Study of the dipole moment of internal rotation in the side chains of some methacrylates

Dipole moment of internal rotation in side chains of methaerflates

1491

CONCLUSIONS

(i) The polydispersity of polyarylate F-2, synthesized in the presence of a tertiary amine under different conditions, was calculated, and parameters K and a of the Mark-Houwink equation were determined. (2) Polyarylate F-2 produced by low temperature polycondensation was f o u n d to h a v e a n a r r o w M~\J). (3) 5Iodel reactions were used to show t h a t e x c h a n g e reactions are p r a c t i c a l l y n o n - e x i s t e n t d u r i n g low t e m p e r a t u r e p o l y c o n d e n s a t i o n .

Translated by K. A. A.LLE~ REFERENCES

1. S. V. VINOGRADOVA, V. A. VASNEV and V. V. KORSHAK, Vysokomol. soyed. B9: 5~2, 1967 (Not translated in Polymer Sci U.S.S.R.) 2. V. V. KORSHAK, S. V. VINOGRADOVA and V. A. VASNEV, Vysokomol. soyed. A10: 1329, 1968 (Translated in Pol}-mer Sci. U.S.S.R. 10: 6, 1543, 1968) 3. V. V. KORSHAK, S. V. VINOGRADOVA, V. A. VASNEV and T. I. MITAISHVILI, Vysokomoh soyed. A l l : 81, 1969 (Translated in Polymer Sci. U.S.S.R. l h 1, 89, 1969) 4. S. V. VINOGRADOVA, V. A. VASNEV, V. V. KORSHAK and T. I. MITAISHVILI, Vysokomol. soyed. A l l : 73, 1969 (Translated in Polymer Sci. U.S.S.R. 11: 1, 79, 1969) 5. W. ARCH:IBALD, J. Phys. Chem. 51: 1204, 1947 6. V. V. KORSHAK, S. V. VINOGRADOVA, S. A. PAVLOVA, L. V. DUBROVINA and R. S. VELICHKOVA, Vysokomol. soyed. A l l : 16, 1969 (Translated in Polymer Sei. U.S.S.R. l h 1, 15, 1969) 7. E. TURSKA and A. DEMS, J. Polymer Sci. C22: 407, 1968 8. G. I. TIMOFEYEVA," S. A. PAVLOVA and V. V. KORSHAK, \'ysokomol. soyed. 7: 1436, 1966 (Translated in Polymer Sci. U:S.S.R. 7: 8, 1591, 1965) 9. G. I. TIMOFEYEVA, L. V. DUBROVINA, V. V. KORSiLkK and S. A. PAVLOVA, Vysokotool. soyed. 6: 2008, 1964 (Translated in Polymer Sci. U.S.S.R. 6: 11, 2221, 1964) 10. V. V. KORSHAK, S. A. PAVLOVA, G. I. TIMOFEYEVA, S. V. VLNOGRADOVAand V. A. PANKRATOV, Dokl. Akad. h'auk SSSR 160: 119, 1965 11. S. A. PAVLOVA, V. V. KORSH_AK, L. V. DUBROVINA and G. I. TI~IOFEYEVA, Vysokomol. soyed. A9: 2624, 1967 (Translated in Polymer Sci. U.S.S.R. 9: 12, 2969, 1967)

STUDY OF T H E D I P O L E MOMENT OF I N T E R N A L ROTATION IN

THE SIDE CHAINS OF SOME METHACRYLATES* L. L. BUI~SHTEII~ and T. P. STEP_%XOVA High Polymers Institute, U.S.S.R. Academy of Sciences

(Received 21 April 1969) THE s t u d y of t h e optical a n i s o t r o p y ofpol}maers with different side chain s t r u c t u r e showed the c o n f o r m a t i o n a l properties of the m a i n chain to be influenced b y t h e s t r u c t u r e a n d rigidity o f t h e side chain [1, 2]. A s t u d y o f the internal r o t a t i o n * Vysokomol. soyed. A12: Xo. 6, 1315-1320, 1970.

1492

L. L. BURSHTEI.N"a n d T. P. STEP.~NOV.-%.

in these branches is o.f special value here, because it determines their mobility and conformational properties. One of the methcds giving information of this kind is that of the dipole moments of polymers in solution. This work describes the study of the effect of the length of the alkyl radical on the conditions of internal rotation of polar groups in the branched polymers of certain methacrylates, and of their low mol.wt, analogues. EXPERIMENTAL Atactic polymethylmethacrylate (PMM), polyethylmethacrylate (PEM) and poly-nbutylmethacrylate (PBM), produced by radical polymerization, and the hydrogenated monomers, methyl- and n-butylmethacrylate, were studied. The polymers were reprecipitated from benzene solutions with methanol and dried to constant weight in a vacuum a: the appropriate temperatures; the mol.wt, according to intrinsic viscosity measurements were: PMM=500,000, PBM----900,000. The solvents used were benzene, toluene, p-xvlene; these were dried and distilled over P205. Some of the characteristics of the studied materials are contained in the Table. PROPERTIES

OF

POLYMERS

MONO)IERS

AT

Materials Hydrogenated MM Hydrogenated BM PM~I PE.~[ PB3I

A~N'D H Y D R O G E N A T E D

20~C nD

p, g/cm a

1.3820 1.4030 1.491 1.483 1.485

0.8896 0.8629 1.197 1.126 1.057

The dipole moments were determined by measuring the dielectric loss as a function of concentration and the specific volume of the solutions, then extrapolating to infinite dilution. The dielectric loss constant was determined in a glass condenser with 3 coaxial Pt-electrodes [3] on a sonar bridge of type T E S L A BM-400; the accuracy of measurement was 0.1 ~o. The specific volumes of the solutions were determined in a capillary pycnometer and pycno-dilatometer, and the accuracy of measurement was 0.02-0.050o. The dipole moments were calculated from the Debye formula, using the Kumler m e t h o d in the extrapolation to infinite dilution [4]: /~----0"0128{(P, ~ - - R o ) "T} 1/2

(1)

3g'vo "M - { - ( v o + # ) ' t ° - - 1 "M P2 ~----(e0d- 2)2 e0+2 '

(2)

in which g is the dipole moment, RD the molar refraction, P ~ , t0 and v0 the molar polarization, dielectric loss factor and specific volume at infinite dilution, and -

-

~ d w z/ w~ffi o

\ d w 2 / w.~mo

which are determined from the dielectric loss and specific volume as a function of the concentration by weight in solution.

Dipole moment of internal rotation in side chains of methacrylates

1493

In the case of studies on low mol.wt, substances, formulae (1)-(2) directly yield the dipole moment ~=#~ of the compound in the respective solvent. As regards the polymers, #=#e~t is more complex [5], and is also dependent on the correlations of polar groups in the polymer chain. The information about a similar correlation can be obtained from comparison of the dipole moments of polymers with those of the hydrogenated monomers through the correlation parameter g=,ueft~-/ao ~-. RESULTS

The study of the dipole moments of low mol.wt, compounds has shown that the most complete information about internal rotation can be obtained b y this m e t h o d f r o m t h e i r t e m p e r a t u r e d e p e n d e n c e in different solvents [6]. W e therefore consider t h e results of t h e dipole m o m e n t s of p o l y m e r s a n d t h e i r low mol.wt, a n a l o g u e s as a f u n c t i o n of t e m p e r a t u r e r a n g i n g f r o m 10 to 120°C. T h e values of (de/dw~.),~.= o a n d (g~'/dw~)~= o as a f u n c t i o n of t e m p e r a t u r e (formulae (1)-(2)), essential to t h e dipole m o m e n t calculation, are c o n t a i n e d in Figs. 1-4. T h e r e ~

2"8

¢z

e}

\ !

-cz

~%=5

2.#

2"0

2"0

1"6 i

1"60

I

20

I

00

I

60 Fro. 1

I

80

~1 I" fO0 120 T,°C

0

20

¢0

60

80

fO0 lZO T,°C

Fro. 2

FXG. I. Parameter ~ of hydrogenated MM as a function of temperatare in: /--toluene, 2--p-xylene, and of hydrogenated BM in 4--toluene and 3--p-xylene. FIG. 2. Parameter ~ of P~I~[ as a function of temperature in: 1--p-xylene, 2--toluene, and of PE-%[ in 3--toluene, and of PBM in 4--p-xylene, 5--toluene. was a linear response in all t h e s t u d i e d s y s t e m s b e t w e e n t h e dielectric loss factor, specific v o l u m e , a n d t h e w e i g h t c o n c e n t r a t i o n of the c o m p o u n d in t h e solution, so t h a t t h e ~- a n d / ? - v a l u e s could be o b t a i n e d a t all t e m p e r a t u r e s f r o m t h e slope o f t h e ~----f (w2) a n d v-----f (w2) r e s p o n s e lines. V a l u e s ~ a n d / ? are a linear f u n c t i o n o f t e m p e r a t u r e in t h e case o f p o l y m e r s a n d t h e i r low mol.wt, analogues. Using t h e f u n c t i o n s illustrated in Figs. 1-4, we c a l c u l a t e d t h e dipole m o m e n t s of the s u b s t a n c e s for the r a n g e 10-120°C, a n d t h e s e a r e s h o w n in Figs. 5 a n d 6. As Fig. 5 shows, t h e dipole m o m e n t changes as a f u n c t i o n of t h e side chz~in s t r u c t u r e . A t e m p e r a t u r e increase to 90°C in t h e case of P3L~[ caused a small increase in t h e dipole m o m e n t ; this was p r a c t i c a l l y i n d e p e n d e n t of t h e solvent t y p e . T h e dipole m o m e n t changes of P E M were similar to those of PMM.

1494

L L. BURSHTEI-X and T. P. STEP.-~NOV.&

Quite different results were obtained with PB_1[. The dipole moment depended here on the t~-pe of solvent, which differed in behaviour for P 3 B [ and PBM, and the nature of the temperature dependence in toluene differed from that in p-xylene. The dipole moment of PBM increased in p-xylene in the range 20 to 90°C, while there was a decrease in the same temperature range when using toluene as solvent.

0"05~"

×-

0 1

"

~

20

~0

. . . . .

80

80

.~

"

#

100 T,°C120

Fro. 3. P aram e t e r fl of hydrogenated M}I as a function of temperature in 1--toluene, 2 - p-xylene, and for n-buty]methacrylate in 3--p-xylene, 4--toluene.

The dipole moment of a polymer is known to depend on the internal rotation in the side chain and on the near order activity in the main chain [7]. lVe shall therefore examine the dipole moment-temperature function in the same solvents

1"3'

O.5

o

"

IIF

""2¢'~ 2

'

~3

2o

~o

8o FzG. 4

8o

~oo

i

i

I

i

i

I

I

I

I

1"¢

1

0.¢

0"2 0

i

~2o

7;,oc

f

~3

~

I

I

f

I

I

I

o

m

~o

6o

8o

loo

12o

T,°C

FZG. 5

FIG. 4. Parsaneter ~ as a function of t e m p e r a t u r e for PM:I%[ in 1--p-xylene, 2--toluene, for PE~I in S--toluene, for P B M in d--p-xy|ene, 5--to|uene. FIG. 5. The dipole m o m e n t of P~L~[ in to|uene (black circles) and in p-xylene (blank circles) (1), of PE~I in toluene (2) of PB~I in p-xy|ene (S),or toluene (4),as a function of temperature

of the respective low mol.wt, compounds to explain the obtained results. T h i s will eliminate the effect of the chain and permit the analysis of internal rotation conditions in the side chain. The dipole moment-temperature functions for the hydrogenated monomers methyl- and butylmethacrylate are sho~-n in Fig. 6. A substantial difference existed here, as found with the polymers. The dipole moment of the hydrogenated

Dipole moment of internal rotation inside chains of methacrylates

1495

methylmethacrylate (~L~I) was independent of the solvent type and remained constant in the studied temperature range. The lack of any effect of the surrounding medium was also confirmed here by the measurements on methyl acetate vapour which has a similar molecular structure, although the C--O group in methyl acetate has a direct bond with the methyl group. The dipole moment determina/zo,D

/'6

l

.

I

2O

I

~0

L

60

t

~

100

8O

•

7;°0

/20

Fxo. 6. Dipole moment-temperature functions of hydrogenated n-butylmethacrylate in 1--p-xylene, 2--benzene, 3--toluene; of hydrogenated MM in 4--p-xylene, 5--toluene, and 6--methyl acetate vapour. tion in the gas phase of this compound was also temperature-independent (35210°C) and was 1.7 D [6], which was almost identical with that found for the hydrogenated MM in different solvents. The largest increase of the dipole moment was found in p-xylene as solvent, and also in benzene. This did not happen in toluene.

~o--~x

04./L

2

L

L

I

I

I

20

~

8O

80

100

I

T,oc

/20

FIG. 7. Correlation parameter g as a function of temperature for PMM in /--toluene, 2-p-xylene, for PB~[ in 3--toluene, 4--p-xylene. The rotation isomerism theory states that a temperature dependence of the dipole moment and an effect of solvent on the latter will exist during the investigation of low mol.wt, compounds where the internal rotation of the polar groups relative to each other is inhibited [6]. The possibility of C = O and OR group rotation, R being the respective alkyl radical, must be taken into account in the case of hydrogenated gl~[ and BM molecules. The results of the dipole moment study on hydrogenated ~L~I does not permit an unequivocal interpretation of the internal rotation conditions of the polar groups in this compound. T h e lack of a temperature dependence can be due to the dominance of one rota-

1496

L . L . BURSHTEINand T. P. STEP.~-~,'OV,t

tional isomer, or to the presence of an equilibrial mixture of rotational isomers, which would be equivalent to free internal rotation conditions [6]. The dependence of the dipole moment on temperature and solvent in the case of the hydrogenated BM is evidence of internal rotation not being free in the quoted temperature range. The described dipole moments of low mol.wt, compounds, which mode[ the polar side-chain structure of a polymer chain, thus show that the conditions for internal rotation of the polar groups in the quoted temperature range are determined b y the structure of the alkyl radical, and will change on changing from M~f to B~L The analysis carried out on the low mohwt, analogues permitted the interpretation of the results obtained in the dipole moment determination on P~[~I and PBM. We have shown earlier that the dipole moment of P~L~f is solvent-independent. As that of the hydrogenated M~[ remains constant in the studied temperature range, the dependence of the dipole moment in P~[~[ on temperature will characterize the conditions of internal rotation changes in the side-chain (branch), as well as in the main chain of the polymer. The results obtained with the hydrogenated BM permit the consideration of an intramolecular mobility in the side chain. The correlation parameter g, which determines the correlation of polar group orientation in the pol~mer chain, gives information about the influence of the chain on the mobility of the appended polar group. The correlation factor g is shown as a function of temperature in two solvents for P~f~[ and P B M in Fig. 7. Accordingly the correlation in the orientation of polar groups in the side chain is independent of the solvent, but the size of g and its temperature dependence is not the same in the two polymers. There is a slight increase in value with temperature in the case of P~L-~ due to decreasing inhibition of internal rotation in the main chain. The correlation factor decreases in the whole temperature range in the case of PBM. All this indicates that a longer side chain will cause a change in correlation of polar group orientation in the side chains of PM~f and P B M ( g p ~ ~gPB~i) when the temperature is raised. Recent studies of the influence of branch radical structure on the optical and conformational properties of the chain have shown t h a t an increase in the length of the branch radical caused changes of main chain rigidity [1, 8]. The results described in this work show that considerable differences exist between the internal rotation conditions in isolated side-chains, a n d there is also a correlation increase in the polar group orientation of side chains when on changing from P~IM to P B M while increasing the 'temperature. CONCLUSIONS

(1) The study of the dipole moments of hydrogenated methyl- and n-butylmethacrylates as a function of temperature has shown that the l e n ~ h of the alkyl radical influences the internal rotation conditions in compounds simulating the structure of the isolated side chain.

Temperature and conee~lt.ration dependence of enthalpy

1497

(2) Different internal rotation conditions in the side chain cause correlational changes of the polar group orientation in polybutylmethacrylate on elevating the temperature, but not in polymethylmethacrylate. Translated by K. A. Ar.T~.,,REFERENCES

1. V.N. TSVETKOV, Vysokomol. soyed. A l l : 132, 1969 (Translated in Pol~uner Sci. U.S.S.R. 11: 1, 148, 1969) 2. V. N. TSVETKOV, D. IrdIARDI, I. N. SHTENNIKOVA, E. V. KORNEYEVA, G. F. PIROGOVA and K. NITRA/, Vysokomol. soyed. A l l : 12, 1969 3. T. P. ANDREYEVA and L. L. BURSHTEIN, Zavod. Labor. 33: 1583, 1967 4. J. IIALVERSTA/}T and W. KUMLER, J. Am. Chem. Soc. 64: 2988, 1942 5. G. P. MEgWA/LOV and L. L. BURSHTEIN, Uspe -khi fiz. nauk 24: 3, 1961 6. S. MXDZU$IM.A, Stroyenie molekul i vnutrennoye vrashchenie (Molecular Structure and Internal Rotation). Izd. inostr, lit., 1957 7. O. B. PTITSYN and T. M. BIRSHTELN, Konformatsii makromolekul (Maeromolecular Conformations). Izd. "Nauka", 1964 8. )I. KURATA and W. H. STOCI4LMAYER, Fortschr. Hochpol. Forsch. 3B: H. 2, 1963

THE TEMPERATURE AND CONCENTRATION DEPENDENCE OF ENTHALPY, FREE ENERGY AND ENTROPY OF MIXING POLYSTYRENE SOLUTIONS WITH AN UPPER AND LOWER CRITICAL TEMPERATURE OF MIXING* A. A. T~GER, A. I. PODLESNY-~K, i~[. V. TSILIPOTKLX~., L. V. ADx_~Iovx, A. A. BA~XREVA and L. V. Dv..~novx A. M. Gor'ki State University of the Urals

(Received 21 April 1969) THE d e p e n d e n c e of t h e h e a t of solution ( e n t h a l p y of mixing, AH ~) of glass-like p o l y m e r s , such as p o l y s t y r e n e , on t e m p e r a t u r e [1-3] a n d c o n c e n t r a t i o n [4-6] has b e e n i n v e s t i g a t e d before, b u t we r e t u r n to this p r o b l e m once m o r e because of some new e x p e r i m e n t a l facts which h a v e b e c o m e a v a i l a b l e r e c e n t l y a n d c o n t r a d i c t t h e existing findings r e f e r r e d to above. These n e w f a c t s concern t h e u p p e r a n d lower critical m i x i n g t e m p e r a t u r e s d e t e c t e d on p o l y m e r - s o l v e n t s y s t e m s , which a s s u m e t h a t t h e sign of ~ H '~, as well as t h e t e m p e r a t u r e d e r i v a t i v e O,4H~/OT, d e p e n d on t h e n a t u r e of t h e solvent. * Vysokomol. soyed. A12: No. 6, 1320-1332, 1970.