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Polymer Chemistry. The Basic Concepts - Himenz P.C.

Himenz P.C. Polymer Chemistry. The Basic Concepts - Copyright, 1984. - 736 p.
Download (direct link): polymerchemistry1984.djvu
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and the intercepts are c/R0 v, where the subscript v indicates vertically
polarized light. In this case Kv = 42 (ndfi/dc2)2 Ao4Na. The following
values of n and dn/dc2 can be used to evaluate Kv:
T = 20 a 22 T = 67C
n dn/dc2 n dn/dc2
Methyl ethyl
ketone 1.378 0.221 1.359 0.230
Dichloroethane 1.444 0.158 1.423 0.167
Toluene 1.496 0.108 1.472 0.118
Evaluate M, (rg2)1/2, and from each piece of pertinent data and
comment on the following points:
a. Agreement between M values.
b. Correlation of (rg2)1/2 and with solvent "goodness."
10. For polystyrene in butanone at 67C the following values of Kc2/Re X
106 were measuredf at the indicated concentrations and angles. Construct
a Zimm plot from the data below using = 100 cm3 g-1 for the graphing
constant. Evaluate M, B, and (rg2)1/2 from the results. In this
experiment Xo = 546 nm and n = 1.359 for butanone at this temperature.
(deg) c2 (g cm 3)
1.9 X 10"3 3.8 X 10'4
25.8 --- 1.48
36.9 1.84 1.50
53.0 1.93 1.58
66.4 1.98 1.62
90.0 2.10 1.74
113.6 2.23 1.87
143.1 2.34 1.98
tB. H. Zimm,J. Chem. Phys. 16:1093 (1948).
722
Light Scattering by Polymer Solutions
11. Benoit et al.f prepared a mixture of two different fractions of
cellulose nitrate and determined the molecular weight of the mixture by
light scattering. The mixture was 25.8% by weight fraction A and 74.2%
fraction B, where the individual fractions have the following properties:

Fraction Mn Mw
A 635,000 1,270,000
199,000 400,000
Calculate Mn and Mw for the mixture on the basis of this information
concerning the components and their proportions. The following light-
scattering data for the mixture allow Mn and Mw to be evaluated by the
procedure shown in Fig. 10.15:
(deg) (Kc2/R0)X 107 (deg) (Kc2/R0)X 107
(mol g_1) (mol g-1)
30 19.6 80 42.2
35 21.7 90 48.7
40 24.4 100 53.0
45 26.4 110 57.0
50 28.3 120 61.3
55 31.0 130 64.9
60 33.0 140 67.4
70 37.4
Evaluate Mn and Mw from the light-scattering data and compare the
values with those calculated from the preparation of the mixture.
Bibliography
1. Dover, S. D., in An Introduction to the Physical Properties of Large
Molecules in Solution, by E. G. Richards, Cambridge University Press,
Cambridge, 1980.
2. Hiemenz, P. C., Principles of Colloid and Surface Chemistry, Marcel
Dekker, New York, 1977.
3. Kerker, ., The Scattering of Light and Other Electromagnetic
Radiation, Academic, New York, 1969.
4. Stacey, K. A., Light Scattering in Physical Chemistry, Butterworths,
London, 1956.
5. Tanford, C., The Physical Chemistry of Macromolecules, Wiley, New
York, 1961.
tH. Benoit, A. M. Holtzer, and P. Doty,/. Phys. Chem. 58:635 (1954).
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