Synthesis, structure and behaviour of polymers of methacrylic series containing anthracene

1818

N . S . SHELEKI~OVet ai.

9. A.A. TAGEIt, A. I. SUVOROVA, V. Ye. DREVAL', N. P. GAKOVA and S. P. LUTSKAYA, Vysokomol. soyed. A10: 2278, 1968 (Translated ir~ Polymer Sci. U.S.S.R. 10: 10, 2649, 1968) 10. A. A. TAGER, V. Ye. DREVAL', G. O. BOTVINNIK, S. B. KENINA, V. I. NOVITSKAYA, L. K. SIDOROVA ai~d T. A. USOLTSEVA, Vysokomol. soyed. A14: 1381, 1972 (Translated ir~ Polymer Sci. U.S.S.R. 14: 6, 1551, 1972) 11. A. A. TAGER, Fiziko-khimiya polunerov (Physical Chemistry of Polymers). ITd. "Khimiyv", 1968 12. S. P. PAPKOV, Studneobraznoye sostoyaniye poliraerov (Gelatinous State of Polymers). Izd. "Khimiya", 1974 13. S. V. BLESHINSKII, ,O vsalivaniye organicheskikh veshchestv (Salt Formatior~ in Organic Materials). Frunze, 1967 14. K. KESTING, J. Appl. Polymer Sci. 9: 663, 1965 15. S. SAITO, J. Polymer Scl. 7: A-l: 1789, 1969 16. B. I. LIROVA, A. L. SMOLYANSKII, A. A. TAGER and V. S. BLINOV, Vysokomol. soyed. AI7: 731, 1975 (Translated in Polymer Sci. U.S.S.R. 17: 4, 838, 1975)

SYNTHESIS, STRUCTURE AND BEHAVIOUR OF POLYMERS OF METHACRYLIC SERIES CONTAINING ANTHRACENE* N. S. SHELEKHOV, M. G. KRAKOVYAK, S. I. KL~.~IN, G. I. LASHKOV, S. P. KOZEL a n d S. S. SKOI~OKHODOV Institute of High Molecular Weight Compounds, U.S.S.R. Academy of Sciences

(Received 3 December 1976) To study photophysical and photochemical propertms of polymers containing anthracene and examine their correlation with the physical and chemical behaviour of macromolecules m free radical polymerization of 9-a~thrylmethyl methacrylate (AMMA) and eopolymerlzation with methyl methacrylate, soluble polymers of methacrylic series eontaming anthracene were synthesized with a molar fraction of AMMA units ranging from 0.03 to 1.0 and a degree of polymerization PsE,]= 1000-1500. The polymers obtained have a mlcro-tacticlty, which is close to that of free radmal PMMA. The existence of 9-anthrylmethyl carboxylate groups in macromolecules changes both the hydrodynamm behaviour of polymers and some optical propertms of anthracene groups themselves (hypochrome effect). The higher the anthracene group content in polymers, the more marked are these changes. A STUDY o f p h o t o p h y s i c a l a n d p h o t o c h e m i c a l properties o f c o m p o u n d s cont a i n i n g a n t h r a c e n e , including polymers, showed t h e prospects of using t h e m for solving n u m e r o u s scientific a n d technical problems [1, 2]. P o l y m e r s y s t e m s con* Vysokomol. soyed. A19: No. 7, 1586-1592, 1977.

P o l y m e r s o f m e t h a c r y l i o series c o n t a i n i n g a n t h r a c e n e

1819

raining anthracene may have several advantages. Thus, photodimerization of anthracene groups combined with polymer chains in a covalent manner takes place wi4h a much higher quantum yield in solution than in the case of corresponding low molecular weight compounds [3]. TABLE 1. CONDITIONS OF PREPARATION, PROPERTIES OF P A M M A A~rD A M M A (M1)-MMA COPOLYMERS ( S o l v e n t - d i o x a n e ; 60% o v e r a l l m o n o m e r c o n c e n t r a t i o n 1 mole]l.; [ A I D ] ~ 2.8 × 10 -s mole/1.)

M1

m~

[t/I, dl/g

So × 1013, Svodberg 111]..

0 0.02 0-10 0.19 0"29 0.48 0.62 0,82 1-00 1,00

0 0.03 0.10 0.21 0-32 0-54 0"56 0.77 1.00 1.00

0.85 0.50 0.45 0.47 0.42 0.26 0.24 0.18 0.15 0-10

1,41 2.00 2.11 2-25 2.94 2.90 3.78 3.85 3.92 .

*

/f/,[,l × 10-~

P,[~I

K'

125 165 170 190 270 210 295 265 250

1280 1560 1440 1380 1720 1080 1490 1120 900

0.19 0.32 0.38 0.41 0,45 0.90 0,87 1.10 1.33

.

.

.

• Polymerization in a toluene--octane ralxture~ 1:2 (by velum0).

Success in developing photosensitive polymer materials containing anthracene is determined by methods of synthesis of polymers with different contents and structures of anthracene groups and a study of the correlation between physical and chemical properties of these polymers and the photochemical behaviour of anthracene nuclei combined. This paper seeks to find methods of synthesizing high molecular weight polymers containing anthracene and examine their physical and chemical behaviour. Well known methods of synthesizing polymers with high anthracene group contents which are based on polycondensation or polymerization of vinyl aromatic monomers normally produce polymers of low molecular weight and irregular structure [4-6]. To avoid these difficulties, we used free radical homo- and copolymerization of monomers of methacrylic series containing anthracene-- 9anthrylmethyhnethacrylate (AMMak) -- previously synthesized [7]. This monomer structure was chosen in view of the following considerations: 1) in contrast to monomers of vinylanthracene type, the anthracene groups in AMNA structure does not, apparently, have a marked effect on the activity of the monomer double bond during polymerization; 2) growing macro-radicals of methacrylic series do not, normally, interact with an anthracene nucleus [7, 8] which is usually highly active in various homo- and heterolytic reactions [9]; 3) polymers obtained from AMMA will not contain structural particles which further absorb light in a

1820

N.S.

SZ~ELE~HOV e~ a/.

spectroscopic range typical of anthracene groups and their photodimers; 4) in polymers and copolymers of AMMA the anthracene group is joined to the polymer chain with a fairly mobile system of bonds which does not exclude the possible structure of anthracene nuclei preceding photodimerization. TABLE 2.

I ~ I I c R O - T A C T I C I T Y OF HOI~IO- A N D COPOLY~I_ERS OF

Experiment N~.

ml

1 2 3 5 6 7 9 10"

0.00 0.03 0.10 0.32 0.54 0.56 1.00 1-00

AMMA

Mmro-tactmity, % (triads) syndioheteroiso62 61 52 49 50 50 51 57

34 34 40 45 46 43 44 39

4 5 8 6 4 7 5 4

* See Note to Table 1.

Considerations expressed in 1) ad 2) established the prerequisites for obtaining high molecular weight polymers from ANMA. In fact, investigations show that during free radical polymerization of AMMA and copolymerization with methyl

200

-

a

?. leO-

w

1

/~S 05

b

\\ /40

ii -w 30

t 25 ~,10-~3cm"¢

U V absorption spectra of dioxane solutions w i t h a cell thickness of 0.05 (a) and

l'0 cm (b): /--AMA, 2--PAMMA. methaerylate (MMA) polymers of fairly high degrees of polymerization /~e[~j are formed (Table 1). I t was shown [10] that monomers of methaerylic series containing 2-anthryl-substituted groups also form polymers of high molecular weight in free radical polymerization. The presence in monomer molecules of AMMA and in polymer macromolecules obtained from it of volumetric anthracene groups with a developed n-electron

Polymers of methacrylic series containing anthracene

1821

system of conjugated bonds could produce specific features of polymerization and properties of polymers formed. It is known that volumetric substituents in monomers of acrylic series m a y have a steric effect on the addition of the next monomer unit to a growing macroradical, thus affecting the micro-tacticity of polymers formed [11]: On the other hand, as a consequence of the possible interaction of anthracene n-electron systems of AMMA molecules labile monomer materials (associates) m a y form. I n the event of the life time of these associates being longer than, or equal to, the time of chain extension, this m a y accelerate polymerization and increase the molecular weight, or degree of polymerization of the homo- and copolymers formed and influence the composition and composition heterogeneity of macromolecules and their micro-tactieity. It is assumed, for example, that a similar effect account.s for the increased rate of free-radical polymerization of benzylmethacrylate [12]. The interaction of anthracene nuclei in the macromolecules formed m a y change the hydrodynamic behaviour of polymers in solution and optical properties of anthracene groups themselves. The composition of AMMA-MMA copolymers obtained was determined by I R spectroscopy b y the measurement of integral intensities of absorption bands of copolymers at 737 cm -1 (out-of-plane deformation vibrations of C - - H bonds of anthracene nuclei) and at 1745 cm -1 (bond-stretching vibrations of C = O groups). The compositions of AMMA and MMA copolymers studied are given in Table 1. I t is interesting to note that AMMA homopolymers and its copolymers with MMA have a fairly narrow unimodal MWD. Polydispersion evaluated from standard deviations as of distribution according to sedimentation constants, dc/ds, bearing in mind concentration effects and the influence of diffusion [13] shows that, the value of as is fairly low for all the polymers examined and Mw/ /Mz= 1.4-1.6. The evaluation of composition heterogeneity of copolymer macromolecules (molar fraction of units containing anthracene m l = 0 . 1 and 0.56) using a method previously described [14], which is based on the separation of copolymers with different increments of the refractive index in the diffusion process, showed t h a t the copolyzners studied have a highly homogeneous composition. The distribution of units containing anthracene inside macromolecular chains (at least for copolymers with m l : 0 . 1 ) m a y also be estimated from PMI% results. I n PMI% spectra of copolymers with m ~ : 0 . 1 the signal of protons of --OCH 3 groups is divided into components, of which the intensity ratio is close to t h a t expected from Bemoullis statistical values, which is evidence of the absence (or slight proportion) of AMMA units closely situated in copolymer macromolecules. Results obtained and data of composition variation of copolymers on changing the composition of the initial monomer mixture (Table 1) suggest that during eopolymerization of MMA and AMMA the distribution of units containing an-

1822

N.S.

S ~ E L E ~ O V et a/.

thracene in the macromolecules formed is close to the statistical distribution (as observed, for example, in free radical copolymerization of MMA with naphthyl methacrylate [15]). A possible consequence of the presence of an anthracene group in an molecule may be the variation of macrotacticity of polymers formed, compared with the microtacticity of PMMA obtained under similar conditions. Cases are known, for example, when the addition of aromatic groups to monomer molecules of acrylic series increased the proportion of isotactic triads in corresponding polymers [16]. The micro-tacticity of polymcthacrylates containing anthracene was evaluated by PMR spectroscopy when studying corresponding PMMA samples, in which homo- and copolymers were transformed by step-by-step polymer analogue conversions--separation of anthrylmethyl carboxylate ester groups--and methylation of carboxyls formed by the action of diazomethane [17]. Results in Table 2 concerning the micro-tacticity of the polymers studied indicate that, compared with PMMA, the proportion of syndiotactic triads somewhat decreases in homoand copolymers of AMMA containing anthracene (this tendency is also typical, to varying degrees, of other methacrylates with volumetric substituents, including aromatic ones [11]); a deterioration in solvent quality during polymerization of AMMA slightly influences the micro-tacticity of polymers formed (Table 2, experiments 9 and 10), whereas for naphthyl methacrylate a similar variation considerably increases the proportion of isotactic triads [16]. It is interesting to observe that with an increase of the contents of anthracene groups in maeromoleculcs, hydrodynamic properties of polymers change. Results in Table 1 show that in dioxane solutions of A1VIMA-MMA copolymers with an increase of the proportion of ~ units, intrinsic viscosity shows a regular decrease, whereas constants of sedimentation increase. This is due to a change in thermodynamic parameters of the solution and a reduction in the dimensions of the sphere as the number of anthracene groups increases in the polymer chain. Huggins constants K' are a qualitative evidence of this which increase noticeably with an increase of the value of ml. A possible cause of this type of effect may be the intramolecular association of anthracene groups with a high local concentration inside the polymer sphere. The interaction of anthracene groups added to polymer chains is shown by a variation of their electron absorption spectra compared with the spectrum of a model compound-- 9-anthrylmethyl acetate (AM_A)(Figure). Absorption of anthraeene chromophores in the near UV range is due to ~ - ~ * transition shown here as two systems of vibration bands corresponding to the orientation of dipole moment of transition along the short (first absorption band (33-25) × 103 cm -1) and long (second absorption band (42-36)× 103 cm -1) axes of the molecule [18]. As the contents of anthracene groups increases in polymer chains, the hypochrome effect increases, i.e. both the peak and the integral intensities of both absorption bands show a reduction (Table 3), which can be seen from the Figure.

Polymers of methacrylie series containing anthracene

1823

Illustrating absorption slcee~ra of outer members of the series--a model compound (ANA) and a homopolymer of A:MMA. The continuous increase of the hypochrome effect in bot h absorption bands with an increase of the proportion of units in polymers containing anthracene is due to the fact ~hat as the number of groups containing anthracene increases in l;olymer chains, the proportion of chromophores perturbing each other also increases. Table 3 and the Figure indicate t h a t s13ectroscopic changes r a t h e r occur in ~he second absoH)~ion band, c c mpar(d with the first and are probably due to resonance interaction of adjacent anthracene ehromophores, situated along t h e polymer chain. TABLE 3. QUANTITATIVE

CHA.RACTEI~ISTICS OF

ABSO1RPTION S P E C T R A O~" D I O X A N E

Compounds containing anthracene Model (AMA) :Homo- and copolymers AMMA

* O= 1

~ -0.10 0.21 0.32 0.56 0.77 1 00

~ × 10-5, 1./mole- em (v~38,950 em_l) 1.90 1.64 1.46 1-36 0.95 0.91 0.74

TIctE / t Y P O C t t R O M E

S O L U T I O N S OF

c,× 10-~, 1./mole.enI (v=25,850 era_l) 8-60 7-61 7.57 7.80 7.46 7.30 6.45

EFFECT

AMMA-MMA

SttO~VN I N

UV

COPOLYMERS

fe(v)dv× 10-8, 1./molecm i (v=42--36× ] 10acre_l) 3.98 -3-70 3.49 -3 29

Hypochromlsm O* @=42--- 36 x 10aem-1) ---0.070 0.124 -0.173

l~(v) dv (copolymer) I~(v)dv(AMA)

The quantitative measure of these i n I e r a d i o n s - - s e p a r a t m n of absorption b a r d s AE and variation of their intensity--is the function of distance between e h r o n - o p h o r e s / / , ~he,~r m ut ual orientation G and the dipole m om ent ~f electron t.ra~lsitl(~n P [19]

Smee ~l~e absolute value of P~ (8.7 Debye) for ihe short wave transition is 3.2 fold higher t h a n P1 (2.7 Debye) for the long waYe transition, the resommce bond ibr the short wave transition is much stronger and, other conditions being equal, stlonger sIJeetroscopie effects a~e observed in this absorption band. Results available e o n c a n i n g the m ut ual sterie arrangement of anthracene groups joined to polymer chains are insufficient for a detailed analysis to be made of the spectroscopic changes taking place. However, a qualitative comparison of absorption spectra of "sandwich dimers" of anthracene [20] and absorption spectra of the eoloolymers obtained is evidence of the fact t h a t on increasing anthracene group content in the latter the effect of structures with "sandwich" arrangement o f interacting ehromophores increases.

!824

N.S.

Sm~LEr~OV e~ a/.

The changes observed in absorption spectra of MMA-AI~MA copolymers disrupt the linear dependence of optical density on anthracene group contents in copolymers. The use of UV spectroscopy to determine the composition of s i m i l a r c o p o l y m e r s m a y t h e r e f o r e i n v o l v e c o n s i d e r a b l e e r r o r (as wi~h c o p o l y m e r s o f s t y r e n e a n d M M A [21]). Solvents were purified b y conventional methods [22]. After ordinary purification i~¢IMA was distilled over CaHz. AMMA was obtained b y the interaction of 9-anthryldiazomethane a n d methacrylie acid b y the methods described [7]. AMMA of m.p. 85-86 ° was used (according to results in the literature m.p. 85.0-86.5 ° [7]). AMMA used as model compound was obtained b y a similar method [23]. To carry out free radical homo. or copolymerization of MMA a n d AMMA, components of the reaction mixture-monomers, solvent (dioxane, or a mixture of toluene and octane in a 1 : 2 volumetric ratio), an initiator (AID, concentration in the reaction solution being 2.8× 10 -s mole/h) were introduced in requisite quantities (Table 1) in argon coLmterflow into pre-hardened ampoules. The reaction m i x t u r e was degasified and the ampoules filled with argon, sealed. Polymerization was carried out for 50 hr a t 60 °. The polymers were purified b y the following method: the polymer was dissolved in dioxane, the solution frozen a n d dioxane removed b y sublimation drying. The solid polymer with a developed surface was washed with methanol or petroleum ether until compounds containing anthracene were absent from the wash water (control was effeeted b y UV spectroscopy). The polymer was t h e n dried, again dissolved in dioxane, subjected to lyophilie drying and washing. This sequence of operations was repeated until the specific absorption of polymer solutions typical of anthracene derivatives, ceased to decrease in the range of (30-25) × 103 om -~. Control experiments show t h a t PMMA can practically be completely freed from 9-authryl. methylacetate dispersed in it after 3-4 cycles of purification under the conditions described. I t should be noted t h a t the reprecipitation of polymers c o n t a i n i n g ~ I0 mole % AMMA units carried out using various solvents (dioxane, o-dlchlorobenzene, anisole) a n d precipirants (petroleum ether lower alcohols) results in a partial loss of solubility. I t m a y be assumed t h a t this is further evidence of specific interactions between anthracene groups of polymers. To determine the compositions of AMMA-MMA copolymers, :JR spectroscopy was used. I R spectra of polymer solutions m T H F were measured using a UR-20 device (German Democratic Republic) in OaFs cells with a layer thickness of 0-159 a n d 0.610 ram. The molecular fraction of AMMA units in copolymers (m~) was determined from their II~ spectra b y two methods (PAMMA a n d PMMA were used as model compounds): 1) using an "internal s t a n d a r d " , from the ratio of integral intensities of absorption bands at 737 em -1, typical of anthracene groups a n d a t 1745 cm -1 corresponding to bond stretching vibrations of C ~ O groups: 2) from the ratio of integral intensities of absorption bands at 737 cm -1 (C-H bonds of anthracene nuclei) in I R spectra of solutions of the copolymer and PAM_I~IA examined. Determining eepolymer composition b y both methods produced results which showed satisfactory agreement (the difference in ml values did not exceed 0-02-0.04). Verifying the accuracy of the method used for determining the composition of copolymers b y P1VI1VIA and PAMMA model mixtures showed t h a t the error in determining the composition of model mixtures was less t h a n 3%. Viscometric measurements were made in dioxane a t 25 ° using an Ubbelohde viseomcter. Sedimentation was investigated in an UTsA-5 ultracentrifuge (SKB BFA) provided with a polarization interferometric optical system [24]. Constants of sedimentation S~ a t different concentrations normally resulted in sbandard conditions (20 °, 1 arm) and b y extrapolation c-*O the value of ~qo was determined and shown in Table 1. Molecular weights were calculated b y a well known method [25] which related So, [t/] and/l~sE,j. Specific partial

Polymers of methacrylic series containing anthracene

1825

volume ~ was the same for all the samples and equal to 0"800~0.005 based on the measurement of ~ for copolymers with ml----0-32 and 0.77; for these ~ values agreed within the range of experimental error. PMR spectra were measured using an S-60N devine (Japan) at a frequency of 60 Me~s, o-dichlorobenzeno was the solvent, the concentration of polymer solutions 10 wt. %, temperature 200 ° and hexamethyldlsiloxaue was the standard material. A Speeord UV-Vis (GDR) spectrophotometer was used for the measurement of UV absorption spectra of dioxane solutions of polymers; the spectrophotometer had quartz cells 1 and 0-05 cm in thackness (for measurements m spectroscopic ranges with v-~(33-25)×10aand(42-36)× × 103 cm -1, respectively). I n spite of t h e presence o f a v o l u m e t r i c a r o m a t i c s u b s t i t u e n t , AMMA can u n d e r g o free radical h o m o - a n d e o p o l y m e r i z a t i o n forming high molecular weigh~ soluble polymers. The presence o f 9 - a n t h r y l m e t h y l c a r b o x y l a t e g r o u p s in polym e r macromolecules results in changes in h y d r o d y n a m i c properties o f p o l y m e r s a n d some optical properties of a n t h r a c e n e groups themselves. The higher t h e a n t h r a c e n e g r o u p c o n t e n t s in polymers, t h e more m a r k e d these changes. The a u t h o r s are grateful to K. K. Kalninsh, A. I. K o l t s o v a n d A. IV[. G r i b a n o v for t h e i r help in I R a n d PMI~ spectroscopic m e a s u r e m e n t s a n d discussing exp e r i m e n t a l results.

Translated by E. S~.~ER~. REFERENCES

1. Ye. V. ANUFRIYEVA, Spektroskopicheskiye metody issledovauiya polimerov (Spectroscopic Methods of Investigating Polymers). Edited by E. Yu. Oleinik, A. P. Buchaehenko and Ye. V. Anufriyeva, Zr~aniye, 1975 2. W. J. TOMLINSON, E. A. CHANDROSS, R. L. FORK, C. A. PRUDE arid A. A. LAMOLA, J. Appl. Optics 11: 533, 1972 3. G. I. LASHKOV, M. G. KRAKOVYAK, N. S. SHELEKHOV, L. S. SHATSEVA and S. S. SKOROKHODOV, Dokl. AN SSSR 214: 850, 1974 4. A. A. BERLIN, V. A. GRIGOROVSKAYA, M. Ya. KUSHNEREV and Ya. G. URMAN, Izv. AN SSSR, ser. khim., 2568, 1969 5. G. MONTAUDO, P. FINOCCHIARO and S. CACCAMESE, J. Polymer Sel. 9, A-l: 3627, 1971 6. A. REMBAUM and A. EISENBERG, Macromolec. Rev. 1: 57, 1966 7. M. G. KRAKOVYAK, Ye. V. ANUFRIYEVA and S. S. SKOROKHODOV, Vysokomol. soyed. A14: 1127, 1972 (Translated in Polymer Sci. U.S.S.R. 14: 5, 1259, 1972) 8. A. S. CHERKASOV and K. G. VOLDAIKINA, Sb. Spektroskopiya polhnerov (Spectroscopy of Polymers). l~aukova dumka, 1968 9. L. lYI. STOCK, Aromatic Substitution Reactions, London, 1968 10. M. STOLKA, Macromolcculcs 8: 8, 1975 11. J. NIEZETTE and V. DESREUX, Makromolek. Chem. 149: 177, 1971 12. M. A. BULATOV and L. G. SUROVTSEV, 23 Internatio1~al Symposium on Macromolecules, Madrid, 1974 13. S. Ye. BRESLER and S. Ya. FRENKEL', Zh. tekhn, fiziki 23: 1502, 1953 14. S. I. KLENIN, V. N. TSVETKOV and A. N. CHERKASOV, Vysokomol. soyed. Ag: 1435, 1967 (Translated in Polymer Sci. U.S.S.R. 9: 7, 1604, 1964) 15. Yu. B. AMERIK, Yu. Yu. BAIRAM0V, B. A. KRENTSEL', L. S. POLAK and B. L KURGANOV, Optika i spektroskopiya 33: 894, 1972

1826

L . A . AVERKo-A_wTONOVlCRet al.

16. J. NISHINO, H. NAKAYATA and Y. SAKAGUCHI, Polymer J. 2: 555, 1971 17. A. KATCHALSKY and H. EISENBERG, J. Polymer Sei. 6: 145, 1951 18. 1%.A. FRIEDEL and M. ORCHIN, Ultraviolet Spectra of Aromatic Compounds, New York 1951 19. R. I~I-IOKHSHTRASSER, Molekulyarnyye aspekty simmetrii (Molecular Aspects of Symmetry). Izd. "Mir". 1968 20. E. A. CHANDROSS, T. FERGUSON and E. G. MCRAE, J. Chem. Phys. 45: 3546, 1966 21. B. M. GALLO and S. RUSSO, J. Macromolec. Sci. A8: 521, 1974 22. A. WEISSBERGER, E. PROSKAUER, D. RIDDICK and E. TOOPS, Orgaxdcheskiyo rastvoriteli (Organic Solvents). Izd. inostr, lit., 1958 23. T. N A K A Y A , If,. OHASIII and M. IMOTO, Bull. Chem. Soc. Japan 40: 691, 1967 24. V. N. TSVETKOV, Vysokomol. soycd. 4: 1575, 1962 (Not translated in Polymer Sei.

U.s.s.R.) 25. V. N. TSVETI~OV, V. Ye. ESNIN and S. Ya. FREI~!I~EL', Struktura makromolekul v rastvorakh (Macromolecular Structure in Solutions). "Nauka", 1964

STUDY OF THE MECHANISM OF OXIDATION OF POLYSULPHIDE 0LIGOMERS USING SODIUM BICHROMATE* L. A. AVERKO-A~TO~OVlCH, V. YE. RUBA~OV a n d L. I. KT,IMOVA S. M. Klrov Chemico-TectmologicM Institute, Kazan (Received 6 December 1976)

A study was made of oxidation of polysulphlde ohgomers usmg sodmrn blchromate. Emetics of oxidation were investigated by the ehronovolt-amperometric method using a PO-5122 oselllopolarograph (TsLA-02A model) with linear voltage scan under monoeyelic conditions. It was established that during oxidation of ohgothiols with sodium biehromate the latter is reduced to Cra+ salt. An assumption was put forward about the amonm meehamsm of oxidation of ohgothlols. Oxidation of polysulphlde ohgomers with sodium blchromate is notmeably accelerated m polar medmm, which is typical of processes taking place by the runic mechanism. Recommendations were made to use monomers and ohgomers prone to undergo polymerlzatmn by the aniome mechamsm, in order to modify polysulphide ohgomers. THERE is extensive a n d often conflicting i n f o r m a t i o n in the literature concerning m e c h a n i s m s of o x i d a t i o n of polysulphide oligomers using lead a n d m a n g a n e s e oxides [1-3]. I n a d d i t i o n to these oxidizing agents, sodium b i c h r o m a t e is also used, w h i c h has r e c e n t l y b e c o m e p o p u l a r in c o n n e c t i o n with t h e i n t r o d u c t i o n o f ~he industrial p r o d u c t i o n of s t r u c t u r a l sealants p r e p a r e d f r o m polysulphide oligo* Vysokomol. soyed. A19: No. 7, 1593-1598, 1977.