990
NOTES I
VOl. 59
I
I
10'0
- 74. I'C. 10s
L
N*
$ c
x
I
a
6c:
0"c.
108
2 5°C.
\
SO"C,
104
0.001
1.0 Time, hr. Fig. 1.-N.B.S. polyisobutylene. 0.01
100
to the rubbery modulus value of 106.88dynes/ Stress relaxation curves a t different temperatures can be superposed by a horizontal translation along the log time axis, and this principle of superposition permits the construction of a master curve that covers the complete time scale. Polytrifluorochloroethylene is a polycrystalline polymer whose melting temperature T m is 212'. Its glass transition temperature has not been accurately determined but should be somewhere in the neighborhood of room temperature if the approximate relation Tg = 2/3Tmis valid. Figure 2 shows stress relaxation data for polytrifluorochloroethylene in the temperature range between 30 and 193". I n this interval the modulus varies from 10'O.l dynes/cm.2 to dynes/cm.2. It is particularly interesting to contrast Figs. 1 and 2. I n Fig. 2 the log E r ( t ) versus log ( t ) curves between 30 and 144" are relatively flat; ie., the modulus change with time in the "transition region" is much less marked for the polycrystalline polymer as compared to the amorphous polymer. Also in Fig. 2 the modulus value of log Er(t) at t = 0.01 hr. changes from a value of 10'O.l dynes/ cm.2 at 30" to a value of a t 144", a very gradual change. The '(transition region," if such it can be called, for a polycrystalline polymer obviously extends over a much wider temperature range than for an amorphous polymer. The "transition region" blends into a high modulus "rubbery region," the crystallites playing the same role that entanglements or cross links do in the amorphous polymers. The relatively rapid decay of stress a t 193" is no doubt associated with a change of microcrystalline
0.1 1 10 100 1000 Time hours. relaxation of polytrifluorochloroethylene.
0.01
Fig. 2.-Stress
structure or texture, i e . , an orientation of crystalline material. Because there are changes with temperature in the microcrystalline structure and in the stress bearing mechanisms, it is certain that the simple time-temperature superposition that is valid for amorphous polymers in the transition region is not valid for polycrystalline polymers. There is not only a horizon displacement along the log time axis due to changing rate of molecular motions with temperature, but also an even more important vertical shift along the log Er(t) axis due to the changing structure and other factors.
METAL-POLYELECTROLYTE COMPLEXES. IV. COMPLEXES OF POLYACRYLIC ACID WITH MAGNESIUM, CALCIUM, MANGANESE, COBALT AND ZINC BY HARRYP. GREGOR, LIONELB. LUTTINGER' AND ERNST M. LOEBL
Contributionfromthe Department of Chemistry of the PoEytechnicInstitute of Brooklyn, New York Received March IO, 1966
I n the first paper in this series2 the formation of complexes of polyncrylic acid (PAA) and copper(11) was reported. In this paper the analogous complexes with magnesium, calcium, manganese(11) cobalt(I1) and zinc are described. The experimental procedure and the mathematical tech(1) A portion of this work is abstracted from the Dissertation of Lionel B. Luttinger, submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry, Polytechnic Institute of Brooklyn, June, 1954. (2) H. P. Gregor, L. R . Luttinger and E. h i . Loebl, T H I B JOURNAL, 69, 34 (1955).
I
a
99 1
NOTES
Sept., 1955
TABLE I COMPLEXATION CONSTANTS OF VARIOUS METALSWITH POLYACRYLIC ACID (PAA, 0.06 N ; neutral salt, 1 M potassium chloride) Metal
Mg Ca Mn co
Zn
log B."
Ba
-3.8 -3.7 -3.0 -3.4 -3.0
2.6 X 4 x 10-8 9 . 1 x lo-' 1.6 x 10-7 8 . 3 x 10-7
niques used to evaluate complexation constants were identical with those used before.2 Experiments were carried out in 1 M potassium chloride throughout, The PAA concentration was 0.06 N and the metal ion concentrations varied from 0.003 to 0.3 M ; at least three different concentrations of each metal were used. I n preparing standard solutions of the metal salts, magnesium and calcium were determined as the oxalate and pyrophosphate, respectively, while manganese and cobalt were titrated according to the procedure of Rosin.* Solutions of zinc chloride were prepared by dissolution of the electrolytic grade metal.
Results and Discussion Figure 1 shows plots of a vs. p ([HA]/ [Hf]) for 0.06 N PAA and various amounts of calcium, cobalt and zinc in the presence of 1 M KC1. Again, as was pointed out in the case of copper(II),2 points pertaining to different concentrations of the same metal generally fall on the same curve. The curves for magnesium and manganese, which are not shown, are very similar. The data can again be represented best by a straight line over the range at = 1. The slope is large, indicating a small spreading factor. Some Of the plots show a distinct flattening Out as the approach a = 2, indicating a probable maximum coordination number of two; this flattening out is especially pronounced it1 the case of cobalt and zinc and is also noticeable for manganese. It may be recalled that copper did not show this phenomenon.2 Table I summarizes the results obtained; the notation is identical with that used previously2; a column indicating a,, = N , i.e., the coordination number, is included. (3) J. Rosin, "Reagent Clieinicals and Standards," D. Van NOStrand C o . Inc.,New York, N. Y . , 1937.
bdba
-0 -0 0.3 1 -0
Kz 6 X 10' 1 x 102 2 . 3 X loa
4 2.1
x x
102 103
nmar = N
*. .. 2 2 2
The complexity constants for the various metals with PAA are much smaller than with copper2 (Kz = 6 X lo5). Formation constants with the alkaline earth metals are smaller than with the transition metals, as expected.
0.5 -
0 -4
-3
-2
P ([HAl/IH*l). Fig. l.-Mo&fied Bjerrum plots for pAA (0.06 N ) and calcium, cobalt and zinc in 1 M potassium chloride. With calcium: 0.00376 ~4 ( n 1; 0.00752 M (m); 0.01504 M ( a ) ; 0.376 M ( 0 ) . With cobalt(I1): 0.00515 M ( A ) ; 0.01287 M (A); 0.0257 M (V). With ainc(I1): 0.00548 M (0); 0.0137 M ( 0 ) ; 0.0274 M ( e ) .
This investigation was supported in part by a research grant, RG 2934(C2) from the Division of Research Grants of the National Institutes o f . Health, Public Health Service. We also wish to express our gratitude to the Rohm and Haas Company Which provided us with m q h s of the polyacry lic acid used in this investigation.
