用FTIR测定邻苯二甲酰化壳聚糖的取代度

富立叶红外光谱;定量分析;用FTIR测定邻苯二甲酰化壳聚糖的取代度     

甲壳素类淮晶高分子的研究Ⅵ．邻苯二甲酰化壳聚糖中酰胺酸取代度对液晶性的影响

通过控制不同反应时间和邻苯二甲酸酐／壳聚糖的摩尔比制备不同取代度的邻苯二甲酰化壳聚糖（PHCS）,用FTIR研究了反应机理和产物结构,观察到PHCS含两类取代即酰胺酸取代和酰亚胺取代,反应时间较短时主要为前景,取代度表示为DS,反应时间较长时主要为后者,取代度表示为DS2,对PHCS在二氯乙酸（DCA）中的液晶行为观察,结果表明,PHCS的临界浓度随DS1的增加而显著增加DS1对PHCS临界浓度的影响明显大于DS2的影响,基本上为酰胺酸取代的PHCS的临界浓度高于溶解度,以至于观察不到。     

甲壳素类液晶高分子的研究Ⅵ.邻苯二甲酰化壳聚糖中酰胺酸取代度对液晶性的影响

通过控制不同反应时间和邻苯二甲酸酐 壳聚糖的摩尔比制备不同取代度的邻苯二甲酰化壳聚糖(PHCS) .用FTIR研究了反应机理和产物结构 ,观察到PHCS含两类取代即酰胺酸取代和酰亚胺取代 .反应时间较短时主要为前者 ,取代度表示为DS1 ;反应时间较长时主要为后者 ,取代度表示为DS2 .对PHCS在二氯乙酸 (DCA)中的液晶行为观察 ,结果表明 ,PHCS的临界浓度随DS1 的增加而显著增加 .DS1 对PHCS临界浓度的影响明显大于DS2 的影响 .基本上为酰胺酸取代的PHCS的临界浓度高于溶解度 ,以至于观察不到     

邻苯二甲酰化壳聚糖的合成与溶致液晶表征

从全脱乙酰化壳聚糖出发,在室温下合成了一系列不同取代度的邻苯二甲酰化壳聚糖(PhCS),由于反应条件温和,产物未发生进一步的酰亚胺化.X射线电子能谱(XPS)被用来测定PhCS的取代度.测定结果表明在N上和O上均发生取代,N上反应的取代度随酸酐用量的增加基本保持不变(0.26±0.03),而O上的取代度却不断变大(0.01～1.54),合成产物的总取代度为0.26～1.81.邻苯二甲酰化壳聚糖可溶解于普通的有机溶剂,如DMSO、二氯乙酸和甲酸,并形成溶致液晶.测定了PhCS在这些溶剂中的临界浓度(c*),结果表明c基本上不受取代度变化的影响.     

邻苯二甲酰化壳聚糖的合成与溶致液晶表征

从全脱乙酰化壳聚糖出发,在室温下合成了一系列不同取代度的邻苯二甲酰化壳聚糖(PhCS),由于反应条件温和,产物未发生进一步的酰亚胺化.X射线电子能谱(XPS)被用来测定PhCS的取代度.测定结果表明在N上和O上均发生取代,N上反应的取代度随酸酐用量的增加基本保持不变(0.26±0.03),而O上的取代度却不断变大(0.01～1.54),合成产物的总取代度为0.26～1.81.邻苯二甲酰化壳聚糖可溶解于普通的有机溶剂,如DMSO、二氯乙酸和甲酸,并形成溶致液晶.测定了PhCS在这些溶剂中的临界浓度(c),结果表明c基本上不受取代度变化的影响.     

红外光谱法测定N-酰化壳聚糖的取代度

以从完全脱乙酰壳聚糖通过均相N-乙酰化法制备的不同脱乙酰度(D.D.)壳聚糖为红外标准样品,通过评价1655,1560,1380和1320 cm^-1 4条可能的分析谱带,3430, 2920,2880,1425,1155,1070,1030和895 cm^-18条可能的参比谱带以及2种基线法组成的48种组合, 选出了适合于壳聚糖脱乙酰度红外测定的最佳组合为A₁₅₆₀ / A₂₉₂₀, A₁₅₆₀ / A₂₈₈₀和A₁₆₅₅ / A₃₄₃₀(推荐使用A₁₅₆₀ / A₂₈₈₀).测量1560和1655 cm^-1谱带的吸光度以第2种基线作法(即此两峰相邻的峰谷连线)为佳.D.D.的测量范围几乎覆盖了全程即1%~100%.后两种最佳组合的工作曲线还可适用于N-丙酰化、N-丁酰化和N-己酰化等N-烷酰化壳聚糖的取代度测定.     

微波促进的取代酚类化合物的邻甲酰化反应研究

以4 氯苯酚（1a）为原料,研究了微波促进的取代酚类化合物的邻甲酰化反应。考察了催化剂种类及其用量、溶剂、1a与多聚甲醛摩尔比（r）、微波辐射功率和辐射时间等对反应的影响。结果表明：以THF为溶剂,MgCl₂/Et₃N（2.5 eq.）为催化剂,r=1/5,在400 W微波功率下辐射反应5 min, 5-氯-2-羟基苯甲醛（2a）的产率为85%,其结构经¹H NMR确证。该反应条件还适用于多种取代酚(1b~1f）的邻甲酰化反应,产率为78%~90%。     

甲壳素类液晶高分子的研究--用CD谱研究N-邻苯二甲酰化壳聚糖溶致胆甾相的形成临界浓度

N邻苯二甲酰化壳聚糖在多种常见有机溶剂中能形成胆甾液晶相.用圆偏光二向色性谱(CD)研究了N邻苯二甲酰化壳聚糖的DMF、DMSO、DMAC和吡啶4种溶剂体系,在形成溶致胆甾液晶相前后的手性变化信息.CD谱图上观测到两类吸收,即在400nm附近较宽的吸收和330nm附近较尖锐的吸收.前者归属于胆甾相层片的超分子螺旋构象,而后者可以归属于分子链的螺旋构象.圆偏光二向色性可以作为测量胆甾液晶临界浓度的一种手段,它能捕捉到胆甾螺旋层片出现那一瞬间的浓度,以CD谱上在波长400nm左右刚出现肩峰的浓度为临界浓度,其值均比偏光显微镜法低1%,说明其灵敏度比偏光显微镜法高,且避免了偏光显微镜法的某种主观性.分别用两种方法旋转玻片进行CD测试,结果证明线性二向色性分量和双折射分量对胆甾层片螺旋的CD信号强度没有大的影响.     

N-取代邻苯二甲酰亚胺类衍生物的设计、合成及活性评价

结合中药脱皮马勃中分离得到的3,5-二羟基邻苯二甲酰亚胺和邻苯二甲酰亚胺类化合物的结构设计合成了一系列N-取代-3,5-二甲氧基邻苯二甲酰亚胺及N-取代-3,5-二羟基邻苯二甲酰亚胺类衍生物,其结构经¹H NMR,¹³C NMR和MS分析确证. 选取人肺腺癌细胞A549及人脐静脉血管内皮细胞HUEVC为测试细胞株,评价了所合成化合物的体外抗肿瘤及抗血管生成活性,结果表明,部分化合物表现出一定的活性.     

灰分分析法测定羧甲基壳聚糖羧甲基取代度

本文建立了表征羧甲基壳聚糖羧甲基取代度的化学分析方法－灰分分析法，并将该方法与元素分析和电位滴定方法进行了比较。统计分析的结果表明，灰分分析方法的精度和准确度要高于电位滴定，其准确度较接近元素分析，是一种准确的分析方法。     

高取代度羧甲基壳聚糖的制备

用非质子溶剂法,以DMSO-H2O为溶剂,在碱性条件下壳聚糖(CTS)与氯乙酸反应,制得取代度为1.93的羧甲基壳聚糖(CMC)。较适宜的反应条件为:CTS 1 g,m(氯乙酸)∶m(CTS)=5∶1,w(NaOH)=35%(以CTS质量计算),w(十六烷基三甲基溴化铵)=5%(以CTS质量计算),于50℃反应6 h。用XRD和IR对CMC进行表征,结果表明CTS的-OH参与了羧甲基化反应,-NH2没有参与反应。     

Preparation and Characterization of Acylated Chitosan

Fully acylated chitosan and N,N-diacyl chitosan were prepared. The products were characterized by elemental analysis, FTIR and IH NMR. The experimental results indicate that the average degree of acylation depends on the volume ratio of pyridine to chloroform in the reaction medium, the chain length of the acylation agent used, and the molecular weight of chitosan raw materials. The XRD measurements were carried out for pure chitosan, fully acylated chitosan and N,N-diacyl chitosan to verify the crystallinity change caused by the acylation.     

High Substitution Synthesis of Carboxymethyl Chitosan for Properties Improvement of Carboxymethyl Chitosan Films Depending on Particle Sizes

This study investigated the effect of chitosan particle sizes on the properties of carboxymethyl chitosan (CMCh) powders and films. Chitosan powders with different particle sizes (75, 125, 250, 450 and 850 µm) were used to synthesize the CMCh powders. The yield, degree of substitution (DS), and water solubility of the CMCh powders were then determined. The CMCh films prepared with CMCh based on chitosan with different particle sizes were fabricated by a solution casting technique. The water solubility, mechanical properties, and water vapor transmission rate (WVTR) of the CMCh films were measured. As the chitosan particle size decreased, the yield, DS, and water solubility of the synthesized CMCh powders increased. The increase in water solubility was due to an increase in the polarity of the CMCh powder, from a higher conversion of chitosan into CMCh. In addition, the higher conversion of chitosan was also related to a higher surface area in the substitution reaction provided by chitosan powder with a smaller particle size. As the particle size of chitosan decreased, the tensile strength, elongation at break, and WVTR of the CMCh films increased. This study demonstrated that a greater improvement in water solubility of the CMCh powders and films can be achieved by using chitosan powder with a smaller size.     

胶体滴定法测定羧甲基壳聚糖的取代度

用胶体滴定法测定羧甲基壳聚糖取代度；讨论pH值、溶液浓度、滴定速度和离子强度对胶体滴定的影响，并比较胶体滴定法、电位滴定法和元素分析法的优劣；结果表明胶体滴定法是一种快速、简便地定量测定CMC取代度的方法，且是测定CMC取代度的优选方法。     

Determination of degree of substitution for N-acylated chitosan using IR spectra

Chitosans with various degrees of deacetylation (D.D.), which were used as standard sample for FTIR determination, were prepared from completely deacetylated chitosan by homogeneous N-acetylation reaction. By combining four probable probe bands, i.e. 1655, 1560, 1380 and 1320 cm-1, eight probable reference bands, i.e. 3430, 2920, 2880, 1425, 1155, 1070, 1030 and 895 cm-1 and two baseline methods, the most suitable ratios Aprobe band/Aeterence band from IR spectra to determine the degree of acetylation of chitosan were evaluated from 48 combinations to be A1560/A2880, A1560/A2920 and A1655/A3430(A1560/A2880 is mostly recommended). The second baseline method, i.e. linking between adjacent two valleys, was better for measuring the absorbances of 1560 and 1655 cm-1 bands. The determination range of the D.D. (1%-100%) covered almost the whole range. The standard curves with A1560/A2880 and A1655/A3430 were also suitable for the determination of degree of substitution of other N-acylated chitosan, such as N-pr     

An Efficient Method for Determination of the Degree of Substitution of Cellulose Esters of Long Chain Aliphatic Acids

The determination of the degree of substitution (DS) of fatty acid cellulose esters, representing a broad range of substituents (C₆, C₁₂, C₁₈ and C₂₂), was performed by alkaline hydrolysis of the ester groups and the quantification of fatty acids by gas chromatography-mass spectrometry (GC-MS) as their trimethylsilyl derivatives. The method was optimized and compared with established techniques for the DS determination (elemental analysis and alkaline hydrolysis/titrimetry). The results demonstrated that alkaline hydrolysis/GC-MS is a rapid, reliable and powerful method for analysis of fatty acid cellulose esters, particularly when different acyl substituents are present.     

高碘酸钠氧化法测定羟丙基瓜尔胶上仲羟基取代度

高碘酸钠氧化可以使邻羟基C-C键发生高选择性断裂, 同时产生两分子醛基. 在pH=4.3及25 ℃的条件下, 对瓜尔胶及其衍生物羟丙基瓜尔胶进行高碘酸钠氧化, 采用红外光谱与核磁共振谱对氧化产物结构进行了表征. 结果表明, 氧化后的瓜尔胶和及羟丙基瓜尔胶结构中醛基主要以半缩醛的形式存在. 通过测定高碘酸钠的消耗量得到不同摩尔取代度羟丙基瓜尔胶糖单元上邻羟基的含量, 结合概率分析方法, 确定摩尔取代度分别为0.04, 0.14, 0.36, 0.51, 0.78, 1.05和1.53的羟丙基瓜尔胶在仲羟基上取代度分别为0.02, 0.09, 0.18, 0.30, 0.46, 0.59和1.03, 与其它方法得到的结果一致.