COMMUNICATIONS TO THE EDITOR
Jan., 1955
95
B.
A.
C. D. Fig. 1.-Electron micrographs of monolayer filins of n-hexatriacontanoic acid: A, blank, no film; B, a t -15 dynes per cm.; C, at 25 dynes per cm.; D, after collapse. Shadows are light, and ari'ows indicate the direction of chrorniuin shadowcast ing.
Shadows a t a small break Jhrough the substrate showed that it remained 50 A. thick. A mechanism for collapse is clearly suggested: as the pressure increases, the monolayer rises from the surface a line Of rupture> polar face to polar face, and Over to form lol1g flat structures, two molecules thick. When n-hexatriaconta1loic acid 'was deposited directly on the collodion support rather than on \vater, different structures Tvere observed. A solution in benzene of less hexatriacontanoic acid than lleeded for a closely packed monolayer \vas deposited on collodion. After evaporation of the benzene and shadovvcastillg, micrographs shelved platelets or flat micelles M,ith rounded edges alld a thickness of two molecu~es. T \ T ~mono~ayer structures were observed. Such observations of monolayer islands, collapsed films and platelets deposited directly from solution provide information basic to two-dimensional and three-dimensional nucleation, crystallization and micelle formation. RESEARCH DEPARTMENT STANDARD OIL COMPANY (INDIANA) HERMAN E. WHITING,INDIANA WAYNEA. RECEIVEUNOVEMBER26, 1954
T H E TEMPERATURE DEPENDENCE O F MECHANICAL AKD ELECTRICAL RELAXATIONS I N POLYMERS'
sir: The temperaturedependence of both viscoelastiC2,3and dielectric4 properties of a polymeric systern can be dWcribed by a single pendent parameter which represents the ratio of any time at temperature to its a! an arbitrary reference temperature To. When different systems are using the same T O for all (e.g., 298"K.),plots of this parameter ( a or~ K from viscoelastic measuremellts, bT frorn tric) against T exhibit little resemblance. However, we have found that, by selecting a different reference temperature T , for each system and plotting
(1) This work was supported by Picatinny Arsenal, Ordnance Corps, Department of the Army. The author wishes to express t o Prof. Jotin D. Ferry and Dr. Robert F. Landel his appreciation for many helpful discussions. (2) (a) R . D. Andrews, N. Hofman-Bang and A. V. Tobolsky, J . Polymer Sci., 3 , 6 6 9 (1948); (b) A. V. Tobolsky and J. R. MoLoughlin, ibid., 8, 543 (1952). (3) J. D. Ferry, J . Am. Chem. Soc., 72, 3746 (1950). RIES,JR. (4) (a) J. D. Ferry and E. R. Fitzgerald. J . Colloid S c i . , 8, 224 KIMBALI, 11953); (b) J. L). Ferry, RT. 1,. W i l l i a ~ ~aird t s fi:, 1 { . l~'iLegevald,Ttils JUUHNIL, in presa.
COMMUNICATIONS TO THE EDITOR
96 I
10
I
I
I
I
System
-
8-
d we-I
b &4-
w
3
2-
0-
-2
-
-4'
TABLE I
(
-
12
'
-60
I
-40
I 0
I -20
I
20
I 40
L 61
VOl. 59 Measurementa
Polyisobut ylene D, s, v Polystyrene D Polyvinyl acetate D, E Polymethyl acrylate D, E Polyvinyl chloroacetate E Polyvinyl acetal E Butadiene-styrene 75/25 S 60/40 S 50/50 S 30/70 S Paracril26 S Polymethyl methacrylate S Polystyrene-Decalin 62% D, V Polyvinyl acetate-tricresyl phosphate 50% D, v Polyvinyl chloride-dimethylthianthrene 10% Dl E 40% D, E Cellulose tributyrate dimethyl phthalate 21% D a D = dynamic mechanical, S = stress steady flow viscosity, E = dielectric.
Reference
Tm,OK,
5a, 1 5b 5c 5f, 4b 4b 4b
243 408 349 324 346 380
6a 6b 6b 6b 6b 6a 5b
268 283 296 328 288 433 29 1
5d
293
4a 4a
293 313
r
247 5e relaxation, V =
Our reference temperature T, is 50 f 4' above the glass transition temperature for 7 of these systems, and it is 46 f 3" above the distinctive temperature T d of TobolskyGGJ for the 6 systems he has analyzed. This suggests that the arbitrary Ts a~ or b~ against T - T a l all such plots coincide for might be replaced by an absolute Tg (from thera wide variety of polymer systems. mal expansion measurements) or T d (from the inFor comparison, T, has been chosen arbitrarily flection of a plot of log UT against temperature). for one system-243OK. for polyisobutylene, a fa- However, because of the difficulty of experimental vorable point with respect to overlapping of dy- measurements near T , or T d , we prefer to base namic mechanical data from this Laboratory. Val- our comparison on one arbitrary selection of T, a t ues of Ts for 18 other systems have been obtained present. by comparing the temperature dependence of their It should be mentioned that divergences may be dynamic m e c h a n i ~ a l ,stress ~ ~ , ~ relaxation, l s 6 steady espected at lower temperatures where properties flow viscosity,6a~b*d and dielectric properties4 with are affected by thermal history. A later communithat of polyisobutylene, and are listed in Table I. cation will discuss the relatioii of this treatment to I n Fig. I, UT and b~ are plotted logarithmically various theoretical formulations of the temperature against T - Ts for all 17 systems, and fall quite dependence of relaxation and viscosity. closely on a single composite curve. DEPARTMENT OF CHEMISTRY T-T,
(OK),
-
Fig. 1.-Log m and log bT plotted against (T T.)for 17 polymer systems: open circles, ref. 5; vertical slots, ref. 4; horizontal slots, ref. 6.
(5) (a) J. D. Ferry, L. D. Grandine, Jr., and E. R. Fitzgerald, J. Appl. Phus.. 2 4 , 9 1 1 (1953); (b) L. D. Grandine, Jr., and J. D. Ferry, dbid., 24, 679, (1953); (c) M. L. Williams and J. L). Ferry, J. Colloid Sci., 9 , 4 7 9 (1954); (d) M. L. Williamsand J. D. Ferry,ibid. (in press); (e) R. F. Landel and J . D. Ferry, (unpublished experimenta); (f) M. L. Williams, J. D. Ferry, S. Axelrod, S. N. Chinai, J. D. Matlack and A. L. Resnick, Presented a t the 126th Meeting of the American Chemical Society, Sept. 1954. ( 6 ) (a) J. Bischoff, E. Catsiff and A. V. Tobolsky, J. Am. Chem. Boc., 74, 3378 (1952); (b) E. Catsiff and A. V. Tobolsky, J . A p p l . Phya., 2 5 , 1092 (1954); (c) A. V. Tobolsky and E. Catsiff, J . A m . Chem. Soc., 76, 4204 (1954).
MALCOLM L. WILLIAMS OF WISCONSIN UNIVERSITY MADISON 6, WIS. RECEIVED NOVEMBER 17, 1951
( 7 ) The reduced viscoelastic equations of Tobolsky and Catsiff.' which also involve a correlation of temperature dependence in different polymers, are based on a filnCtiOnf(T/Td) rather than a difference T T.. Within the temperature range where J is a linear function of T/Td (roughly between -60 and - 3 O O in Fig. l ) , i t can be shown t h a t log C&T is actually a linear function of (T !I'd). Thus in this range the two treatments predict the same temperature dependence. At higher teiiiperatures, however, they would differ.
-
c
r
