LIGHT-SCATTERING STUDIES OF COPOLYMERS: I. EFFECT OF HETEROGENEITY OF CHAIN COMPOSITION ON THE MOLECULAR WEIGHT

1958 ◽  
Vol 36 (12) ◽  
pp. 1616-1626 ◽  
Author(s):  
W. Bushuk ◽  
H. Benoit
Keyword(s):  
Molecular Weight ◽  
Refractive Index ◽  
Light Scattering ◽  
Average Molecular Weight ◽  
Apparent Molecular Weight ◽  
Scattering Data ◽  
Refractive Index Increment ◽  
Molecular Weights ◽  
Chain Composition ◽  
Total Molecular Weight

The classical light-scattering theory for polymer solutions is extended to solutions of copolymers which may be polydisperse in chain composition as well as in molecular weight. It is shown that much too high molecular weights will result from light-scattering data for copolymers owing to fluctuations in chain composition; the magnitude of this effect increases rapidly as the absolute value of the refractive index increment approaches zero. The methods for determining the usual weight-average molecular weight and polydispersity of composition are described.The theory was tested with experimental results on: (1) a mixture of polystyrene and poly(methylmethacrylate), considered as a copolymer with the highest possible polydispersity of composition; (2) a high conversion, statistical copolymer of styrene and methylmethacrylate (copolymer I); and (3) a block copolymer of the same monomers (copolymer II). The apparent molecular weight for copolymer I (Mw = 1.83 × 105) varied markedly with refractive index increment in much the same way as the total molecular weight for the mixture. The molecular weight of copolymer II (Mw = 1.20 × 106) remained essentially constant in the same series of solvents. The polydispersities of composition obtained were 0.72 and 0.05 for copolymer I and II respectively compared with the maximum possible value equal to 1.0.

Physico-chemical studies of poly-d-glutamic acid from Bacillus anthracis grown in vitro

1957 ◽  
Vol 250 (972) ◽  
pp. 1-43 ◽  
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Diffusion Coefficients ◽  
Free Acid ◽  
Average Molecular Weight ◽  
Scattering Data ◽  
Effective Volume ◽  
A Value ◽  
Alkali Salts

The behaviour of polyglutamic acid and of its alkali salts in aqueous electrolyte solutions of varying ionic strengths has been examined by light scattering and in the ultracentrifuge, and parallel diffusion and viscosity studies have been made. Both behave in solution as flexible chain molecules of effective volume large for their weight. The effective volume per mole is much greater for the ionized form than for the largely unionized form (free acid), and the effective volume of the alkali salts increases markedly with reduction in the ionic strength of the solvent as would be expected from their polyelectrolyte nature. Sedimentation studies indicate a substantial degree of ion-pair formation between the polyglutamate ion and the cation of the solvent electrolyte. Despite this, the alkali polyglutamates show a ‘secondary charge effect’ of considerable magnitude, much greater than that predicted from the measured electrophoretic mobility of the polyglutamate ion. In contrast to the free acid, both the sedimentation and diffusion coefficients are markedly concentration-dependent. These coefficients have been extrapolated to infinite dilution, the sedimentation coefficients on the assumption that their inverse varies linearly with concentration and the diffusion coefficients by the method of Mandelkern & Flory (1951 ), using a value of the second virial coefficient derived from light-scattering data. Combination of these extrapolated values leads to a molecular weight for the free acid of 172000 and for sodium polyglutamate of 200000 ± 5000 after allowance for the effects of selective solvation. Detailed analysis of the sedimentation data for sodium polyglutamate in salt solutions of varying density indicates that the molecule is selectively solvated with not more than its own weight of water, a more probable figure being approximately 60 %. Detailed light-scattering studies of sodium polyglutamate have been made at ionic strengths 0.2 and 1.1. The mean of a number of determinations gives a weight-average molecular weight of 238000 and a number-average of 88000, the latter figure being in good agreement with a value obtained by assay of free amino groups. Values of the root-mean-square end-to-end distance of coils having the number- and MATHS FORMULA-average molecular weights are also given.

scholarly journals Self-association of dermatan sulphate proteoglycans from bovine sclera

1981 ◽  
Vol 197 (2) ◽  
pp. 483-490 ◽  
Author(s):  
L Cöster ◽  
L A Fransson ◽  
J Sheehan ◽  
I A Nieduszynski ◽  
C F Phelps
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Guanidine Hydrochloride ◽  
Apparent Molecular Weight ◽  
Sedimentation Equilibrium ◽  
Gel Chromatography ◽  
Side Chains ◽  
Dermatan Sulphate ◽  
Molecular Weights ◽  
High Particle

1. Two proteodermatan sulphate fractions (I and II) from bovine sclera were studied by gel chromatography, light-scattering and ultracentrifugation under various conditions. 2. Gel chromatography of proteoglycans in the absence or presence of hyaluronate was performed under associative conditions. No effect on the elution profile was noted. 3. Ultracentrifugation experiments (sedimentation-velocity and sedimentation-equilibrium) with proteoglycan I and II in 6 M-guanidine hydrochloride gave molecular weights (Mw) of 160000-220000 and 70000-100000 respectively. As the protein contents were 45% and 60% respectively, it may be calculated that proteoglycan I contained four to five side chains, whereas proteoglycan II contained one or two. Sedimentation-equilibrium runs performed in 0.15 M-NaCl gave an apparent molecular weight (Mw) of 500000-800000 for proteoglycan I and 90000-110000 for proteoglycan II. 4. In light-scattering experiments both proteoglycans I and II yielded high particle weights in 0.15 M-NaCl (3.1 × 10(6) and 3.4 × 10(6) daltons respectively). In the presence of 6 M-guanidine hydrochloride the molecular weights decreased to 410000 and 130000 respectively. The particle weights in 0.15 M-NaCl were not altered by the addition of hyaluronate or hyaluronate oligosaccharides. 5. The dermatan sulphate side chains of scleral proteoglycans (L-iduronate/D-glucuronate ratio 7:13) gave a particle weight of 100000 daltons in 0.15 M-NaCl. In 1.00 M-KCl/0.02M-EDTA the molecular weight was 24000. Addition of free scleral dermatan sulphate chains to a solution of proteoglycan II promoted further multimerization of the macromolecule.

scholarly journals Comparative Study on Molecular Weight of Konjac Glucomannan by Gel Permeation Chromatography-Laser Light Scattering-Refractive Index and Laser Light-Scattering Methods

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Mei Xu ◽  
Dong-Sheng Li ◽  
Bin Li ◽  
Chao Wang ◽  
Yu-Peng Zhu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Refractive Index ◽  
Light Scattering ◽  
Laser Light ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Konjac Glucomannan ◽  
Laser Light Scattering ◽  
Gel Permeation ◽  
Single Method

The gel permeation chromatography, combined with laser light scattering and refractive index (GPC-LLS-RI) online method and laser light scattering (LLS) single method, researched the weight-average molecular weight (Mw) of konjac glucomannan (KGM) in this paper. The results show that the determination results of molecular weight of KGM are similar by two method, the molecular weight of KGM is2.476×105 g/mol by online method measured, and it is2.508×105 g/mol by single method measured, compared with only 1.3% difference between the two methods. At the same time, the molecular weight distributions of KGM and conformation index were analyzed by online method, while the second virial coefficient (A2) that characterizes the interaction between KGM molecules and solvent molecules was acquired by single method, which can provide reliable foundation for the molecular chain morphology research of KGM.

INFLUENCE OF METHANOL ON VISCOSITY AND LIGHT SCATTERING PROPERTIES OF DEXTRAN SOLUTIONS

1956 ◽  
Vol 34 (4) ◽  
pp. 445-450 ◽  
Author(s):  
W. Donald Graham ◽  
Odette Patry ◽  
E. Helen Jackman
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Intrinsic Viscosity ◽  
Marked Effect ◽  
Average Molecular Weight ◽  
Alcohol Concentration ◽  
Methanol Concentration ◽  
Weight Average Molecular Weight ◽  
Molecular Weights ◽  
Apparent Weight

Failure to consider the presence of up to 16% by volume of methanol in solutions of dextran fractions had a very marked effect on apparent intrinsic viscosity determinations (the term apparent signifies that measurements were made assuming that the solvent was water only). Unless methanol were removed or otherwise taken into account, high erroneous results were obtained. Apparent weight average molecular weights determined by light scattering were not significantly affected at these alcohol concentrations. The relations found over the range 0 to 16% methanol for dextran samples with weight average molecular weights of 265,000, 155,000, and 72,000 held for the latter sample up to 44% methanol. In the higher range of alcohol concentration the apparent weight average molecular weight was depressed. The true intrinsic viscosity of dextran solutions decreased as methanol concentration was increased.

LIGHT-SCATTERING APPARATUS AND TECHNIQUES FOR MEASURING MOLECULAR WEIGHTS OF HIGH POLYMERS

1949 ◽  
Vol 27b (10) ◽  
pp. 791-806 ◽  
Author(s):  
H. J. Hadow ◽  
H. Sheffer ◽  
J. C. Hyde
Keyword(s):  
Molecular Weight ◽  
Refractive Index ◽  
Light Scattering ◽  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Bovine Serum ◽  
Scattered Light ◽  
Molecular Weights ◽  
Sources Of Error ◽  
Reduced Intensity

Apparatus is described for the measurement of small amounts of scattered light, dissymmetry of radiation, depolarization, and very small refractive index differences. Methods of calibration are critically examined. Benzene was adopted as a turbidity standard. Measurements were made on fractionated polystyrene of known molecular weight and on bovine serum albumin solutions. Values of the reduced intensity for benzene were obtained:[Formula: see text]Degree and sources of error are discussed

scholarly journals The molecular weight of Artemia ribosomes, as determined from their refractive-index increment and light-scattering intensity

1981 ◽  
Vol 197 (3) ◽  
pp. 689-693 ◽  
Author(s):  
Paul Nieuwenhuysen ◽  
Frank De Voeght ◽  
Julius Clauwaert
Keyword(s):  
Molecular Weight ◽  
Refractive Index ◽  
Light Scattering ◽  
Brine Shrimp ◽  
Artemia Salina ◽  
Refractive Index Increment ◽  
Scattering Intensity ◽  
A Value ◽  
Light Scattering Intensity ◽  
Cytoplasmic Ribosomes

Cytoplasmic ribosomes were isolated from the cryptobiotic embryos of the brine shrimp Artemia salina. Measurements of their refractive-index increments and light-scattering intensities give a value for their molecular weight of (3.4±0.2)×106.

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