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.     

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).     

Gel permeation chromatography of poly(styrene-co-divinylbenzene) microgels. Effect of electrolyte concentration in the solvent system dimethylformamide plus lithium bromide

Tightly crosslinked poly(styrene-co-divinylbenzene) microgels with molecular weights in the range 10⁷-10⁸gmol^?1 have been dissolved in dimethylformamide containing LiBr and investigated by gel permeation chromatography and viscometry. The effect of LiBr concentration on the elution volume in GPC can be explained in terms of a diffuse double layer. The product [η]M adequately describes the separation in GPC provided that the LiBr concentration is high and adsorption is absent.     

Determination of molecular weights and monosaccharide compositions in Abelmoschus manihot polysaccharides

Abelmoschus manihot polysaccharide, AMP-1, AMP-2, AMP-3, and AMP-4, were purified from four kinds of Abelmoschus manihot gum (AMG). The molecular weights and monosaccharide compositions of AMP-1, AMP-2, AMP-3 and AMP-4 were characterized by gel permeation chromatography, Fourier transform-infrared spectroscopy and high performance anion-exchange chromatography with pulsed amperometric detection. Results indicated that the molecular weights of AMP-1, AMP-2, AMP-3, and AMP-4 were approximately 3.91 × 10³, 5.36 × 10⁵, 3.87 × 10³, and 5.12 × 10⁵ Da, respectively. The Abelmoschus manihot polysaccharide was mainly composed of galactose, glucose and mannose with the molar ratios at 0.29: 1.00: 0.41 (AMP-1), 0.56: 0.13: 1.00 (AMP-2), 0.10: 1.00: 0.11 (AMP-3) and 0.55: 0.17: 1.00 (AMP-4), respectively.     

Effect of molecular weight on radiation chemical degradation yield of chain scission of γ-irradiated chitosan in solid state and in aqueous solution

Chitosan A₁, A₂ and A₃ with molecular weight of 471, 207 and 100 kDa respectively, produced from squid pen chitin was degraded by gamma rays in the solid state and in aqueous solution with various doses in air at ambient temperature. Effect of molecular weight on radiation chemical degradation yield of chain scission and degradation rate constants of γ-irradiated chitosan in solid state and in aqueous solution was investigated. The radiation chemical degradation yield G_(s) and degradation rate values were calculated. The molecular weight changes were monitored by capillary viscometry method and the chemical structure changes were followed by UV analysis. The results showed that, the degradation of chitosan was faster in solution, than in solid state. The values of G_(s) in solid state and in aqueous solution were respectively 1.1×10^?8 mol/J and 0.074×10^?7 mol/J for A₁, 4.42×10^?8 mol/J and 0.28×10^?7 mol/J for A₂ and 6.08×10^?8 mol/J and 0.38×10^?7 mol/J for A₃. Degradation rate constants values ranged from 0.41×10^?5 to 2.1×10^?5 kGy^?1 in solid state, whereas in solution they ranged from 13×10^?5 to 68×10^?5 kGy^?1. The chitosan A₃ was more sensitive to radiolysis than A₁ and A₂. The chain scission yield, G_(s) and degradation rate constants seems to be greatly influenced by the initial molecular weight of the chitosan. Structural changes in irradiated chitosan are revealed by the apparition of absorption peaks at 261 and 295 nm, which could be attributed to the formation of carbonyl groups. In both conditions the peak intensity was higher in chitosan A₃ than in A₁ and A₂, the oxidative products decreased with increasing molecular weight of chitosan.     

Molecular properties of modified chitosan containing a quaternary amino group

A homologous series of the chitosan derivative N-[(2-hydroxy-3-trimethylammonium)pro-pyl]chitosan in a 0.33 M CH₃COOH + 0.2 M CH₃COONa mixture is studied via viscometry and static and dynamic light scattering. The molecular masses of the homologous series are determined, and the scaling relationships for the intrinsic viscosity, translational-diffusion coefficient, and hydrodynamic radius of molecules are derived. For the mentioned polymer-solvent system, the mean hydrodynamic invariant is estimated as A ₀ = (3.4 ± 0.1) × 10⁻¹⁵ kg m²/(s² deg mol^1/3). The equilibrium thermodynamic rigidity of modified chitosan chains is found to be 20 ± 2 nm. This value, like the parameters of the scaling relationships, suggests that the chitosan derivative under investigation belongs to the class of rigid-chain polymers. It is shown that, in the selected mixed solvent, the molecules of the modified chitosan are more compact than molecules of its nonmodified analog having close degrees of polymerization.     

Preparation,fractionation, and dilute-solution behavior of ABA poly(methyl methacrylate-b-α-methylstyrene) block copolymers

The preparation by anionic polymerization of six ABA poly(methyl methacrylate-b-α-methylstyrene) block copolymers and of sixteen poly(α-methylstyrene)s is described. The block copolymers, of similar molecular weight but with different chemical compositions, were fractionated by preparative gel permeation chromatography and their behavior in dilute solution was investigated using viscometry. The results obtained indicate that the intramolecular phase separation does not occur under the conditions utilized, the block copolymers assuming randomcoil configurations in all of the copolymer/solvent systems studied. Consequently the block copolymer molecules are more expanded than homopolymers of the same molecular weight. The series of poly(α-methylstyrene)s covered the molecular weight range 2.7 × 10³–1.3 × 10⁶ and enabled the determination of Mark–Houwink–Sakurada constants for poly(α-methylstyrene) in the solvents chosen for the block copolymer studies.     

Hydrodynamic and conformational properties of cellulose myristate molecules in solution

Cellulose myristate samples with a degree of substitution of 230–250 have been studied by the methods of molecular hydrodynamics (viscometry, analytical ultracentrifugation (flotation), and isothermal translational diffusion) in chloroform in the range M = (56–652) × 10³. The experimental evidence has been interpreted within the framework of the generalized wormlike Yamakawa-Fuji model with the following parameters: the persistence length a = 115 × 10^?8 cm, the chain diameter d = 45 × 10^?8 cm, and the molecular mass per unit chain length M _L = 270 × 10⁸ cm^?1. It has been inferred that the polymer dissolves in chloroform in the form of dimers.     

Aliphatic-aromatic poly(ether amide)s containing oxyethylene units. Synthesis and characterization

The synthesis and characterization of aromatic polyamides containing oxyethylene units is reported, and the differences observed in polycondensation yields, molecular weights, and molecular weight distributions, as a function of the method of synthesis, are discussed. Four diamines containing oxyethylene units and aromatic rings, meta and para oriented, and their corresponding hydrochlorides were prepared as condensation monomers to be combined with isophthaloyl chloride (IPC) and terephthaloyl chloride (TPC). High molecular weight polyamides were obtained by interfacial and low-temperature solution methods. Values of (OVERLINE)M(/OVERLINE)_n up to 6 × 10⁴ g/mol and (OVERLINE)M(/OVERLINE)_w up to 2 × 10⁵ g/mol could be measured by gel permeation chromatography using aromatic polyamide standards, and values of (OVERLINE)M(/OVERLINE)_n up to 2 × 10⁵ g/mol and (OVERLINE)M(/OVERLINE)_w up to 5 × 10⁵ g/mol by using polystyrene standards. © 1996 John Wiley & Sons, Inc.     

Molecular mass distribution of oligomers in products of tetrafluoroethylene radical telomerization

The molecular mass distributions (MMD) of perfluorinated oligomers in products of tetra-fluoroethylene (TFE) radical polymerization in various solvents (telogens) were determined from an analysis of differential thermogravimetric curves and data of gel permeation chromatography and mass spectrometry. Radiolysis of the telogens generates radicals initiating polymer chain growth. The choice of the solvent and TFE concentration makes it possible to obtain oligomers with the controlled average chain length from 4 for 40 CF₂ fragments and specified terminal groups. The polymerization of TFE in THF and propylene oxide affords oligomers with cyclic terminal groups capable of further polymerization due to ring opening. The appearance of two MMD maxima (low-molecular-weight at n ₁ ～6–8 and high-molecular-weight at n ₂ > 10 shifting towards high n with an increase in the TFE concentration) is caused by the formation of colloidal solutions of oligomers.     

Graft polymerization of acrylic monomers onto starch fractions. III. Effect of carbohydrate structure

Grafted PMMA was isolated by the acid hydrolysis method. Weight-average and number-average molecular weights were determined by gel permeation chromatography. The number-average molecular weight of the grafted chains was about 475,000 for amylopectin and 403,000 for amylose. The number of grafted chains (mmol) ranged from 2.4 × 10^?3 to 4.6 × 10^?3 for amylopectin graft copolymers and from 2.9 × 10^?3 to 6.8 × 10^?3 for those of amylose. These results were related to others obtained from ceric ion consumption studies. The values suggest that amylopectin, because of its complex structure, favors a higher consumption of ceric ion in homopolymerization reactions and inhibits the initiation reactions of the copolymerization.     

Solution properties of poly p-isopropyl α-methylstyrene

Two series (S and F) of poly p-isopropyl α-methylstyrene were characterized by viscometry, light scattering (LS), osmometry and gel permeation chromatography (GPC). S-samples were prepared by bulk anionic polymerization whereas F-samples were obtained on fractionation by preparative GPC of a polymer also prepared in bulk but with a different initiator. The K parameter in the Mark-Houwink relation was 5.55 × 10^?4 for series-S and 4.50 × 10^?4 for series-F, whereas the exponent a was 0.55 for both series. The Mark-Houwink equations for series-S and -F hold good at 25 and 30° for both toluene and tetrahydrofuran as solvents and have been corrected for polydispersity. The chain dimensions obtained with LS were much higher than those computed from the viscosity data indicating that the hydrodynamic theories in their present state should not be used for the calculation of chain dimensions. The deviations from the GPC universal calibration curve of polystyrene observed with some samples were attributed to structural differences among the polymers and to their high polydispersity.     

Lumped kinetic model for degradation of chitosan by hydrodynamic cavitation

The lumped kinetic model for the degradation reactions of chitosan by hydrodynamic cavitation was investigated in this study. The molecular weight distributions and mass concentrations were determined by gel permeation chromatograph (GPC). The degradation products were divided into several lumps according to their molecular weights. The appropriate number of lumps for the kinetic study was determined by comparing the residual sum of squares (RSS) values among different models. The RSS of six-lumped model (5.36 × 10^?3) was relatively small and the estimation of parameters was simpler than other models. In this paper, six-lumped kinetic model was adopted and the corresponding reaction network was established. The kinetic parameters were estimated with the Levenberg-Marquardt, and the results showed that the degradation reaction of chitosan was mainly dominated by the formation of degradation products with similar molecular weights. The maximum value of kinetic parameters on the diagonal of the reaction network (1.63 × 10^?1) was much larger than that of non-diagonal kinetic parameters (3.78 × 10^?2). According to the results calculated and measured under different conditions, this model could accurately predict the concentration distributions of lumps in the reaction network, and most of the average absolute deviation were smaller than 9.3%.     

Effect of molecular mass on the optical activity of chitosan

The optical activity of chitosan has been examined by the optical rotary dispersion method in a wide molecular mass range, beginning from low-molecular analogs of the monomer unit and oligomers. In the spectral range from 300 to 710 nm, all samples demonstrate smooth curves of the optical rotary dispersion. For the polymers and oligomers, these curves lie in the region of negative values of specific optical rotation [α], while for monosaccharides, these curves are in the positive region. High-molecular-mass samples are characterized by maximal ?[α] values that are practically independent of molecular mass. For partially depolymerized samples with M < 2 × 10⁵ and for oligomers, the smaller the molecular mass of the sample, the greater the decrease in the modulus of ?[α]. The passage to D-glucosamine chlorohydrate and to N-acetyl-D-glucosamine is characterized by inversion of the sign of rotation and achievement of high +[α] values.     

Determination of molecular weights and Mark–Houwink constants for soluble electronically conducting polymers

Intrinsic viscosities and gel permeation chromatography data were used to evaluate the Mark–Houwink constants of the soluble electronically conducting polymer, poly(3-hexylthiophene) (P3HT):K and a are 2.28 × 10^-3 cm³/g and 0.96, respectively, in tetrahydrofuran (THF) at 25°C. Mark–Houwink constants were used to calibrate gel permeation chromatography (GPC) columns for P3HT. Number-average molecular weights of P3HT determined with modified calibration curves agreed well with those determined by an absolute method, embulliometry. Molecular weights estimated using unmodified polystyrene calibration procedures were significantly larger than true values.     

Nanofibrillar Cellulose‐Chitosan Composite Film Electrodes: Competitive Binding of Triclosan,Fe(CN)63−/4−, and SDS Surfactant

Glassy carbon electrodes are modified with a thin film of a cellulose‐chitosan nanocomposite. Cellulose nanofibrils (of ca. 4 nm diameter and 250 nm length) are employed as an inert backbone and chitosan (poly‐D ‐glucosamine, low molecular weight, 75–85% deacetylated) is introduced as a structural binder and “receptor” or molecular binding site. The composite films are formed in a solvent evaporation method and prepared in approximately 0.8 μm thickness. The adsorption of three molecular systems into the cellulose‐chitosan films is investigated and approximate Langmuirian binding constants are evaluated: i) Fe(CN)₆^4? (K_Ferrocyanide=2.2×10³ mol^?1 dm³ in 0.1 M phosphate buffer at pH 6) is observed to bind to ammonium chitosan functionalities (present at pH<7), ii) triclosan (K_Triclosan=2.6×10³ mol^?1 dm³ in 0.1 M phosphate buffer pH 9.5) is shown to bind only weakly and under alkaline conditions, and iii) the anionic surfactant dodecylsulfate (K_SDS=3.3×10⁴ mol^?1 dm³ in 0.1 M phosphate buffer pH 6) is shown to bind relatively more strongly in acidic media. The competitive binding of Fe(CN)₆^4? and dodecylsulfate anions is proposed as a way to accumulate and indirectly determine the anionic surfactant.     

Electrostatic long-range and short-range interactions in linear poly(allylamine hydrochloride) chains

The efficiencies of two azo initiators in the polymerization of allylamine salts in water and organic solvents were compared. The hydrodynamic and molecular characteristics of poly(allylamine hydrochloride) in 0.1 M NaCl in the molecular mass range M×10^?3=18?65 were studied, and the scaling relationships were derived for the intrinsic viscosity ([η]=7.65×10^?3 M ^0.8±0.1), translational diffusion coefficient (D ₀=2.41×10^?4 M ^{?(0.59±0.05)}), and velocity sedimentation coefficient (s ₀=2.77×10^?15 M ^0.41±0.05). The hydrodynamic data were interpreted in terms of electrostatic long-range and short-range interactions. The equilibrium rigidity of poly(allylamine hydrochloride) chains in 0.1 M NaCl and its structural and electrostatic constituents were quantitatively estimated. It was shown that the conformation of poly(allylamine hydrochloride) chains in pure water is close to rodlike.     

Hydrodynamic, electrooptical, and conformational properties of fullerene-containing poly(2-vinylpyridines) in solutions

For C₆₀ fullerene-containing poly(2-vinylpyridines) synthesized by anionic polymerization, the molecular mass and hydrodynamic size of macromolecules in solutions have been determined by molecular hydrodynamics (translational diffusion and viscometry) and electrooptics in dilute benzene and THF solutions. Under the same conditions in the molecular mass range (9.8–123) × 10³, the hydrodynamic behavior of linear poly(2-vinylpyridines) and their molecular-mass dependences have been examined and the conformational characteristics of macromolecules have been established. The branching of macromolecules has been characterized by comparing the properties of star-shaped fullerene-containing and linear poly(2-vinylpyridines). With consideration of the hydrodynamic data interpreted within the framework of regular star model, it is inferred that on average three to four linear polymer chains with a molecular mass of (8 ± 3) × 10³ for each chain are attached to a fullerene core of C₆₀ in molecules of fullerene-containing poly(2-vinylpyridines). The specific Kerr constant of fullerene-containing poly(2-vinylpyridines) in dilute benzene solution is ?(14 ± 1) × 10^?12 cm⁵/[g (300 V)²]. As evidenced by the electrooptical data, the incorporation of fullerene into the polymer weakens self-association of macromolecules in solution.     

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     

Hydrodynamic and molecular characteristics of graft copolymers of chitosan with acrylamide

The conformational properties of macromolecules of chitosan and its copolymers with acrylamide in a mixed solvent 0.33 M CH₃COOH + 0.3 M NaCl have been investigated by means of translation diffusion and viscometry. The copolymer macromolecules in a solvent suppressing polyelectrolyte effects possess a higher intracoil density (ρ_av = 0.010 g/cm³) than the chitosan macromolecules (ρ_av = 0.006 g/cm³), even though the hydrodynamic radius R _h of chitosan is smaller by a factor of ～1.5.