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The molecular weight distribution (MWD) characteristics of vinylidene fluoride copolymers with 3,7-dioxaperfluoro-1-octene
k~t~olymer Science U.S.S.R. Vol. 21, pp. 2496-2502. O Pergamon Press Ltd. 1980. Printed in Poland
0082-3950/7911001-2496507.50/0
THE MOLECULAR WEIGHT DISTRIBUTION (MWD) ~CHARACTERISTICS OF VINYLIDENE FLUORIDE COPOLYMERS WITH 3,7-DIOXAPERFLUORO-I-OCTENE* YE.
G. ERENBURO,
L . V . PAVLOVA, Y E .
O . OSIPCHUK, I . M .
DOLGOrOL'SKII,
A. I. Kol~sm~, A. M. GREIS and I. YA. PODDUBNYI S. V. L e b e d e v A l l - U n i o n S y n t h e t i c R u b b e r R e s e a r c h I n s t i t u t e
(Received
18
August
1978)
E l u t i o n f r a e t i o n a t i o n i n a c o l u m n h a s b e e n u s e d t o s t u d y t h e M W D of t h e vinylid e n e fluoride e m u l s i o n c o p o l y m e r w i t h 3 , 7 - d i o x a p e r f l u o r o - l - o c t o n e ( V F - D O P F O e o p o l y m e r ) . T h e d e p e n d e n c e bf t h e i n t r i n s i c v i s c o s i t y o n t h e m o l . w t , h a s b e e n e s t a b l i s h e d a n d t h e M W D of t h e c o p o l y m e r s h a s b e e n f o u n d t o b e b i m o d a l . T h e effect o n t h e M W D of t h e c o m o n o m e r r a t i o in t h e original m i x t u r e , of t h e emulsifier concent r a t i o n a n d t h e m o n o m e r c o n v e r s i o n h a s b e e n e x a m i n e d . T h e p o l y m e r i z a t i o n was f o u n d t o p r o c e e d in t w o p a r a l l e l phases, i.e. a m i c r o - e m u l s i o n of tim m o n o m e r a n d of t h e l a t e x p a r t i c l e s b a s e d o n t h e emulsifier micelles.
AN important position amongst the fluorine containing elastomers if held by t h e vinylidene fluoride copolymers with perfluoro-alkyl vinylester. There is little information about the molecular structure of this group and the reason is largely t h e poor solubility of F containing polymers in the usual organic solvents, so that a n y fractionation method and determination of the mol.wt, requires special research in each case. Our earlier studies dealt with the MWD and flexibility of the vinylidene fluoride copolymers with perfluoromethyl vinylester. Their MWD were found to be typically those of a classical emulsion polymerization, i.e. close to the most probable in the initial process stage (up to a 20~o conversion), but broader at larger conversion where it was enriched with the larger mol.wt, fractions. This report deals with the MWD of the vinylidene fluoride copolymers with another perfluoroalkyl vinylester--the 3,7-dioxaperfluoro-l-oetene (the V F DOPFO copolymer). EXPERIMENTAL T h e p o l y m e r i z a t i o n was c a r r i e d o u t in a n all m e t a l a p p a r a t u s f i t t e d w i t h s a m p l i n g m e a n s a t v a r i o u s c o n v e r s i o n stages. T h e e l u t i o n f r a c t i o n a t i o n m a d e use of a glass c o l u m n p a c k e d w i t h 0.1-0.2 m m m e s h g r o u n d q u a r t z glass b e a d s a n d s o a k e d w i t h a h e x a f l u o r o b e n z e n e - h e x a n e m i x t u r e . T h e p o l y m e r was d e p o s i t e d o n t h e p a c k i n g b y s o l v e n t e v a p o r a t i o n while c o n t i n u o u s l y s t i r r i n g i n a n a i r s t r e a m . P r e l i m i n a r y s t u d i e s e s t a b l i s h e d t h e sedi* V y s o k o m o l . soyed, h 2 1 : No. 10, 2 2 6 1 - 2 2 6 6 , 1979. 2496
MWD characteristics of VF copolymers with DOPFO
2497
m e n t a t i o n c o n d i t i o n s for v a r i o u s e o p o l y m e r c o m p o s i t i o n s ; t h e f r a c t i o n a t i o n was f o u n d t o t a k e place o n l y a c c o r d i n g to m o l e c u l a r weights. T h e following were tile o p t i m u m f r a c t i o n a t i o n c o n d i t i o n s : a s t e p w i s e g r a d i e n t of solv e n t c o n c e n t r a t i o n s f r o m 35 t o 1 0 0 % o f h e x a f l u o r o b e n z e n e , e l u t i o n t e m p e r a t u r c = 6 0 ° C , a 1 g p o l y m o r s a m p l e for 75 ml of p a c k i n g , a 50 m l / 5 0 m i n e l n t i o n r a t e w i t h some v a r i a t i o n d u r i n g t h e (~xperiment. w h i c h d e p e n d e d (:n t h e i n t r i n s i c viscosity of t h e original s a m p l e . T h e s a m p l e s were first w a s h e d w i t h h o t e t h a n o l in a S o x h l e t to r e m o v e a n y s u r f a c t a n t p r e s e n t ; t h e l a t t e r h a d been f o u n d to be t h e factor' decisive for t h e s e p a r a t i o n q u a l i t y . T h o s()lutions w e r e also c e n t r i f u g e d 1 h r a t 25,000 r p m before f r a c t i o n a t i o n to r e m o v e s m a l l a m o u n t s of colloidal s u s p e n d e d m a t t e r .
l°9 ['t]
04 /'7
D
7"S I
5"0
5"5
I
6.0 1o9 M
FIr'. 1. Th(" intrinsic viscosity of tile VI;- I ) O P F O e o p e l y m e r as a f u n c t i o n of t h e molecular weight. T h e s e c o n d i t i o n s m a d e t h ? r e s u l t s r e p r o d u c i b l e a n d m e t tile u s u a l c r i t e r i a for c o l u m n f r a c t i o n a t i o n efficiency; t h e p o l y m e r yield a v e r a g e d 9 6 % , t h e c o n c e n t r a t i o n c a t tile c o l u m n e x i s t was < 0 . 4 g/100 ml; Cm~xM~max<400 [2, 3]. T h e i n t r i n s i c v i s c o s i t y [~/] of t h e s a m p l o b a s e d o n t h e f r a e t i o n a t i o n r e s u l t s c o i n c i d e d w i t h t h a t of t h e original p o l y m e r w i t h i n t h e <,rror l i m i t s of d e t e r m i n a t i o n . T h e d e p e n d e n c e of [~] o n t h e m o l . w t , u n d e r t h e s e c o n d i t i o n s was e s t a b l i s h e d in a p r e p a r a t i v e f r a e t i o n a t i o n of 8 g of one of t h e s t u d i e d samples. T h e mol.wt, of a n u m b e r o~ f r a c t i o n s were d e t e r m i n e d b y o s m o l n e t r y in h e x a f l u o r o b e n z e n e ( H F B ) , t h e q u a l i t y of t h o f r a c t i o n s in a e o m p a r i s c n e f t h e ff/~ w i t h t h e ~ . , b u t t h i s was n o t d o n e s y s t e m a t i c a l l y beca.use t h e e o p o l y m e r d i s s o l v e d o n l y in a l i m i t e d n u m b e r of p e r f l u o r i n a t e d s o l v e n t s in w h i c h t h e r e f r a c t i v e i n d e x was u n u s u a l l y small. T h e d e t e r m i n a t i o n b y light, s c a t t e r i n g was also h i n d e r e d b y t h e u s u a l c o n t e n t of a s m a l l a m o u n t of s u p e r m o l e e u l a r a g g r e g a t e s w h i c h m o s t p r o b a b l y f o r l n e d as a r e s u l t e f t h e e a s y c r y s t a l l i z a t i o n of t h e VF. T h e p r e s e n c e of s u c h b l o c k s e x p l a i n s t h e fact. t h a t some s a m p l e s o n l y dissolved w h e u t h e s o l u t i o n s were h e a t e d a l t h o u g h n o p r e c i p i t a t e f o r m e d w h e n t h e t e m p e r a t u r e was subsoqucntly reduced. A s e c o n d f r a c t i o n a t i o n of t w o of t h e frt~ctions w i t h a large mol.wt., u s i n g s m a l l e r c h a n g e s of t h e e l u t i o n m i x t u r e c o m p o s i t i o n , p r o d u c e d 80°~) of t h e p o l y m e r f r o m t h e m ; [q] e q u a l l e d t.he a v e r a g e v i s c o s i t y of t h e r e s p e c t i v e f r a c t i o n w i t h i n a ~: 10°{; error. T h e M W D c u r v e s of t h e s e f r a c t i o n s h a d h o w e v e r a specific shape, i.e. h a d a " t a i l " of low mol.wt, w h i c h m a d e t h e m u n s u i t a b l e for o s m o m e t r i e d e t e r m i n a t i o n s . (This u n u s u a l s h a p e of t h e large m o l . w t , f r a c t i o n M W D c u r v e s s e e m s to be l i n k e d w i t h t h e larger w i d t h a n d t h e i n i t i a l b i m o d a l d i s t r i b u t i o n ) . C u r v e s for [ ~ / ] = f ( M ) for t h e f r a c t i o n s f r o m e l u t i o n f r a c t i o n a t i o n -~,ere t h e r e f o r e p l o t t e d o n l y for t h o s e w i t h M < 3 5 0 × 103; a large m o l . w t , f r a c t i o n ( 3 I ~ 600 x
Y E . G. ERENBURG ~$ al.
2498
X 10') was produced from a sample with a narrow MWD b y combining precipitation with elution fractionation, h~/w carefully determined by light scattering in H F B (dn/dc= 0.0185) gave /~w//%7/,= 1.3.
d14 ,dM,lO 5
5
'~krL/k~ !\\\\ I \~
~J'/X"l
I0
\\1
30
50 M,lO -~
Fro. 2. The MWD of the copolymers containing various VF quantities in the original mixture. YF, %: 1-- 52; 2-- 83. A fitting description of the [~]=f(M) illustrated in Fig. 1 is given by the equations: [~]----3.24X 10-s~/°'77; log_M=l-31og [~]-r5"83. These equations were used to determine the mol.wt, of all the isolated fractions. RESULTS
The MWD curves calculated for the samples produced under various conditions from the fractionation results are reproduced in Figs. 2-4. These show that the curves have distinct peaks at fairly mol.wt. All the samples showed a bimodat distribution regardless of the polymerization conditions, such as the purity, the original ratio (Fig. 2), and the monomer ~o conversion (Fig. 3).
high
d~ IdM ~lO6
d W/dM.m~
(\
a 4O
i I Ii I I
3o
It I
f~
I I
2
20
•
b
,/- \
2 f
0
5
MxlO_510
0
./!i/I//'' I
4
I
6
I
X
8M.:-SlO
Fro. 3. The MWI) of samples produced at various conversions, a: 1 - 3; 2--33 e/o; the samples were produced in various tests under identical conditions, b: 1--21; 2--75; 3--100~/o; samples from a single batch by sampling.
I0
MWD characteristics of VF copolymers with DOPFO
2499
I t must be pointed out t h a t the bimodality of the MWD is apparent at very low conversions ( < 3%, Fig. 3a) and is retained thr6ughout the polymerization. This bimodality cannot be the result of a subsequent realization of various reaction mechanisms. I t can therefore be regarded is the consequence of a two phase process, i.e. a polymerization in two different phases having differing kinetics. dW/dM.~ s
q I
20
I
I/7
I
5
1o
15 M , I O -#
]~i(~. 4. The MWD dependence of the copolymers as a function of the emulsifior content, ~o: 1--1; 2--3; 3--10. More ~ttention has recently been given in the literature to the topochemistry o f emulsion polymerizations. Parallel with the articles describing such a reaction on the classic lines, there appeared some which proved the formation of a stable micro-emulsion of the monomer in some condition which caused the polymerization to took place in the droplets. This was detected for the first time when nonionic emulsifiers were used, or their blends with ionic ones [4-9], as well as in systems containing monomers with limited water solubility [10, 11]. Such a spontaneous emulsification and the formation of polymer-monomer particles based on monomer droplets was recently also established in styrene polymerization when C15H31SO3Na was used as the emulsifier [12]. A bimodal distribution was observed in some of these studies [4] and was explained by simultaneous progress of a polymerization in two phases, namely the latex particles and the continuous phase of the monomer. The systems containing monomers with a limited solubility in water possessed multi-modal distribution which was linked by the authors [13] with polymerizations in the aqueous solution and in the latex particles. The existence of colloidal solubility was later established for one of these monomers (in the vinyl acetate-water system) and the presence of 500 .~ radius droplets even when there was no emulsifier [11]. We used ionic emulsifiers in our study and the water solubility of the monomers in our polymerization conditions was not examined. The vinylidene fluoride
YE.
2500
IVF) is normally @lob
G. ERENBURG et al.
not water-soluble
[14],
at normal pressure and temperature
fier is used or not; this was established two phase process to apply.
Apart
while that of the comonomer of polymerization, by chromatography.
from the bimodality
is about
whether an emulsiWe assume also a
of the MWD
curves,
confirmation of it is the fact that the copolymers represented by the two peaks on the MWD curve usually show a noticeable difference in composition. The compositions Specbrospin
of some of t’he examined materials were got by NMR on a “BriikerHX-90”
instrument
[15]
VF content,
and are given below.
96
I max ITIM
63
74
69
60
67
G4
76
83
83
65
75
59
Confirmation was sought for the presence of a second phase in the shape of .a micro-emulsion of the rnonomer by studying the MWD of the copolymers produced with various emulsifier contents. , l/10, arb. un. I
FIG. 5. The angular dependence latices
of:
1, Z-VF-DOPFO
of the inverse light scattering
copolymer;
3-VF
copolymer
intensity
for the
with perfluoroalkyl
vinylate.
Reduction
of the emulsifier concentration
from 3% to near the critical micelle-
formation concent,ration (CMC, around 1%) showed that the area enclosed by the large mol.wt. peak on the MWD curve became much smaller, as Fig. 4 .shows. The ratio of the two areas represented by the two peaks was reduced to 35 : 65 from 60 : 40 which is that t’ypifying the MWD of polymers produced with a .3% emulsifier concentration. The reduction of the amount of polymer equivalent to the peak on the MWD curve when the number of micelles present in the system is greatly reduced (near the CMC) is in our opinion confirmation -for a simultaneous progress of the polymerization in the monomer droplets
MWD characteristics of VF eopolymers with DOPFO
25 01
a n d the l a t e x particles b a s e d o n t h e emulsifier mieelles. T h e f a c t t h a t an increase in emulsifier c o n t e n t to 1 0 % (Fig. 4, c u r v e 3) does n o t give a r e v e r s i b l e d e p e n d e n c e is a s s o c i a t e d w i t h the existence of a so-called second CMC [1 6] a t w h i c h t h e r e is a s u d d e n change of size (and shape) of the mieelles; a n e m u l s i f i e r c o n c e n t r a t i o n increase does n o t increase the n u m b e r of micelles nor t k e prop o r t i o n of t h e p o l y m e r p r o d u c e d b y the m e c h a n i s m of emulsion. T h e a s s u m p t i o n of t h e p o l y m e r i z a t i o n progressing s i m u l t a n e o u s l y in t w o p h a s e s is also confirmed b y t h e results for m e a s u r e m e n t of t h e l a t e x p a r t M e (limensions fi'om, m i n i m a l light s c a t t e r i n g i n t e n s i t y [17, 18]. Curves 1 "rod in Fig. 5 show t h e existence of two well defined p e a k s on the angle d e p e n d e n c e o f inverse light s c a t t e r i n g i n t e n s i t y for t h e latices of the im~estigated eopolymers; this c o n t r a s t s w i t h the a n a l o g o u s d e p e n d e n c e (Fig. 5, curve 3) for the VF cop o l y m e r w i t h p e r f l u o r o m e t h y l vinylester, which h a s a m f i m o d a l M W D . T h e r e are l a t e x particles of t w o sizes/>resent in our s y s t e m (Fig. 5, curves 1 a n d 2) a l t h o u g h these are fairly similar. A t t e n t i o n is d r a w n to the specific shape o f the high mol.wt, p e a k on t h e M W D curve, whictl is p r a c t i c a l l y s y m m e t r i c a l for m o s t of our copolymers. A n e s t i m a t i o n of its p o l y d i s p e r s i t y g a v e a M,,:.Q+, close to n n i t y (while a similar a s s e s s m e n t of the M W D widtl~ on the low m o l . w t . p e a k g a v e a p o l y d i s p e r s i t y of 1.4-1-9). Such a M W D is t y p i c a l for m a c r o m o l e eules p r o p a g a t i n g b y the " l i v e " chain m e c h a n i s m . T h e shift of the higt~ m o l . w t . p e a k t o w a r d s larger mol.wt, was d e t e c t e d only at. v e r y low conversions (Fig. 3). T h e M W D curves r e m a i n p r a c t i c a l l y the s a m e f r o m a t least a 20°~ conversion o n w a r d s cFi~ 4). T h e d e t e c t e d s h a p e of the large mol.wt, p e a k on the M W D curve is t h e r e i b r e not linked w i t h a p o l y m e r i z a t i o n b y a " l i v e " elmin m e c h a n i s m , b u t is p o s s i b l y e x p l a i n a b l e only b y the specific t y p e of t e r m i n a t i o n r e a c t i o n which sets in at some stage of the chain p r o p a g a t i o n reaction. Transloted by K. A. ALLEN REFERENCES
1. Ye. G. ERENBURG, L. V. PAVLOVA, Ye. O. OSIPCHUK, I. M. DOLGOPOL'SKII et cd.,
2. :;. 4. 5. 6, 7. S.
9. ]0. II.
Vysokomol. soyed. A20: 382, 1978 (Translated in l'olymer Sei. U.S.S.R. 20: 2, 431, 1!!78) D. C. PEPPER and P. P. RUTHERFORD, J. Appl. Polymer Sei. 2: 100, 1959 K. IAMAGUCHI, Makromol. Chemic 132: 143, 197(i V. V. DUDUKIN, Dissertation, Moscow, 1967 I.A. GRITSKOVA, S. MEDVEDEVand M. F. MARGARITOVA, Kolloid. Zhur. 26:16~. 1!164 I. A. GRITSKOVA, M. F. MARGARITOVA and S. S. MEDVEDEV, Vysokomol. s~Wed. 6: 1880. 1964 (Translated in Polymer Sei. U.S.S.R. 6: 10, 2084, 1964) V. V. DUDUKIN, S. S. MEDVEDEV and I. A. GRITSNOVA, Dokl. Akad. Nauk SS,qt/ 172: 1125, 1967 V. V. DUDUKIN, N. K. NAZAR, I. A. GRITSKOVA, and S. S. MEDVEDEV, \-3sok()mol, soyed. A9: 188, 1967 (Translated in Polymer Sei. U.S.S.I£ 9: l, 206, 1!167) J. UGELSTAD and F. K. HANSEN, tfubber Chem. Teehnol. 49: 536, 1976 V. A. SPIRIDONOVA, S. A. NIKITINA and A. B. TAUBMAN, Dokl. Akad. Nauk SSS[ / 182: 640, 1968 O. A. SMORGAN, N. P. SHPENZER and S. L. TALMUD, Kolloid. Zhm'. 40: 376. 1!~78
2502
YE. A. SA~OAT.OV et al.
12. I. A. GRITSKOVA, L. I. S E D A K O V A , D. S. M U R A D Y A N a n d A. N. P R A V E D N I K O V , Dokl. Akad. Nauk SSSR 238: 607, 1978
13. S. Ya. FRENKEL, Vvedenie v statisticheskuyu teoriyu polimerizatsii (Introduction to the Statistical Polymerization Theory) Izd. "Nauka", 1965 14. Entsiklopediya polimerov, t. 1 (The Encyclopedia of Polymers, vol. 1). Izd. "Sovetskaya Entsiklopediya", 393, 1972 15. V. P. SASS, A. S. SHASHKOV, A. I. KONSHIN, R. L. RABINOVICH et al., Vysokomol. soyed. A17: 1086, 1975 (Translated in Polymer Sci. U.S.S.R. 17: 5, 1246, 1975) 16. K. SHINODA, T. NAKACHAVA, B. TATATUSI and T. ISEMURA, Kolloidnye poverkhnostno-aktivnye veshchestva (Colloidal Surfactants). Izd. "Mir", 1966 17. G. MIE, Ann. Phys. 25: 377, 1908 18. H. SAMUEL, MARON, E. MAX and ELDER, J. Coll. Sci. 18: 107, 1963
Polymer Science U.S.S.R. Vol. 21, pp. 2502-2511. C Pergamon Press Ltd. 1980. Printed in Poland
0032-3950/79/1001-2502507.50/0
THE TYPE OF REACTI~/E CENTRES PRESENT IN THE ALKYLALUMINIUM AQUO-COMPLEX USED IN THE ELECTROPHILIC POLYMERIZATION OF OLEFINS* Y u . A. SANGALOV, YU. YA. NEL'KENBAUM, O. A. PONO1KA_~EVa n d K . S. MXNSKER Chemistry Institute, U.S.S.R. Academy of Sciences (Received 21 August 1978) Calculation and experimental results (the physical and chemical properties, a n d the activity in the isobutylene polymerization) concerning the n a t u r e of the reactive centres of aquo-complexes C~HsA1C1~. I-I20 are described. These compounds are shown to digress from the analogous complexes with HC1 and not to be an H acid, b u t are characterized b y a lov~ Lewis acidity. An initiation of the isobutylene polymerization over C2HsA1CI~'H20 presumes a prior C2HsA1CI~ reaction with H20 in the presence of the monomer and the formation of an alumoxane aquo-complex as the actual initiator. The transformation of the alkylaluminium dichloride aquo-complex to t h a t of alumoxane has been proved by direct methods (IR spectroscopy, the use of isobutylene models, C~HsA1CI~.D20), as well as by analyses of the dependences of the isobutylene (IB) polymerization (the polymer yield and the initial process rates as a function of the H20 content of the aquo-complex); an initiation scheme of the I B polymerization b y the alumoxane aquo-complex which is characterized by a sufficientl y large strength of the acid centres (H 0 ~<-- 8) is suggested. I n contrast with the A1C1a complexes, C2H~A1C12"H20 is highly selective in the IB polymerization when the latter is present i n a mixture with other olefines; the selectivity drops rapidly on changing from an inert solvent (hexane) to a polar (CH2CI~). I t is concluded that the C~HsA1C1.H20 complexes forming in the absence of IB differ in type of reactive centres from those forming in situ a n d those based on AIC13. * Vysokomol. soyed. A21: No. 10, 2267-2274, 1979.
0082-3950/7911001-2496507.50/0
THE MOLECULAR WEIGHT DISTRIBUTION (MWD) ~CHARACTERISTICS OF VINYLIDENE FLUORIDE COPOLYMERS WITH 3,7-DIOXAPERFLUORO-I-OCTENE* YE.
G. ERENBURO,
L . V . PAVLOVA, Y E .
O . OSIPCHUK, I . M .
DOLGOrOL'SKII,
A. I. Kol~sm~, A. M. GREIS and I. YA. PODDUBNYI S. V. L e b e d e v A l l - U n i o n S y n t h e t i c R u b b e r R e s e a r c h I n s t i t u t e
(Received
18
August
1978)
E l u t i o n f r a e t i o n a t i o n i n a c o l u m n h a s b e e n u s e d t o s t u d y t h e M W D of t h e vinylid e n e fluoride e m u l s i o n c o p o l y m e r w i t h 3 , 7 - d i o x a p e r f l u o r o - l - o c t o n e ( V F - D O P F O e o p o l y m e r ) . T h e d e p e n d e n c e bf t h e i n t r i n s i c v i s c o s i t y o n t h e m o l . w t , h a s b e e n e s t a b l i s h e d a n d t h e M W D of t h e c o p o l y m e r s h a s b e e n f o u n d t o b e b i m o d a l . T h e effect o n t h e M W D of t h e c o m o n o m e r r a t i o in t h e original m i x t u r e , of t h e emulsifier concent r a t i o n a n d t h e m o n o m e r c o n v e r s i o n h a s b e e n e x a m i n e d . T h e p o l y m e r i z a t i o n was f o u n d t o p r o c e e d in t w o p a r a l l e l phases, i.e. a m i c r o - e m u l s i o n of tim m o n o m e r a n d of t h e l a t e x p a r t i c l e s b a s e d o n t h e emulsifier micelles.
AN important position amongst the fluorine containing elastomers if held by t h e vinylidene fluoride copolymers with perfluoro-alkyl vinylester. There is little information about the molecular structure of this group and the reason is largely t h e poor solubility of F containing polymers in the usual organic solvents, so that a n y fractionation method and determination of the mol.wt, requires special research in each case. Our earlier studies dealt with the MWD and flexibility of the vinylidene fluoride copolymers with perfluoromethyl vinylester. Their MWD were found to be typically those of a classical emulsion polymerization, i.e. close to the most probable in the initial process stage (up to a 20~o conversion), but broader at larger conversion where it was enriched with the larger mol.wt, fractions. This report deals with the MWD of the vinylidene fluoride copolymers with another perfluoroalkyl vinylester--the 3,7-dioxaperfluoro-l-oetene (the V F DOPFO copolymer). EXPERIMENTAL T h e p o l y m e r i z a t i o n was c a r r i e d o u t in a n all m e t a l a p p a r a t u s f i t t e d w i t h s a m p l i n g m e a n s a t v a r i o u s c o n v e r s i o n stages. T h e e l u t i o n f r a c t i o n a t i o n m a d e use of a glass c o l u m n p a c k e d w i t h 0.1-0.2 m m m e s h g r o u n d q u a r t z glass b e a d s a n d s o a k e d w i t h a h e x a f l u o r o b e n z e n e - h e x a n e m i x t u r e . T h e p o l y m e r was d e p o s i t e d o n t h e p a c k i n g b y s o l v e n t e v a p o r a t i o n while c o n t i n u o u s l y s t i r r i n g i n a n a i r s t r e a m . P r e l i m i n a r y s t u d i e s e s t a b l i s h e d t h e sedi* V y s o k o m o l . soyed, h 2 1 : No. 10, 2 2 6 1 - 2 2 6 6 , 1979. 2496
MWD characteristics of VF copolymers with DOPFO
2497
m e n t a t i o n c o n d i t i o n s for v a r i o u s e o p o l y m e r c o m p o s i t i o n s ; t h e f r a c t i o n a t i o n was f o u n d t o t a k e place o n l y a c c o r d i n g to m o l e c u l a r weights. T h e following were tile o p t i m u m f r a c t i o n a t i o n c o n d i t i o n s : a s t e p w i s e g r a d i e n t of solv e n t c o n c e n t r a t i o n s f r o m 35 t o 1 0 0 % o f h e x a f l u o r o b e n z e n e , e l u t i o n t e m p e r a t u r c = 6 0 ° C , a 1 g p o l y m o r s a m p l e for 75 ml of p a c k i n g , a 50 m l / 5 0 m i n e l n t i o n r a t e w i t h some v a r i a t i o n d u r i n g t h e (~xperiment. w h i c h d e p e n d e d (:n t h e i n t r i n s i c viscosity of t h e original s a m p l e . T h e s a m p l e s were first w a s h e d w i t h h o t e t h a n o l in a S o x h l e t to r e m o v e a n y s u r f a c t a n t p r e s e n t ; t h e l a t t e r h a d been f o u n d to be t h e factor' decisive for t h e s e p a r a t i o n q u a l i t y . T h o s()lutions w e r e also c e n t r i f u g e d 1 h r a t 25,000 r p m before f r a c t i o n a t i o n to r e m o v e s m a l l a m o u n t s of colloidal s u s p e n d e d m a t t e r .
l°9 ['t]
04 /'7
D
7"S I
5"0
5"5
I
6.0 1o9 M
FIr'. 1. Th(" intrinsic viscosity of tile VI;- I ) O P F O e o p e l y m e r as a f u n c t i o n of t h e molecular weight. T h e s e c o n d i t i o n s m a d e t h ? r e s u l t s r e p r o d u c i b l e a n d m e t tile u s u a l c r i t e r i a for c o l u m n f r a c t i o n a t i o n efficiency; t h e p o l y m e r yield a v e r a g e d 9 6 % , t h e c o n c e n t r a t i o n c a t tile c o l u m n e x i s t was < 0 . 4 g/100 ml; Cm~xM~max<400 [2, 3]. T h e i n t r i n s i c v i s c o s i t y [~/] of t h e s a m p l o b a s e d o n t h e f r a e t i o n a t i o n r e s u l t s c o i n c i d e d w i t h t h a t of t h e original p o l y m e r w i t h i n t h e <,rror l i m i t s of d e t e r m i n a t i o n . T h e d e p e n d e n c e of [~] o n t h e m o l . w t , u n d e r t h e s e c o n d i t i o n s was e s t a b l i s h e d in a p r e p a r a t i v e f r a e t i o n a t i o n of 8 g of one of t h e s t u d i e d samples. T h e mol.wt, of a n u m b e r o~ f r a c t i o n s were d e t e r m i n e d b y o s m o l n e t r y in h e x a f l u o r o b e n z e n e ( H F B ) , t h e q u a l i t y of t h o f r a c t i o n s in a e o m p a r i s c n e f t h e ff/~ w i t h t h e ~ . , b u t t h i s was n o t d o n e s y s t e m a t i c a l l y beca.use t h e e o p o l y m e r d i s s o l v e d o n l y in a l i m i t e d n u m b e r of p e r f l u o r i n a t e d s o l v e n t s in w h i c h t h e r e f r a c t i v e i n d e x was u n u s u a l l y small. T h e d e t e r m i n a t i o n b y light, s c a t t e r i n g was also h i n d e r e d b y t h e u s u a l c o n t e n t of a s m a l l a m o u n t of s u p e r m o l e e u l a r a g g r e g a t e s w h i c h m o s t p r o b a b l y f o r l n e d as a r e s u l t e f t h e e a s y c r y s t a l l i z a t i o n of t h e VF. T h e p r e s e n c e of s u c h b l o c k s e x p l a i n s t h e fact. t h a t some s a m p l e s o n l y dissolved w h e u t h e s o l u t i o n s were h e a t e d a l t h o u g h n o p r e c i p i t a t e f o r m e d w h e n t h e t e m p e r a t u r e was subsoqucntly reduced. A s e c o n d f r a c t i o n a t i o n of t w o of t h e frt~ctions w i t h a large mol.wt., u s i n g s m a l l e r c h a n g e s of t h e e l u t i o n m i x t u r e c o m p o s i t i o n , p r o d u c e d 80°~) of t h e p o l y m e r f r o m t h e m ; [q] e q u a l l e d t.he a v e r a g e v i s c o s i t y of t h e r e s p e c t i v e f r a c t i o n w i t h i n a ~: 10°{; error. T h e M W D c u r v e s of t h e s e f r a c t i o n s h a d h o w e v e r a specific shape, i.e. h a d a " t a i l " of low mol.wt, w h i c h m a d e t h e m u n s u i t a b l e for o s m o m e t r i e d e t e r m i n a t i o n s . (This u n u s u a l s h a p e of t h e large m o l . w t , f r a c t i o n M W D c u r v e s s e e m s to be l i n k e d w i t h t h e larger w i d t h a n d t h e i n i t i a l b i m o d a l d i s t r i b u t i o n ) . C u r v e s for [ ~ / ] = f ( M ) for t h e f r a c t i o n s f r o m e l u t i o n f r a c t i o n a t i o n -~,ere t h e r e f o r e p l o t t e d o n l y for t h o s e w i t h M < 3 5 0 × 103; a large m o l . w t , f r a c t i o n ( 3 I ~ 600 x
Y E . G. ERENBURG ~$ al.
2498
X 10') was produced from a sample with a narrow MWD b y combining precipitation with elution fractionation, h~/w carefully determined by light scattering in H F B (dn/dc= 0.0185) gave /~w//%7/,= 1.3.
d14 ,dM,lO 5
5
'~krL/k~ !\\\\ I \~
~J'/X"l
I0
\\1
30
50 M,lO -~
Fro. 2. The MWD of the copolymers containing various VF quantities in the original mixture. YF, %: 1-- 52; 2-- 83. A fitting description of the [~]=f(M) illustrated in Fig. 1 is given by the equations: [~]----3.24X 10-s~/°'77; log_M=l-31og [~]-r5"83. These equations were used to determine the mol.wt, of all the isolated fractions. RESULTS
The MWD curves calculated for the samples produced under various conditions from the fractionation results are reproduced in Figs. 2-4. These show that the curves have distinct peaks at fairly mol.wt. All the samples showed a bimodat distribution regardless of the polymerization conditions, such as the purity, the original ratio (Fig. 2), and the monomer ~o conversion (Fig. 3).
high
d~ IdM ~lO6
d W/dM.m~
(\
a 4O
i I Ii I I
3o
It I
f~
I I
2
20
•
b
,/- \
2 f
0
5
MxlO_510
0
./!i/I//'' I
4
I
6
I
X
8M.:-SlO
Fro. 3. The MWI) of samples produced at various conversions, a: 1 - 3; 2--33 e/o; the samples were produced in various tests under identical conditions, b: 1--21; 2--75; 3--100~/o; samples from a single batch by sampling.
I0
MWD characteristics of VF copolymers with DOPFO
2499
I t must be pointed out t h a t the bimodality of the MWD is apparent at very low conversions ( < 3%, Fig. 3a) and is retained thr6ughout the polymerization. This bimodality cannot be the result of a subsequent realization of various reaction mechanisms. I t can therefore be regarded is the consequence of a two phase process, i.e. a polymerization in two different phases having differing kinetics. dW/dM.~ s
q I
20
I
I/7
I
5
1o
15 M , I O -#
]~i(~. 4. The MWD dependence of the copolymers as a function of the emulsifior content, ~o: 1--1; 2--3; 3--10. More ~ttention has recently been given in the literature to the topochemistry o f emulsion polymerizations. Parallel with the articles describing such a reaction on the classic lines, there appeared some which proved the formation of a stable micro-emulsion of the monomer in some condition which caused the polymerization to took place in the droplets. This was detected for the first time when nonionic emulsifiers were used, or their blends with ionic ones [4-9], as well as in systems containing monomers with limited water solubility [10, 11]. Such a spontaneous emulsification and the formation of polymer-monomer particles based on monomer droplets was recently also established in styrene polymerization when C15H31SO3Na was used as the emulsifier [12]. A bimodal distribution was observed in some of these studies [4] and was explained by simultaneous progress of a polymerization in two phases, namely the latex particles and the continuous phase of the monomer. The systems containing monomers with a limited solubility in water possessed multi-modal distribution which was linked by the authors [13] with polymerizations in the aqueous solution and in the latex particles. The existence of colloidal solubility was later established for one of these monomers (in the vinyl acetate-water system) and the presence of 500 .~ radius droplets even when there was no emulsifier [11]. We used ionic emulsifiers in our study and the water solubility of the monomers in our polymerization conditions was not examined. The vinylidene fluoride
YE.
2500
IVF) is normally @lob
G. ERENBURG et al.
not water-soluble
[14],
at normal pressure and temperature
fier is used or not; this was established two phase process to apply.
Apart
while that of the comonomer of polymerization, by chromatography.
from the bimodality
is about
whether an emulsiWe assume also a
of the MWD
curves,
confirmation of it is the fact that the copolymers represented by the two peaks on the MWD curve usually show a noticeable difference in composition. The compositions Specbrospin
of some of t’he examined materials were got by NMR on a “BriikerHX-90”
instrument
[15]
VF content,
and are given below.
96
I max ITIM
63
74
69
60
67
G4
76
83
83
65
75
59
Confirmation was sought for the presence of a second phase in the shape of .a micro-emulsion of the rnonomer by studying the MWD of the copolymers produced with various emulsifier contents. , l/10, arb. un. I
FIG. 5. The angular dependence latices
of:
1, Z-VF-DOPFO
of the inverse light scattering
copolymer;
3-VF
copolymer
intensity
for the
with perfluoroalkyl
vinylate.
Reduction
of the emulsifier concentration
from 3% to near the critical micelle-
formation concent,ration (CMC, around 1%) showed that the area enclosed by the large mol.wt. peak on the MWD curve became much smaller, as Fig. 4 .shows. The ratio of the two areas represented by the two peaks was reduced to 35 : 65 from 60 : 40 which is that t’ypifying the MWD of polymers produced with a .3% emulsifier concentration. The reduction of the amount of polymer equivalent to the peak on the MWD curve when the number of micelles present in the system is greatly reduced (near the CMC) is in our opinion confirmation -for a simultaneous progress of the polymerization in the monomer droplets
MWD characteristics of VF eopolymers with DOPFO
25 01
a n d the l a t e x particles b a s e d o n t h e emulsifier mieelles. T h e f a c t t h a t an increase in emulsifier c o n t e n t to 1 0 % (Fig. 4, c u r v e 3) does n o t give a r e v e r s i b l e d e p e n d e n c e is a s s o c i a t e d w i t h the existence of a so-called second CMC [1 6] a t w h i c h t h e r e is a s u d d e n change of size (and shape) of the mieelles; a n e m u l s i f i e r c o n c e n t r a t i o n increase does n o t increase the n u m b e r of micelles nor t k e prop o r t i o n of t h e p o l y m e r p r o d u c e d b y the m e c h a n i s m of emulsion. T h e a s s u m p t i o n of t h e p o l y m e r i z a t i o n progressing s i m u l t a n e o u s l y in t w o p h a s e s is also confirmed b y t h e results for m e a s u r e m e n t of t h e l a t e x p a r t M e (limensions fi'om, m i n i m a l light s c a t t e r i n g i n t e n s i t y [17, 18]. Curves 1 "rod in Fig. 5 show t h e existence of two well defined p e a k s on the angle d e p e n d e n c e o f inverse light s c a t t e r i n g i n t e n s i t y for t h e latices of the im~estigated eopolymers; this c o n t r a s t s w i t h the a n a l o g o u s d e p e n d e n c e (Fig. 5, curve 3) for the VF cop o l y m e r w i t h p e r f l u o r o m e t h y l vinylester, which h a s a m f i m o d a l M W D . T h e r e are l a t e x particles of t w o sizes/>resent in our s y s t e m (Fig. 5, curves 1 a n d 2) a l t h o u g h these are fairly similar. A t t e n t i o n is d r a w n to the specific shape o f the high mol.wt, p e a k on t h e M W D curve, whictl is p r a c t i c a l l y s y m m e t r i c a l for m o s t of our copolymers. A n e s t i m a t i o n of its p o l y d i s p e r s i t y g a v e a M,,:.Q+, close to n n i t y (while a similar a s s e s s m e n t of the M W D widtl~ on the low m o l . w t . p e a k g a v e a p o l y d i s p e r s i t y of 1.4-1-9). Such a M W D is t y p i c a l for m a c r o m o l e eules p r o p a g a t i n g b y the " l i v e " chain m e c h a n i s m . T h e shift of the higt~ m o l . w t . p e a k t o w a r d s larger mol.wt, was d e t e c t e d only at. v e r y low conversions (Fig. 3). T h e M W D curves r e m a i n p r a c t i c a l l y the s a m e f r o m a t least a 20°~ conversion o n w a r d s cFi~ 4). T h e d e t e c t e d s h a p e of the large mol.wt, p e a k on the M W D curve is t h e r e i b r e not linked w i t h a p o l y m e r i z a t i o n b y a " l i v e " elmin m e c h a n i s m , b u t is p o s s i b l y e x p l a i n a b l e only b y the specific t y p e of t e r m i n a t i o n r e a c t i o n which sets in at some stage of the chain p r o p a g a t i o n reaction. Transloted by K. A. ALLEN REFERENCES
1. Ye. G. ERENBURG, L. V. PAVLOVA, Ye. O. OSIPCHUK, I. M. DOLGOPOL'SKII et cd.,
2. :;. 4. 5. 6, 7. S.
9. ]0. II.
Vysokomol. soyed. A20: 382, 1978 (Translated in l'olymer Sei. U.S.S.R. 20: 2, 431, 1!!78) D. C. PEPPER and P. P. RUTHERFORD, J. Appl. Polymer Sei. 2: 100, 1959 K. IAMAGUCHI, Makromol. Chemic 132: 143, 197(i V. V. DUDUKIN, Dissertation, Moscow, 1967 I.A. GRITSKOVA, S. MEDVEDEVand M. F. MARGARITOVA, Kolloid. Zhur. 26:16~. 1!164 I. A. GRITSKOVA, M. F. MARGARITOVA and S. S. MEDVEDEV, Vysokomol. s~Wed. 6: 1880. 1964 (Translated in Polymer Sei. U.S.S.R. 6: 10, 2084, 1964) V. V. DUDUKIN, S. S. MEDVEDEV and I. A. GRITSNOVA, Dokl. Akad. Nauk SS,qt/ 172: 1125, 1967 V. V. DUDUKIN, N. K. NAZAR, I. A. GRITSKOVA, and S. S. MEDVEDEV, \-3sok()mol, soyed. A9: 188, 1967 (Translated in Polymer Sei. U.S.S.I£ 9: l, 206, 1!167) J. UGELSTAD and F. K. HANSEN, tfubber Chem. Teehnol. 49: 536, 1976 V. A. SPIRIDONOVA, S. A. NIKITINA and A. B. TAUBMAN, Dokl. Akad. Nauk SSS[ / 182: 640, 1968 O. A. SMORGAN, N. P. SHPENZER and S. L. TALMUD, Kolloid. Zhm'. 40: 376. 1!~78
2502
YE. A. SA~OAT.OV et al.
12. I. A. GRITSKOVA, L. I. S E D A K O V A , D. S. M U R A D Y A N a n d A. N. P R A V E D N I K O V , Dokl. Akad. Nauk SSSR 238: 607, 1978
13. S. Ya. FRENKEL, Vvedenie v statisticheskuyu teoriyu polimerizatsii (Introduction to the Statistical Polymerization Theory) Izd. "Nauka", 1965 14. Entsiklopediya polimerov, t. 1 (The Encyclopedia of Polymers, vol. 1). Izd. "Sovetskaya Entsiklopediya", 393, 1972 15. V. P. SASS, A. S. SHASHKOV, A. I. KONSHIN, R. L. RABINOVICH et al., Vysokomol. soyed. A17: 1086, 1975 (Translated in Polymer Sci. U.S.S.R. 17: 5, 1246, 1975) 16. K. SHINODA, T. NAKACHAVA, B. TATATUSI and T. ISEMURA, Kolloidnye poverkhnostno-aktivnye veshchestva (Colloidal Surfactants). Izd. "Mir", 1966 17. G. MIE, Ann. Phys. 25: 377, 1908 18. H. SAMUEL, MARON, E. MAX and ELDER, J. Coll. Sci. 18: 107, 1963
Polymer Science U.S.S.R. Vol. 21, pp. 2502-2511. C Pergamon Press Ltd. 1980. Printed in Poland
0032-3950/79/1001-2502507.50/0
THE TYPE OF REACTI~/E CENTRES PRESENT IN THE ALKYLALUMINIUM AQUO-COMPLEX USED IN THE ELECTROPHILIC POLYMERIZATION OF OLEFINS* Y u . A. SANGALOV, YU. YA. NEL'KENBAUM, O. A. PONO1KA_~EVa n d K . S. MXNSKER Chemistry Institute, U.S.S.R. Academy of Sciences (Received 21 August 1978) Calculation and experimental results (the physical and chemical properties, a n d the activity in the isobutylene polymerization) concerning the n a t u r e of the reactive centres of aquo-complexes C~HsA1C1~. I-I20 are described. These compounds are shown to digress from the analogous complexes with HC1 and not to be an H acid, b u t are characterized b y a lov~ Lewis acidity. An initiation of the isobutylene polymerization over C2HsA1CI~'H20 presumes a prior C2HsA1CI~ reaction with H20 in the presence of the monomer and the formation of an alumoxane aquo-complex as the actual initiator. The transformation of the alkylaluminium dichloride aquo-complex to t h a t of alumoxane has been proved by direct methods (IR spectroscopy, the use of isobutylene models, C~HsA1CI~.D20), as well as by analyses of the dependences of the isobutylene (IB) polymerization (the polymer yield and the initial process rates as a function of the H20 content of the aquo-complex); an initiation scheme of the I B polymerization b y the alumoxane aquo-complex which is characterized by a sufficientl y large strength of the acid centres (H 0 ~<-- 8) is suggested. I n contrast with the A1C1a complexes, C2H~A1C12"H20 is highly selective in the IB polymerization when the latter is present i n a mixture with other olefines; the selectivity drops rapidly on changing from an inert solvent (hexane) to a polar (CH2CI~). I t is concluded that the C~HsA1C1.H20 complexes forming in the absence of IB differ in type of reactive centres from those forming in situ a n d those based on AIC13. * Vysokomol. soyed. A21: No. 10, 2267-2274, 1979.