Application of gel permeation chromatography to determination of the molecular weight distribution of polyorganosiloxanes

532

K. A. A_wDvz~wove$ a/.

6. D. N. YEMEL'YANOV, I. Ye. KONONOVA, A. V. RYABOV and N. F. SMIRNOVA,

Vysokomol. soyed. B17: 163, 1975 (Not translated in Polymer Sci. U.S.S.R.) 7. Kh. S. BAGDASARYAN, Teoriya radikal'noi polimerizatsii (Theory of Radical Polymerization). 2nd cd., Izd. "Nauka", 1966 8. A. A. TAGER, Fiziko-khimiya polimerov (Physical Chemistry of Polymers). Izd. "Khinfiya", 1968 9. V. V. KORSHAK and K. K. MOZGOVA, Uspekhi khimii 28: 783, 1959 10. S. GLASSTONE, K. J. LAIDIER and H. EYRING, Teoriya absolutnykh skorostei reaktsil (Theory of Rate Processes). Foreign Literature Publishing House, 1948 (Russian translation) 11. A. EINSTEIN, Sobranie nauchnykh trudov, t. I I I (Collected Scientific Works, Vol. III), p. 75, 1966 (Russian translation) 12. Ya. L FRENKEL', Kineticheskaya teoriya zhidkostei (Kinetic Theory of Liquids). Izd. Akad. Nauk SSSR, 1945 13. K. A. ANDRIANOV, Kremniiorganicheskie soyedineniya (Organosilicon Compounds). p. 342, Goskhimizdat, 1955 14. E. HATSCHEK, Vyazkost' zhidkostei (Viscosity of Liquids). ONTI, 1935 (Russian translation)

APPLICATION OF GEL PERMEATION CHROMATOGRAPHY TO DETERMINATION OF THE MOLECULAR WEIGHT DISTRIBUTION OF POLYORGANOSILOXANES* K. A. ANDRIANOV, S.-S. A. PAVLOVA, I. P. TVERDOKHLEBOVA, N. V. PERTSOVA V. A. TEMNIKOVSKII a n d L. N. PRO~'IxA Institute of Hetero-organic Compounds, U.S.S.R. Academy of Sciences

(Received 2 Apt// 1976) An universal calibration curve for polystyrene, polydimethylsiloxane and polymethylphenylsiloxanc has been obtained by means of a combination of the GPC and viseometrie methods. The MWD of polydimethylsiloxane has been determined by use of the universal calibration curve and this is compared with the MWD obtained by high speed sedimentation in the ultracentrifuge.

II~ :DETERMI~ATIO~ of molecular weight and molecular weight distribution by the GPC method, calibration of the gel chromatograph is a very important problem. The results of analysis by the GPC method are of course obtained in the form of a continuous relationship between polymer concentration and the retention volume of the eluent. In order to determine molecular weight and MWD by gel chromatography it is necessary to construct a calibration curve relating * Vysokomol. soyed. A19: No. 3, 466-t68, 1977.

Determination of molecular weight distribution of polyorganosiloxanes

833

the molecular weight of standard samples, of narrow MWD (~J~w/2tTn~<1.1) to the retention volume of eluent Vel. I t is assumed t h a t the position of the peak of the narrow standard corresponds to a molecular weight Mm~x-~Jtlw" ~ n - Hazzel [1] found t h a t within the limits of experimental error the value of Mw can be used for standards of narrow MWD. logM

0"3

i

I

58

60

[

70

I

50 62

80

I

90

64,

[

100 HO

66

i

68

I

70{3)

Ve/ , m l

Fro. 1. Relationship between log M and retention volume for polydimothylsiloxane (1), polystyrene (2) and polymethylphenylsiloxane (3). Standard samples of PS of narrow MWD and narrow fractions of polydimethyl- and polymethylphenylsiloxane were used for calibration of the gel chromatograph. The results of measurement of retention volumes for fractions of PS, polydimethyl- and polymethylphenylsiloxane are given in the Table. l~rom these results graphs of the dependence of Voi on MW were constructed. It is seen from comparison of these graphs for polydimethylsiloxane, polymethylphenylsiloxane and PS (Fig. 1) that a disadvantage of calibration with respect to MW is its non-universality, i.e. its dependence on the chemical structure of the macromolecule. Therefore interest naturally arises in the possibility of calibration of the chromatograph with respect to hydrodynamic characteristics of the macromolecules, such as their volume or dimensions. Benoit [2, 3] and Dawkins [4] showed theoretically and then experimentally that for PS, PMMA and polydimethylsiloxane in chloroform the calibration curves coincide if t h e y are constructed as the relationship between the logarithm of the unperturbed dimensions log (~,)J and the retention volume Vet. Experiments carried out by a number of authors [3, 5] show t h a t for macromolecules, having a not very small coefficient of diffusion D, there is a universal relationship, general for all polymers, between the retention volumes Vei and the hydrodynamic volume of the macromolecules Vm, which is proportional to the product of the intrinsic visco-

K. A. A m ~ m ~ o v e~ a/.

534

airy a n d molecular weight: Vm ~[t/] M

Vel=a--bIn {[vl]M}=a--b'In ]7"= ~ i g u r e 2 shows t h e d e p e n d e n c e o f log [~] M o n F~, c o n s t r u c t e d f r o m d a t a in t h e Table. I t is seen f r o m t h e g r a p h t h a t for t h e given p o l y m e r s t h e experim e n t a l points lie satisfactorily on a s t r a i g h t line. log[ ,.].H 6"8

I.o~ ~ , ~

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80

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FZG. 2. Universal oalibration graph. Fzo. 3. Molecular weight distribution curves for polydimethylsiloxane obtained by the GPC method (1) and by ultracentrifugation (g). W e used this calibration curve for calculation o f t h e ~ of un~actionated polydimethylsiloxane. T h e integral distribution c u r v e o f p o l y d i m e t h y l s i l o x a n e is shown in Fig. 3 (curve 1). T h e coefficient o f polydispersity, calculated f r o m t h e curve, is 1.44. F o r comparison o f t h e results o b t a i n e d b y t h e GPC m e t h o d , t h e M W I ) o f t h e same p o l y d i m e t h y i s i l o x a n e was d e t e r m i n e d in t h e ultracentrifuge. F i g u r e 3, c u r v e 2 shows t h e integral molecular w e i g h t distribution c u r v e for t h e p o l y d i m e t h y l s i l o x a n e o b t a i n e d in this way. T h e coefficient o f polydispersity c a l c u l a t e d f r o m t h e curve is again 1.44. The linear polydimethylsiloxane used in this investigation was prepared by polymerization of octamethylcyclotetrasiloxaue at 80 °, with trimethylammonium trimethylsilanolate as catalyst. The active end groups were blocked by treatment with trimethylchlorosilane in the presence of an acceptor (pyridine), the latter being subsequently removed by extraction with water. The polymethylphenylsiloxane was obtained by polymerization of c/a-trimethyltriphenylcyelotrisiloxane, with =,m-trimethylammonium hydroxymethyL phenylpolysiloxane as catalyst. The preparation was carried out in two stages [6], first in hexane at 47 ° for 3 rain, then at room temperature after removal of the hexane The polydimethyl- and polymethylphenylsiloxanes were separated into eleven and nine fractions respectively, by fractional extraction with methanol of a solution of the polymer in a 3 : I mixture of eyclohexane and CC14. The weight average molecular weights of the f r ~ -

in vacuo.

Determination of molecular weight d i ~ r i b u t i o n of polyorgano~iloxanos

6~

M O L E C U L A R W E I G H T S , I N T R I N S I C VISCOSITY AND R E T E N T I O N VOLUMES O F FRACTIONS OF L I N E A R P O L Y D I M E T H Y I ~ I L O X A N E , P O L Y M E T H Y L P H E N Y L S I L O X A N E AND P O L Y S T Y R E N E

/~,X 10-'

[q], dl/g I log [~/]-M (toluene,[

25°)

I

Ve,

/~¢, x ×104

99'7 100.0 100.0 93"3 106.3 85'9 83"4 83"7 83.2 82.7 82.2 80.8 71.0 77.3 69.1

267 345 434 477 578 587 718 934 1025

Polydimethylsiloxane 13.5 14 17 18 22 50 60 76 81.5 85 88 112 157 175 242

0.07 0.07 0.08 0.09 0.11 0.23 0.28 0.34 0.36 0.38 0.39 0-42 0.55

0.69 0.77

2.9666 2.9924 3.1498 3.2073 3.3373 4-0573 4.2273 4.4119 4.4708 4.5103 4.5339 4.6702 4.9358 5.0616 5.2714

[•], dl/g] [ (toluene,[ log [r/] x M

25o)

V,I

i

Polymethylphenylsiloxane 1"14 1 "40 1"67 1"80 2"09 2"11 2"48 3"04 3"27

5.4849

5.6852 5.8607 5.9341 6.0820 6.0941 6.2499 6.4532 6.5253

71"2 67"8 67"5 70"2 65"7 67"0 64"8 65"5 60"0

Polystyrene 5.0 10.3 20.4 51.0 97.2 173.0

0"06 0"09 0"16 0"30 0"48 0"72

2"4624 2"9905 3'5110 4"1917 4"6717 5"0973

103.4 96.9 92.8 85.0

80.6 75.2

tions, /l~w, were measured by the light scattering method. The viscosity was measured in toluene at 25 °, in an Ubbelohde viscometer, and the molecular weights h:/of the fractions were calculated from the Mark-Houwink equation [7]: [7]----0"67× 10-' .M °'~'. A KhZh-1302 gel chromatograph was used for the GPC investigations. The working systems consisted of two columns ( l = 90 cm, d = 8 ram), packed with macroporous, soda. boroeilicate glass of pore size 250 A and 1600 A, with a range of separation of molecular weights of 5 × 103-2X l0 t. The size of the granules was 40-80 ~. Toluene was used as the eluent. The eluent flow rate was 45 ml/hr. The elution volumes of all the fractions of the polymers were calculated from the chromatograms. The elution volume was taken as the distance covered from the m o m e n t of introduction of the sample to the m a x i m u m of the peak in the chromatogram. The results of fractionation and of measurement of viscosity, molecular weights a n d retention volumes, axe presented in the Table. Sedimentation gradient curves were obtained in a MOM-120 ultracentrifuge at a rotor speed of 50,000 rev/min, in benzene at concentrations of 0.5, 0.75 and 1 g/dl. The distribution with respect to sedimentation constants was converted to molecular weight distribution by use of the Flory-Mandelkern formula [8]:

M[~=~p-~(1-- ~Vol For polydimethylsiloxane the value of (l--~p,) is 0.1718 (in benzene at 20 °) and [q] for this polymer was found from the viscosity distribution curve. Transited by E. O.

536

K . A . ANDRIANOV et a~. REFERENCES

1. J. E. HAZZEL, L. A. PRINCE and H. E. STAPELFELDT, J. Polymer Sci. C21: 43, 1968 2. Z. GRUBISIC, P. REMPP and H. BENOIT, J. Polymer Sci. ]35: 753, 1967 3. H. BENOIT, Z. GRUBISIC, P. REMPP, D. DECKER and J. G. ZILLIOX, J. ehim. phys. phys.-chim, biol. 63: 1507, 1966 4. J. V. DAWKINS, R. DANYEL and J. W. MADDOCK, Polymer 10: 154, 1969 5. J. V. DAWKINS, J. Maeromolec. Sci. B2: 623, 1968 6. K. A. ANDRIANOV, V. A. TEMNIKOVSKII, L. M. KHANANASHVILI and N. A. LYANINA, Dokl. Akad. Nauk SSSR 189: 311, 1969 7. K. A. ANDRIANOV, S. A. PAVLOVA, I. I. TVERDOKHLEBOVA, N. V. PERTSOVA and V. A. TEMNIKOVSKII, Vysokomol. soyed. A14: 1816, 1972 (Translated in P o l y m e r Sei. U.S.S.R. 16: 8, 2035, 1972) 8. L. M. MANDELKERN and P. J. FLORY, J. Chem. Phys. 20: 212, 1952

SYNTHE,SIS AND CONFORMATIONAL CHARACTERISTICS OF SOME LADDER POLYPHE, NYLSILOXANES* K. A. A~DRm~OV, S. V. BUSHn~, M. G. VITOVSKAYA, V. N. YEMEL'YANOV, P. N. LAVRE~XO, N. N. IWA~AROV~, A. M. MUZAFAROV, V. YA. NXXOLAYEV, G. F. KOLBINA, I. N. SHTEIVNIKOVA and V. N. TSVETKOV Institute of Macromolecular Compounds, U.S.S.R. Academy of Sciences

(Received 31 May 1976) Controlled synthesis of samples of polyphenylsilsesquioxane has been achieved b y two different routes from a previously isolated, individual cyclic compound c/~1,3,5, 7 -tetrahydrotetraphenylcyclotetrasiloxane. The hydrodynamic and optical prop erties of molecular weight optical anisotropy and equilibrium rigidity of the polyphenylsilsesquioxane molecules are substantially greater t h a n the anisotropy and chain rigidity of previously studied ladder polyphenylsiloxanes, prepared by anionic polymerization of the products of complete hydrolysis of phenyltrichlorosilano. Analysis suggests t h a t this greater rigidity, in comparison with the rigidity of the polymers studied previously, is explained by the fact t h a t the present polymers contain a substantiaUy smaller number of defective units upsetting the ladder structure of the macromolecules.

THE problem of the relationship between the molecular structure of polyorganosilsesquioxanes and the structure of the parent compounds, as well as the conditions of preparation, is very important for controlled synthesis of organosilicon polymers of the ladder type. Experimental investigations of this problem have been concerned mainly with cyclolinear polyphenylsilsesquioxane [1-9]. * Vysokomol. soyed. AI9: No. 3, 469-474, 1977.