Synthesis and Characterization of a Novel Liquid Crystalline Chitin Quaternary Ammonium Chitosan Salt

N -Butyl chitosan(NBCS) derivatives were prepared by introducing butyl groups into the amine groups of chitosan via Schiff base intermediates. The quaternization of NBCS was carried out by using ethyl iodide to produce water-soluble cationic polyelectrolytes. The degree of the substitution of the products was measured by means of the electron spectroscopy for a successful chemical analysis. The quaternary ammonium chitosan salt(QACS) was proved to be a novel cholesteric liquid crystalline chitin, by means of the polarized optical microscopy and the circular dichroism spectropolarimetry. The critical mass fraction of the QACS/formic acid solution forming a lyotropic liquid crystal phase was 50%, which was almost the same as that of the NBCS/formic acid solution, but much higher than that of the chitosan in the same solvent.

LYOTROPIC LIQUID CRYSTALLINE BEHAVIOR OF FIVE CHITOSAN DERIVATIVES

Five chitosan derivatives, i.e. O-butyryl chitosan, O-benzoyl chitosan, N-phthaloyl chitosan, N-maleoyl chitosan and O-cyanoethyl chitosan, were prepared from chitosan. All of them had better solubility than chitosan, and demonstrated lyotropic liquid crystalline behavior in various solvents. The critical liquid crystalline behavior of three O-substituted chitosan derivatives was evidently different from two N-substituted analogues. Typical fingerprint textures of cholesteric phase were only observed in three O-substituted derivatives. The critical concentration (v/v%) of three O-substituted derivatives does not depend on the acidity of acidic solvents.

CHOLESTERIC LIQUID CRYSTALLINE CHARACTER ON THE SURFACE OF CHITOSAN/POLYACRYLIC ACID COMPOSITES

The cholesteric liquid crystalline structure in chitosan/polyacrylic acid composite films was studied by surface techniques. A periodical lamellar-like structure was observed in the permanganic acid etched film surface by both scanning electron microscopy (SEM) and atomic force microscopy (AFM), instead of the thumb-print texture which can be detected with polarized optical microscopy. It is suggested that the periodical lamellar-like structure is induced by the etching selectivity between cholesteric layers due to different molecular arrangement on the film surface. Four kinds of perpendicular disclinations, i.e. chi --> tau (-) + lambda (+), chi --> lambda (-) + tau (+), chi --> tau (-) + tau (+) and chi --> lambda (-) + lambda (+) were found in the composite films from SEM observations. The smallest periodicity of lamellar-like structure (equals to half pitch) is 20 similar to 40 nm measured with AFM.

O-Alkylation of Chitosan for Gene Delivery by Using Ionic Liquid in an in- situ Reactor

An in-situ reactor was elaborately designed for O-alkylation of chitosan in an ionic liquid ([BMIM]Cl) solvent, using N, N'-carbonyldiimidazole? as bonding agent. The original chitosan and the modified chitosan were characterized by FT-IR and XRD analysis. FT-IR spectra revealed that the alkylation of chitosan selectively occurred at hydroxyl groups, with unprotected amino groups untouched. It was proposed that the particular properties of the ionic liquid solvent should be responsible for the selectively alkylation. The result from X-ray diffraction showed that the crystallinity of O-alkylation of chitosan decreases, most likely due to the decomposition of CS in the ionic liquid. The solubility test of O-alkylated chitosan in aqueous HAc solution (w/w: 0.1%) confirmed that the product could be easily dissolved in aqueous HAc solution because of its abundant free amino groups. It was suggested that the O-alkylated chitosan was suitable for the coming cell transfection test in vitro.

MORPHOLOGICAL STUDY ON THE ORIENTED CHITOSAN FILM OBTAINED FROM PRE-SHEARED LIQUID CRYSTALLINE SOLUTION IN DICHLOROACETIC ACID

The oriented chitosan films obtained from pre-sheared liquid crystalline chitosan/dichloroacetic acid (DCA) solutions were studied by means of polarized optical microscopy (POM), scanning electron microscopy (SEM), infra-red dichroism technique and wide angle X-ray diffraction (WAXD). The sheer induced band texture in the film was found to correspond to the sinusoidal fibrillar microstructure along the shearing direction on the basis of POM and SEM observations. The sinusoidal fibril was found to be lying within the film plane. The model of chitosan molecular orientation in the pre-sheared film with band texture can be established assuming that the main chain orients in the shearing direction and the side group is perpendicular to the shearing direction. The WAXD azimuthal scanning at 2 theta = 20 degrees indicates that the (002) plane orients perpendicular to the shearing direction.

INFLUENCE OF MOLECULAR WEIGHT OF CHITIN AND ITS THREE DERIVATIVES ON CRITICAL CONCENTRATION OF LYOTROPIC LIQUID CRYSTALLINE PHASE TRANSITION

The critical concentration of lyotropic liquid crystalline phase transition for chitin derivatives was determined using a polarization microscope. The influence of molecular weight on critical concentration of liquid crystalline solution for chitin, chitosan, cyanoethyl chitosan and propionyl chitin successively increases as the chain rigidity decreases. Therefore it can be used as an indicator of the chain rigidity.

Preparation of CTS Coatings Containing Calcium and Phosphorus on Titanium Surface by the Cathode Liquid Phase Plasma Technology

Chitosan （CTS） coatings contained calcium （Ca） and phosphorus （P） on titanium （Ti） surface are prepared by the cathode liquid phase plasma technology （CLPT）, in a certain concentration electrolyte solution with selective additions of ammonium dihydrogen phosphate and calcium nitrate. It is indicated that the parameters for a stable discharge are voltage of 400 V, frequency of 100 Hz, duty cycle of 30% based on a large amount of experiment data. The morphology, structure and composition of the coated samples are studied by SEM, FTIR, XRD, XPS. The results demonstrate that the composite coatings are uniform, and some solid particles of inorganic salt containing calcium and phosphorus dispersed on the coatings. CA tests show that the samples treated by the liquid plasma became less hydrophilic. The variation of hydrophilicity on the CLPT treated titanium is attributed to the change of the function groups on the sample surface. Meanwhile, a possible formation mechanism of the composite coatings is discussed.

壳聚糖液晶膜生物相容性的研究

壳聚糖因具有良好的生物相容性、生物可降解性、无口服毒性等而广泛应用于组织工程领域。近年来一些研究表明,液晶态普遍存在于生命体中。本研究从仿生角度出发,制备出壳聚糖液晶薄膜。采用偏光显微镜和动态接触角测定仪分别研究其织构和亲水性能,并通过体外细胞培养法研究了生物相容性。实验结果表明,壳聚糖液晶薄膜呈现典型的胆甾相液晶织构,与非液晶薄膜相比,它不仅具有更好的亲水性能,而且能更好地促进L929细胞黏附、生长、增殖及分化,表现出良好的生物相容性。本研究为开发新型生物材料和更好地模拟体内微环境提供了新的思路。

一种新的液晶高分子──丁酸壳聚糖的合成与表征

Butyryl chitosan was synthesized and characterized by using FTIR, DSC, WAXD and PLM. Liquid crystallinity of butyryl chitosan was first reported in this paper. Comparing with chitosan, thermal stability and crystallinity of butyryl chitosan decreased but solubility increased, because hydrogen bond interactions between macromolecules were disrupted.

壳聚糖对药液絮凝作用的研究

以壳聚糖为絮凝剂，研究了它对丹参水提液的絮凝情况。比较了絮凝剂加入量不同和分子量不同时，絮凝物的沉降速率，从而考察了它们对絮凝效果的影响以及所得产品的质量。探讨了在高分子絮凝剂浓度不同时的絮凝机理，对影响絮凝效果的因素作出了合理的解释。

N-烷基壳聚糖的合成及其溶致液晶行为

合成了一系列具有不同取代基甲基、乙基、丙基、丁基的壳聚糖衍生物——N烷基壳聚糖,通过控制反应物摩尔比获得了一系列不同取代度的产物.不同取代基及不同取代度的衍生物均具有溶致液晶性,考察了同一碳链不同取代度和相近取代度不同碳链长度的衍生物对其液晶临界行为的影响.结果表明:同一碳链长度时,取代度对临界浓度的影响不大;而当取代度相近时,随着碳链长度增加,临界浓度也随之增大.此结果与Onsager和Flory的刚性棒理论相符.粉末X射线衍射实验进一步证实了这一结果.

甲壳素类液晶高分子研究——低分子量壳聚糖溶致液晶性及分子量对液晶临界浓度的影响

研究了两种用酶降解法得到的低分子量壳聚糖样品(CS1和CS2)的溶致液晶性.用GPC并辅以质谱法确定了两样品的数均相对分子质量为622和2311 g/mol.在相对分子质量低至622的低分子量壳聚糖(相当于四糖)水溶液中仍发现了溶致液晶现象,并确定出相对分子质量为622和2311的低分子量壳聚糖液晶临界浓度为73%和36%(W/W%),这些结果与已报道的中、高分子量壳聚糖液晶临界浓度随分子量升高而降低的基本规律是一致的.实验结果与经典的KS理论预测值不符,因为低分子量壳聚糖的相对分子质量超过了KS理论对高分子临界浓度的预测范围.

一种制备丁二酰化壳聚糖的新方法

合成了甘氨酸盐酸盐离子液体([Gly]Cl),由1H-NMR对其结构进行了确证,并以其质量分数2%的水溶液为反应介质,制备水溶性丁二酰化壳聚糖。用XRD和FT-IR对产物进行了表征,结果表明:壳聚糖(CS)中引入了丁二酰基,并削弱了壳聚糖分子内和分子间的氢键作用,大大改善其水溶性。考察了反应时间、温度和反应物配比对丁二酰化壳聚糖取代度(DS)的影响,得到较佳的反应条件:反应时间4h,n(丁二酸酐):n(壳聚糖)=2.75,反应温度40℃,在该条件下丁二酰化壳聚糖的取代度达到90%以上。离子液体具有重复使用性,反应后的离子液体未经处理重复使用3次后,丁二酰化壳聚糖的取代度仍大于90%。

氨基酸离子液体对壳聚糖溶解性能的影响

合成了一系列氨基酸类离子液体,从中筛选出对溶解壳聚糖具有良好性能的离子液体——甘氨酸盐酸盐离子液体。在常温常压下考察了该离子液体1%～10%水溶液对壳聚糖的溶解能力,溶解壳聚糖能力最大能达到6.32%(质量分数,下同)。对离子液体重复使用5次后,溶解能力没有明显下降。采用X射线衍射(XRD)和红外光谱(FT-IR)对再生的壳聚糖进行表征,结果表明,壳聚糖在溶解过程中没有发生衍生化。甘氨酸盐酸盐离子液体水溶液是壳聚糖的良溶剂。

纤维素/壳聚糖复合材料的制备与应用研究进展

纤维素/壳聚糖复合材料利用纤维素提高了共混材料的力学性能,同时保持了壳聚糖优良的生物相容性和抗菌性,无毒无污染。但是二者分子内和分子间含有大量的氢键,使得在水和常规有机溶剂中很难溶解,限制了复合材料的加工和应用,离子液体的出现为二者的溶解和复合提供了新的思路。综述了纤维素/壳聚糖复合材料的制备方法、制备体系及在工业吸附、生物医疗、食品包装和纺织工业领域的应用,重点介绍了离子液体在此复合材料制备过程中的应用,以为纤维素/壳聚糖复合材料的制备工艺和应用发展提供参考。

在氨基酸离子液体中均相合成马来酰化壳聚糖

合成了氯化2-氨基乙酸离子液体([Gly]Cl),由FTIR、1HNMR对其结构进行了确证,并以其质量分数2%的水溶液为反应介质,制备水溶性马来酰化壳聚糖(MACH)。用XRD和FTIR对产物进行了表征,测试结果表明:壳聚糖(CS)中引入了马来酰基,并且反应主要发生在氨基上。考察了反应时间、温度和反应物摩尔比对马来酰化壳聚糖取代度(DS)的影响,得到较佳反应条件为:n(马来酸酐)/n(壳聚糖)=2.5、反应温度60℃,反应时间5h,在该条件下马来酰化壳聚糖的取代度达90%以上。离子液体[Gly]Cl具有重复使用性,反应后的离子液体未经处理重复使用3次后,马来酰化壳聚糖的取代度仍大于89%。

N-苄基壳聚糖液晶材料的制备及表征

以甘氨酸和质量分数36%盐酸为原料合成出甘氨酸盐酸盐离子液体,利用间歇碱处理方式对壳聚糖原料进行处理,制备出脱乙酰度可达92.2%的高脱乙酰度壳聚糖。采用N-烷基化化学改性方法,使苯甲醛与高脱乙酰度壳聚糖分别在乙酸和甘氨酸盐酸盐离子液体两种溶剂中进行反应,制备N-苄基壳聚糖。红外光谱测试表明:由这两种方法制备出的产物均为N-苄基壳聚糖,证明了甘氨酸盐酸盐离子液体是壳聚糖的良溶剂。用偏光显微镜测得N-苄基壳聚糖在二氯乙酸中形成液晶相的临界质量分数为10.0%,形成的液晶相为胆甾相。

N-苄基壳聚糖的合成和液晶性表征

合成了新的液晶性壳聚糖衍生物—— N-苄基壳聚糖 ,N-苄基壳聚糖 /二氯乙酸浓溶液呈现液晶相 .用偏光显微镜测得形成液晶有序的临界浓度为 9% (重量百分数 ) .在溶液的红外光谱中 ,二氯乙酸的羰基吸收谱带 1738cm-1在相变时位移到 1731cm-1.利用这一突变测得 N-苄基壳聚糖的临界浓度为 10 % ,与光学显微镜法基本相符 .

壳聚糖溶致液晶性的研究

将壳聚糖溶于体积分数36%的乙酸溶液中浇涛制膜,在干燥下壳聚糖质量分数达到一定的临界质量分数形成溶致液晶.利用FTIR仪、原子力显微镜和X 射线衍射仪为表征手段,研究了壳聚糖溶致液晶相转变过程中分子间的相互作用以及液晶相微观结构的变化.结果表明,在该薄膜中有被冻结的液晶滴状结构,随着溶剂的挥发,膜体系内氢键的种类和数目发生改变,壳聚糖胶束颗粒聚集成圆盘或六角状,体现为同心环堆积,一定时间后转变为立方环状结构.这种液晶结构是壳聚糖胶束颗粒在分子间的相互作用下形成的自组装构型,是一种非平衡状态下的耗散结构.

以[Gly]Cl离子液体为溶剂制备壳聚糖纤维

以甘氨酸和36%盐酸为原料合成出甘氨酸盐酸盐离子液体,并采用间歇碱处理方式对壳聚糖原料进行处理,制备出高脱乙酰度壳聚糖。将高脱乙酰度壳聚糖溶解于离子液体的水溶液中制备出合适黏度的纺丝液,经湿法纺丝将其纺制成纤维,再对纤维进行一定程度的表面交联,可得到较好力学性能的壳聚糖纤维。结果表明,壳聚糖的质量分数(相对于3%离子液体水溶液)为6.5%,溶解温度40℃,溶解时间6 h,凝固浴中无水乙醇与5%Na2SO4水溶液的体积比为50∶50时,在此条件下制得的纤维的断裂强度为0.307 CN/dtex,断裂伸长率为35.93%,经交联处理后纤维的断裂强度达1.977 CN/dtex。