly polar (chloroform-d, CDCl₃) and polar ((CD₃)₂SO, DMSO) deuterated solvents on bound water structure in these systems was also analysed at 200-280 K. The energetic and structural boundaries between weakly (unfrozen at 250-260 < T < 273 K) and strongly (unfrozen at 200 < T < 250-260 K) bound waters become nonabrupt after the addition of these solvents to quercetin/starch/nanosilica composites because of the differences in water interaction with these substances differently affecting its freezing point depression.     

Tetraf luoromethane Injected into a dc Argon Glow Discharge

Low partial pressures (10^?5 to 10^?3 Torr) of tetrafluoro-methane have been injected into a dc argon glow discharge (85 × 10^?3 Torr, 1000 V) and the discharge-induced removal rate of the CF₄ molecules from the vapor phase has been studied with a mass spectrometer as a function of the discharge current and the CF₄ concentration. The ultimate disposition of the CF₄ is believed to be in the form of polymeric deposit on the walls of the discharge vessel. The removal rate of CF₄ is proportional to the discharge current and also proportional to the concentration of CF₄in the low concentration regime. At higher partial pressures of CF₄ (～1 × 10^?3 Torr) the removal rate tends to saturate, becoming independent of the CF₄ concentration.     

Starch vermicelli template for synthesis of magnetic iron oxide nanoclusters

A novel method for fabricating magnetic iron oxide nanoparticles was achieved by using transparent vermicelli template as a new stabilizing material. The morphology of the as-prepared magnetic iron oxide deposited on the surface of vermicelli was observed as nanoclusters. The magnetization of the magnetic iron oxide nanoparticles at room temperature was decreased after carbonization at 200 °C. Therefore the thermal decomposition of iron oxide nanoparticles stabilized by starch vermicelli template yielded iron oxide/carbon nanocomposites with the soft magnetic behavior which are useful for biomedical applications.     

Rapid monitoring of grapevine reserves using ATR–FT-IR and chemometrics

Predictions of grapevine yield and the management of sugar accumulation and secondary metabolite production during berry ripening may be improved by monitoring nitrogen and starch reserves in the perennial parts of the vine. The standard method for determining nitrogen concentration in plant tissue is by combustion analysis, while enzymatic hydrolysis followed by glucose quantification is commonly used for starch. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR–FT-IR) combined with chemometric modelling offers a rapid means for the determination of a range of analytes in powdered or ground samples. ATR–FT-IR offers significant advantages over combustion or enzymatic analysis of samples due to the simplicity of instrument operation, reproducibility and speed of data collection. In the present investigation, 1880 root and wood samples were collected from Shiraz, Semillon and Riesling vineyards in Australia and Germany. Nitrogen and starch concentrations were determined using standard analytical methods, and ATR–FT-IR spectra collected for each sample using a Bruker Alpha instrument. Samples were randomly assigned to either calibration or test data sets representing two thirds and one third of the samples respectively. Signal preprocessing included extended multiplicative scatter correction for water and carbon dioxide vapour, standard normal variate scaling with second derivative and variable selection prior to regression. Excellent predictive models for percent dry weight (DW) of nitrogen (range: 0.10–2.65% DW, median: 0.45% DW) and starch (range: 0.25–42.82% DW, median: 7.77% DW) using partial least squares (PLS) or support vector machine (SVM) analysis for linear and nonlinear regression respectively, were constructed and cross validated with low root mean square errors of prediction (RMSEP). Calibrations employing SVM-regression provided the optimum predictive models for nitrogen (R² = 0.98 and RMSEP = 0.07% DW) compared to PLS regression (R² = 0.97 and RMSEP = 0.08% DW). The best predictive models for starch was obtained using PLS regression (R² = 0.95 and RSMEP = 1.43% DW) compared to SVR (R² = 0.95; RMSEP = 1.56% DW). The RMSEP for both nitrogen and starch is below the reported seasonal flux for these analytes in Vitis vinifera. Nitrogen and starch concentrations in grapevine tissues can thus be accurately determined using ATR–FT-IR, providing a rapid method for monitoring vine reserve status under commercial grape production.     

淀粉与聚丁二酸己二醇酯的反应及其生物降解性研究

合成了一种新型的完全生物降解型材料－淀粉－聚丁己二醇酯共聚物，对影响聚丁二酸己二醇酯的分子量及淀粉与聚丁二酸己二醇酯反应接枝率的主要因素进行了研究，当聚丁二酸己二醇酯酰氯化物与淀粉投料重量比为４：１时，聚酯的接枝率达到３８．２０％，接枝共聚物用枯草芽孢杆菌和金黄色葡萄球菌降解４０ｄ，其失重率达８９．６０％，在土壤中堆埋９０ｄ，接枝共聚物基本完全被降解。     

Optimized synthesis and characterization of polystyrene graft copolymers and preliminary assessment of their biodegradability and application in water pollution alleviation technologies

With more and more plastics being employed in human lives and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. Keeping in view the environmental pollution caused by the waste polystyrene and to make the waste polystyrene technologically important, we have modified/functionalized the polystyrene with natural polymers and hydrophilic monomer through graft copolymerization. The present paper discusses the optimum conditions for the synthesis of graft copolymers and characterization of these polymers with SEMs and FTIR and thereafter biodegradation studies of these polymers by soil burial method. The present paper also discusses the effect of crosslinker concentration on the swelling and metal ion sorption (As⁺⁵ uptake) through the functionalized polystyrene, with the intention to make use of these polymeric networks in water pollution alleviation technology. It has been observed that percent As⁵⁺ uptake decreases from 80% to 60% as the crosslinker concentration increases from 0.032 mM to 0.162 mM in the polymeric networks. It has also been observed from the degradation studies that the grafting of starch onto polystyrene has induced 37% degradation after 160 days soil burial treatment and no degradation has been observed in case of grafting of acrylic acid onto polystyrene.     

The Preparation of B-type Starch Spherocrystals by Freezing Crystallization

The B-typed starch spherocrystals were prepared by the dissolution and freezing crystallization of acid-hydrolyzed starch obtained by the mild hydrolysis of maize starch. The spherocrystals were characterized with scanning electron microscope (SEM), X-ray diffraction, thermogravimetry (TG) and gel pervasion chromatogram (GPC). The results show that the preparation was a B-type spherocrystal with the average degree of polymerization of 14 glucose units, and the average diameter of crystal particles was about 7μm.     

Influence of various starch types on PCL/starch blends anaerobic biodegradation

Research concentrated on the biodegradable capability of PCL blends with various types of starch in an anaerobic aqueous environment of mesophilic sludge from a municipal wastewater treatment plant. For blend preparation, use was made of a native starch Meritena from maize, another from Waxy – a genetically modified type of maize, as well as Gel Instant, a gelatinized starch, and an amaranth starch. Additional PCL/starch blends were prepared from the same starch types, but these were initially plasticized with glycerol. The biodegradability tests were supplemented with thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC); morphology was identified using scanning electron microscopy (SEM), plus mechanical properties were also tested. While mixtures of PCL with starches plasticized with glycerol exhibited improved mechanical properties and a higher degree of biodegradation in the anaerobic environment, mixtures of PCL with pure forms of starch were ascertained as rather resistant to the anaerobic aqueous environment. TGA and DSC analysis confirmed the removal of starch and glycerol from the PCL matrix. SEM then proved these results through the absence of starch grains in the samples following anaerobic biodegradation.     

Bionanocomposites of Cassava Starch and Synthetic Clay

Starch-based biofilms containing synthetic Laponite clay and glycerol were prepared using a solvent casting technique. Electron microscopy images showed predominance of the exfoliated type of nanocomposite. Dynamic mechanical analysis revealed a larger influence of glycerol content on the polymer β relaxation and T _g than the clay content. Gas barrier properties were influenced by clay particles and plasticizer content. An increase of clay content led to lower gas permeability values. Although both glycerol and Laponite are hydrophilic, no significant changes were observed on the water sorption by starch films at different relative humidity values. Mechanical properties are kept similar after the inorganic filler incorporation.     

Silylation of Cellulose and Starch – Selectivity, Structure Analysis, and Subsequent Reactions

The silylation of cellulose and starch under different starting conditions is reviewed. The control of the degree of substitution (DS) and regioselectivity in dependence of the reaction pathway are discussed in detail. The synthesis of trimethylsilyl cellulose (TMSC) in the system hexamethyldisilazane (HMDS)/ammonia leads to partially and completely silylated products controlled by the amount of the components. Hydrolytic desilylation of TMSC in tetrahydrofuran (THF)/ammonia gives the partially desilylated products. The desilylation proceeds statistically along the polymer chains. The reaction of cellulose dissolved in N,N-dimethylacetamide (DMA)/LiCl with bulky thexyldimethylchlorosilane (TDSCl) in the presence of imidazole leads to 2,6-di-O-TDS cellulose. The silylation of starch dissolved in dimethylsulfoxide (DMSO) with TDSCl/pyridine results in the formation of regioselectively 2-O and 6-O functionalized silyl ethers with DS values up to 1.8. 6-O Silyl ethers of cellulose and starch were synthesized with TDSCl highly activated in the reaction system N-methylpyrrolidone (NMP)/ammonia. Two- dimensional NMR techniques after subsequent modifications of the remaining OH groups have been established as important methods for the characterization of the substitution pattern of the described silyl ethers. In the case of starch, the distribution of the substituents could be detected not only in the anhydroglucose units (AGU) but also in the non-reducing end groups (NEG).