Designing Starch‐Based Nanospheres to Make Hydrogels with High Mechanical Strength

A robust method to prepare hydrogels with high mechanical strength is presented. Core/shell nanospheres with derivatizable allyl groups in the shell were first prepared. Starch‐based nanospheres were used as crosslinker to prepare polyacrylamide hydrogels. The starch‐based nanospheres were bridged by acrylamide to form crosslink points in the hydrogel network. They possess an extremely high mechanical strength. The results show that starch‐based nanosphere hydrogels can sustain strengths of 10.34 MPa, which is 60 times greater than for a normal hydrogel. The mechanical properties of SNH can be tailored by varying the content of SN. This approach offered a new way of making functional hydrogel with biodegradable component as a substitute for tissue.

     

Adsorption of hexavalent chromium on cationic starches with different degree of crosslinking

The influence of the degree of crosslinking in the association with the degree of cationization on the adsorption of Cr(VI) by crosslinked cationic starches (CCS) was examined. The amount of adsorbed Cr(VI) depends on the preparation of CCS before adsorption experiments (dry or preswollen CCS) and has a higher value when dry CCS are used. The amount of crosslinks in CCS needed to reach the maximum effectiveness of the cationic groups of CCS in the binding of Cr(VI) depends also on the form in which CCS are used. The adsorption capacity for Cr(VI) decreases both with dry and preswollen CCS when the adsorption temperature increases. The thermodynamic parameters are calculated. The negative values of ΔG° and ΔH° indicated that the adsorption process in both cases was spontaneous and exothermic. If preswollen CCS is used, the entropy change has a positive value and indicates that the randomness of the system increases, whereas the negative value of entropy change when Cr(VI) species are adsorbed by dry CCS shows that in this case the order of the system increases like in the classical adsorption process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

酶-微波辅助提取紫薯花青素的工艺研究

以紫薯为原料,0.3%盐酸-90%乙醇为溶剂（酸醇比为50∶50）,在料液比为1∶10 g/mL时,采用单因素实验法对提取工艺条件进行优化,确定了纤维素酶-微波辅助提取紫薯中花青素的最佳工艺条件为：纤维素酶用量3 mg/g,纤维素酶提取温度40℃,酶提取时间15 min,微波平均辐射功率600 W（温度70℃）,微波辐射时间7 min。对比实验结果表明,酶-微波辅助提取法较单纯盐酸乙醇浸提法,花青素的产率提高了1.86倍,而提取时间缩短了82%。     

超声作用下辛烯基琥珀酸淀粉酯合成工艺及反应机理研究

以木薯淀粉为原料,辛烯基琥珀酸酐为变性剂,采用湿法工艺,在超声作用下制备辛烯基琥珀酸淀粉酯.用单因素实验探索最佳制备工艺条件及酯化反应机理.结果表明,超声作用制备辛烯基琥珀酸淀粉酯的最佳工艺条件为：超声作用时间30 min,超声功率250 W,酯化pH 8.5,反应温度35℃,在最佳工艺条件下制备所得辛烯基琥珀酸淀粉酯取代度达0.0181,比未施加超声作用所制得的产品取代度提高了28.4％.超声波强化淀粉变性反应机理是超声波的空化效应对木薯淀粉的颗粒结构有一定影响,使淀粉颗粒表面变粗糙,增加了反应物之间的接触面积,强化了酯化反应的发生.     

Fibre diffraction in the analysis of filamentous virus structure

In many plant and bacterial viruses, a filamentous nucleocapsid makes up the entire virus particle. These viruses usually form fibres naturally, but they do not crystallize. Fibre diffraction has therefore been the method of choice for structural studies, aided in recent years by cryo-electron microscopy (EM) and solid state nuclear magnetic resonance (ssNMR). Filamentous viruses, particularly tobacco mosaic virus (TMV), have been important in developing fibre diffraction methods, and fibre diffraction allowed TMV to be among the first virus structures determined. Structures of several viruses related to TMV and several filamentous bacterial viruses have been determined at resolutions of 3?Å or better, and lower resolution structures have been determined by fibre diffraction, sometimes in conjunction with other methods, for many other, unrelated, filamentous viruses.     

可生物降解热熔胶粘剂的研究进展

综述了近年来可生物降解热熔胶的发展、合成、性能、应用、最新的研究进展。     

Physical characteristics of sweet potato pulp/polycaprolactone blends

Sweet potato pulp (SSP) obtained as a by‐product from starch extraction was blended with polycaprolactone (PCL) to prepare a biodegradable plastic material. In the blends, PCL was used as a reinforcing agent. The SPP/PCL blends were prepared by compression‐molding under high temperature and pressure, at different SPP/PCL ratios, and the mechanical properties of the molded specimens were tested. Matrix structure and thermal properties were measured by using a Fourier transform infrared (FTIR) spectrophotometer, scanning electron microscope (SEM), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). Mechanical properties (tensile and flexural properties) were also measured to find the most suitable ratio in a SSP/PCL blend. During compression molding of the SPP/PCL blends under high pressure and temperature, chemical reaction occurred between SPP and PCL, and thus, thermal stability and mechanical strength of the blends increased and water uptake decreased. Also, by increasing the PCL content in the blend, the matrix in the blend became more homogeneous, and consequently, mechanical strength of the molded specimen increased. At 7/3 or 6/4 weight ratio of SSP/PCL, water uptake of the molded specimen became substantially less than that at 8/2. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 861–866, 2004     

Removal of Cu(II) from aqueous solutions by chelating starch derivatives

Two chemically modified starch derivatives, crosslinked amino starch (CAS) and dithiocarbamates modified starch (DTCS), were prepared and used for the removal of Cu(II) from aqueous solutions. CAS was found to be effective for the adsorption of Cu(II), which tended to form a stable amine complex. Adsorption of Cu(II) onto DTCS was higher than that onto CAS. Experiments showed that the adsorption processes of Cu(II) on both CAS and DTCS were endothermic, and followed Freundlich isothermal adsorption. For both adsorbents, dynamic modeling of their adsorption showed that the first‐order reversible kinetic model described the adsorption process. The adsorption rate constants of CAS and DTCS were 1.578 and 10.32 h^?1, respectively. From the results of the thermodynamic analysis, free energy ΔG, enthalpy ΔH, and entropy ΔS of the adsorption process were calculated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3881–3885, 2004     

Preparation and characterization of starch-based composite films reinforced by apricot and walnut shells

Starch-based biodegradable films were prepared by using solution-casting method and reinforced by agricultural residues [apricot and walnut shell (APS and WNS) powder]. The powder of both shells was added in different ratios (0, 2.5, 5, 7.5, and 10%) to investigate the microstructures and performances (mechanical and thermal properties) of the starch-based film. Different techniques such as impact, tensile testing, scanning electron microscope, optical microscope (OM), X-ray diffraction (XRD), water vapor transmission rate (WVTR), and dynamic mechanical analysis were applied to study the thermomechanical and barrier properties of the composite films. Results showed that the incorporation of both shells significantly improved the WVTR and mechanical properties of starch-based films. The shells powder was significantly increased the Young's modulus and tensile strength of the starch-based films. Both OM and SEM results showed reasonably good compatibility between starch and reinforced shells. OM and XRD indicated that the APS and WNS not only retained their crystalline structure in the film but they also strengthened the peak intensity of the film. This phenomenon can be used to explain the mechanism of mechanical reinforcement. Since all the components used in the preparation of the films are food grade ingredients, it is expected that the films developed in this work will be used for food packaging applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47978.     

淀粉-苯乙烯接枝共聚的分析与评定

采用悬浮聚合的方法,对淀粉进行接枝共聚改性,制得的接枝共聚物具有淀粉和单体的双重优良性能.