Synthesis of soluble polymers from dimethacrylate compounds

]Polymer Science U.S.S.R. Vol. 27, No. 8, pp. 1817-1823, 1985

0032-3950/85 $10.00 +,00 Pergamon Journals Ltd.

]Printed in Poland

SYNTHESIS OF SOLUBLE POLYMERS FROM DIMETHACRYLATE C O M P O U N D S * N. M. BOL'BIT, A. L. ][ZYUMNIKOV, YE. D. ROGOZHKINA, N. KH. FAIZI and Yu. A. CHIKIN Branch of the Karpov Physicochemical Research Institute (Received 13 December 1983)

The possibility of obtaining soluble (co)polymers on polymerization of ~,e~-dimethacrylates in dilute solutions with radiation and "material" modes of initiation is shown, In the polymer based on TGM-3 free double bonds are absent. From the data of viscornetry light scatter and GPC the authors evaluate the magnitudes of the statistical Kuhn segment and the parameter of braking of the internal rotation of the soluble TGM-3 polymer. The totality of the experimental factors is due to the cyclolinear structure of the soluble polymer containing one to two long chain branches per macromolecule. THE possibility of obtaining soluble (co)polymers from polyfunctional vinyl compounds has been shown in a number of cases: 1) on polymerization to low (~< 1%) degrees of conversion [1]; 2) in conditions of oxidative copolymerization [2]: 3) on low temperature post-polymerization [3] and also on polymerization of m~thacrylic anhydride in dilute solutions [4]. The formation of the soluble T G M - 3 copolymer with styrene (for degrees of conversion to 10 %) coexisting in the polymerization mass together with gel was eastablished in [5]. Cyclization, i.e. incorporation of the "hanging" bond (double bond in the side chain) iuto its " o w n " growing polymer chain is of a general character in the crosslinking reaction [6]. The presence of cyclization has been demonstrated on copolymerization of styrene with dimethacrylate ethylene glycol ( D M E G ) [7]. It has been shown that there exist threshold concentrations of D M E G below which only a soluble polymer forms not containing double bonds and having cycles in the main chain. It was natural to assume that fall in the concentration of the bifunctional m o n o m e r (TGM-3) in solution below the threshold value may lead to a situation when the pendant double bond enters the polymer chain and forms a cycle (ring) earlier than the following molecule attaches to the growing chain. In this case it is possible to obtain a completely soluble, linear (or weakly branched) polymer with ring structures in the main •chain i.e. a polymer of cyclolinear structure of the type

o =c oI

(cH CH

• Vysokomol. soyed. A27: No. 8, 1621-1626, 1985. 1817

I

o/ oL)~ |J,~

c

1818

N . M . BOL'BIT et al.

We used the dimethacrylates of ethylene and triethylene glycol vacuum distilled by the technique in [8] to the pure state (99.99 ~). The solvents were purified by rectification and benzoyl peroxide (BP) by recrystallization by the usual techniques. The other oligomers and substances used were not additionally purified. The solutions of the oligomers were degassed three to four times in ampoules. Polymerization was initiated either with BP at 60-70°C (3-10~ of the amount of oligomer) or with 6°Co y-rays with an intensity of 0.5 G-r/see at room temperature. The concentration of the oligomer (0.5-2~) was so chosen that the mean distance between the oligomer molecules was greater by about one order than that between the double bonds in one molecule. The polymerization time varied from 2 to 8 hr. After arrest of polymerization the contents of the ampoule were filtered to separate the gel and the soluble TGM-3 polymer-poly TGM-3 ( P T G M ) - w a s precipitated with heptane. The content of double bonds in the soluble polymer was analysed by IR spectroscopy with the Specord IR-75 two-beam spectrometer. The light scatter of the PTGM solutions in MEK (and in THF) was measured with the Sofica nephelometer at the wave length of incident light 2= 546 nm and at 25°C, The solutions and solvents were cleared of dust by passing them through Sartorius filters (pore diameter 0"15/zm). After filtration the PTGM solutions revealed no appreciable angular dependence of the intensity of light scatter. The values of the increment of the refractive index of the PTGM solutions measured with the differential refractometer were 0.123 cm3/g in MEK and 0.095 cm3/g in THF (2=546 nm). GPC analysis of the samples was made in THF with the Waters instrument (model 200) calibrated from a PS standard on a set of columns 20, l0 s, 103 and 2"5 × 103 nm [9]. The values of the characteristic viscosity [r/] in THF at 25°C were measured with a viscometer, of the Bishof type. The temperature transitions were determined by the DTA method with the Q 1500 D derivatograph. To elucidate the structure of the molecules of the soluble polymers of TGM-3 they were hydrolysed over the complex ester groups after which the "characteristic" polymer was isolated and analysed (in the case in point polymethacrylic acid) [10]. T h e kinetics o f p o l y m e r i z a t i o n o f T G M - 3 in s o l u t i o n in M E K on initiation b y B1~ a n d 7-radiation is c h a r a c t e r i z e d by a m o n o t o n i c d r o p in the rate o f the process which is t y p i c a l o f p o l y m e r i z a t i o n in s o l u t i o n (Fig. 1). It s h o u l d be n o t e d t h a t the rate o f p o l y m e r i z a t i o n insignificantly d e p e n d s on the c o n c e n t r a t i o n o f BP (within the limits 3 1 0 ~ o f the weight o f T G M - 3 ) , the f o r m o f the solvent a n d the initial c o n c e n t r a t i o r t o f T G M - 3 in those cases when a soluble p o l y m e r forms. I f a gel forms, the reactiort r a t e is a p p r e c i a b l y higher (Table 1), which is r e a d i l y c o n n e c t e d with fall in the r a t e o f t e r m i n a t i o n in the gel particles. T a b l e 1 shows t h a t the soluble p o l y m e r can be o b t a i n e d solely in solutions in M E K a n d c y c l o h e x a n o n e at sufficiently l o w (~<2 ~o) c o n c e n t r a t i o n s o f T G M - 3 . A t high c o n c e n t r a t i o n s a n d also in acetone a n d b u t y l a c e t a t e b o t h the soluble p o l y m e r a n d gel f o r m ; in cyclohexane only the gel is obtained. A p p a r e n t l y b o t h increase in the c o n c e n t r a t i o n a n d w o r s e n i n g o f the t h e r m o d y n a m i c quality o f the solvent help to raise the r a t e o f a t t a c h m e n t o f the following o l i g o m e r molecule as c o m p a r e d with the c o m p e t i n g r e a c t i o n o f cyclization. In the p o l y m e r chain there r e m a i n the " p e n d a n t " d o u b l e b o n d s , further c o n v e r s i o n o f which leads to crosslinking. A d d i t i o n o f a s t r o n g chain transfer agent ( d o d e c y l m e r c a p t a n ) n o t only does n o t r e d u c e the a m o u n t o f gel, but, on the c o n t r a r y , increases it. This is p r o b a b l y connected, with the fact t h a t transfer o f a radical occurs before the d o u b l e b o n d o f the side chaio~

1819

Synthesis of soluble polymers TABLE 1. POLYMERIZATIONOF T G M - 3 IN VARIOUS SOLVENTS AT 65°C

Solvent

Concentration of T G M - 3 , grav. %

BP, % of a m o u n t of TGM-3

PTGM

gel

0"41 1"1

7-6 4"5

20 5

16 49

1.1

8'0

0

80

43 45 84 32 54 59

45 0 0 0 0 25

Butyl acetate Butyl acet + dodecylmercaptan Cyclohexane + dodecylmercaptan Acetone Cyclohexanone MEK

0'54 0-61 0-4 0"54 2'3 7"6

Time of reaction, hr

o/ Yield,/o •

7.0 4.6 7-4 8.1 3.3 7-initiation

is incorporated into the polymer chain. Moreover, the " d e a d " polymer molecules formed as a result of the act of chain transfer to the modifier have a relatively small M M and possess raised mobility in solution, which facilitates attachment of the hanging double bond to the radical of the network gel.

lO0

qo

0

2

q 6 77me, ~p

8

32

28

2:4 VR. ::~',ts

FIG. 2

FIG. 1

FIG. 1. Kinetic curves of polymerization of T G M - 3 in MEK. [ T G M - 3 ] = 2 (1), 1 (2) and 0.5 (3) vol.%; temperature 22 ° (1) and 65 (2, 3) °C; 1 - 7 - i n i t i a t i o n ; 2, 3 - - B P in an a m o u n t of 5"3 (2) and

8 % (3). FIG. 2. Gel c h r o m a t o g r a m of sample of soluble P T G M polymer with M w = 18 × 10 3.

The possibility of obtaining soluble (co)polymers from other polyfunctional oligomers on polymerization in solution is shown in Table 2. Completely soluble products are obtained only for TGM-3 and its copolymer with styrene. In the other cases the soluble polymer is either not obtained at all or a soluble polymer and a gel form. In the IR spectra of soluble (co)polymers (apart from the polymer based on D M E G ) the absorption band 1645 cm-1 corresponding to the valence vibrations of the double bond is absent. We would note that on polymerization of methacrylic oligomers in

1820

N. M. BOL'BITet aL TABLE 2.

YIELD OF POLYMER ON POLYMERIZATION OF DIFFERENT MONOMERS

(Concentration of monomer in MEK 2 gray. Yo, 7-initiation, room temperature) Monomer TGM-3 TGM-3 + styrene (20 vol. %) DMEG Oligocarbonate (OKM-2) Tetramethacrylate diglycerylphthalate (TMGP-11)

Time, hr

5 4.5

Yield, ~o soluble polymer 55 20

gel

7 20

62 28

30

60

bulk complete depletion of the double bonds, as a iule, is not achieved [1, 11, 12]. Total expenditure of the double bonds appaiently supports the hypothesis of cyclopolymerization, i.e. attachment of the pendant double bond to the main chain. In the case of a polymer based on D M E G the content of the double bonds is , ~ 1 2 ~ of the initial number. Apparently, because of the high rigidity of the chain between the methacrylate double bonds in this case, too, the following molecule attaches before the double bond in the side chain reacts. The presence of these bonds again leads to crosslinking o f the macromolecules. The structure of P T G M was studied in detail by a number of methods. The various molecular characteristics of P T G M found by the methods of light scatter, viscometry and GPC favour the proposed model of the polymer chain with rings in the main chain. The dilute solutions of some P T G M samples were slightly turbid, but after filtration did now show asymmetry of light scatter. The concentrations of the solutions before and after filtration within the limits of error did not differ, i.e. the particles of the microgel causing opalescence of the initial solution were present in negligible quantity. Below are given the results of measurements of the weight average molecular mass of the P T G M for two series of experiments for different conversions (0.5 ~ TGM-3 in M E K and 7 ~ BP (in parenthesis 4.5 ~ BP)). Conversion, ~ Mwxl0 -4

22"0 (27"7) 32'0 (37"6) 45'5 (43-8) 51"5 2"2 (2"5) 1'8 (2"4) 2"0 (1.4) 1"65

It will be seen that the values of M w tend to fall with rise in conversion as follows from the theory of quasisteady polymerization in solution [13]. The polydispersity of the samples was evaluated by the GPC method [9]. Figure 2 gives the typical gel-chromatogram of the P T G M sample with M w = 1 8 x 103. According to the GPC data polydispersity in the course of the process practically does ,not change, with a ratio of the mean M M Mw/M,= 1.5-1.6 and Mz/M~= 1.4-1.5. These data support the quasi-steadiness of the process. The magnitude Mw of the characteristic polymer isolated after hydrolysis of the P T G M samples in all cases was 5.5-6 × 103 . On hydrolysis of the ester groups of the

Synthesis of soluble polymers

1821

TGM-3 molecule 0.4 of its mass splits off. Therefore, the linear chains of the initial polymer have M,~I x 104. (The control experiments showed that hydrolysis of the polymers of the esters of methaerylic acid activates rupture of the main chain - - C - C - whereas polymethacrylic acid itself in the same condition does not degrade). F r o m all this it may be considered that the P T G M macromolecules with M ~ , = l . 5 - 2 . 5 x 104 have not more than one to two branch points, i.e. ester bridges between the chains. The bulk of the hanging double bonds is taken up in the reaction of interchain cyclization. The probability of formation of a purely ladder polymer is extremely low. The unperturbed dimensions of the chains of the P T G M sample were evaluated flora its magnitude It/I=0.01 m3/kg in T H F with use of the known Flory-Fox relation [14] En-I = q~o

[i.2~3/2 k'lO]

M

3 •~ ,

(1)

where 4 0 = 2.86 x 1021 is the Flory constant, h~ is the unperturbed mean square of the distance between the ends of the chain, cc is the swelling coefficient of the coil. According to the light scatter data of the solutions of this sample in THF, Mw = 22 x 103 and the value of the second virial coefficient A2~0. Therefore, it may be considered that e ~ 1. As a result of the calculations for P T G M we obtained the value of the Kuhn segment A = 2 . 2 nm. This value is appreciably higher than the values A = l ' 5 1 nm for P M M A and 1.66 nm for polybutylmethacrylate [14]. In principle, this was to be expected since the regular fastening of the side chain onto the main chain in the neighbouring unit increase its equilibrium rigidity. The degree of this increase depend on the rigidity o~"the ring formed and in the limiting case of an absolutely rigid ring (for an unchanged degree of braking of the internal rotations a) the size of the segment A must be twice as big as in the linear analogue without rings in the main chain. But on the other hand tt~e more rigid the ring the longer are the corresponding virtual bonds, which may lead to fall in the braking of the internal rotation about these bonds as a result of fall in the interdependence of the rotations. To a certain extent this is true of the P T G M chains. In fact if it is accepted that the rings in P T G M are absolutely rigid then on completely free rotation about the virtual bonds the size of the segment As = 0.755 rim. The degree of braking in real P T G M chains o.=(A/As)~=l.7 while for P M M A o'=2.0 and for polybutylmethacrylate o-=2.1. Since the P T G M rings are not absolutely rigid, the value A = 2"2 nm found for them may be considered quite realistic. The results of GPC analysis of the P T G M sample agree with those of light scatter and viscometry. In fact, it is assumed that separation of the polymer macromolecules in the GPC method occurs in line with their hydrodynamic volum.~s proportional to the value of the product [r/]M. F r o m the condition of equality of the hydrodynamic volumes of the molecules of the test and standard polymers using relation (1), for the magnitude MM of the polymer studied one may write M = ~3o~bo(A o Lo)a/2/[rl],

(2)

where % , Ao and Lo are the swelling coefficient, the length of the Kuhn segment and

1822

N . M . BOL'BITet aL

the equivalent contour length of the standard polymer, respectively and [0] is the intrinsic viscosity of the polymer analysed. F r o m the gel-chromatogram of the P T G M sample investigated we calculated the following values of the mean contour lengths of the macromolecules: L, = 25.3, Lw = 31.3 and L z = 40-4 nm. F o r PS of the corresponding M M the evaluation made gives do = 1.1. Then according to equation (2) for P T G M we obtain Mw= 18.4× 103 which is close to the M M of this sample found by the light scatter method. The minor difference in the M M values may be due to the different hydrodynamic interaction in the P T G M and PS molecules determining the effective dimensions of the macromolecules in solution. We would note that the hydrodynamic data do not contradict the conclusion based upon the results of hydrolysis of the P T G M samples since the presence of one to two branching nodes in the macromolecules reduces their size by only 10-20 ~ [15] which is within the limits of error of the evaluation made of the dimesnions of the P T G M chains. As shown above, the presence in the P T G M cycles of hinge compounds of the - - C - - O - - C - - type insignificantly reduces its equilibrium flexibility. Simultaneously the model of the linear chain with cycles implies increase in the kinetic rigidity of such a polymer. However, in the derivatograms of the P T G M samples a transition is observed at 100°C associated with change in the thermal capacity of the polymer. This value of Tg concurs with Tg ~ 100 ° for P M M A . The physicomechanical properties of P T G M could not be determined since the samples poured from the solution or pressed out are prone to spontaneous cracking. Thus the experimental findings taken as a whole suggest that on polymerization of T G M - 3 in very dilute solution a soluble polymer of cyclolinear structure forms containing not more than one to two branching nodes per macromolecule. Translated by A. CROZY

REFERENCES

1. A. A. BERLIN, T. Ya. KEFELI and G. V. KOROLEV, Poliefirakrilaty (Polyester Acrylates), p. 247, Nauka, Moscow, 1967 2. M. M. MOGILEVICH, Okislitel'naya polimerizastiya v protsessakh plenkoobrazovaniya (Oxidative Polymerization in the Processes of Film Formation), p. 74, Khimiya, Moscow, 1977 3. Ye. I. SHKLYAROVA, V. V. GOLUBEV, V. P. ZUBOV and V. A. KABANOV, Vysokomol. soyed. A22: 1001, 1980 (Translated in Polymer Sci. U.S.S.R. 22: 5, 1104, 1980) 4. A. MATSUMOTO, T. KITAMURA and M. OIWA, Makromolek. Chem. Rapid Commun. 2: 683, 1981 5. N. M. BOL'BIT and S. Ya. FRENKEL', Vysokomol. soyed. A20: 294, 1978 (Translated in Polymer Sci. U.S.S.R. 20: 2, 332, 1978) 6. K. DUSEK and M. HAVSKY, J. Polyhaer Sci. Polymer Symp., No. 53, 57, 75, 1975 7. H. GALINA and K. RUPICZ, Polymer Buil. 3: 473, 1980 8. V. R. DUFLOT, I. G. NIKULINA, Yu. A. CHIKIN, V. A. FOMIN, V. Ya. KISELEV, V. L SHIDKOV and V. A. VOROB'EV, U.S.S.R. 857107. Pub1. in B. I., No. 31, 1981 9. A. L. IZYUM.NIKOV, T. T. VELICHKO, L. B. KRENTSEL and A. D. LITMANOVICH~ Vysokomol. soyed. A25: 326, 1983 (Translated in Polymer Sci. U.S.S.R. 25: 2, 379, 1983)

Characteristic viscosity of polyamide benzimidazole molecules

1823

10. N. M. BOL'BIT, U.S.S.R. Pat. 525706. PuN. in B. I., No. 31, 1976 11. V. R. DUFLOT, N. Kh. FAIZI and Yu. A. CI-IIKIN, Vysokomol. soyed. A24: 2263, 1982 (Translated in Polymer Sci. U.S.S.R. 24: 11, 2598, 1982) 12. V. M. MUNIKHES, S. I. KUZINA, D. P. KIRYUKHIN, A. I. MIKHAILOV and L M. BARKALOV, Ibid. A20: 810, 1978 (Translated in Polymer Sei. U.S.S.R. 20: 4, 913, 1978) 13. Kh. S. BAGDASAR'YAN, Teoriya radikal'noi polimerizatsii (Theory of Radical Polymerization), p. 18, Akad. Nauk SSSR, Moscow, 1959 14. V. N. TSVETKOV, V. Ye. YESKIN and S. Ya. FRENKEL', Struktura makromolekul v rastvorakh (Structure of Macromolecules in Solutions), pp. 126, 287, Nauka, Moscow, 1964 15. S. R. RAFIKOV, V. P. BUDTOV and Yu. B. MONAKOV, Vvedeniye v fizikokhimiyu r astvorov polimerov (Introduction to the Physicochemistry of Polymer Solutions), p. 276, Nauka, Moscow, 1978

Polymer ScienceU.S.S.R. Vol. 27, No. 8. pp. 1823-1829, 1985 Printed in Poland

0032-3950/85 $10.00+.00 Pergamon Journals Ltd.

TRANSLATIONAL FRICTION AND THE CHARACTERISTIC VISCOSITY OF POLYAMIDE BENZIMIDAZOLE MOLECULES IN SOLUTION* G. M. PAVLOV, S. G. SELYUNIN, N . A. SHIL'DYAYEVA, S. M. YAKOPSON, L. S. EFROS a n d S. V. USOVA Institute of Physics at the Zhdanov State University, Leningrad Leningrad Branch of the All-Union Artificial Fibre Research and Design Institute

(Received 13 December 1983) The authors have investigated the intrinsic viscosity It/], the coefficient of translational diffusion D and the sedimentation coefficient S of 32 samples and fractions of poly-(2,2'-pphenylene-(5-benzimidazole)) isophthalamides in D M A A + 3 ~o LiCI in the interval of molecular masses 5~ 10¢ they obtained the ratios It/]=4"1 x x 10-SM °'81, Do=4"3x 10-9M -°'57 and So=7"1 x 10-16M °'43. The value of t h e hydrodynamic invariant .4o = (3"2 + 0"12) x 10 - 17 j . deg - 1. mole - ~, temperature coefficient of viscosity negative d In [,l]/dT= - 2 . 3 x 10 -a. The equilibrium rigidity of the chains modelling the molecules of poly-(2,2"-p-phenylene-(5-benzimidazole)) isophthalamide is estimated and the length of the Kuhn segment A lies within the limits 64-<
RECENTLY, close a t t e n t i o n has b e e n p a i d to study o f the m o l e c u l a r characteristics o f polymers used to o b t a i n t h e r m a l ly stable a n d h i g h strength fibres [1, 2]. These a l s o i n c l u d e p o l y m e r s based o n th e b e n z i m i d a z o l e s [3, 4]. * Vysokomol. soyed. A27: No. 8, 1627-1632, 1985.