Spectroscopic and conformational study of chitosan acid salts

The efficient procedure for preparation of chitosan acid salts in isopropyl alcohol under mild condition has been demonstrated. The salts were prepared by dissolving chitosan into ascorbic acid, p-amino benzoic acid and p-nitro benzoic acid, respectively, and then washed with an isopropyl/water mix-solvent. The prepared crystal salt and molecular conformation of modified chitosan derivatives are characterized by using ultraviolet, Fourier transform infrared (FTIR), ¹H nuclear magnetic resonance (NMR), X-ray diffraction and Circular dichroism (CD) techniques. The formation of salts was confirmed by FTIR (∼1,523–1,557 cm⁻¹) and NMR (∼7–8 ppm) with respect to the bonding between NH₂ group on chitosan and COOH group on acid. The CD spectra of chitosan salts showed negative at (253, 285 and 295 nm band) in chitosan ascorbic acid, p-amino benzoic acid and p-nitro benzoic acid salt respectively in DMSO, indicating that the polymer adopted a helical secondary structure. The polymers are highly soluble in a wide pH range, which opens new perspectives for the biomedical application of chitosan based-materials.     

广谱水溶性壳聚糖的研究进展

拓宽能够溶解壳聚糖的水介质的pH范围,是克服壳聚糖应用和研究受局限的有效途径,因而一直得到人们广泛的关注。作者综述了近年来改善壳聚糖溶解于宽pH范围水溶液的方法,并简要介绍了水溶性壳聚糖的应用研究。     

Solid-state NMR study of N labelled polyaniline upon reaction with DPPH

The quantitative investigation of the radical scavenging properties of polyaniline (PANI) upon reaction with excess of the stable DPPH radical (a 4:1 ratio of DPPH to aniline units in the polymer) was carried out using ¹⁵N and ¹³C solid state NMR spectroscopy. During the process the polyaniline was oxidised so that the imine content increased from 45 to 65%. The extent of oxidation measured by NMR was confirmed by N1s XPS analysis. However, within a 30 min reaction time, about 85% of the DPPH radicals were scavenged as monitored by the decay in its EPR signal. This is about 20 times greater than the fraction of DPPH required to oxidize PANI from an imine content of 45-65%. An identification of further redox processes is required to explain the high degree of radical scavenging. At the same time, there was no evidence of significant chemical binding or trapping of DPPH in the PANI structure.     

A fundamental study of chitosan/PEO electrospinning

A highly deacetylated (97.5%) chitosan in 50% acetic acid was electrospun at moderate temperatures (25-70 °C) in the presence of a low content of polyethylene oxide (10 wt% PEO) to beadless nanofibers of 60-80 nm in diameter. A systematic quantitative analysis of the solution properties such as surface tension, conductivity, viscosity and acid concentration was conducted in order to shed light on the electrospinnability of this polysaccharide. Rheological properties of chitosan and PEO solutions were studied in order to explain how PEO improves the electrospinnability of chitosan. Positive charges on the chitosan molecule and its chain stiffness were considered as the main limiting factors for electrospinability of neat chitosan as compared to PEO, since surface tension and viscosity of the respective solutions were similar. Various blends of chitosan and PEO solutions with different component ratios were prepared (for 4 wt% total polymer content). A significant positive deviation from the additivity rule in the zero shear viscosity of chitosan/PEO blends was observed and believed to be a proof for strong hydrogen bonding between chitosan and PEO chains, making their blends electrospinnable. The impact of temperature and blend composition on the morphology and diameter of electrospun fibers was also investigated. Electrospinning at moderate temperatures (40-70 °C) helped to obtain beadless nanofibers with higher chitosan content. Additionally, it was found that higher chitosan content in the precursor blends led to thinner nanofibers. Increasing chitosan/PEO ratio from 50/50 to 90/10 led to a diameter reduction from 123 to 63 nm. Producing defect free nanofibrous mats from the electrospinning process and with high chitosan content is particularly promising for antibacterial film packaging and filtration applications.     

壳聚糖季铵盐及其复合物的研究进展

壳聚糖季铵盐及其复合物是一种很有应用前景的材料,作者综述了壳聚糖季铵盐及其复合物在载基因、载药、抗菌创伤材料、抗凝血材料、水处理材料等领域的研究进展。     

壳聚糖多糖膜的性能与应用研究

综述了壳聚糖多糖膜的性质、制备、性能及应用等方面的研究进展。     

Contribution to the study of the complexation of copper by chitosan and oligomers

The complexation of copper ions by chitosan and its oligomers is investigated using potentiometric and spectrophotometric methods to study the nature of the complexes involved and the role of the degree of polymerisation. Two complexes are demonstrated. Their structure is proposed, the pH range in which they are respectively stable is determined and their stability constants calculated. Finally a degree of polymerisation of 6 appeared as the threshold value for an efficient complexation of copper ions by chitosan oligomers.     

壳聚糖功能膜

本文简要介绍壳聚糖的功能膜的研究状况     

胶原蛋白与壳聚糖相容性研究

将胶原蛋白与两种去乙酰度（95％,85％）的壳聚糖分别配成不同质量比的HAc共混溶液,在28℃下测定了共混液的黏度,利用Δb法则比较共混液中两种物质的相容性。结果表明在28℃的HAc溶液中,任何质量比的胶原蛋白和壳聚糖均相容,并且两者相容性不受壳聚糖去乙酰度的影响。     

壳聚糖与DNA作用的共振光散射特征及微量DNA的光散射测定

通过光谱法研究壳聚糖和核酸的作用 ,结果表明通过共振光散射法用壳聚糖检测微量的 DNA方法可靠、准确且简单。     

NMR study of intrinsic diffusion and reaction in CsNaX type zeolites

In this contribution the catalytic behaviour of the zeolites CsNaX-60 and CsNaX-60·8CsOH (impregnated with eight CsOH per unit cell) was studied. As a model reaction, the conversion of isopropanol to acetone as the product of basic catalysis or to propene as the product of acid catalysis was chosen. The intracrystalline self-diffusivities of isopropanol, acetone and propene in these zeolites and in NaX were measured with the pulsed field gradient (PFG) NMR technique. Self-diffusivity measurements of propane and water were performed to characterize these three zeolites. ¹³C MAS NMR studies with proton decoupling were used to test the cesium containing zeolites for acid or basic catalytic activity.     

NMR and FT Raman characterisation of regioselectively sulfated chitosan regarding the distribution of sulfate groups and the degree of substitution

Chitosan sulfates (CHS) were prepared with chlorosulfonic acid homogeneously and non-homogeneously. The total degrees of substitution (DS) ascribed to sulfate groups (DS_S) were determined with elemental analysis and the partial DS at 6-O-position was estimated via ¹³C NMR. CHS with diverse total DS_S and sulfation patterns were obtained according to the analysis. The effects of selected reaction parameters that can influence the distribution of sulfate groups were examined. The structure of CHS was then characterized with various NMR techniques, i.e. one- (1D-) and two-dimensional (2D-) NMR, and FT Raman spectroscopy. It was found that the primary hydroxyl groups were always predominantly sulfated for CHS prepared under homogeneous or non-homogeneous conditions and no sulfate groups at 2-N-position could be detected. Finally, the feasibility of using FT Raman spectroscopy as another alternative for determining the total DS_S of CHS was presented.     

硬脂酸壳聚糖复合物的合成与吸油研究

合成了硬脂酸壳聚糖复合物,用红外光谱表征了复合物,再将复合物加入到小麻油与橄榄油中,用紫外光谱研究了它对油脂的吸附情况。结果证明,壳聚糖与硬脂酸间主要以盐键结合,复合物能明显吸附中性油脂;实验证明用紫外光谱法研究油脂吸附是可行的。     

明胶对明胶/壳聚糖共混膜性能影响的研究

采用溶液共混法制备出了一系列明胶／壳聚糖共混膜,并考察了制备条件对膜性能的影响。结果表明：明胶的溶解方式对吸水率和溶胀比影响很小;随明胶分子量增加,共混膜的吸水率和孔洞体积增大;而随共混体系中明胶质量分数的增加,吸水率和孔洞体积亦增加,但溶胀比下降。     

磷改性ZSM-5分子筛在甲醇制芳烃反应中催化性能的固体核磁研究

甲醇制芳烃反应在化工领域具有重要的现实意义,ZSM-5分子筛是这一反应的优良催化剂,磷改性是提高ZSM-5分子筛催化性能的常见方法。利用固体核磁共振技术对改性催化剂进行1H、27Al和31P表征,结合催化考评结果,推测或论证影响催化活性的因素,对反应条件的优化提出有益的帮助和支持。     

壳聚糖接枝共聚反应的研究进展

对壳聚糖与醇类、酯类、酸类、酰胺类、盐类等的接枝共聚及其在各个领域中的应用进行了综述,以期推进壳聚糖更广泛的应用。     

壳聚糖羟丙基三甲基季铵盐的合成及絮凝净水性能

在有机溶剂中合成了壳聚糖羟丙基三甲基季铵盐（HTAC）,探索了最佳反应条件,得到了转化率较高、水溶性好的产品。该产品6mg／L与60mg／L的聚合铝复配,使孤一、孤五污水站污水浊度分别由90．4mg／L、64．0mg／L降到3．6mg／L、4．2mg／L。加入该产品40mg／L和聚合铝50mg／L,使孤二联污水油质量浓度由2706．8mg／L降到18．5mg／L．浊度由960mg／L降到4．4mg／L,絮凝净水效果十分显著。     

壳聚糖水热交联炭材料研究

壳聚糖水热炭是通过水热交联壳聚糖制备得到的含有丰富氨基的炭材料。制备过程只需一步,条件温和无需任何特殊溶剂和有毒交联剂;材料自带氨基容易改性,有较好的耐酸性,是非常好的吸附剂材料。     

Electrochemical study of chitosan films deposited from solution at reducing potentials

We report the electrochemical characterization of chitosan films deposited at gold electrodes from an acidic solution at reducing potentials. Cyclic voltammetry was used to characterize the deposition and electroactivity of chitosan coated gold electrodes. Chitosan films were found to deposit at gold electrodes at potentials more negative than −1.0 V versus Ag/AgCl, a potential associated with the onset of water reduction and increase in pH near the electrode. The chitosan films are electrochemically inactive; similar background charging currents are observed at bare gold and chitosan coated electrodes. The chitosan films are permeable to both cationic [Ru(NH₃)₆^3+/2+] and anionic [Fe(CN)₆^3−/4−] redox couples, but anionic complexes are retained in the chitosan film. Semiintegral analysis was used to examine adsorbed redox species at the chitosan coated electrode surface. Electrochemical parameters, including apparent diffusion coefficients for the redox probes at the electrodeposited chitosan modified electrodes are presented and are comparable to values reported for cast chitosan films.     

改性累托石/壳聚糖复合絮凝剂的絮凝机理研究

介绍了铝交联改性累托石的制备方法及处理石化废水的效果。结果表明,质量分数为3%的改性累托石复配絮凝剂对石化废水的COD去除率可达到91.27%。对改性前后的累托石进行的X-衍射及红外光谱分析表明,改性累托石层间距从2.55 nm扩大到了2.66 nm,这是改性累托石复配絮凝剂絮凝效果有效提高的机理所在。