pH and ionic sensitive chitosan/carboxymethyl chitosan IPN complex films for the controlled release of coenzyme A

pH and ionic sensitive interpenetrating polymer network (IPN) complex films based on chitosan (CS) and carboxymethyl chitosan (CM-CS) were prepared by using glutaraldehyde as crosslinking agent. Its structure was characterized by FT-IR, which indicated that the IPN was formed. The films were studied by swelling, weight loss with time, and release of coenzyme A (CoA). It was found that the IPN films were sensitive to pH and ionic strength of the medium. The cumulative release rate of CoA decreased with CoA loading content, ionic strength or crosslinking agent increasing. The composition of the IPN films and pH of release medium also had significant effect on the release of CoA. The differences in the rates and amounts of released CoA may be attributed to the swelling behavior, the degradation of films, and interaction between drug molecule and polymer matrix. These results suggested CS/CM-CS IPN films could be used as drug delivery carrier.     

光交联壳聚糖膜的制备及其性能研究

成功制备了光交联壳聚糖膜,并用傅立叶红外光谱(FTIR)和扫描电子显微镜(SEM)方法对其结构进行了表征,并测试了其力学性能。结果表明:光交联作用明显提高了膜的抗张强度和抗水性,并有效地降低了溶菌酶对其降解速率。该光交联膜有望用作可控降解生物医用材料。     

Thermal stability and degradation products analysis of benzocyclobutene-terminated imide polymers

Benzocyclobutene-terminated imides were prepared and fully characterized with ¹H NMR, MS, and FT-IR. The thermal degradation of polymers was investigated by using thermogravimetric analyzer (TGA) and high-resolution pyrolysis-gas chromatography–mass spectrometry (HR-Py-GC–MS). TGA showed that thermal degradation of the polymer was a single-stage process in N₂, whereas a three-stage degradation in air atmosphere. The major involved products were found to be CO₂, naphthalene and naphthalene derivatives. Degradation mechanism of the polymer was suggested and the relationship between structures of the polymer and degradation products was also discussed.     

交联壳聚糖膜的制备及其性能的研究

用环氧氯丙烷成功地制备出交联壳聚糖膜。用FTIR,XRD和SEM方法表征其结构,并测试了其力学性能。结果表明,壳聚糖在低温下只有氨基参与交联反应,反应温度高于40℃时,羟基才发生反应;环氧氯丙烷的交联作用显着提高了壳聚糖膜的抗张强度,并有效地降低了溶菌酶对其降解速率;该交联膜有望用作可控降解的生物医用材料。     

Synthesis and characterization of a new conducting polymer composite

Organic conductive composite films have been synthesized by electropolymerization of pyrrole in the presence of chitosan and p-toluene sulfonic acid sodium salt. The obtained conductive polymer composite films have been characterized by Fourier Transform Infrared spectroscopy, dynamic mechanical analysis, scanning electron microscopy, X-ray diffraction and conductivity measurements. The prepared polymer composite films had the amorphous structure and exhibited the enhanced conductivity and mechanical properties due to the presence of chitosan in the composite films.     

The study of the interaction between chitosan and 2,2-bis(hydroxymethyl)propionic acid during solid-phase synthesis

New polymer salts and N-acetylated chitosan derivatives are prepared in an extruder by the method of solid-phase synthesis via the interaction of chitosan and 2,2-bis(hydroxymethyl)propionic acid. The effect of the initial component ratio and temperature on the yield and structure of the target products is studied. Joint deformation of solid components at room temperature is found to cause the quantitative formation of salt bonds between carboxylic groups of the acid and amino groups of chitosan. At elevated temperatures of synthesis, the corresponding acetylated derivatives with a degree of substitution of amino groups varying from 0.16 to 0.43 are prepared. The relaxation and phase transitions in the polymer salts and acetylated chitosan derivatives and their sorptional activity are studied. The films prepared from aqueous solutions of the new salt modification of chitosan are characterized by a homogeneous structure and improved mechanical characteristics relative to those of the films based on chitosan acetates. An additional thermal treatment of the products of the solid-phase synthesis leads to the formation of crosslinked and water-swollen materials that can be used for the development of novel polymeric chitosan-based membranes and sorbents.     

溶胶-凝胶法制备壳聚糖/SiO2杂化材料

以正丁酐（Butyric anhydride)、壳聚糖(Chitosan）、甲基丙烯酰氧基丙基三甲氧基硅烷（MPTMS）、正硅酸乙酯（TEOS）为原料,采用迈克尔加成反应合成了丁酰壳聚糖-MPTMS,配合酸催化sol-gel过程,制备了透明的壳聚糖/SiO2杂化材料,FTIR表征了杂化材料的结构。TGA,SEM以及力学性能测试结果表明,杂化材料的成型工艺对材料的表面形貌、热分解温度以及力学性能的影响显著。     

Vitamin A and vitamin E interaction behavior on chitosan microspheres

Chitosan is a biodegradable natural polymer with great potential for pharmaceutical applications due to its biocompatibility, high charge density, and non-toxicity. In this study, chitosan microspheres were successfully prepared by an adapted method of coagulation/dispersion. The degree of deacetylation of chitosan powder was obtained by NMR ¹H and FTIR techniques. Chitosan powder and chitosan microspheres were characterized by BET surface area and scanning electron microscopy (SEM). The interactions among the chitosan microspheres and the vitamins A and E were characterized by FTIR. In order to evaluate the ability of interaction of vitamin A and vitamin E with the chitosan microspheres, the thermodynamic parameters were followed by calorimetric titration. Different experimental approaches were applied, such as adsorption isotherms, kinetics and thermodynamics studies. The obtained results showed that the interactions of chitosan microspheres with the vitamins were spontaneous, enthalpically and entropically favorable, indicating that the chitosan microspheres can be used with success in the controlled release of these vitamins.     

Preparation, characterization and biodegradation of biopolymer nanocomposites based on fumed silica

PLA and PCL based nanocomposites prepared by adding three different types of fumed silica were obtained by melt blending. Materials were characterized by means of Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Dynamic–Mechanical Thermal Analysis (DMTA).A good distribution of the fumed silica into both polymer matrices was observed. The highest thermo-mechanical improvements were reached by addition of the fumed silica with higher surface area. PLA and its nanocomposites were degraded in compost at 58 °C; at this temperature all samples presented a significant level of polymer degradation, but a certain protection action of silica towards PLA degradation was observed, whereas the addition of fumed silica did not show considerable influence on the degradation trend of PCL. These dissimilarities were attributed to the different degradation mechanism of the two polymers.     

磁性Fe3O4 /壳聚糖的化学修饰及包覆机理研究

Nano-sized Fe₃O₄ powder was prepared through an Oxygenation-Hydrothermal method. The chitosan magnetic complex was prepared by coating chitosan on the surface of Fe₃O₄ powders through Microlatex-Crosslinking Method. The product was characterized by IR， XRD， TEM， Vibrating Sample Magnetometer (VSM)， TG methods. Results show that the as-prepared powder is 25 nm in size and shows supermagnetism. The content of magnetite in microspheres is 37.8%. The mechanism for the coating reaction of chitosan to Fe₃O₄ nanoparticles is also suggested.     

壳聚糖吸附Cd2+的机理

壳聚糖分子中的大量氨基及部分酰胺基的存在 ,能够选择性地配位或吸附一些金属离子 ,尤其是对过渡金属离子具有较好的螯合能力。Ｐｉｒｏｎ等[2 ] 利用放射性85Ｓｒ研究了壳聚糖的氨基与碳酸锶离子对Ｓｒ2 +、ＣＯ2 -3 之间形成的三元络合物的结构。季君晖[3] 通过光电子能谱研究发现 :壳聚糖螯合Ｃｕ2 +,只与壳聚糖中的—ＮＨ2 配位。Ｔｓｅｚｏｓ[4] 利用ＩＲ、ＭＳ和ＥＰＲ说明铀与壳聚糖的络合点为氨基的氮原子。Ｇｕｉｂａｌ等[5] 用ＩＲ、ＣＰ ＭＡＳ1 3ＣＮＭＲ及反射光谱法证实吸附机理涉及氨基。含镉废水是危害较大的工业废水之一 …     

铅离子印迹聚合物的制备、表征及其在水溶液中的吸附行为研究

以Pb2+为模板,壳聚糖为单体,硅胶为载体,γ-(2,3环氧丙氧)丙基三甲氧基硅烷(KH-560)为偶联剂,利用表面分子印迹技术和溶胶-凝胶法制备了Pb2+ 印迹聚合物.采用傅立叶变换红外光谱法(FT-IR)、紫外光谱法、扫描电镜对Pb2+ 印迹和非印迹聚合物的表面形貌和结构进行表征;并用电感耦合等离子体原子发射光谱法考察了吸附酸度、吸附剂用量、静置时间等对聚合物吸附性能的影响;研究了印迹聚合物在混合溶液中对Pb2+ 的选择性,比较了印迹和非印迹聚合物的吸附容量;并提出了印迹聚合物的印迹吸附机理.在最佳吸附酸度pH=4.5时,0.3 g 吸附剂吸附5 h达到平衡,Pb2+印迹聚合物对模板离子具有较高的选择性,其饱和吸附容量是非印迹聚合物的2倍.     

甲壳素类液晶高分子的研究Ⅷ. N-邻苯二甲酰化壳聚糖/DMSO液晶溶液的热致相转变

合成了氮上完全取代的邻苯二甲酰化壳聚糖 (PhthCS) .用DSC研究了PhthCS DMSO液晶溶液的热致相转变 .偏光显微镜和DSC测定都表明临界浓度为 43wt% .在浓度高于 43wt%的溶液的DSC曲线中观察到了除了液晶 各向同性液体转变 (清亮点 )外还有一个明显的凝胶 溶胶转变 .凝胶 溶胶转变温度和转变焓均比文献报道的不规则取代的N 邻苯二甲酰化 O 乙酰化壳聚糖大得多 ,可见取代的规整性对凝胶 溶较转变有很大的影响 .根据DSC研究结果绘制了PhthCS DMSO体系的相图     

Binding cellulose and chitosan via click chemistry: Synthesis,characterization, and formation of some hollow tubes

A novel cellulose‐click‐chitosan polymer was prepared successfully in three steps: (1) propargyl cellulose with degrees of substitution (DS) from 0.25 to 1.24 was synthesized by etherification of bamboo Phyllostachys bambusoide cellulose with propargyl chloride in DMA/LiCl in the presence of NaH. The regioselectivity of propargylation on anhydrous glucose unit determined by GC‐MS was in the order of 2 >> 6 > 3; (2) the functional azide groups were introduced onto the chitosan chains by reacting chitosan with 4‐azidobenzoic acid in [Amim]Cl/DMF and the DS ranged from 0.02 to 0.46; (3) thus, the cellulose‐click‐chitosan polymer was obtained via click reaction, that is, the Cu(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction, between the terminal alkyne groups of cellulose and the azide groups on the chitosan backbone at room temperature. The successful binding of cellulose and chitosan was confirmed and characterized by FTIR and CP/MAS ¹³C NMR spectroscopy. TGA analyses indicated that the cellulose‐click‐chitosan polymer had a higher thermal stability than that of cellulose and chitosan as well as cellulose–chitosan complex. More interestingly, some hollow tubes with near millimeter length were also observed by SEM. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effects of ionic strength on the size and compactness of chitosan nanoparticles

In this work, chitosan nanoparticles were prepared by ionotropic gelation of chitosan with tripolyphosphate (TPP). The effects of the ionic strength of the solvent employed in the particle preparation on the average size and compactness of the particles were investigated. In addition, the effects of the chitosan concentration and the crosslinker to polymer ratio on the particle characteristics were studied. The chitosan–TPP nanoparticles were characterized by dynamic light scattering, zeta potential, and turbidity measurements. The compactness of the nanoparticles was estimated with a method based on the size of the nanoparticles and the turbidity of the nanoparticle suspension. All the investigated preparation parameters, i.e., the ionic strength of the solvent, the chitosan concentration, and the TPP to chitosan ratio, affected the particle characteristics. For instance, smaller and more compact particles were formed in saline solvents, compared to particles formed in pure water. Further, the addition of monovalent salt rendered it possible to prepare particles in the nanometer size range at a higher polymer concentration. Solvent salinity is thus an important parameter to address in the preparation of chitosan nanoparticles crosslinked with TPP.     

Preparation and characterization of collagen/chitosan poly (ethylene glycol)/nanohydroxyapatite composite scaffolds

Porous three‐dimensional collagen/chitosan scaffolds combined with poly (ethylene glycol) (PEG) and hydroxyapatite were obtained through a freeze‐drying method. Physical cross‐linking was examined by dehydrothermal treatment. The prepared materials were characterized by different analyses, eg, scanning electron microscopy (SEM), measurements of porosity and swelling, mechanical properties, and resistance to enzymatic degradation. The porosity of scaffolds and their swelling ratio decreased with the addition of hydroxyapatite. Moreover, after exposure to collagenase, the collagen/chitosan matrices containing PEG showed much faster degradation rate than matrices with the addition of hydroxyapatite. The results indicated that the addition of hydroxyapatite led to improvement of stiffness. The highest degree of porosity and swelling were demonstrated by collagen/chitosan/PEG matrices without hydroxyapatite.     

Preparation and Characterization of Quaternized Chitosan Under Microwave Irradiation

For the first time, N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) was prepared through a fast, easy and efficient method with the assistance of microwave irradiation, and the quaternized chitosan was also degraded via the microwave irradiation. A comparative study was performed by using the conventional heating method to prepare HTCC. The structure and property of the quaternized chitosan obtained by these two methods were characterized by GPC, XRD, FTIR, NMR, TG and elemental analysis. It was shown that quaternized chitosan was successfully prepared within 50 min via microwave irradiation method, while a much longer time of 6–7 h was needed with the conventional heating method. The substitutions both occurred on the C2 position of chitosan with the two different methods, and their HTCC products had weight average similar molecular weight (Mw), structure and thermal stability. The HTCC prepared by the microwave irradiation method had a little lower degree of substitution (DS) than those prepared via conventional heating with the same mole ratio (6:1) of the intermediate to chitosan. The degradation study showed that the Mw of HTCC decreased rapidly from 4.6 × 10⁵ to 1.1 × 10⁵ in 1 h under microwave irradiation, while it only decreased from 4.6 × 10⁵ to 2.1 × 10⁵in 1 h through conventional heating degradation. These results revealed that microwave irradiation is a more efficient and environment-friendly way to obtain the water-soluble chitosan derivatives and their degraded products.     

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     

Structure and characteristics of chitosan-based fibers containing chrysotile and halloysite

With the use of the methods of X-ray diffraction and electron microscopy, chitosan fibers prepared by coagulation into an alcohol-alkali mixture are shown to possess a two-phase structure containing C- and O-type crystallites. These fibers and composite fibers containing halloysite and Mg chrysotile nanotubes are characterized by anisotropic structure, i.e., by the orientation of both chitosan crystallites and Mg chrysotile particles along the fiber axis. A comparison of the rates of shear induced by passing of a polymer solution through a die and the data of rheological studies allows the conclusion that the structuring of chitosan solution under the applied field of shear stresses and the orientation of polymer macromolecules and filler nanotubes occur. An increase in the draw ratio during fiber spinning does not assist orientation of polymer crystallites but, in contrast, increases surface defectiveness and leads to the nucleation of longitudinal cracks; as a result, the strength of fibers decreases. The introduction of 5 wt % Mg chrysotile into the chitosan matrix markedly increases the mechanical characteristics of the composite fibers owing to the reinforcing action of oriented filler nanotubes.     

Synthesis and Flocculation Property of Chitosan-Acrylamide Graft Copolymer

Chitosan, as a kind of natural polymer, has many advantages, such as abundant sources, biological degradation, no secondary contamination and facile modification. In this work, we prepared modified chitosan flocculants with double electrical behavior via polymerizing chitosan, acrylamide and sodium carboxymethyl cellulose together by using ammonium persulfate as the indicator in water. The product is a comb-type of chitosan copolymer and a polymeric ampholyte. And then we studied the product by FTIR, UV-Vis, TG, DSC spectrometeries and viscometry, etc. We also performed CACM‘s water treat experiment. The effects of pH values, reaction time and dose of the new floccalant on treating various of waste water have been investigated, too.