Mittelwerte des Molekulargewichtes und anderer Eigenschaften

Elias, Hans‐Georg; Bareiss, Rolf E.; Watterson, J. G.

doi:10.1007/3-540-06054-5_12

Cited by 76 publications

(7 citation statements)

References 175 publications

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“…Ref. 22): a, -1 E = (2a, -1)/3 (11) It is clear that this relation does not hold in the present case, for E from Eq. (10) equals 0.13 and E from the viscosity exponent (Table 111) equals 0.24.…”

Section: Light-scatteringmentioning

confidence: 67%

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Physicochemical investigation of k‐carrageenan in the random state

1980

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SynopsisLight-scattering, viscosity, and sedimentation experiments on aqueous solutions of y-carrageenan show that this sulfated polygalactose is an expanded flexible random coil. This expansion is due to long-range interactions that are predominantly electrostatic. Extrapolation of viscosity data to infinite ionic strength provided values for the intrinsic viscosity which were subjected to the Stockmayer-Fixman analysis, giving a value for the Mark-Houwink coefficient under theta-conditions, KO, of 0.27. The characteristic ratio, C,, under these conditions is 7.8, and the conformation factor u is 2. In a solution of 0.118 ionic strength, where a Mark-Houwink exponent a , of 0.86 is found, the radii of gyration calculated from viscosity data are lower than those found from the angular dependence of scattered light. On the other hand, the radius of gyration found from the sedimentation rate agrees well with the lightscattering radius. The relations between molecular parameters are corrected for the polydispersity of the sample.

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Section: Light-scatteringmentioning

confidence: 67%

“…Bloomfield and Zimm37 extended the calculation for values of E > 0.2; for 6 = 0.24, + ( E ) = 1.4 X For the z-average radius of gyration, Eq. (22) becomes in which qzn is the polydispersity correction factor, which for a Schulz-Zimm distribution is given by22…”

Section: Application Of the Ptitsyn And Eizner Theorymentioning

confidence: 99%

Physicochemical investigation of k‐carrageenan in the random state

1980

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“…For colligative methods, one gets4 = w.w3. (A)1 (2) and for weight average methods (light scattering, equilibrium ultracentrifugation) 46 = (…”

Section: (1)mentioning

confidence: 99%

Polymolecularity and polydispersity in molecular weight determinations

Elias¹

1975

Pure and Applied Chemistry

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The influence of polymolecularity on molecular weight determinations is reviewed. Several molecular weight methods give so-called mixed averages, i.e. averages which are based on more than one moment of the molecular weight distribution or on powers of the moment. Molecular weight averages can be subdivided into simple, exponential resolved, order resolved and power resolved averages. Mixed averages depend on the shape of the solute and its interaction with the solvent. Simple averages of molecular weight can be calculated from combinations of averages of different properties with the help of the H-theorem. A related problem is that of the so-called polymolecularity corrections. New experiments show a definite influence of the type and the width of the molecular weight distribution on the second osmotic virial coefficients which is not predicted by present theories. Methods are given to distinguish between open, closed, molecule-based and segment-based associations. The influence of the polymolecularity of unimers on the polydispersity of the resulting multimers is discussed for several types of association. In general, a sharpening effect is observed. Equations are given which may help detect polydispersity in open and closed association. Debye's treatment of micellar solutions cannot be used to determine premicellar equilibria.

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“…When dealing with polydisperse samples, the experimental intrinsic viscosity of each sample is a weight av-erage of the intrinsic viscosities of the monomolecular species present in it. 21 However, the same Mark-Houwink equation valid for the monomolecular species holds with the M(exptl) of the polydisperse samples if their viscosity-average molecular weights, Mv, are used in eq 3 in place of M, namely log = log K + a log Mv (7) (K and a having the same values as in eq 3). The product M-Mv for polydisperse samples is then log (MMV) = log K + (1 + a) log Mv (8) If in eq 2 we use an average molecular weight, M, in place of M, we obtain a corresponding average elution volume, V (using the same coefficients A0lA1; ..., determined for monomolecular species).…”

Section: Resultsmentioning

confidence: 99%

Gel permeation chromatography of poly(N-vinyl-3,6-dibromocarbazole). Universal calibration, nonexclusion effects, and incompatibility

Barrales‐Rienda¹,

Gómez²,

Horta³

et al. 1985

Macromolecules

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Nonexclusion effects in the GPC of poly(N-vinyl-3,6-dibromocarbazole) ) in tetrahydrofuran, at 25 "C, using cross-linked polystyrene (PS) as the gel phase, are analyzed by use of the universal calibration method. The first point in order to determine such nonexclusion effects is to use values for the hydrodynamic volume and the elution volume truly representative of the samples. We show that an adequate set of average magnitudes is the weight-average intrinsic viscosity of the sample, the viscosity-average molecular weight, and the elution volume defined as the viscosity average by means of vv, = log {J3?,(V)[l(P1v] dVJ('/OAL), where H,( V) represents the relative weight of the normalized chromatogram for sample i at elution volume V , a is the exponent in the Mark-Houwink equation for the system under study, and A, is the coefficient of the linear term in the log M vs. V calibration of GPC valid for samples constituted of monomolecular species. The early elution of PVK-3,6-Br2 in THF, as compared with PS standards, can be represented by the equationwhere V , is the retention volume, V,, the interstitial volume, V , the solvent volume within the gel, KD the distribution coefficient for steric exclusion, which is given by KD = -A log ([TIM) + B (A and B are constants), and K is a distribution coefficient for solute-gel interactions. The values of K , found in the present system are gelow unity, and their molecular weight dependence can be represented by -In K, -X,, where X, is the degree of polymerization of the polymer molecule in the mobile phase. In the formulation of Dawkins this corresponds to incompatibility between eluted polymer (2) and gel (3), and -In K,/X, = @3(l + x23), where @3 is the volume fraction of the gel in the stationary phase and ~2 3 the polymer-gel interaction parameter per polymer repeating unit. The compatibility of PVK-3,6-Br2 with PS in THF solution is studied by determining the phase-separation diagram of the ternary system THF (1) + PVK-3,6-Br, (2) + linear PS(3), from which a value of xB at the plait point is determined. The equilibrium distribution of solute polymer (2) between the mobile phase and the gel is treated thermodynamically as a problem in preferential sorption in a ternary system (selective adsorption or desorption of 2 by 3 from the 1 + 2 solution). The result of this thermodynamic treatment is -In K,/X, = b3(l + g23 -g12 -g13), which is similar to the one given by Dawkins, but now it includes the additional contribution of the polymersolvent and gel-solvent interaction parameters g,, and g13. These g,'s and the x,,'s defined on the basis of chemical potential are connected through xi, = g,, -(1 -@,)(dg,,/d@,). The value of gl, + g13 can be of the order of unity so that (1 -g12 -g13) can approximately cancel. This expression gives thus the conditions under which K, can be unity or differ from unity depending on the balance of the interaction parameters. IntroductionAs has been recognized for a long time, steric exclusion from a theoretical point of view is the only...

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Mittelwerte des Molekulargewichtes und anderer Eigenschaften

Cited by 76 publications

References 175 publications

Physicochemical investigation of k‐carrageenan in the random state

Physicochemical investigation of k‐carrageenan in the random state

Polymolecularity and polydispersity in molecular weight determinations

Gel permeation chromatography of poly(N-vinyl-3,6-dibromocarbazole). Universal calibration, nonexclusion effects, and incompatibility

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