Hydration of Temperature-Responsive Polymers Observed by IR Spectroscopy

Summary: Phase separation of aqueous solutions of temperature-responsive polymers such as poly(N-isopropylacrylamide) (PNiPAm) and poly(N,N-diethylacrylamide) (PdEA) was investigated. IR spectroscopy was proved to be a quite useful method observing changes in the hydration states of individual chemical groups of the polymers. For example, the analyses of the amide I and II bands provides important information concerning the hydrogen bonding of the CO group and the N-H group, respectively. Changes in the C H stretching bands indicate hydration changes of the alkyl groups. In addition, molecular simulations based on quantum chemistry give a strong support to the interpretation on molecular level. Our recent progress on this subject was presented and the relationship between the molecular interactions and the macroscopic phase behaviors was discussed.     

Pretreatment of corn stover by low-liquid ammonia recycle percolation process

A pretreatment method using aqueous ammonia was investigated with the intent of minimizing the liquid throughput. This process uses a flow-through packed column reactor (or percolation reactor). In comparison to the ammonia recycle percolation (ARP) process developed previously in our laboratory, this process significantly reduces the liquid throughput to one reactor void volume in packed bed (2.0–4.7 mL of liquid/g of corn stover) and, thus, is termed low-liquid ARP (LLARP). In addition to attaining short residence time and reduced energy input, this process achieves 59–70% of lignin removal and 48–57% of xylan retention. With optimum operation of the LLARP to corn stover, enzymatic digestibilities of 95, 90 and 86% were achieved with 60, 15, and 7.5 filter paper units/g of glucan, respectively. In the simultaneous saccharification and fermentation test of the LLARP samples using Saccharomyces cerevisiae (NREL-D₅A), an ethanol yield of 84% of the theoretical maximum was achieved with 6% (w/v) glucan loading. In the simultaneous saccharification and cofermentation (SSCF) test using recombinant Escherichia coli (KO11), both the glucan and xylan in the solid were effectively utilized, giving an overall ethanol yield of 109% of the theoretical maximum based on glucan, a clear indication that the xylan content was converted into ethanol. The xylooligomers existing in the LLARP effluent were not effectively hydrolyzed by cellulase enzyme, achieving only 60% of digestibility. SSCF of the treated corn stover was severely hampered when the substrate was supplemented with the LLARP effluent, giving only 56% the overall yield of ethanol. The effluent appears to significantly inhibit cellulase and microbial activities.     

Synthesis and electrochemical properties of chemically substituted LiMn2O4 prepared by a solution-based gel method

Lithium manganese oxide, LiMn(2)O(4), and its substituted samples LiM(0.05)Mn(1.95)O(4) (M=Al, Co, and Zn) were first prepared by a cost-saving and effective new solution-based gel method using a mixture of acetate and ethanol as the chelating agent. The physical properties of the synthesized samples were investigated by thermogravimetry/differential thermal analysis, X-ray diffraction, and scanning electronic microscopy. The as-prepared powders were used as positive materials for a lithium-ion battery, whose charge/discharge properties and cycle performance were examined. The results revealed that all the substituted samples had better cycle performance than pure LiMn(2)O(4). Among these synthesized materials, the LiCo(0.05)Mn(1.95)O(4) sample had the best cycle performance. After 30 cycles, its capacity loss was only 3%. Therefore, cyclic voltammetry and electrochemical impedance spectroscopy were employed to characterize the reactions of Li ion insertion into and extraction from LiCo(0.05)Mn(1.95)O(4) electrodes.     

NaBr对杂双子表面活性剂C_mOhpNC_8水溶液吸附和聚集的影响

以表面张力和荧光探针技术研究了NaBr对杂双子表面活性剂CmOhpNC8(m:10,14,16)水溶液性质的影响。结果表明,NaBr强烈促进了CmOhpNC8在气/液界面上的吸附和在水相中的聚集,其中c20在cNaBr≥10mmol/L时降到极低的微摩尔/升数量级,显示了相当高的降低水表面张力效率。在NaBr促进下,水溶液中CmOhpNC8表现出强烈的预胶团化行为。这些均是对应的2种单头基单烷烃链表面活性剂简单1:1混合所无法实现的,显示了在头基处引入短联接链形成杂双子结构的表面活性优势以及对盐效应的敏感性。     

手性胺催化不对称水相aldol反应研究进展

Aldol反应作为最重要的碳碳键形成反应之一,在有机合成中有着重要作用,本文综述了手性伯胺,仲胺催化剂催化的水相aldol反应的最新研究进展。     

聚乙二醇双水相萃取光度法测定锌

A novel method of extraction spectrophotometric determination of Zn~(2+) in aqueous two-phase system formed by polyethylene glycol-2000,sodium sulfate and zincon has been established.Amounts of PEG solution,zincon solution,sodium sulfate added and the acidity of the system were optimized.The interference effects of various coexistent ions and the method to remove the interference were investigated.The Zn-zincon complex that had been formed in the presence of H_2BO_3-Na_2B_4O_7 buffer solution at pH 7.4 was extracted into the upper PEG-rich phase,and the absorbance of the extracted complex in the upper PEG-rich phase was measured at 630 nm.The apparent molar absorptivity was 7.3 × 10~4 L / (mol·cm).Beer's law was obeyed over the range of 0～2.0 μg / mL Zn~(2+).The analytical results obtained for Zn~(2+) in water samples were in good agreement with values measured by atomic absorption spectrometry.     

Investigation of the structure of concentrated aqueous solution of LiCl at low temperatures by the method of integral equations

Peculiarities of the formation of the structure of aqueous LiCl solution (at a salt: water molar ratio of 1:5.3) in the temperature range 298-138 K were studied by the method of integral equations. Analysis of the results obtained suggests that transition of the system into the supercooled and glassy state is accompanied by an increase in the tetrahedral ordering of solvent molecules and a decrease in the number of interactions between the water molecules in unbound solvent. Lowering the temperature leads to an increase in the degree of structurization of water molecules surrounding the cation. Preferable formation of hydrogen bonds with the anion under extreme conditions was established. The glassy state of the solution is characterized by the absence of direct anion-cation correlations and increased (compared to standard conditions) probability of the formation of ion-water chains. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1881–1886, October, 1999.     

Synthesis of β-aminoesters and α-selenoesters via Active Metal Bismuth Produced by Sm/BiCl_3 System in Aqueous Media

Since the general approach for the preparation of highly reactive metal powders wasreported in 1972', active metals have attracted considerable attention in organicsynthesis'. Due to the high reactivity of active metals, reactions are typically carriedout more efficiently, under milder conditions, and with a wider array of substrates thanwith other current methods. UP to noW, active metal magnesium', zinc', indium',calcium', manganese', samarium', elc have been reported..Meanwhile, metal-medi…     

Tin Oxide Thin Film with Three‐Dimensional Ordered Reticular Morphology as a Lithium Ion Battery Anode

Three‐dimensional (3D) reticular SnO₂ thin films deposited on copper and stainless steel substrates were prepared by the electrostatic spray deposition (ESD) technique. The 3D reticular SnO₂ film exhibit a high reversible capacity near 300 mAh g^?1 up to the 50th cycle.