壳聚糖稀溶液性质的研究

本文在前工作基础上.对不同脱乙酰度壳聚糖在0.2mol/l CH_3COOH+0.1mol/l CH_3COONa的缓冲溶液中进行了分子量、特性粘数、分子尺寸、第二维利系数和扩张因子等稀溶液性质的深入研究.发现Mark-Houwink方程常数K和α有规律地依赖于壳聚糖的脱乙酰度而变化.而且相同分子量时,随着脱乙酰度的增加,壳聚糖在稀溶液中的分子尺寸、特性粘数和扩张因子等增加,而特性比和空间位阻因子随着脱乙酰度的增加而减小.     

ASSOCIATION OF ETHYLENE—VINYL ACETATE COPOLYMER IN DILUTE SOLUTIONS Ⅲ. CRITICAL ASSOCIATION CONCENTRATION*

Association behavior of ethylene vinyl acetate (EVA) copolymer in foursolvents 1, 2-dichloroethane (DCE), cyclohexane (CYH), xylene (XYL) and chloroform(CF) has been investigated by dilute solution viscometry The critical association concen-tration (C_A) was determined at which the incipient decrease in slope of the η_(sp)/C～ Ccurve in solutions at the dilute regime. Our results showed that whether the CA couldexist depends on solvent property. The values of CA in DCE increase with increasing, oftemperature and vinyl acetate (VA) content in EVA and decreasing of molecular weight ofEVA.     

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 solubilitythan chitosan, and demonstrated lyotropic liquid crystalline behavior in various solvents. The critical liquidcrystalline 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 dependon the acidity of acidic solvents.     

COMPUTER SIMULATION OF A SINGLE POLYMER CHAIN IN DIFFERENT SOLVENTS

In the present paper, the behavior of a single polymer chain under various solvent conditions was modeled by self-avoiding walks (SAW) with nearest neighbors attraction Δε on a simple cubic lattice. Determination of the θ-condition wasbased on the numerical results of the mean square radius of gyration and end-to-end distance. It was found that at the θtemperatue Δε/kT equals -0.27. The exponents a in the Mark-Houwink equation with different interaction parameters areconsistent with the results of experiments: under θ-condition, a = 0.5, and for a good solvent α= 0.74-0.84, respectively.     

平菇多糖稀溶液行为的研究

平菇多糖属生物高分子, 文章对平菇多糖稀溶液性质进行了研究。实验系采用Elias浊点滴定法测定平菇多糖溶液的θ组成, 用快速动态膜渗透计和粘度法测定平菇多糖的数均分子量、维利系数与分子链的构型参数。探讨其在θ条件下的分子形态及用Tung函数法等处理分级数据, 从而获得平菇多糖的分子量分布。     

CROSS-LINKING OF CHITOSAN WITH GLUTARALDEHYDE IN THE PRESENCE OF CITRIC ACID——A NEW GELLING SYSTEM*

The procedure for preparing a new type of uniform and porous chitosan gel from citric acidmedium is described. Its swelling behavior in different media was compared with those of the gels preparedby other methods. The ultrastructure of the xerogel prepared from citric acid was characterized using electronmicroscopy (SEM).     

壳聚糖在二氯乙酸中的溶致液晶性

制备了不同脱乙酰度和分子量在１－３ ～１５－１ ×１０５ 范围内的壳聚糖样品,并用傅里叶变换红外光谱法（ＦＴＩＲ）和粘度法进行了表征．借助偏光显微镜研究了不同壳聚糖样品在二氯乙酸中的液晶相转变和液晶状态．实验结果表明,分子量在１０５ ～１０６ 范围内的增大使壳聚糖形成液晶相的临界浓度（ Ｃ＊ ） 略有降低;脱乙酰度在７０ ～９０ ％ 范围内,对Ｃ＊ 的影响基本可以忽略．临界浓度的实验值与根据Ｋｈｏｋｈｌｏｖ Ｓｅｍｅｎｏｖ Ｏｄｉｊｋ 理论预示的值比较一致,说明蠕虫链模型可以很好地描述壳聚糖分子链在二氯乙酸中的溶致液晶行为．     

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 surfacetechniques. A periodical lamellar-like structure was observed in the permanganic acid etched film sufface by both scanningelectron microscopy (SEM) and atomic force microscopy (AFM), instead of the thumb-print texture which can be detectedwith polarized optical microscopy. It is suggested that the periodical lamellar-like structure is induced by the etchingselectivity between cholesteric layers due to different molecular arrangement on the film surface. Four kinds of perpendiculardisclinations, i.e. χ→τ→λ~+, χ→λ+τ~+, χ→τ+τ~+ and χ→λ~- +λ~+, were found in the composite films from SEMobservations. The smallest periodicity of lamellar-like structure (equals to half pitch) is 20～40 nm measured with AFM.     

VISCOSITY BEHAVIOR OF PS／TOLUENE SOLUTION IN DILUTE AND EXTREMELY DILUTE CONCENTRATION REGION

The influences of both the volume of PS/toluene solution in the Ubbelohde viscometer and the precision of the time measuring on the viscosity behavior in dilute and extremely dilute concentration region are investigated. It was found that the influence of the former can neglect, but that of the latter is so prominent that the data fluctuate bitterly and linearity of the curve of the reduced viscosity vs. concentration (ηsp/c-c) becomes too bad to obey the Huggins equation down to the extremely dilute region, despite the error of the flow times Δt≤0.2s, which is permitted by the conventional method of viscosity measurement. Through strict mathematical analyses, it was found that the error (E) of the reduced viscosity is in proportion and inverse propor tion to Δt and concentration c, respectively. So the less the concentration, the more the error is. Consequently, a lowest concentration limit cL corresponding to given experimental error may exist and it will be meaningless for further operation below CL because of the great fluctuation of the data. Therefore, it needs to seriously reconsider the application of the conventional method of Ubbelohde viscosity measurement in the extremely dilute polymer solution under traditional conditions because of the great influence of the experimental error.     

VISCOSITY BEHAVIOR OF PS/TOLUENE SOLUTION IN DILUTE AND EXTREMELY DILUTE CONCENTRATION REGION

1.INTRODUCTIONAsearlyas1950sitwasfoundthatsolutionviscosityofasinglepolymerinextremelydiluteconcentrationregionusuallyrevealssomeabnormalities,i.e.,thereducedviscosityconcentration(hsp/c~c)curvesdeviatefromlinearrelationshippredictedasHugginsequationandshoweitheranupwardoradownwardturnasconcentrationisverylow[1].Evenifforthe[()-0.2()]identicalPMMA/toluenesolution,therearetwocontraryresults:onereportedthecurvebendsupward[2],whiletheotherfounditdownward[3].Inordertointerpretthisabnormalphe…     

香云多糖的分子表征和稀溶液性质研究

香菇和云芝是一类高等腐生真菌,菌种系由树上采集的子实体分离得到,由菌种培养得到的香菇和云芝菌丝体可以用来提取香云多糖。据国内外文献报道,香云多糖不仅对多种疾病有较好的疗效,而且还具有强烈的抑瘤作用。近年来国内外学者对其化学特性进行了研究,发现由不同的培养方法和经不同的纯化处理可以得到不同的产物。Sasaki的研究指出,香云多糖的抗肿瘤活性是以分子量适当高的较之分子量低的活性要高。但     

EFFECT OF ADSORPTION ON THE VISCOSITY OF DILUTE POLYMER SOLUTION*

Careful measurements of the dilute solution viscosities of polyethylene glycol and polyvinylalcohol in water were carried out. The reduced viscosities of both polymer solutions plot upward curves atextremely dilute concentration levels similar to the phenomena observed for many polymer solutions in theearly 1950's. Upon observation of the changes of the flow times of pure water in and the wall surfacewettability of the viscometer after measuring solution viscosity, a view was formed that the observed viscosityabnormality at extremely dilute concentration regions is solely due to the effect of adsorption of polymerchains onto the wall surface of viscometer. A theory of adsorption effect based on the Langmuir isothermswas proposed and a mathematical analysis for data treatment was performed. The theory could adequatelydescribe the existing viscosity data. It seems necessary to correct the viscosity result of dilute polymersolutions measured by glass capillary viscometer by taking into account the effect of adsorption in all cases.     

RHEOLOGICAL BEHAVIOR OF ERWINIA GUM IN AQUEOUS SOLUTION*

Erwinia (E) gum, an extracellular polysaccharide, is composed of fucose, galatose, glucose andglucuronic acid. Its viscosity behavior was investigated by a low-shear-rate multiball viscometer and arotational viscometer. Its weight-average molecular weight M_w and intrinsic viscosity [η] in 0.2 mol/L NaClaqueous solution were measured by light scattering method at 35℃and viscometry at 25℃and found to be1.06×10~6 g/mol and 1050 mL/g, respectively, and its aggregates in aqueous solution were proved by gelpermeation chromatography (GPC). These results indicated that E gum in water has exceedingly highviscosity and exhibits Binham fluid behavior, owing to its aggregation. The viscosity of E gum decreasedwith increasing temperature, and the turning point appeared at 38℃for dilute solution and 80℃forconcentrated solution suggesting that the aggregates of E gum in water started to disaggregate under thesetemperatures. In addition, the aggregates can be disrupted by adding either acid or base. The experimentalresults indicated that the E gum is a good thickening agent, and its fluid behavior is similar to xanthan.     

A NOVEL INTERPRETATION OF CONCENTRATION DEPENDENCE OF VISCOSITY OF DILUTE POLYMER SOLUTION*

The concentration dependence of the reduced viscosity of dilute polymer solution is interpreted in the light of anew concept of the self-association of polymer chains in dilute solution. The apparent self-association constant is defined asthe molar association constant divided by the molar mass of individual polymer chain and is numerically interconvertiblewith the Huggins coefficient. The molar association constant is directly proportional to the effective hydrodynamic volume ofthe polymer chain in solution and is irrespective of the chain architecture. The effective hydrodynamic volume accounts forthe non-spherical conformation of a short polymer chain in solution and is a product of a shape factor and hydrodynamicvolume. The observed enhancement of Huggins coefficient for short chain and branched polymer is satisfactorily interpretedby the concept of self-association. The concept of self-association allows us to predict the existence of a boundaryconcentration C_s (dynamic contact concentration) which divides the dilute polymer solution into two regions.     

COMPUTER SIMULATION OF POLYMER SOLUTION THERMODYNAMICS

The statistical counting method for the computer simulation of the ther-modynamic quantities of polymer solution has been reviewed. The calculating results fora single athermal chain confirm the theory of the renormalization group. The results forthe athermal solution are consistent with the scaling law of the osmotic pressure with theexponent 2.25. The results for a single chain with the segmental interaction are in a goodagreement with the exact results obtained by the direct counting method. The results forthe polymer solution show us that the Flory-Huggins parameter is strongly dependent onboth the polymer concentration and the interaction energy between segments. Monte carlo simulation; Polymer solution; Thermodynamic quantities;Translational entropy; Conformational entropy; Scaling law     

水溶性高聚物聚丙烯酰胺的稀溶液性质(Ⅰ)

本工作利用光散射和粘度方法,使用辐射聚合聚丙烯酰胺(PAAM)的级分样品,研究了在较宽分子量范围(10~4-10~7)内PAAM的特性粘数,分子尺寸及第二维利系数对重均分子量的依赖性.从实验上得到了PAAM在0.2mol/lNaCl水溶液中的均方旋转半径与均方末端距之间的关系及高分子-溶剂相互作用参数.     

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-reddichroism technique and wide angle X-ray diffraction (WAXD). The shear induced band texture in the film was found tocorrespond 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 sidegroup is perpendicular to the shearing direction. The WAXD azimuthal scanning at 2θ= 20° indicates that the (002) planeorients perpendicular to the shearing direction.     

壳聚糖/聚丙烯酸纳米粒子对蛋白质的吸附行为

以马来酸酐改性的壳聚糖(MAH-chitosan)和丙烯酸(AA)为单体,采用反相微乳液聚合法制备了AA含量分别为77%(AA-Cs)和29%(Cs-AA)壳聚糖/聚丙烯酸复合纳米粒子。TEM结果表明,该复合纳米粒子平均粒径为125~150nm,进而研究了其对牛血红蛋白(Hb)、牛血清白蛋白(BSA)和溶菌酶(Ly)吸附和脱附行为。AA-Cs对各种蛋白的吸附量均较高;而Cs-AA对3种蛋白的吸附则具有一定选择性。AA-Cs对等电点低于脱附pH值的Hb的脱附量较大。Cs-AA粒子在较低pH值(pH=3.4)时对吸附有利,但在高pH值(pH=6.6)进行吸附时,对脱附更为有利。     

聚电解质──壳聚糖浓溶液流变学性质研究：浓度、温度、溶剂pH值和外加盐对粘度及流动性的影响

本工作用日本岩本ＲＰＸ－７０５多功能流变仪测定了在不同浓度、温度、溶剂ｐＨ值和外加盐浓度对壳聚糖在甲酸水溶液中其浓溶液粘度η随剪切速率γ的变化关系．讨论了浓度、温度等对溶液粘度、流动活化能Ｅ_γ和流动指数ｎ的影响．发现溶剂ｐＨ值减小或溶液中外加盐浓度增加，溶液粘度变小，ｎ增大，表明非牛顿流动性减弱，并且进一步讨论了零剪切粘度η_０和外加盐浓度Ｃ_ｓ的依赖关系．     

A NEW METHOD TO PREPARE CHITOSAN MEMBRANE AS A BIOMEDICAL MATERIAL*

This paper reports a new method to prepare chitosan membrane which could be used as a biomedical material.Addition of a fixation agent composed of alcohol, glycerol and potassium hydroxide can acceletate the sol-gel transformationprocess and hence shorten the prepedion perod. The present method takes about 6 h to get a flexible membrane with fineappearance. The physical and biological properties of the membrane were also investigated and compared with the membraneprepared by conventional method.