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Static and dynamic light scattering of high molecular weight polystyrene in good solvents

Saeed, Akhtar
http://rave.ohiolink.edu/etdc/view?acc_num=case1059401322

Abstract Details

1991, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science.
We have carried out detailed static and dynamic light scattering as well as viscosity measurements on narrow molecular weight distribution polystyrene samples in carbon tetrachloride at 25°C. These experiments furnish information regarding the thermodynamic properties i.e. weight average molecular weight(M W), second osmotic viral coefficient(A2), radius of gyration(R g) and hydrodynamic properties i.e. diffusion coefficient(D t,z), hydrodynamic radius(R h) and intrinsic viscosity( (η)). We have identified certain problems in the usual graphical methods used to interpret static light scattering data from good solvents, and proposed an alternative treatment which combines square root fit of the concentration dependence with a Zimm plot treatment of the angle dependence. Universal ratios and chain expansion parameters computed from these data for polystyrene in carbon tetrachloride are similar to those generated for polystyrene in aromatic good solvents. Large differences reported previously in similar experiments on PS/THF are significantly reduced when the new graphical treatment is applied. Universal ratios for PS/CCl4 are in quite good agreement with prediction of Oono and Kohmoto for non-draining self avoiding chains. However exp erimental values for the expansion ratios suggest partial draining. The origin of this discrepancy is unclear at present. Analysis of the first cumulant of the autocorrelation function of light scattered by the PS/CCl4 system in the intermediate q-vector regime shows q3 dependence in the qR g > 2 region, consistent with the theoretical predictions in the non-draining limit. The asymptotic value of the reduced cumulant, Γ e* (=Γ e/(K BT/η o)q3), is numerically similar to those reported earlier for polystyrene in the aromatic good solvents. Biexponential analysis of the correlation function in the region 1 ≤ qR g ≤ 2 leads to values of the longest intramolecular relaxation time, τ1, and the relative amplitude of the translational diffusive mode, P O/P. The numerical value of τ1 is consistent with Rouse-Zimm theory for gaussian chains in the non-draining limit. The behavior of P O/P deviates from prediction for non-draining gaussian chains. These deviations are in the same direction as those observed in the static light scattering data for the particle scattering function in good solvents. Our results suggest that approximate universality exists in the static and dynamic properties of high molecular weight polymers in good solvents. However, based on our experiments, when comparing chemically distinct good solvents small systematic differences remain. Because of numerical variations in universal ratios predicted by different theoretical treatments, we cannot unequivocally decide on the question of partial draining in good solvents
Alexander Jamieson (Advisor)
269 p.
Chemistry, Polymer
Polystyrene; Light scattering, static and dynamic

Recommended Citations

Citations

  • Saeed, A. (1991). Static and dynamic light scattering of high molecular weight polystyrene in good solvents [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1059401322

    APA Style (7th edition)

  • Saeed, Akhtar. Static and dynamic light scattering of high molecular weight polystyrene in good solvents. 1991. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1059401322.

    MLA Style (8th edition)

  • Saeed, Akhtar. "Static and dynamic light scattering of high molecular weight polystyrene in good solvents." Doctoral dissertation, Case Western Reserve University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1059401322

    Chicago Manual of Style (17th edition)

case1059401322
652
© 1991, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.