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.     

Molecular weight and aggregation of Aeromonas gum treated with dimethyl sulfoxide in aqueous solution

Aeromonas (A) gum, an acidic hetero polysaccharide, in 0.2 M LiCl/dimethyl sulfoxide (DMSO) was fractionated satisfactorily according to the nonsolvent addition method. Eight fractions were chosen to examine their aggregation behavior in aqueous solution. The weight‐average molecular weight (M_w), radius of gyration 〈S²〉^1/2, and intrinsic viscosities [η] of the fractions in 0.2 M LiCl/DMSO and 0.5 M NaCl aqueous solution at 25 °C were measured by static light scattering and viscometry. The results indicated that the A gum was aggregated in 0.5 M NaCl aqueous solution at 25 °C, and the aggregates were broken in 0.2 M LiCl/DMSO. The apparent weight‐average aggregation number (N_ap) of the fractions increased with the process of fractionation, that is, N_ap increased from 1.1 to 15 with decreasing M_w of the single chain. The fractions obtained by treating with DMSO were more easily dissociated in the aqueous solution, and its N_ap was lower than that of the A gum fractions that were not treated with DMSO. Moreover, the A gum molecules with relatively low M_w aggregated easily to form a compact spherelike structure in the aqueous solution. Elemental analysis and ¹³C NMR spectroscopy indicated that DMSO was adsorbed on the A gum molecules caused by the fractionation program; DMSO not only prevented the polysaccharide aggregation but also increased the solubility. A model has been proposed to describe the aggregation behavior of the A gum chains with DMSO overcoat in the aqueous solution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2269–2276, 2002     

Effects of the thermal history and concentration on the aggregation of Erwinia gum in an aqueous solution

The aggregation of Erwinia (E) gum in a 0.2 M NaCl aqueous solution was investigated by multi‐angle laser light scattering and gel permeation chromatography (GPC) combined with light scattering. The GPC chromatograms of five fractions contained two peaks; the fractions had the same elution volume but different peak areas, suggesting that aggregates and single chains coexisted in the solution at 25 °C. The apparent weight‐average molecular weights (M_w) of the aggregates and single chains for each fraction were all about 2.1 × 10⁶ and 7.8 × 10⁴, respectively. This indicates that the aggregates were composed of about 27 molecules of E gum in the concentration range used (1.0 × 10⁻⁶ to 5.0 × 10⁻⁴ g/mL). The weight fraction of the aggregates (w_ag) increased with increasing concentration, but the aggregates still existed even in an extremely dilute solution. The fractionation process and polymer concentration hardly affected the apparent aggregation number but significantly changed w_ag. The E‐gum M_w decreased sharply with an increase in temperature. When the E‐gum solution was kept at 100 °C, w_ag decreased sharply for 20 h and leveled off after 100 h. Once the aggregates were decomposed at a higher temperature, no aggregation was observed in the solution at 25 °C, indicating that the aggregation was irreversible. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1352–1358, 2000     

LIGHT SCATTERING OF POLYSACCHARIDE FROM LACQUER IN AQUEOUS SOLUTION

The polysaccharide having weight-average molecular weight M_w=1. 09×10~5, isolated from the sap of lac trees (Vietnam), was separated into 12 fractions by aqueous-phase preparative gel permeation chromatography. The molecular weights and molecular weight distributions of the fractions were measured in aqueous 0.08M KCl/0.01 M NaAc and 0.4M KCl/0.05M NaAc at pH =7. 6 by light scattering, viscometry and gel permeation chromatography. The Mark-Houwink equation in aqueous 0.08M KCl/0.01M NaAc at 30℃was found to be [η]= 2.28×10~(-2) M_w~(0.52) (cm~3/g), which indicated the polysaccharide chain in the aqueous solution to be a spherical random coil.     

聚乙酸乙烯酯的溶液性质及长链支化度

用粘度法,GPC和LALLS测定了线型及不同转化率的PVAc分级级份的粘度与分子量。提出了以线型和支化聚合物的K,α计算临界分子量的方法。讨论了表征PVAc长链支化的各种参数与分子量和转化率之间的关系以及不同条件下迭代法计算的支化频率λ的差异。实验结果表明,特性粘数和数均分子量乘积所表示的流体力学体积更适合GPC的普适标定概念。     

聚氯乙烯-马来酸二乙酯分子量与特性粘数关系的研究

<正> 氯乙烯-马来酸二乙酯共聚树脂(氯-马树脂)是一种聚氯乙烯改性树脂。其特点为:可以用廉价的氯化石蜡代替增塑剂DBP,而树脂仍具有好的使用性能。本工作是先将氯-马树脂样品进行童沉淀分级,取得分子量较均一的各个级场,然后用快速动态渗透压和静态渗透压法测走其数均分子量;用光散射法测定其重均分子量;用粘度法测     

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。     

小角激光光散射法测定聚甲基丙烯酸-6-磺己基钠特性粘数-分子量关系

<正> 聚甲基丙烯酸己磺酸钠(PSSHMA)是我们最近合成的,具有较好的抗凝血性能。对于带磺酸基聚合物抗凝血性能的研究,文献报道还不多。我们用羟基己磺酸钠与甲基丙烯酸反应制备了甲基丙烯酸己磺酸钠(SSHMA)新单体,在此异相酯化反应中,使用了四丁基硫酸氢铵(TBAB)作为催化剂,使反应较顺利的进行,得纯单体。经复钙时     

红栓菌多糖的分级、表征、分子链构型参数和抗癌活性研究

本文研究了以水为溶剂,乙醇为沉淀剂,获得6个级分的红栓菌多糖,并运用动态膜渗透压法、VPO法、超速离心沉降法、小角激光光散射和高效液相色谱等,对其进行了表征。使用分光光度计,以浊点滴定法与修正的Elias公式确定红栓菌多糖溶液的θ组成为:V_(H_2O):V_(CH_3COCH_3)=89.82:10.18(体积比)。再在θ条件下建立红栓菌多糖的Mark-Houwink方程:[η]=5.01×10~(-4)M~(0.502)计算出它的无扰尺寸。由色谱法和董履和函数适应法解得红栓菌多糖的分子量分布。 通过抗癌药理活性实验,发现该多糖对小白鼠肉瘤S_(180)有较强的生理活性,能抑制肿瘤生长。同时还发现多糖Ⅱ活性高于多糖Ⅰ活性。     

Polymerization of vinyl chloride with organolithium compounds. V. Fractionation and solution properties of high molecular weight poly(vinyl chloride)

A sample of high molecular weight poly(vinyl chloride) (PVC) was fractionated by classical precipitation fractionation and gel-permeation chromatography (GPC) on a preparative scale. The fractions thus obtained were characterized by light scattering, viscometry, and by the GPC method. The measured weight-average molecular weights M?_w, intrinsic viscosity [η], and polydispersity index M?_w/M?_n values were used for the determination of the Mark-Houwink equation, [η] = KM^a, for PVC in cyclohexanone (CHX) at 25°C valid for molecular weights from 100,000 to 625,000.     

聚[4-(4′-八甲基四硅氧基)二苯醚]分子量与特性粘数的关系

本工作对本体聚合的交替共聚物,聚[4-(4′-八甲基四硅氧基)二苯醚]作了重沉淀分级,再用粘度法、动态渗透压,光散射及GPC对级分和未分级试样作了分子量和分布宽度的测定。实验数据经多分散性改正后,得到该共聚物单分散的特性粘数-分子量关系式: [η]=2.33×10~(-3)M~(0.88)(毫升/克,25℃,四氢呋喃)该共聚物在四氢呋喃溶液中的第二维利系数A_2随分子量的增加而降低,依从A_2=3.60×10~(-2)的关系. 该共聚物在水中加热后放置几天会产生降解。紫外和红外光谱说明降解后共聚物的化学组成没有明显变化。     

动态膜渗透压法测定生漆多糖水溶液

<正> 生漆是一种性能优异的超耐久涂料,其主要成份为漆酚、漆酶、糖蛋白、多糖和水。多糖由D-半乳糖(65％),4-O-甲基-D-葡萄糖醛酸(24％),D-葡萄糖醛酸(3％),L-阿拉伯糖(4％)和鼠李糖(3％)组成。它带大量支链,在侧链上有大约1/4mol羧基从而显示聚电解质溶液性质。     

CHARACTERIZATION OF MOLECULAR MASS OF SIX WATER-SOLUBLE POLYSACCHARIDE -PROTEIN COMPLEXES FROM GANODERMA TSUGAE MYCELIUM

Six water-soluble polysaccharide-protein complexes coded as GM1, GM2, GM3, GM4, GM5 and GM6 wereisolated from the mycelium of Ganoderma tsugae by extracting with 0.2 mol/L phosphate buffer solution at 25, 40 and80℃, water at 120℃, 0.5 mol/L aqueous NaOH solution at 25 and 65℃, consecutively. Their chemical components wereanalyzed by using IR, GC, HPLC and ~(13)C-NMR, and some new results were obtained. The four samples GM1, GM2, GM3and GM4 are heteropolysaccharide-prote in complexes, in which, α- (1→3) linked D-glucose is the major monosaccharidewhile galactose, mannose and ribose are the secondary ones. GM5 and GM6 are β-(1→3)-D-glucan-protein complexes. Theprotein content increased from 32% to 69% with the progress of isolation. Weight-average molecu1ar mass M_w and theintrinsic viscosity [η] of the GM samples in 0.5 mol/L aqueous NaCl solution at 25℃ were measured systematically by laserlight scartering (LLS), size exclusion chromatography (SEC) combined with LLS, and viscometry. The M_w of GM1 to GM6are 35.5, 46.8, 58.9, 41.6, 3.3 and 22.0×10~4, respectively. The conformation and molecular mass of the two fractions of sample GM5 were characterized satisfactorily by SEC-LLS without further fractionation.     

Intrinsic viscosities of four homopolymers and one copolymer in nonpolar solvents. I. Effect of correlations of molecular orientations

Intrinsic viscosities [η] of four homopolymers, polyisobutylene (PIB), polypentene-1 (PP-1), polypentenamer (PPmer), and polydimethylsiloxane (PDMS), and of an ethylene-propylene copolymer containing 81% ethylene (81% E) have been measured at 25°C in seven linear alkanes ranging from n-C₆ to n-C₁₆ and three highly branched alkanes, 2,2,4-trimethylpentane, 2,2,4,6,6-pentamethylheptane, and 2,2,4,4,6,8,8-heptamethylnonane. Correlation of molecular orientations (CMO) in the polymers was investigated. The difference Δ[η] = [η](lin) ? [η](br) is used as a test of CMO with the supporting assumption that CMO lowers the free energy and the destruction of CMO raises it. The positive value of Δ[η], which varies from 20% to 40% for PPmer and 81% E, is indicative of orientational order in these two polymers. The negative value of Δ[η] for PDMS results from the disordering of linear alkanes by the nonordered PDMS. δ[η] is near zero for PP-1 and small for PIB implying that these two polymers are indifferent to solvent molecular shape. The variation of [η] with alkane chain length of the linear alkanes gives additional information about size and solvent quality. The dependence is small for ordered polymers due to the short range of CMO. [η] diminishes rapidly with n for PDMS probably because of the increased difference of cohesive energy between polymer and solvent. The dependence is small for PIB but very large for PP-1. The much better quality of small-molecule solvents for PP-1 may be an indication of a helicoidal conformation of this polymer in solution.     

加盐浓度及水解度对PAM和HPAM的特性粘数的影响

聚丙烯酰胺(PAM)和部分水解聚丙烯酰胺(HPAM)的特性粘数[η]等物性参数与样品的水解度(DH%)、加盐浓度(C_s)密切相关。在实际应用中,无论油田水、矿山水、洗煤水,一般矿化度都较高,影响PAM和HPAM的使用性能,所以研究DH%、C_s对[η]的影响很有必要。本文在以往工作的基础上研究了[η],C_s,DH%,tgx间的关系,得出了一些有用的结果。     

Chain dimensions and transport coefficients of sodium poly(isoprenesulfonate) in aqueous sodium chloride

Sodium poly(isoprenesulfonate) (NaPIS) fractions consisting of 1,4‐ and 3,4‐isomeric units (0.44:0.56) and ranging in molecular weight from 4.9 × 10³ to 2.0 × 10⁵ were studied by static and dynamic light scattering, sedimentation equilibrium, and viscometry in aqueous NaCl of a salt concentration (C_s) of 0.5‐M at 25 °C. Viscosity data were also obtained at C_s = 0.05, 0.1, and 1 M. The measured z‐average radii of gyration 〈S²〉_z^1/2, intrinsic viscosities [η], and translational diffusion coefficients D at C_s = 0.5‐M showed that high molecular weight NaPIS in the aqueous salt behaves like a flexible chain in the good solvent limit. On the assumption that the distribution of 1,4‐ and 3,4‐isomeric units in the NaPIS chain is completely random, the [η] data for high molecular weights at C_s = 0.5 and 1 M were analyzed first in the conventional two‐parameter scheme to estimate the unperturbed dimension at infinite molecular weight and the mean binary cluster integral. By further invoking a coarse‐graining of the NaPIS molecule, all the [η] and D data in the entire molecular weight range were then analyzed on the basis of the current theories for the unperturbed wormlike chain combined with the quasi‐two‐parameter theory. It is shown that the experimental 〈S²〉_z, [η], and D are explained by the theories with a degree of accuracy similar to that known for uncharged linear flexible homopolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2071–2080, 2001     

Synthesis and characterization of multiarm star-branched polyisobutylenes: Effect of arm molecular weight

A series of star-branched polyisobutylenes with varying arm molecular weights was synthesized using the 2-chloro-2,4,4-trimethylpentane/TiCl₄/pyridine initiating system and divinylbenzene (DVB) as a core-forming comonomer (linking agent). The resulting star-branched polymers were characterized with regard to the weight-average number of arms per star molecule (N̄_w) and dilute solution viscosity behavior. As the molecular weight of the arm (M̄_{w, arm}) was increased, dramatically longer star-forming reaction times were needed to produce fully developed star polymers. It was calculated that N̄_w varied from 50 to 5 as the M̄_{w, arm} was increased from 13,000 to 54,000 g/mol. The radius of gyration, R_g, of the star polymers was observed to increase as M̄_{w, arm} was increased. The solution properties of the star polymers were evaluated in heptane using dilute solution viscometry. It was determined that the stars had a much higher [η] compared to the respective linear PIB arms, but a much lower [η] compared to a hypothetical linear analog of an equivalent molecular weight. The dependence of [η] on temperature for the stars and linear arms was very small over the temperature range 25 to 75°C, with only a very slight decrease with increasing temperature. [η]_star was also determined to increase with increasing M̄_{w, arm}, but decrease with increasing M̄_{w, star}. The branching coefficient, g′, calculated for the stars at 25°C, increased as N̄_w decreased and agre ed well with literature values for other star polymer systems. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3767–3778, 1997     

INVESTIGATION ON THE RELATIONSHIP BETWEEN INTRINSIC VISCOSITY AND MOLECULAR WEIGHT OF POLY (VINYL CHLORIDE-DIETHYL MALEATE)

A poly (vinyichloride-diethyl maleate) copolymer has been fractionated by repeated precipitation method. All fractions and the unfractionated sample have been characterized by viscometry, dynamic osmometry, Zimm static osmometry, light scattering and gel permeation chromatography. After correction for polydispersity, a [η]～M relationship for monodisperse polymer solutions has been obtained:[η]=1.99×10~(-3)M~(0.87) (ml/g, at 25℃, in cyclohcxanone)For the copolymer solution in THF, the second virial coefficient A_2 decreases as the molecular weight increases. The relationship isA_2=2 slope ((?)_n RT)~(-1/2).     

纤维素硫酸半酯钠盐的分子链相对僵硬性测算

本文测定了已知分子量的纤维素硫酸半酯钠盐在不同离子强度(I)NaCl溶液中,25℃的特性粘数[η],确立了与此相对应的[η]与1/I~(1/2)和logs(=△[η]/△(I)~(-1/2)与 log[η]_(0.1)的线性关系.依 Smidsrod 方程(S=B·[η]_(0.1)~v),求得纤维素硫酸半酯钠盐的分子链相对僵硬性参数B值0.088。参数B不仅用作各种高分子链的相对僵硬性的量度,还可以用来定量地表征各种聚电解质溶液特性粘数对外加盐的响应。     

聚辛烯-1Mark-Houwink常数的确定及其分子量分布研究

本文用GPC结合特性粘度的方法,对聚辛烯-1四氢呋喃体系的Mark-Houmink常数进行订定。数据处理采用了Weiss法和流体力学平均分子量(?)_x两种方法,α值分别为0.701和0.625,相对误差10％左右,所得Mark-Hon-Wink方程Weiss法为:[η]_(THF)~(25℃)=3.89×10~(-4)[M]~(0.701)(?)_x法为[η]_(THF)~(℃25)=4.14×10~(-4)M~(0'625)。本文还研完了聚合反应条件对聚辛烯-1分子量及分子量分布的影响。发现三种TiCl_3为主催化剂,三乙基铝为助催化剂时,其GPC谱图均为双峰型,两个峰的比例随聚合反应条件不同而变化。表明聚合体系至少有两种不同性质的活性中心,有着不同的形成和增长速率。