Quasi-elastic light scattering from polymethylmethacrylate in a good and a theta solvent

Meer, Hendrik; Burchard, Walther; Wunderlich, Winfried

doi:10.1007/bf01384359

Cited by 53 publications

(36 citation statements)

References 33 publications

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“…From the result for r = 0 we find DIDo = af = DO(1 -0.60927z + ...), [17] which checks the calculation of Stockmayer and Albrecht (19). Here z is the familiar (12) excluded-volume parameter Z f 3N2(41r(S2)o) 32, [18] in which p represents the binary intersegment cluster integral or effective excluded volume per pair of segments.…”

Section: General Formulationsupporting

confidence: 75%

“…'This shortcoming has been discussed theoretically (14,15). Experimentally, numerous QELS experiments on polystyrene in 0 solvents indicate (16) that the Kirkwood formula overestimates the observable D by about 15%; and for poly(methylmethacrylate) the discrepancy is even greater (17). Some ofthe approximations implied by the Kirkwood result can be avoided (14,18), but it is possible that the underlying Oseen interaction of Eq.…”

Section: General Formulationmentioning

confidence: 99%

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Excluded-volume effect on quasi-elastic light scattering by flexible macromolecules

Tanaka¹,

Stockmayer²

1982

Proc. Natl. Acad. Sci. U.S.A.

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First-order perturbation expressions are developed for the first cumulant (initial time derivative) of the dynamic structure factor observable by photon-correlation measurements of the light scattered by flexible chain molecules in solution. A dimensionless coefficient C, which measures the initial departure ofthe first cumulant from proportionality to the square ofthe scattering vector, is found to be only slightly altered by excluded-volume effects.Quasi-elastic light scattering (QELS) offers a powerful method for the characterization ofmacromolecules in solution (1). With modem photon-correlation methods, the dynamic structure factor S(q,t) can be measured with quite high precision, and in most cases an accurate value of the first cumulant (initial time derivative) of the dynamic structure factor can be obtained (2, 3). By invocation of the known properties (4) of the usual polymer diffusion equation, Akcasu and Gurol (5) showed that the first cumulant can be expressed as an equilibrium average:where q is the scattering vector with a magnitude q = (41r/A)sin(0/2), involving the scattering angle 6 and the wavelength A in the solvent medium; t is time. The denominator of Eq. 1 is the wellknown (5) equilibrium particle scattering factor:where Rjk iS the vector-between structural elementsj and k. The numerator of Eq. 1 requires a knowledge ofthe diffusion tensor DJk. In most applications, this is given the form applied to polymer problems by Kirkwood and Riseman (6), which reads Djk/kBT = ajk C11k + (1 -6jk)(81T7oROk) (1 + IRRk Ok). [3] In this formula, kB is the Boltzmann constant, T is absolute temperature, ; is the friction coefficient of a chain element, qO is the solvent viscosity, and PJk = IRikI . The Akcasu-Gurol recipe, Eq. 1, has been applied to a number of different polymer models (5, 7-11), and it has been shown (10, 11) how such calculations can aid in the estimation of branching and polydispersity in polymer samples, provided that excluded volume effects can be neglected.In most polymer solutions, excluded volume effects on chainlength-dependent properties must be taken into account (12).Supplementing previous work on the excluded volume effect in QELS, we offer here a rigorous first-order perturbation treatment, using well-established methods. Our results indicate that the estimation of branching or polydispersity from QELS will not be seriously affected by excluded-volume interactions. General formulationIt is convenient to implement the averaging process of Eq. 1 in two stages: first, an average over orientations of R with respect to q, and then the average over magnitudes ok. After the first stage, we have N N r/q2 = (NkBT/I) 1 + (C/41r%)q N2

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Section: General Formulationsupporting

confidence: 75%

Section: General Formulationmentioning

confidence: 99%

Excluded-volume effect on quasi-elastic light scattering by flexible macromolecules

Tanaka¹,

Stockmayer²

1982

Proc. Natl. Acad. Sci. U.S.A.

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“…Kirkwood-Riseman theory, i.e., R, = 1.5 R,, where R, was calculated from 0 2 using the Stokes-Einstein equation, which is accurate for random coils in good solvents. 30 In the case of human cervical mucin (HCM)8 and bovine cervical mucin (BCM),* the percentage protein of the native material was used to calculate M,, of the various modified much species.…”

Section: Resultsmentioning

confidence: 99%

Conformation of mucous glycoproteins in aqueous solvents

et al. 1986

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SynopsisLight-scattering techniques have been used to measure the z-average radius of gyration R, z-average translational diffusion coefficient Dt and weight-average molecular weight M , of porcine submaxillary much (PSM) in solution. PSM isolated at low shear in the presence of protease inhibitors has a M , about twice as large as a sample prepared without these precautions. The former sample has a M, of 17 X lo6 in 0.1M NaCI, which decreases to 8 X lo6 in 6M guanidine hydrochloride (GdnHC1) and then to 2 X lo6 on addition of 0.1M mercaptoethanol to the 6M GdnHCl solution. The R , or 0 ; ' values obtained for PSM in this work superimpose with those of other authors for different mucin glycoproteins, leading to linear log-log relationships to the molecular weight of the protein core. Comparison of these results with those in the literature for denatured proteins suggest that mucins are linear random coils in which the protein core is stiffened by the presence of the oligosaccharide side chains. The length of the oligasaccharides and the nature of the solvent have little effect on the extension of the protein core. This suggests that the stiffness of the protein core is maintained by steric repulsion of the residues at the beginning of the oligosaccharide chains.

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“…23) reveals that in fact the measured diffusion coeff icients are no less than 15% lower than the Kirkwood value; and even lower results have been recorded for poly(methylmethacrylate) (Ref. 24). Zirnm (25) has recently reported Monte Carlo studies of unperturbed Gaussian chains in which pre-averaging of the hydrodynamic interactions has been avoided, and has found rather good agreement with the experimental data, but his method contains one approximation that needs further exploration (Ref.…”

Section: Translational Diffusionmentioning

confidence: 99%

Effects of polydispersity, branching and chain stiffness on quasielastic light scattering

Stockmayer¹,

Schmidt²

1982

Pure and Applied Chemistry

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-Aspects of polarized coherent quasi-elastic scattering by dilute macromolecular solutions are discussed. Effects of polydispersity, branching and chain stiffness are considered, particularly in respect to the observable first cumulant of the dynamic structure factor and its dependence on the scattering angle. A combination of integrated and time-resolved scattering data yields the maximum information.

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Quasi-elastic light scattering from polymethylmethacrylate in a good and a theta solvent

Cited by 53 publications

References 33 publications

Excluded-volume effect on quasi-elastic light scattering by flexible macromolecules

Excluded-volume effect on quasi-elastic light scattering by flexible macromolecules

Conformation of mucous glycoproteins in aqueous solvents

Effects of polydispersity, branching and chain stiffness on quasielastic light scattering

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