丁酸壳聚糖液晶的临界行为研究

用偏光显微镜法测定了丁酸壳聚糖在四种酸性溶剂中的临界浓度值．发现临界浓度值（ｖ／ｖ％）与溶剂的酸性无关，都是１６％～１７％．在以二氯乙酸为溶剂时，不同丁酰化程度的丁酸壳聚糖有相同的临界浓度．用ＤＳＣ法测定了丁酸壳聚糖／二氯乙酸体系的临界温度，并绘制了相图．结果表明，浓度达６０％（ｗ／ｗ％）后，临界温度基本不再变化，稳定在３９℃左右．     

阳离子淀粉-壳聚糖-丙烯酰胺的接枝共聚研究

以硝酸铈铵为引发剂,合成阳离子淀粉(CS)-壳聚糖(CTS)-丙烯酰胺(AM)接枝共聚物,讨论了反应温度、引发剂浓度、单体用量、反应时间以及壳聚糖用量对接枝共聚反应的影响。结果表明:淀粉中葡萄糖环浓度(cAGU)为0.20 mol/L,mCTS/mCS=1/6,cAM=1.0mol/L,cCe4 =5 mmol/L,反应温度60℃,反应时间3 h时,转化率和接枝效率可分别达到88%和92%以上;转化率随mCTS/mCS增大而增大,接枝效率则随着CTS用量增大降低,CTS的存在使AM均聚的几率增大。     

Pre-irradiation induced grafting of styrene into crosslinked and non-crosslinked polytetrafluoroethylene films for polymer electrolyte fuel cell applications. II: Characterization of the styrene grafted films

Crosslinked and non-crosslinked polytetrafluoroethylene films (RX-PTFE and V-PTFE films, respectively) were irradiated by γ-ray and then grafted with styrene in liquid phase. Microscope FT-IR spectroscopy, TGA, solid state ¹³C CP/MAS and high resolution HS/MAS NMR spectroscopy, wide-angle X-ray diffraction (WAXD) study were used to get the structural information of the styrene grafted RX-PTFE and V-PTFE films. From microscope FT-IR spectra of the grafted RX-PTFE films, the “grafting front mechanism” was proved. TGA analysis showed that the grafted films have a small degradation step and two main degradation steps. In the ¹³C CP/MAS NMR spectra of the non-grafted films, there are no signal due to the absence of the hydrogen atom. While in the spectra of the grafted films, there are signals attributed to the polystyrene grafts. In the ¹³C HS/MAS NMR spectra of the grafted films, the relative intensity of the peaks attributed to the polystyrene grafts increased while the relative intensity of the peak attributed to PTFE matrix decreased with the increase in the DOG. From WAXD patterns, the intensity of the crystalline peak decrease with the increase in the DOG. The grafted films were sulfonated by chlorosulfonic acid and the results of highest IEC value exceeded 3.0. Those results will be reported in the near future.     

一种新的液晶高分子——丁酸壳聚糖的合成与表征

甲壳素几乎不溶于任何溶剂,由于其脱乙酰化产物壳聚糖含自由氨基,能被酸质子化而溶解,所以壳聚糖的应用领域远多于甲壳素.但是壳聚糖也仅能溶于酸性介质中,并不能溶于纯水和普通有机溶剂,因而人们对甲壳素或壳聚糖进行各种化学改性[1,2],寻求溶解性更好尤其能溶于水的衍生物,以扩大其应用范围.本文按文献[2～4]方法合成了O-丁酰化壳聚糖(简称丁酸壳聚糖),首次报道它具有溶致液晶性.     

A novel method for the synthesis of the PEG-crosslinked chitosan with a pH-independent swelling behavior

In this study, a simple method was developed to crosslink chitosan using poly(ethylene glycol) (PEG) with different molecular weights. Crosslinking of chitosan was confirmed by various spectral analyses. The differential scanning calorimetric (DSC) study indicated that the rigid crystalline structure of chitosan was decreased after crosslinking with PEG. The PEG-crosslinked chitosan (PEG-Ch) showed a pH-independent swelling behavior: swelled in both the simulated stomach (pH 1.1) and intestinal (pH 7.4) solutions. The swelling ratio of PEG-Ch increased significantly with a higher molecular weight of PEG used. In contrast, chitosan dissolved completely in a simulated stomach solution and showed a comparatively less swelling in a simulated intestinal solution. Thus, the prepared PEG-Ch could be a better biomaterial than chitosan in the development of orally sustained drug-delivery devices.     

Water‐Soluble N‐(n‐Fatty acyl)chitosans

Chitosan was partially N‐acylated by treatment with n‐fatty acid anhydrides in a homogeneous solution in 2 vol.‐% aqueous acetic acid‐methanol (1:2 v/v). The degree of substitution (d.s.) for N‐acyl groups in the water‐soluble N‐acylchitosan derivatives was in the range of 0.42–0.82 for N‐acetyl, 0.37–0.76 for N‐propionyl, 0.52–0.71 for N‐butyryl and 0.54–0.64 for N‐pentanoyl and ca. 0.58 for N‐hexanoyl, respectively.

Water soluble N‐(n‐fatty acyl)chitosans.     

Synthesis of chitosan resin possessing 3,4-diamino benzoic acid moiety for the collection/concentration of arsenic and selenium in water samples and their measurement by inductively coupled plasma-mass spectrometry

A chitosan resin functionalized with 3,4-diamino benzoic acid (CCTS-DBA resin) was newly synthesized by using a cross-linked chitosan (CCTS) as base material. The adsorption behavior of trace amounts of elements on the CCTS-DBA resin was examined by the pretreatment with a mini-column and measurement of the elements by inductively coupled plasma-Mass spectrometry (ICP-MS). Arsenic(V) could be retained on the CCTS-DBA resin at pH 3 as an oxoanion of H₂AsO₄⁻. Selenium(VI) is strongly adsorbed at pH 2 and pH 3 as an oxoanion of SeO₄²⁻, while selenium(IV) as HSeO₃⁻ is adsorbed on the resin at pH 3. The sorption capacities are 82, 64, and 88 mg g⁻¹resin for As(V), Se(IV), and Se(VI), respectively. The effect of common anions and cations on the adsorption of As(V), Se(IV), and Se(VI) were studied; there was no interference from such anionic matrices as chloride, sulfate, phosphate, and nitrate up to 20 ppm, as well as from such artificial river water matrices as Na, K, Mg, and Ca after passing samples through the mini-column containing the resin. The CCTS-DBA resin was applied to the collection of arsenic and selenium species in bottled drinking water, tap water, and river water.     

Antibacterial activity of methylated chitosan and chitooligomer derivatives: Synthesis and structure activity relationships

The purpose of this study was to synthesize series of methylated chitosaccharide derivatives, possessing various degree of methylation, and to determine their structure activity relationship (SAR) with regard to their antibacterial effect against Staphylococcus aureus. Chitosan polymer and chitooligomers were used as starting materials and were methylated by reaction with methyl iodide. Depending on the reaction conditions the degree of N-quaternization ranged from 0% to 74%, with varying degree of N,N-dimethylation, N-monomethylation and O-methylation. More selective N-quaternization could be obtained with protection group strategy. At pH 5.5 the chitosaccharide polymers and their methylated derivatives were active against S. aureus with minimal inhibitory concentration (MIC) ranging from 16 to 512 μg/mL. At pH 7.2 the non-quaternized derivatives were inactive but their highly N-quaternized derivatives showed MIC as low as 8 μg/mL. The chitooligomers, as well as their derivatives, were inactive at both pH’s. The SAR studies revealed that N-quaternization was mainly responsible for the antibacterial effects at pH 7.2, whereas it did not contribute to the antibacterial activity under acidic conditions.     

分子印迹壳聚糖膜分离手性苯丙氨酸

以L-苯丙氨酸(L-Phe)为印迹分子,采用相转化法制备了分子印迹壳聚糖膜。分别采用碱液处理和硫酸交联两种方法对膜进行处理,降低了壳聚糖膜的溶胀度,印迹膜内识别位点的结构得以保持。采用FT-IR和SEM对膜的化学组成和结构形态进行了表征。通过渗透实验考察了分子印迹壳聚糖膜和非印迹空白壳聚糖膜对D,L-苯丙氨酸(D,L-Phe)混合物的手性拆分性能,并与空白膜进行了比较。印迹膜的分离因子达到1.43。     

壳聚糖季铵盐/滤纸复合膜对胆红素的吸附研究

用2,3-环氧丙基三甲基氯化铵对壳聚糖进行化学修饰,在壳聚糖的分子结构中引入季胺盐基团,提高其阳离子含量。将壳聚糖季铵盐涂在滤纸上,用戊二醛交联,制得壳聚糖季铵盐/滤纸复合膜,考察该复合膜的强度以及对胆红素的吸附性能。实验结果表明,壳聚糖季铵盐/滤纸复合膜具有良好的力学性能;对胆红素的吸附在3h基本达到平衡,其吸附量远大于壳聚糖/滤纸复合膜;适当取代度及高交联度的复合膜吸附效果较好。复合膜对胆红素的吸附量随离子强度的增加而降低;血清白蛋白的加入使吸附量下降。