Synthesis and properties of thermoplastic propyl-etherified amylose

Amylose was etherified with 1-bromopropane in DMSO. The degree of substitution (DS) was varied by altering the feed ratio of 1-bromopropane. The structures of the products were characterized by IR and 1H-NMR spectroscopy. When the molar feed ratio of 1-bromopropane to hydroxyl groups of amylose was beyond 7.5, the hydroxyl groups were completely substituted with propyl ether groups. The etherified amylose with DS 1.9 showed a glass transition temperature (T_g), and that with DS 2.3 or 3.0 showed both T_g and melting temperature (T_m) (DS 3.0 means complete substitution). The etherification imparted melt processability and solubility in nonpolar organic solvent to amylose.     

Study on the morphology, crystalline structure and thermal properties of yam starch acetates with different degrees of substitution

This study was carried out to understand and establish the changes in physicochemical properties of starch extracted from Chinese yam (Dioscorea opposita Thunb.) after acetylation. Yam starch acetates with different degrees of substitution (DS) were prepared by the reaction of yam starch with glacial acetic acid/acetic anhydride using sulfuric acid as the catalyst. Their formation was confirmed by the presence of the carbonyl signal around 1750 cm-1 in the Fourier transform infrared (FT-IR) spectra. The thermal behavior of the native starch and starch acetate were investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results reveal that the starch acetates are more thermally stable than the native starch. The starch esters showed 50% weight loss at tem- peratures from 328℃ to 372 ℃ , while the native starch underwent 50% weight loss at 325℃ . The glass transition temperature (Tg) of the starch decreased from 273℃ to 226℃. The X-ray diffraction (XRD) patterns could be classified as typical of the C-type for yam starch. X-ray diffraction also showed the loss of the ordered C-type starch crystalline structure and the degree of crystallinity of starch de- creased from 36.10% to 10.96% with the increasing DS. The scanning electron microscopy (SEM) sug- gested that the most of the starch granules disintegrated with many visible fragments with the in- creasing DS.     

Thermal stability and degradation of starch derivatives

Thermal behaviour of different starch derivatives, i.e. starch esters and ethers having degree of substitution (DS) in the range of 0.02–0.18 were studied. Potato, maize and wheat starches were used. Measurements were carried out by coupled thermal analysis/ mass spectrometry method (STA-MS) in air atmosphere. The major DTG peak during the investigation for starch derivatives is observed below 300°C. The mass loss up to a temperature of 300°C is about 50%. The most abundant ions found areH₂O⁺ and CO₂ ⁺. For the studied starch derivatives with a low degree of substitution (DS<0.18) no correlation was found between thermal stability and the level of substitution regardless of the nature of substitution.     

Study on the morphology, crystalline structure and thermal properties of yellow ginger starch acetates with different degrees of substitution

Yellow ginger starch acetates with different degrees of substitution (DS) were prepared by reacting native starch with glacial acetic acid/acetic anhydride using sulfuric acid as catalyst. X-ray diffraction (XRD) of acetylated starch revealed that the crystal structure of native starch was disappeared and new crystalline regions were formed. Their formation was confirmed by the presence of the carbonyl signal around 1750 cm⁻¹, as well as the reduced hydroxyl groups, in the Fourier transform infrared spectroscopy (FT-IR). The scanning electron microscopy (SEM) suggested most of the starch granules disintegrated with many visible fragments along with the increasing DS. The thermal behavior of the native starch and starch acetate were investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), it was observed that the thermal stability of acetylated starch depends on the degree of substitution. Thermal stability of high DS acetylated starch is much better than that of the original starch when DS reached to 2.67.     

Comparative thermal analysis study of two biopolymers, starch and cellulose

The degradation of cellulose and starch samples in air and nitrogen has been investigated by thermal analysis techniques. The techniques employed were differential thermal analysis, rising temperature and temperature jump thermogravimetry. Rate data were obtained from these experiments and Arrhenius parameters calculated from these values. This data was used to determine the mechanism by which the cellulose and starch samples degraded. The Arrhenius parameters were also calculated. The behavior of starch and cellulose upon thermal analysis were compared and are reported.E _act for corn starch was found to be 474 kJ mol^–1 and for a cellulose 242 kJ mol^–1.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday     

Tartaric Acid Starch Ether: A Novel Biopolymer‐Based Polyelectrolyte

New tartaric acid starch ethers have been synthesized applying starch sources of different amylose content. The reactions were carried out heterogeneously in ethanol/water mixtures with cis‐disodiumepoxysuccinate as etherifying reagent leading to products of a degree of substitution (DS) up to 0.3. The molecular structure of the new starch ethers was evaluated by elemental analysis, FTIR and ¹³C NMR spectroscopy. Preliminary studies using a convenient titration method indicate a high binding capacity for Ca²⁺ ions which is dependent on the starch source and DS.

Tartaric acid starch ethers.     

Starch derivatives of high degree of functionalization 9: carboxymethyl starches

This paper describes the synthesis of carboxymethyl starch (CMS) ID various alcohols (methanol, ethanol, isopropyl alcohol) as slurry media and with different starch types. The products were investigated regarding their degree of substitution (DS), their reaction efficiency (RE), and their pattern of functionalization. The highest DS obtained ID a one-step procedure was 1.40 with a RE of 82%, applying isopropyl alcohol as slurry medium. Moreover, by using the synthesis concept via a reactive microstructure, CMS samples with high DS values can be achieved ID a one-step synthesis as well. A multi-step carboxymethylation ID methanol, on the other hand, leads to maximal DS values of 2.3 after 10 conversions, dependent on the amylose content of the starch. ¹H NMR spectroscopic investigations show a reactivity ID the order O-2 > O-6 O-3 for the samples prepared ID alcoholic slurry media. ID contrast, the CMS synthesized via reactive microstructure reveals a preferred substitution ID position 6 and a non-statistic distribution of the carboxymethyl groups along the chain. A significant amount of 2,3,4,6-tetra--functionalization, caused by the branched structure of starch, was found.     

The synthesis conditions, characterizations and thermal degradation studies of an etherified starch from an unconventional source

Starch isolated from an under-utilized legume plant (pigeon pea) was carboxymethylated. Influences of reaction parameters were investigated on the degree of substitution (DS) and the reaction efficiency (RE). Studies showed that optimal DS of 1.12 could be reached at reaction efficiency of 80.6% in isopropanol-water reaction medium (40 °C, 3 h). Scanning electron microscopy showed that after carboxymethylation, the granular appearance of the native starch was distorted. Wide-angle X-ray diffractometry revealed that crystallinity was reduced significantly after carboxymethylation. The infrared spectra revealed new bands in the carboxymethyl starch at ν = 1600, 1426 and 1324 cm⁻¹ which were attributed to carbonyl functional groups vibration, -CH₂ scissoring and OH bending vibration, respectively. Broad-band ¹³C NMR of carboxymethyl starch showed an intense peak at δ = 180.3 ppm which was assigned to carbonyl carbon on the carboxymethyl substituent on the AGU (Anhydroglucose Unit). DEPT (Distortionless Enhancement by Polarization Transfer) 135 NMR showed negative signals which correspond to methylene carbons on the AGU. Differential Scanning Calorimetry (DSC) suggests loss of crystallinity after carboxymethylation. Thermogravimetry (TG), Derivative Thermogravimetry (DTG) and Differential Thermal Analysis (DTA) show that thermal stability improved after carboxymethylation. The study provides information on the preparation and characterization of a biomaterial from a new source which could be used alone or in the preparation of other functional polymers for diverse polymer applications.     

Syntheses and characterizations of allyl cellulose and glycidyl cellulose

Allyl cellulose was synthesized by reacting cellulose with allyl bromide in homogeneous LiCl/DMAc solution containing NaOH powder. The degree of substitution (DS) per anhydroglucose (AHG) unit was determined by titrating the allyl cellulose with bromine in chloroform solution, and an allyl DS of 2.80 was found. Glycidyl cellulose was then prepared by reacting this allyl cellulose with peracetic acid in methylene chloride at ambient temperature for 6 days. The measured reaction rate constant was 1.33 × 10^?3 min^?1. The glycidyl cellulose thus obtained with a glycidyl DS of 2.58 was determined by titrating the product with perchloric acid in conjunction with tetrabutylammonium iodide. The 2.58 of glycidyl DS was also confirmed by ¹H-NMR integration. Both allyl cellulose and glycidyl cellulose were analyzed and characterized with FTIR, ¹H-NMR, ¹³C-NMR, TGA, and GPC. During epoxidation of allyl cellulose, possible side reaction leading to ester formation was evidenced from the continuous increase of v_{C? O} at 1735 cm^?1 in FTIR analyses. In addition, a bimodal distribution and a decreased molecular weight for glycidyl cellulose were found from GPC data, which might suggest a possible chain scission at the cellulosic ether linkage. © 1992 John Wiley & Sons, Inc.     

Two-step preparation and thermal characterization of cationic 2-hydroxypropyltrimethylammonium chloride hemicellulose polymers from sugarcane bagasse

Cationic sugarcane bagasse hemicellulose derivatives with a relatively low degree of substitution (0.01-0.54) containing quaternary ammonium groups were prepared by etherification with 3-chloro-2-hydroxypropyltrimethylammonium chloride or preferably with 2,3-epoxypropyltrimethylammonium chloride using sodium hydroxide as a catalyst in aqueous solution. The extent of etherification was measured by yield percentage and degree of substitution (DS). The DS values of the products could be controlled by adjusting the molar ratio of etherifying agent to anhydroxylose units in hemicelluloses and the molar ratio of sodium hydroxide to etherifying reagent. In comparison, the etherified hemicellulose preparations were characterized by both degradative methods such as thermal analysis, and non-degradative techniques such as gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), and ¹³C nuclear magnetic resonance (NMR) spectroscopy. It was found that a significant degradation of the hemicellulose polymers occurred during etherification under the alkaline conditions used. The thermal stability of the etherified hemicelluloses was lower than that of the unmodified hemicellulose polymers.     

Carboxymethylation of corn starch and characterization using asymmetrical flow field-flow fractionation coupled with multiangle light scattering

Asymmetrical flow field-flow fractionation (AsFlFFF) was coupled online with multiangle light scattering (MALS) to study the changes in the molecular weight and the size distribution of the corn starch during carboxymethylation. A corn starch was derivatized with sodium chloroacetate in alcoholic medium under alkaline condition to produce carboxymethyl starches (CMS) having various degrees of substitution (DS). The change in thermal characteristics and granule structure of the native corn starch and CMS were compared using Thermogravimetric analysis and scanning electron microscope. The ionic strength of the carrier liquid (water with 0.02% NaN₃) was optimized by adding 50 mM NaNO₃ to minimize the interactions among the starch molecules and between the starch molecules and the AsFlFFF membrane. A field-programmed AsFlFFF allowed determination of the molecular weight distribution (MWD) of starches within about 25 min. It was found that carboxymethylation of starch results in reduction in the molecular weight due to molecular degradation by the alkaline treatment. The weight-average molecular weight (M_w) was reduced down to about 4.4 × 10⁵ from about 7.2 × 10⁶ when DS was 0.14. It seems AsFlFFF coupled with MALS (AsFlFFF/MALS) is a useful tool for monitoring the changes taking place in the molecular weight and the size of starch during derivatization.     

Synthesis of carboxymethyl potato starch and comparison of optimal reaction conditions from different sources

Carboxymethyl potato starch (CMPS) was synthesized under heterogeneous reaction conditions. The influences of etherification temperature, alkalization and etherification time, sodium hydroxide to monochloroacetic acid (MCA) molar ratio (n_NaOH/n_MCA), theoretical degree of substitution (DS_t), the ratio of isopropyl alcohol (IPA) volume to starch mass (v_IPA/m_st) on degree of substitution (DS) and reaction efficiency (RE) of CMPS were investigated. Compared with the previous literature data, the results had significant difference for the optimal carboxymethylation conditions of potato starch from different sources. CMPS prepared under optimal conditions showed the highest DS and RE, which were 1.36 and 0.88, respectively. Furthermore, the RE value in this work is considerably higher than that reported in the literature. The time of alkalization and etherification were also discussed independently. In addition, CMPS was characterized by Fourier transform infrared spectrophotometry and scanning electron microscopy (SEM). Copyright © 2008 John Wiley & Sons, Ltd.     

Structure and properties of the graft copolymer of starch and p‐hydroxybenzoic acid using horseradish peroxidase

A modified starch tannage was synthesized by free radical graft copolymerization of degraded starch with p‐hydroxybenzoic acid (pHA) using horseradish peroxidase/H₂O₂ as the initiator. In this study, the effects of the degree of degradation of the starch, dosage of pHA, polymerization temperature, system pH, and horseradish peroxidase content on the tanning properties of the graft copolymer were investigated. The shrinkage temperature of leather tanned by the graft copolymer was 78 °C. The thickness increment ratio of the retanned leather was 21.6%, and meanwhile the retanned leather showed better softness. The results indicate that the graft copolymer has excellent tanning and retanning properties. The structure of the graft copolymer was analyzed by Fourier Transform Infrared Spectroscopy (FTIR), ¹Hydrogen‐Nuclear Magnetic Resonance (¹H‐NMR), and ¹³Carbon‐Nuclear Magnetic Resonance (¹³ C‐NMR) and Gel Permeation Chromatography (GPC). Compared with conventional methods, we show that a “green” leather tannage could be achieved using a radical graft copolymerization of starch and phenols. Copyright © 2011 John Wiley & Sons, Ltd.     

Reactions between cellulose diacetate and alkenylsuccinic anhydrides and characterization of the reaction products

Cellulose diacetate (CDA) with degree of substitution (DS) of 2.4 was dissolved in dimethylsulfoxide and reacted with octadecenyl succinic anhydrides (OSAs) using 1-methylimidazole as a promoter. FT-IR and ¹H-NMR analysis of the reaction products revealed that half-esterification occurred on residual hydroxyl groups of CDA by OSA, providing CDA/octadecenyl succinic acid (OSAcid) half esters at yields of more than 90%. The effects of reaction time and temperature on DS of CDA/OSAcid esters were studied in detail. The higher the reaction temperature, the higher the esterification rate to form CDA/OSAcid half esters. The maximum DS values were 0.41 and 0.33 for CDA/n-OSAcid and CDA/i-OSAcid esters, respectively. The original X-ray diffraction pattern of CDA changed with the introduction of OSAcid substituents into CDA, and CDA/OSAcid esters seemed to have thermoplasticity, depending on DS and the chemical structure of the OSAcids. A soil-embedding test of films of CDA and CDA/OSAcid esters indicated that the CDA/OSAcid esters that were prepared maintained the biodegradability of the original CDA.     

Development of a Third Generation Snack of Rice Starch Enriched with Nopal Flour (Opuntia ficus indica)

This study aimed to obtain a third-generation snack from native rice starch (NS), rice starch modified by extrusion (MS), nopal flour (NF) and xanthan gum (XG). These raw materials were characterized by proximal analysis, pH, particle size distribution, water absorption index (WAI) and water solubility index (WSI), degree of substitution (DS), differential scanning calorimetry (DSC), rheology, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The analysis of the response variables in the nine formulations of the snack: expansion index (EI), apparent density (AD), hardness (H), luminosity (L*) and tendency to green-red (a*), was performed through a composite central design (CCD), the selected formulations were characterized by SEM. Results showed an increase in WAI, 4.69 ± 0.04, and WSI, 12.61 ± 0.10, for MS, higher than NS values due to chemical modification. According to the color analysis the NF obtained a value of 60.73 ± 0.008 in L* and −6.51 ± 0.004 in a* with green tendency. The DS value obtained was 0.09 ± 0.005, being within the FDA’s permissible range for food use. By FTIR analysis, the acetyl group was corroborated. Finally, employing microwave cooking, snacks made from NS with concentrations of NF (5%) and XG (0%) obtained the highest EI value, 4.47, as well the low Dap and D value (0.37 g/cm³, 2.25 N, respectively), corroborated by SEM analysis.     

Lipase-catalyzed green synthesis of starch–maleate monoesters and its characterization

The present study reports the green synthesis of starch–maleate (SM) at ambient temperature in solvent-free system using Rhizopus arrhizus lipase as a biocatalyst and maleic acid (MA) as an esterification agent. The synthetic scheme was found to be efficient, economical, and ecofriendly. The newly synthesized SM samples were characterized using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopic techniques. The degree of substitution (DS) was found in the range of 0.53–0.62. Moreover, DS was found to be temperature and time-dependent. X-ray diffraction (XRD) exhibited that maleation did not change the crystalline nature of native starch. Scanning electron microscopy (SEM) revealed that size of SM granules was in the range of 4–18 µm. The activation energy (E_a) of SM formation was calculated to be 42.94 kcal mol^?1 which clearly indicated the effective and rapid interaction of functional groups. Hence, the solvent-free solid-state synthetic methodology proved to be excellent for the synthesis of novel biomaterials with appreciable high DS for drug delivery and sorption of heavy metal ions from water.     

Synthesis of cellulose benzoates under homogeneous conditions in an ionic liquid

The ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as a reaction medium was studied for the synthesis of cellulose benzoates by homogeneous acylation of dissolved cellulose with benzoyl chlorides in the absence of any catalysts. Cellulose benzoates with a degree of substitution (DS) in the range from about 1 to 3.0 were accessible under mild conditions. The DS of cellulose derivatives increased with the increase of the molar ratio of benzoyl chloride/anhydroglucose unit (AGU) in cellulose, reaction time, and reaction temperature. Benzoylation of cellulose with some 4-substituted benzoyl chlorides including 4-toluoyl chloride, 4-chlorobenzoyl chloride and 4-nitrobenzoyl chloride was also readily carried out under mild conditions. Furthermore, regioselectively substituted mixed cellulose esters were synthesized in this work. All products were characterized by means of FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. In addition, at the end of benzoylation of cellulose, the ionic liquid AmimCl was easily recycled. When the recycled AmimCl was used as the reaction media, the cellulose benzoate with a similar DS was obtained under comparable reaction conditions.     

羧甲基木薯淀粉的取代方式研究

采用高效液相色谱(HPLC)和核磁共振波谱(^1HNMR)分析了混水/有机介质中合成羧甲基木薯淀粉的取代方式。发现HPLC是一种测定不同条件下合成的羧甲基木薯淀粉取代度(DS)的可靠方法。在测量的范围内,未取代、一取代、二取代和三取代无水葡萄糖单元的摩尔分数分布和Spurlin模型非常吻合。用高分辨率500MHz^1HNMR分析了木薯淀粉羧甲基过程的取代度和反应顺序。依据淀粉和羧甲基淀粉(CMS)的结构确定了各个峰位置。比较所得数据发现：依据HPLC计算的DSHPLC小于从500MHz^1HNMR计算所得的DSNMR。无水葡萄糖单元中C2、C3和C6的羧甲基化反应顺序为C6＞C2＞C3。     

高直链淀粉乙酸酯的均相合成及其静电纺丝

离子液体1-烯丙基-3-甲基咪唑氯盐(amimCl)可以有效地溶解高直链淀粉.以amimCl为均相反应介质,在无外加催化剂的存在下一步合成了取代度范围较宽的高直链淀粉乙酸酯.考察了反应时间和酰化试剂用量对酰化程度的影响.不同取代度的酰化淀粉在水、丙酮和DMAc等溶剂中表现出不同的溶解性.进一步对高直链淀粉乙酸酯溶液进行静电纺丝,制备出了由直径在数十至数百纳米、表面光滑、连续的纳米纤维组成的超细纤维多孔膜.     

Novel route to synthesis of allyl starch and biodegradable hydrogel by copolymerizing allyl‐modified starch with methacrylic acid and acrylamide

Maize starch was modified by allyl chloride adopting an interfacial reaction technique with cetyltrimethyl ammonium bromide as a phase‐transfer catalyst and pyridine as an acid acceptor. The degree of substitution was determined from an increasing carbon content of the modified starch. The percentage of carbon and hydrogen of the allyl‐modified starch was estimated by elemental analysis (C, H, and N), and the product characterization was done through ¹H NMR and ¹³C NMR analyses. The allyl‐modified starch was then copolymerized with methacrylic acid and a combination of methacrylic acid and acrylamide at 50 and 70 °C with potassium persulfate as an initiator. The copolymer thus formed swelled in distilled water after neutralization with sodium carbonate. The percentage of absorption capacity of the hydrogels was determined with distilled water and 0.9% NaCl solution. The highest percentage of absorption, 6500%, was achieved for the developed hydrogel containing allyl starch and acrylic monomer in a 1.7:1 w/w ratio and acrylic monomer, namely, methacrylic acid and acrylamide in a 3.2:1 w/w ratio. The study on biodegradability of the developed hydrogel showed that the hydrogel is degradable in the presence of diastase (amylase). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1650–1658, 2003