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Effect of the structure of synthetic cis-1,4-polyisoprene and natural rubber on diffusion of solid low molar mass substances
990
L.V. SOKOLOVAand V. A. SUERSnNEV
REFERENCES 1. L. VROMAN and E. F. LEONARD, Ann. N.Y. Acad. Sci., p. 156, 1977 2. S. L. COOPER and N. A. PEPPAS, Biomaterials: Interfacial Phenomena and ApplicatiOns, p. 199, Marcell Decker, New York, 1982 3. E. BRYNDA, J. DOBNIK, J. VACIK and J. KALAL, Biomed. Mater. Res. 12: 55, 1978 4. E. BRYNDA, M. HOUSKA, Z. POKORNA, N. A. CEPALOVA, Yu. V. MOISEYEV and J. KALAL, Bioeng. 2: 411, 1978 5. E. BRYNDA, i . HOUSKA, N. A. CEPALOVA and J. KALAL, Ann. Biomed. Engng. 8: 245, 1980 6. Yu. V. MOISEYEV, N. K. BOROVKOVA and N. A. TSEPALOVA, Vysokomol. soyed. BI9: 3, 1977 (Not translated in Polymer Sci. U.S.S.R.) 7. S. M. KIM, R. G. LEE, C. ADAMSON and D. J. LYMAN, Symposium on Biomedical Applications of Polymers, vol. 33, p. 2, Marcell Decker, New York, 1973 8. B. BLOMB)~CK and M. BLOMB)~CK, Acta Chem. Scand. 10: 147, 1956 9. Handbook of Biochemistry Selected Data for Molecular Biology, edited by. H. A. Sober, The Chem. Rubber Co., New York, 1970 10. L. BACHMAN, W. W. SCHMITT-FUMIAN, R. HAMMEL and M. LEDERER, Makromolek. Chem, 176: 2603, 1975 II. R . J . MCCLURE and B. M. CRAVEN, J. Molec. Biol. 83: 551, 1974
Polymer Science U.S.S.R. Vol. 27, No. 4, pp. 990-997, 1985 Printed in Poland
0032-3950/85 $10.00 +:.00 © 1986 Pergamon Press Ltd.
EFFECT OF THE STRUCTURE OF SYNTHETIC cis-I,4-POLYISOPRENE AND NATURAL RUBBER ON DIFFUSION OF SOLID LOW MOLAR M A S S SUBSTANCES * L. V. SOKOLOVA a n d V. A. SHERSHNEV M, V. Lomonosov Institute of Fine Chemical Technology, Moscow
(Received 14 February 1984)
A study of the structure of SKI and N R carried out using molecular probes (sulphur and diphenyl guanidine) by the diffusion-sorption method in the range of 30-110 ° indicates that these elastomers are characterized by several high temperature structural transitions. The presence of transitions was confirmed by IR spectroscopy. A marked difference was noted in the structure of SKI and N R matrices. * Vysokomol. soyed. A27: No. 4, 879-884, 1985.
Diffusion of solid low molar mass substances
991
SVt,rrHETtC SKI differs from N R not only in its ability to crystallize (process rate a n d Tmtlt of the crystalline phase), but also in the efffeet a n this property o f changing structural parameters. It is k n o w n t h a t during elongation crystallization of N R is accelerated to a m u c h greater exteDt t h a n t h a t of SKI. R u b b e r mixtures based o n N R therefore have higher cohesive strength. It is assumed that the main causes of this are the higher M, regular structure of macromoleeular chains a n d the presence in N R of n o n - r u b b e r components (proteins, amino acid, resin in the proportion of ~<3 ~ ) [1 ]. A comparative study was m a d e in this paper of diffusion parameters of SKI and N R in a wide temperature range (30-110°). Kariflex JR-305 SKI was used in the study with Mw=2-3 x 105 a n d N K ("pale crepe") previo u s l y precipitated from solutions in toluene with methal alcohol. Sulphur was used as molecular probe of the polymer matrix in the interval of 30-80 °, diphenylguanidine ( D P G ) in the interval of 45--110 °, previously purified by two-foid recrystallization from solutions in corresponding solvents. The rate of solution of low molar mass substances in samples previously heated to 70 ° in 2 hr, was determined b y diffusion [2]. The rate of solution is characterized by the inverse value of time ~during which 10 ~ of the substance is dissolved. The error of the method when determining the rate o f solution was + 5 ~ . I R spectra of elastomer films in the range of 25-110°C were obtained using a UR-10 spectrometer a n d a high temperature cell. Films were obtained on KBr discs with slow evaporation of the solvent from dilute solutions in CCI,. The accuracy of temperature measurement was +0-5 °. It was confirmed using the m e t h o d previously described [3] that the effect of heat radiation of the sample a n d cell may be ignored. W h e n recording IK spectra temperature was raised suddenly by 5-6 °, followed by thermostatic control of the polymer film at constant temperature for 90 rain The film placed in a high temperature cell was first heated for 24 hr to ~ 100 °, then cooled to 25 "~ This cycle was repeated three times for each film. The intensity of the absorption bands was measured at m a x i m u m frequencies of bands. F o r the convenience of comparison the optical density of abs o r p t i o n bands was staodardized for all samples bringing it to unity at ~ 30 °. The temperature dependence of the rate of solution of sulphur in N R in the interval of 30-80 ° ~conforms to the Arrhenius equation. In the range of 4 5 + 3 ° (D the temperature dependence of tl,~e rate of solution of sulphur shows a break, while in the range of 52-55 ° (I') a n d 65-70 ° (II) changes suddenly, which is due to three structural transitions. The a p p a r e n t activation energy values of solution of sulphur are tabulated. Temperature dependences of t h e diffusion coefficient a n d equilibrium solubility of sulphur in N K are also complex: a break in the range of structural transition I a n d a sudden chal~ge of these parameters in transition ranges I ' a n d II (Fig. 1). A sudden increase of the diffusion coefficient a n d a reduction in equilibrium solubility of sulphur in N R in the range of transitions I ' and II indicates a vigorous structural change of the polymer matrix, particularly on transition of II. The activation energy of diffusion Ea of sulphur as a result of transition I is more t h a n halved, while as a result of Iransitions I ' a n d II, it increases (Table). The varying change of solubility parameters of sulphur ir~ N R proves a noticeable difference in the structural transitions observed. It should be noted that relaxation transitions in vulcanisates based on N R were observed when studying mechanical properties [4] a n d creep [5]. Transitions in N R observed by relaxation spectrometry [6], the dielectric loss m e t h o d [7] a n d differential scanning calorimetry [8], in the view of authors of earlier papers [6, 7], are due to the existence in the matrix of microregions of 150-240 A dimension [9]. Let us examine special features of solution in SKI. In the range of 4 7 + 3 ° (I) temperature dependences of the rate of solution of sulphur show a break, in the range of 67 + 3 ° (II) they show a sudden change. Temperatures of transition in SKI show satisfactory agreement with temperatures of transitions I a n d II observed in N R (Fig. 1). The presence of two transitions in SKI, in contrast with three in N R a n d the different variation of the apparent activation energy of solution, Es of sulp h u r (Table) suggests t h a t the structure of SKI a n d N R matrices is not the same. Temperature dependence of the coefficient of diffusion D and equilibrium solubility Co of sul-
992
L . V . SOKOLOVA and V. A . SHERSHNEV
D I F F U S I O N AND SOLUBILITY PARAMETERS OF SOLID LOW MOLAR MASS SUBSTANCES IN POLYISOPRENES
Polymer SKI
NR
Penetrant Sulphur
~ Sulphur
SKI
I DPG
NR
DPG
H,
T° 35 50 60 80 35 50 60 80 50 70 95 50 70 95
kJ/mole 76-0 70"0 70.0 42'4 75.8 38"3 60"6 76'6 50.7 63"3 74"2 39.0 63"0 100.0
59'3 34"4 34"4 2'5 67"9 26"0 42"0 65"9 16'5 59"7 47"0 10"7 58'9 75"4
18-5 41 '6 41 "6 4'4 16"8 14"8 14"0 34-6 7-4 22-1 23-8 12"4 22"1
D × 10 7, cm2/sec 0-24 0.656 0.81 2-76 0.35 0"93 2.1 7-3 0.74 2.0 10.8 0"5 1.87
Co x 10 z, g/cm 3 1"19 1'65
2'56 3"0 0"94 1"16 1"29 1"29
0"31 0"39 0"37 0"41 0"53 0"37
Note. H, is the heat of solution.
p h u r in SKI also prove the presence of two structural transitions. As a result of b o t h transitions in SKI the activation energy of diffusion of sulphur decreases suddenly, particularly as a result of transition H. This transition also results in a sudden reduction of co of sulphur ( ~ l-5-fold). Transition II is evidently due to the structural rearrangement of the matrix, since as a result of. transition its free volume changes. It is possible that microregions break down from closely packed macrochain fragments, accompanied by a n increase in the free volume of the matrix. However, during this transition microregions either break down incompletely, or remain as microregions with different structural organization. This is confirmed by the temperature dependence of D in t h e range I> 70 °, which points to the possibility of existence of a high temperature transition in SKI (Fig. 1). In fact, the use of D P G as molecular probe enables structural transitions to be observed ~ in the range of 55-57 (II) and 84--90° (III) for SKI a n d in the range of 57-60 (II) a n d 80-85 ° ( l i d f o r N R . It is interesting that the rate of solution a n d values of D of D P G in the temperature range below transition II is higher in SKI than in NR. Transition II enables values of D to be equalized in SKI a n d NR. Transition III results in such a rearrangment of the SKI matrix that rates of solution of D P G a n d D of D P G become higher in N R than in SKI. We note that when dissolving sulphur D values in the entire temperature range studied (35-80 °) remain in N R noticeably higher than in SKI (Fig. 1). Values of Co for dissolved sulphur are always higher in SKI than in N R , whereas in the case of D P G equilibrium solubility is higher in N R in the range of 40-80 ° a n d decreases to a level of t h e co values in SKI as a result of the last structural transition. The fact that in the temperature range above transition III D values of D P G (penetrant w i t h a higher molar volume (177 cma/mole) t h a n sulphur (130 cma/mole)) are higher in N R (a polymer with a well k n o w n lower free volume [9]), is evidently explained by the effect of fragments of protein origin in macrochains of NR. It may be assumed that macroehain segments of N R form more extended microregions than in SKI as a result of higher M and more regular structure, in a way similar to that of butadiene elastomers [9]. The formation of ordered microregions from densely packed macrochain sections has the result that chain fragments of protein are concentrated exclusively in the disordered part of the matrix; therefore, the higher concentation of polar groups is achieved in this part of matrix volume, which explains the higher equilibrium solubility values of D P G in N R , compared with PI. The formation of ordered microregions exclusively from units of the same type was noted previously in the case of copolymers of butadiene with styrene [10] a n d acrylonitrile [11,121.
Diffusion of solid low molar mass substances
993
IogD,cm%'cc
"x Z
-
X "Ng
~
6.8
I ~ Q
?>~K
- 7.0
~I"
"~\ × g
L
2"8
O'O
8-2
tog Co, glcrn ~
-1.7
- Z'O
-2"6 1
2.6
I
!
I
2.8
~'0
1
l
J.Z
/oJt T, K" Fro. !. Temperature dependences of the diffusion coefficient D (a) and the coefficient of equilibrium solubility co (b) of sulphur and D P G (1", 2") in SKI (l) and N R (2).
L. V. 50~OLOWt and V. A. SrmRSXNEV
994
Transition III results in the breakdown of ordered formations and the free volume of the polymer suddenly increases, as confirmed by the increased diffusion coefficient of D p G (3.5-fold) and the reduction of Co (2-fold) in the case of N R . During this transition to SKI the D value in D P G only increases 1-9 times, co decreases 1.25-fold accordingly, i.e. re-arrangement or the volume of ordered microregions in higher in N R than in SKI. In the temperature range above transition III matrices
-Ol azzo ' q--X--X--v~--X---x'--X---X--X--X---X-
0.8
a ~~i !
1
I
I
__
I
I
/2
B/Oza*
1.0!
5
0"8 t
0.8
.
C L
;~Q
......
I
t
60
80
J0
60
8D
T~
FI6. 2. Temperature dependences of the optical density of absorption bands at 840 (1), 899 (2), 1130 (3), 1310 (4) and 1665 (5) c m - 1 in the I R spectrum of SKI (a, b) and N R (c, d) for the first (a, c) and third cycles of heating (b, d).
Diffusion of solid low m o l a r mass substances
995
N R and SKI have similar free volumes. It m a y be assumed t h a t transition IH belongs to " l i q u i d l i q u i d " transitions. D a t a o b t a i r ~ d by the dielectric loss m e t h o d [13] a n d by differential scanning calorimetry [8] c~mfirm a noticeable difference in the structure o f N R and SKI. Let us examine temperature dependences of the optical density of absorption bands of the ] R s p e c t r u m of S K I in the 700-1700 c m - 1 range (Fig. 2}. The optical density of the absorption b a n d at 840 c m - 1 = C - H of the out-of-plane vibration o f the C(CH3) = CH, at 899 c m - 1 of the d~form a t i o n vibration o f the CH group of C H z - C ( C H s ) , at 1130 c m - t o f C - C H 3 vibration, at 1375 a n d 1448 c m - 1 of deformation vibrations of CH3 a n d at 1665 c m - t of bond-stretching vibrations o f C = C [14] changes suddenly in the range of 47-50, 67-71 a n d 95-100 ° for the case of the t h i r d cycle o f heating. The degree of variation o f the optical density of these bands varies within the range o f t 3-24~0. Optical density shows the most marked variation for absorption bands at 840 a n d 899 c m - 1 The optical density of a n absorption band at 1312 c m - 1 of - C H vibration during three successive cycles of heating is practically unchanged, which proves a slight variation of polymer film thickness (~< 1%) d u r i n g measurements in the temperature range of 25-110 °. The sudden change observed in the intensity of absorption bands observed is the result of structural transitions, since the intensity of all absorption bands is completely restored during cooling the film to 25 °. Complete restoration of the intensity of absorption bands during three consecutive cycles o f heating atso proves the absence of noticeable changes in the chemical structures of the polymer during the experiment. It is interesting that temperatures of structural transitions in SKI, detected by 1R spectoscopy, agree with temperatures of transition established during the study of diffusion of low m o l a r mass substances. D u r i n g the first cycle of heating a clear structural transition was not observed for all absorption bands in the range of ~ 5 0 ° . F u r t h e r m o r e , the degree of intensity reduction of absorption b a n d s in the range of 700-1700 c m - ~ is m u c h lower for the first cycle t h a n for subsequent ones. D u r i n g repeated cycles of heating temperatures of structural transitions were displaced to the range of lower values. In other words, polymer film structure is " a c t i v a t e d " from one cycle to a n o t h e r due to the breakdown of ordered micro-regions during heating a n d their subsequent formation with smaller dimensions during cooling. Let us revert to special features of temperature changes of I R spectra of N R (Fig. 2). Structural transitions for N R in the case of the third cycle are observed in the range of 55-63, 75-78 and > 110 °, i.e. at higher temperatures than in SKI (Fig. 2). The temperature dependence of the absorption band intensity at 1665 c m - 1 is also different in spectra of N R a n d SKI. In the case of N R the optical density of this b a n d is pracitcally unchanged during the first cycle of heating to 90 °. D u r i n g repeated cycles of heating the extent of its variation increases, but is only 5 instead of 13 % for SKI even for the third cycle. The degree of variation of the optical density of absorption b a n d s in the case of N R for the first cycle is noticeably lower t h a n for SKI (13 instead of 2 1 ~ ) a t the same rates of heating a n d cooling the polymer film, which is the result of different M of SKI a n d N R samples. A similar effect of M on the temperature dependence of absorption b a n d intensity was observed for polybutadienes [9]. In spite of the fact that I R spectra of cis- a n d trans-polyisoprenes have been examined repeatedly, there is, so far, n o clear classification available of absorption bands [14]: I R spectra of eisa n d trans-polyisoprenes differ slightly. However, trans-l,4-polyisoprene, in the opinion of authors of an earlier paper [15], has a helical conformation, confirmed by X-ray analysis a n d IR-spectroscopy in polarized light. In the case of N R , as for trans-l,4-polyisoprene, chain structure in the crystal is n o n p l a n a r [16]. The absorption b a n d at 1665 c m - t in the spectrum of N R is characterized by parallel orientation, whereas at 1670 c m - 1 in the spectrum of trans-l,4-polyisoprene orientation is perpendicular. The possibility of helical chain c o n f o r m a t i o n for SKI a n d N R is also confirmed by their tendency to undergo ring f o r m a t i o n [17, 18]. This reaction takes place in polyisoprene under mild ,conditions a n d is a secondary reaction in halogenation [19], hydrochlorination a n d vulcanisation [201.
996
L . V . SOKOLOVAand V. A. SHERSHNEV
T h e very slight change in the optical density of the absorption band at 1665 cm-~ in N R suggests that in the temperature range studied (30-110 °) helical sections of N R have not yet shown complete breakdown, while in the case of SKI they break down more readily, as confirmed by transition in the range of 95-100 °, i.e. the latter are less stable possibly as a result of their shorter length. Study of special features of diffusion of solid substances and changes of I R spectra in the range of 25-I10 ° indicates that the structure of SKI and N R matrices differs in size and the number o f defects in ordered microregions; the higher the M of the polymer, the more perfect is the structure of micro-regions and the more extended they are in the matrix, since the content of free ends (larger free volume) is higher for polymers of lower M, which impedes the formation of extended ordered microregions. Analysis of data obtained by the diffusion method and I R spectroscopy indicates that SKI is characterized by three structural transitions in the temperature range of 30-110 ° . Temperatures of transition I show satisfactory agreement with Tmc, of crystalline cis-l,4-polyisoprene [21]. However, according to I R spectroscopy [21], SKI samples are amorphous due to the conditions of preparation. A similar pattern was observed for non-crystallizing S K D L rubber with structural transitions in the range of 50-55, 70-75 and 120 °, cooresponding to Tmclt of two crystalline modifications o f trans-l,4-polybutadiene [9]. The temperature of transition I in SKI is linked to its Tz by the equation T * = Ts+ 110 °, which is higher than the "liquid-liquid" transition temperature [22, 23]. Authors of an earlier paper [23~ assume that transition T* is explained by the loss of the fundamental property of macromolecular c h a i n s - c o o p e r a t i v e property. However, above this transition (T*) three further transitions are observed which, according to data obtained by the diffusion method, result in more intense rearrangement of the elastomer matrix. It is interesting that the temperature of transition III is higher than temperatures of transition I (by ,,~ 50°). A similar pattern was observed in the case of PS, polymethylaerylate, P M M A , PVC and poylisobutylene [24]. According to the classification of Boyer transitions this is the so-called T*-transition. The form of variation of Do and Co in PI and N R suggests that transition III may only be regarded as transition of the system to a structureless liquid, while in the temperature range below transition II sufficiently extended ordered microregion are present in the elastomer matrix, consisting of helical coiled macrochain fragments.
Translated by E. SEMERF REFERENCES 1. Fizicheskiye svoistva elastomerov, edited by A. I. Marei, p. 48, Khimiya, Moscow, 1975 2. B. S. GRISHIN, I. A. T U T O R S K I I and Ye. E. POTAPOV, Vysokomol. soyed. A16: 130~ 1974 (Translated in Polymer Sci. U.S.S.R. 16." 1, 156, 1974) 3. F. F. S U K H O V and N. A. SI.X)VOKHOTOVA, Zh. prikl, spektroskopii 9: 11, 167, 1968 4. E. M A E K A W A , R. C. M A H C K E and J. D. FERRY, J. Chem. Phys. 69: 281, 1965 5. D. J. PLAZEK, J. Polymer Sci. A-2, 4: 745, 1966 6. G. M. BARTENEV and J . V. ZELENEV, Plaste und Kautschuk 23: 166, 1977 7. M. G. BARTENEV and M. N. LJOLIN, Plaste und Kautschuk 24: 741, 1976 8. V. A. VOLGIN, Yu. A. L A Z A R E V and I. A. TUTORSKII, (book): Tez. dokl. Vses. nauchnotekhn, konf. Yaroslavl' (Proc. of the All-Union Sci.-Techn. Conf. Yaroslavl') p. 205, 198~ 9. L. V. SOKOLOVA, O. A. CHESNOKOVA, O. A. NIKOLAYEVA and V. A. SHERSHNEV~ Vysokomol. soyed. A27: 352, 1985 (Translated in Polymer Sci. U.S.S.R. 27: 2, 392, 1985) I0. L. V. SOKOLOVA, O. A. CHESNOKOVA, O. A. NIKOLAYEVA and V. A. SHERSHNEV,. (book): Tez. dokl. VIII Vses. konf. po koUoidnoi khimii i fizikokhim, mekhanike (Proceedings of the VIIIth All-Union Conf. on Colloid Chemistry and Physico-Chemical Meth-ods). p. 80, Tashkent, 1983 11. L. V. SOKOLOVA, O. A. C H E S N O K O V A and V. A. S H E R S H N E V , Vysokomol. soyed.. A22: 2305, 1980 (Translated in Polymer Sci. U.S.S.R. 22: 10, 2529, 1980)
Determining the size of drops of dispersed phase during polycondensation
997
12. L. V. SOKOLOVA, O. A. CHESNOKOVA and V. A. SHERSHNEV, Vysokomol. soyed. A26: 314, 1984 (Translated in Polymer Sci. U.S.S.R. 26: 2, 346, 1984) 13. R. BAHULE, K. HAJEK and J. NEDBAL, Polymer Bull. 4: 399, 1981 14. I. DEKHANT, R. DANTS, V. KIMMER and R. SHMOL'KE, IK spektroskopiya polimerov, p. 252, Khimiya, Moscow, 1976 15. V. N. NIKITIN and B. Z. VOLCHEK, Zh. prikl, spektroskopii 4: 546, 1966 16. M.V. VOL'KENSHTEIN, Konfiguratsionnaya statistika makromolekul, p. 138, Izd. AN SSSR, Moscow-Leningrad, 1959 17. I. A. TUTORSKII, L. V. SOKOLOVA and B. A. DOGADKIN, Kolloidn. zh. 32: 590, 1970 18. I. A. TUTORSKII, L. V. SOKOLOVA, A. L. IZYUMNIKOV, V. M. KHARLAMOV and B. A. DOGADKIN, Vysokomol. soyed. AI5: 1587, 1973 (Translated in Polymer Sci. U.S.S.R. 15: 7, 1777, 1973) 19. L. V. SOKOLOVA, Dis. na soiskaniye uch. st. kand. khim. nauk, p. 175, MITKHT, Moscow, 1970 20. E. FETTES, Khimicheskiye reaktsii polimerov, vol. 1, p. 177, Mir, Moscow 1967 21. M. F. BUKHINA, Kristallizatsiya kauchukov i rezin, p. 150, Khimiya, Moscow, 1973 22. R. F. BOYER, J. Appl. Polymer Sci. 20: 1245, 1976 23. A. M. LOBANOV and S. Ya. FRENKEL', Vysokomol. soyed. A22: 1045, 1980 (Translated in Polymer Sci. U.S.S.R. 22: 5, 1150, 1980) 24. J. B. ENNS and R. F. BOYER, Polymer Preprints 18: 475, 1977
Polymer Science U.S.S.R. Vol. 27, No. 4, pp. 997-1000, 1985 Printed in Poland
0032-3950/85 $10.00+.00 © 1986PergamonPress Ltd.
M E T H O D S FOR DETERMINING THE SIZE OF D R O P S OF THE D I S P E R S E D P H A S E DURING H E T E R O P H A S E POLYCONDENSATION * A. E. HOLLAND, O. S. MATYUKHINA, M. I. SILING, N. I. GEL'PERIN, L. A. KARPENKO a n d G. 1. FAIDEL' Scientific Industrial Association "Plastics"
(Received 23 March 1984) Methods are proposed for determining the interface during heterophase polycondensation, which are based on the recovery of drops of the dispersed phase. It was shown by heterophase synthesis of polycarbonate that these methods enable the interface to be determined during synthesis with an accuracy of + 13 ~ , one measurement taking 10--15 min. MANY polymers are synthesized in liquid heterophase systems. The structure of the emulsion formed and the interface (IF) may have a considerable effect on process rate and the composition of the products formed. Similar dependences are typical of reactions in the diffusion range, which take place * Vysokomol. soyed. A27: No. 4, 884--886, 1985.
L.V. SOKOLOVAand V. A. SUERSnNEV
REFERENCES 1. L. VROMAN and E. F. LEONARD, Ann. N.Y. Acad. Sci., p. 156, 1977 2. S. L. COOPER and N. A. PEPPAS, Biomaterials: Interfacial Phenomena and ApplicatiOns, p. 199, Marcell Decker, New York, 1982 3. E. BRYNDA, J. DOBNIK, J. VACIK and J. KALAL, Biomed. Mater. Res. 12: 55, 1978 4. E. BRYNDA, M. HOUSKA, Z. POKORNA, N. A. CEPALOVA, Yu. V. MOISEYEV and J. KALAL, Bioeng. 2: 411, 1978 5. E. BRYNDA, i . HOUSKA, N. A. CEPALOVA and J. KALAL, Ann. Biomed. Engng. 8: 245, 1980 6. Yu. V. MOISEYEV, N. K. BOROVKOVA and N. A. TSEPALOVA, Vysokomol. soyed. BI9: 3, 1977 (Not translated in Polymer Sci. U.S.S.R.) 7. S. M. KIM, R. G. LEE, C. ADAMSON and D. J. LYMAN, Symposium on Biomedical Applications of Polymers, vol. 33, p. 2, Marcell Decker, New York, 1973 8. B. BLOMB)~CK and M. BLOMB)~CK, Acta Chem. Scand. 10: 147, 1956 9. Handbook of Biochemistry Selected Data for Molecular Biology, edited by. H. A. Sober, The Chem. Rubber Co., New York, 1970 10. L. BACHMAN, W. W. SCHMITT-FUMIAN, R. HAMMEL and M. LEDERER, Makromolek. Chem, 176: 2603, 1975 II. R . J . MCCLURE and B. M. CRAVEN, J. Molec. Biol. 83: 551, 1974
Polymer Science U.S.S.R. Vol. 27, No. 4, pp. 990-997, 1985 Printed in Poland
0032-3950/85 $10.00 +:.00 © 1986 Pergamon Press Ltd.
EFFECT OF THE STRUCTURE OF SYNTHETIC cis-I,4-POLYISOPRENE AND NATURAL RUBBER ON DIFFUSION OF SOLID LOW MOLAR M A S S SUBSTANCES * L. V. SOKOLOVA a n d V. A. SHERSHNEV M, V. Lomonosov Institute of Fine Chemical Technology, Moscow
(Received 14 February 1984)
A study of the structure of SKI and N R carried out using molecular probes (sulphur and diphenyl guanidine) by the diffusion-sorption method in the range of 30-110 ° indicates that these elastomers are characterized by several high temperature structural transitions. The presence of transitions was confirmed by IR spectroscopy. A marked difference was noted in the structure of SKI and N R matrices. * Vysokomol. soyed. A27: No. 4, 879-884, 1985.
Diffusion of solid low molar mass substances
991
SVt,rrHETtC SKI differs from N R not only in its ability to crystallize (process rate a n d Tmtlt of the crystalline phase), but also in the efffeet a n this property o f changing structural parameters. It is k n o w n t h a t during elongation crystallization of N R is accelerated to a m u c h greater exteDt t h a n t h a t of SKI. R u b b e r mixtures based o n N R therefore have higher cohesive strength. It is assumed that the main causes of this are the higher M, regular structure of macromoleeular chains a n d the presence in N R of n o n - r u b b e r components (proteins, amino acid, resin in the proportion of ~<3 ~ ) [1 ]. A comparative study was m a d e in this paper of diffusion parameters of SKI and N R in a wide temperature range (30-110°). Kariflex JR-305 SKI was used in the study with Mw=2-3 x 105 a n d N K ("pale crepe") previo u s l y precipitated from solutions in toluene with methal alcohol. Sulphur was used as molecular probe of the polymer matrix in the interval of 30-80 °, diphenylguanidine ( D P G ) in the interval of 45--110 °, previously purified by two-foid recrystallization from solutions in corresponding solvents. The rate of solution of low molar mass substances in samples previously heated to 70 ° in 2 hr, was determined b y diffusion [2]. The rate of solution is characterized by the inverse value of time ~during which 10 ~ of the substance is dissolved. The error of the method when determining the rate o f solution was + 5 ~ . I R spectra of elastomer films in the range of 25-110°C were obtained using a UR-10 spectrometer a n d a high temperature cell. Films were obtained on KBr discs with slow evaporation of the solvent from dilute solutions in CCI,. The accuracy of temperature measurement was +0-5 °. It was confirmed using the m e t h o d previously described [3] that the effect of heat radiation of the sample a n d cell may be ignored. W h e n recording IK spectra temperature was raised suddenly by 5-6 °, followed by thermostatic control of the polymer film at constant temperature for 90 rain The film placed in a high temperature cell was first heated for 24 hr to ~ 100 °, then cooled to 25 "~ This cycle was repeated three times for each film. The intensity of the absorption bands was measured at m a x i m u m frequencies of bands. F o r the convenience of comparison the optical density of abs o r p t i o n bands was staodardized for all samples bringing it to unity at ~ 30 °. The temperature dependence of the rate of solution of sulphur in N R in the interval of 30-80 ° ~conforms to the Arrhenius equation. In the range of 4 5 + 3 ° (D the temperature dependence of tl,~e rate of solution of sulphur shows a break, while in the range of 52-55 ° (I') a n d 65-70 ° (II) changes suddenly, which is due to three structural transitions. The a p p a r e n t activation energy values of solution of sulphur are tabulated. Temperature dependences of t h e diffusion coefficient a n d equilibrium solubility of sulphur in N K are also complex: a break in the range of structural transition I a n d a sudden chal~ge of these parameters in transition ranges I ' a n d II (Fig. 1). A sudden increase of the diffusion coefficient a n d a reduction in equilibrium solubility of sulphur in N R in the range of transitions I ' and II indicates a vigorous structural change of the polymer matrix, particularly on transition of II. The activation energy of diffusion Ea of sulphur as a result of transition I is more t h a n halved, while as a result of Iransitions I ' a n d II, it increases (Table). The varying change of solubility parameters of sulphur ir~ N R proves a noticeable difference in the structural transitions observed. It should be noted that relaxation transitions in vulcanisates based on N R were observed when studying mechanical properties [4] a n d creep [5]. Transitions in N R observed by relaxation spectrometry [6], the dielectric loss m e t h o d [7] a n d differential scanning calorimetry [8], in the view of authors of earlier papers [6, 7], are due to the existence in the matrix of microregions of 150-240 A dimension [9]. Let us examine special features of solution in SKI. In the range of 4 7 + 3 ° (I) temperature dependences of the rate of solution of sulphur show a break, in the range of 67 + 3 ° (II) they show a sudden change. Temperatures of transition in SKI show satisfactory agreement with temperatures of transitions I a n d II observed in N R (Fig. 1). The presence of two transitions in SKI, in contrast with three in N R a n d the different variation of the apparent activation energy of solution, Es of sulp h u r (Table) suggests t h a t the structure of SKI a n d N R matrices is not the same. Temperature dependence of the coefficient of diffusion D and equilibrium solubility Co of sul-
992
L . V . SOKOLOVA and V. A . SHERSHNEV
D I F F U S I O N AND SOLUBILITY PARAMETERS OF SOLID LOW MOLAR MASS SUBSTANCES IN POLYISOPRENES
Polymer SKI
NR
Penetrant Sulphur
~ Sulphur
SKI
I DPG
NR
DPG
H,
T° 35 50 60 80 35 50 60 80 50 70 95 50 70 95
kJ/mole 76-0 70"0 70.0 42'4 75.8 38"3 60"6 76'6 50.7 63"3 74"2 39.0 63"0 100.0
59'3 34"4 34"4 2'5 67"9 26"0 42"0 65"9 16'5 59"7 47"0 10"7 58'9 75"4
18-5 41 '6 41 "6 4'4 16"8 14"8 14"0 34-6 7-4 22-1 23-8 12"4 22"1
D × 10 7, cm2/sec 0-24 0.656 0.81 2-76 0.35 0"93 2.1 7-3 0.74 2.0 10.8 0"5 1.87
Co x 10 z, g/cm 3 1"19 1'65
2'56 3"0 0"94 1"16 1"29 1"29
0"31 0"39 0"37 0"41 0"53 0"37
Note. H, is the heat of solution.
p h u r in SKI also prove the presence of two structural transitions. As a result of b o t h transitions in SKI the activation energy of diffusion of sulphur decreases suddenly, particularly as a result of transition H. This transition also results in a sudden reduction of co of sulphur ( ~ l-5-fold). Transition II is evidently due to the structural rearrangement of the matrix, since as a result of. transition its free volume changes. It is possible that microregions break down from closely packed macrochain fragments, accompanied by a n increase in the free volume of the matrix. However, during this transition microregions either break down incompletely, or remain as microregions with different structural organization. This is confirmed by the temperature dependence of D in t h e range I> 70 °, which points to the possibility of existence of a high temperature transition in SKI (Fig. 1). In fact, the use of D P G as molecular probe enables structural transitions to be observed ~ in the range of 55-57 (II) and 84--90° (III) for SKI a n d in the range of 57-60 (II) a n d 80-85 ° ( l i d f o r N R . It is interesting that the rate of solution a n d values of D of D P G in the temperature range below transition II is higher in SKI than in NR. Transition II enables values of D to be equalized in SKI a n d NR. Transition III results in such a rearrangment of the SKI matrix that rates of solution of D P G a n d D of D P G become higher in N R than in SKI. We note that when dissolving sulphur D values in the entire temperature range studied (35-80 °) remain in N R noticeably higher than in SKI (Fig. 1). Values of Co for dissolved sulphur are always higher in SKI than in N R , whereas in the case of D P G equilibrium solubility is higher in N R in the range of 40-80 ° a n d decreases to a level of t h e co values in SKI as a result of the last structural transition. The fact that in the temperature range above transition III D values of D P G (penetrant w i t h a higher molar volume (177 cma/mole) t h a n sulphur (130 cma/mole)) are higher in N R (a polymer with a well k n o w n lower free volume [9]), is evidently explained by the effect of fragments of protein origin in macrochains of NR. It may be assumed that macroehain segments of N R form more extended microregions than in SKI as a result of higher M and more regular structure, in a way similar to that of butadiene elastomers [9]. The formation of ordered microregions from densely packed macrochain sections has the result that chain fragments of protein are concentrated exclusively in the disordered part of the matrix; therefore, the higher concentation of polar groups is achieved in this part of matrix volume, which explains the higher equilibrium solubility values of D P G in N R , compared with PI. The formation of ordered microregions exclusively from units of the same type was noted previously in the case of copolymers of butadiene with styrene [10] a n d acrylonitrile [11,121.
Diffusion of solid low molar mass substances
993
IogD,cm%'cc
"x Z
-
X "Ng
~
6.8
I ~ Q
?>~K
- 7.0
~I"
"~\ × g
L
2"8
O'O
8-2
tog Co, glcrn ~
-1.7
- Z'O
-2"6 1
2.6
I
!
I
2.8
~'0
1
l
J.Z
/oJt T, K" Fro. !. Temperature dependences of the diffusion coefficient D (a) and the coefficient of equilibrium solubility co (b) of sulphur and D P G (1", 2") in SKI (l) and N R (2).
L. V. 50~OLOWt and V. A. SrmRSXNEV
994
Transition III results in the breakdown of ordered formations and the free volume of the polymer suddenly increases, as confirmed by the increased diffusion coefficient of D p G (3.5-fold) and the reduction of Co (2-fold) in the case of N R . During this transition to SKI the D value in D P G only increases 1-9 times, co decreases 1.25-fold accordingly, i.e. re-arrangement or the volume of ordered microregions in higher in N R than in SKI. In the temperature range above transition III matrices
-Ol azzo ' q--X--X--v~--X---x'--X---X--X--X---X-
0.8
a ~~i !
1
I
I
__
I
I
/2
B/Oza*
1.0!
5
0"8 t
0.8
.
C L
;~Q
......
I
t
60
80
J0
60
8D
T~
FI6. 2. Temperature dependences of the optical density of absorption bands at 840 (1), 899 (2), 1130 (3), 1310 (4) and 1665 (5) c m - 1 in the I R spectrum of SKI (a, b) and N R (c, d) for the first (a, c) and third cycles of heating (b, d).
Diffusion of solid low m o l a r mass substances
995
N R and SKI have similar free volumes. It m a y be assumed t h a t transition IH belongs to " l i q u i d l i q u i d " transitions. D a t a o b t a i r ~ d by the dielectric loss m e t h o d [13] a n d by differential scanning calorimetry [8] c~mfirm a noticeable difference in the structure o f N R and SKI. Let us examine temperature dependences of the optical density of absorption bands of the ] R s p e c t r u m of S K I in the 700-1700 c m - 1 range (Fig. 2}. The optical density of the absorption b a n d at 840 c m - 1 = C - H of the out-of-plane vibration o f the C(CH3) = CH, at 899 c m - 1 of the d~form a t i o n vibration o f the CH group of C H z - C ( C H s ) , at 1130 c m - t o f C - C H 3 vibration, at 1375 a n d 1448 c m - 1 of deformation vibrations of CH3 a n d at 1665 c m - t of bond-stretching vibrations o f C = C [14] changes suddenly in the range of 47-50, 67-71 a n d 95-100 ° for the case of the t h i r d cycle o f heating. The degree of variation o f the optical density of these bands varies within the range o f t 3-24~0. Optical density shows the most marked variation for absorption bands at 840 a n d 899 c m - 1 The optical density of a n absorption band at 1312 c m - 1 of - C H vibration during three successive cycles of heating is practically unchanged, which proves a slight variation of polymer film thickness (~< 1%) d u r i n g measurements in the temperature range of 25-110 °. The sudden change observed in the intensity of absorption bands observed is the result of structural transitions, since the intensity of all absorption bands is completely restored during cooling the film to 25 °. Complete restoration of the intensity of absorption bands during three consecutive cycles o f heating atso proves the absence of noticeable changes in the chemical structures of the polymer during the experiment. It is interesting that temperatures of structural transitions in SKI, detected by 1R spectoscopy, agree with temperatures of transition established during the study of diffusion of low m o l a r mass substances. D u r i n g the first cycle of heating a clear structural transition was not observed for all absorption bands in the range of ~ 5 0 ° . F u r t h e r m o r e , the degree of intensity reduction of absorption b a n d s in the range of 700-1700 c m - ~ is m u c h lower for the first cycle t h a n for subsequent ones. D u r i n g repeated cycles of heating temperatures of structural transitions were displaced to the range of lower values. In other words, polymer film structure is " a c t i v a t e d " from one cycle to a n o t h e r due to the breakdown of ordered micro-regions during heating a n d their subsequent formation with smaller dimensions during cooling. Let us revert to special features of temperature changes of I R spectra of N R (Fig. 2). Structural transitions for N R in the case of the third cycle are observed in the range of 55-63, 75-78 and > 110 °, i.e. at higher temperatures than in SKI (Fig. 2). The temperature dependence of the absorption band intensity at 1665 c m - 1 is also different in spectra of N R a n d SKI. In the case of N R the optical density of this b a n d is pracitcally unchanged during the first cycle of heating to 90 °. D u r i n g repeated cycles of heating the extent of its variation increases, but is only 5 instead of 13 % for SKI even for the third cycle. The degree of variation of the optical density of absorption b a n d s in the case of N R for the first cycle is noticeably lower t h a n for SKI (13 instead of 2 1 ~ ) a t the same rates of heating a n d cooling the polymer film, which is the result of different M of SKI a n d N R samples. A similar effect of M on the temperature dependence of absorption b a n d intensity was observed for polybutadienes [9]. In spite of the fact that I R spectra of cis- a n d trans-polyisoprenes have been examined repeatedly, there is, so far, n o clear classification available of absorption bands [14]: I R spectra of eisa n d trans-polyisoprenes differ slightly. However, trans-l,4-polyisoprene, in the opinion of authors of an earlier paper [15], has a helical conformation, confirmed by X-ray analysis a n d IR-spectroscopy in polarized light. In the case of N R , as for trans-l,4-polyisoprene, chain structure in the crystal is n o n p l a n a r [16]. The absorption b a n d at 1665 c m - t in the spectrum of N R is characterized by parallel orientation, whereas at 1670 c m - 1 in the spectrum of trans-l,4-polyisoprene orientation is perpendicular. The possibility of helical chain c o n f o r m a t i o n for SKI a n d N R is also confirmed by their tendency to undergo ring f o r m a t i o n [17, 18]. This reaction takes place in polyisoprene under mild ,conditions a n d is a secondary reaction in halogenation [19], hydrochlorination a n d vulcanisation [201.
996
L . V . SOKOLOVAand V. A. SHERSHNEV
T h e very slight change in the optical density of the absorption band at 1665 cm-~ in N R suggests that in the temperature range studied (30-110 °) helical sections of N R have not yet shown complete breakdown, while in the case of SKI they break down more readily, as confirmed by transition in the range of 95-100 °, i.e. the latter are less stable possibly as a result of their shorter length. Study of special features of diffusion of solid substances and changes of I R spectra in the range of 25-I10 ° indicates that the structure of SKI and N R matrices differs in size and the number o f defects in ordered microregions; the higher the M of the polymer, the more perfect is the structure of micro-regions and the more extended they are in the matrix, since the content of free ends (larger free volume) is higher for polymers of lower M, which impedes the formation of extended ordered microregions. Analysis of data obtained by the diffusion method and I R spectroscopy indicates that SKI is characterized by three structural transitions in the temperature range of 30-110 ° . Temperatures of transition I show satisfactory agreement with Tmc, of crystalline cis-l,4-polyisoprene [21]. However, according to I R spectroscopy [21], SKI samples are amorphous due to the conditions of preparation. A similar pattern was observed for non-crystallizing S K D L rubber with structural transitions in the range of 50-55, 70-75 and 120 °, cooresponding to Tmclt of two crystalline modifications o f trans-l,4-polybutadiene [9]. The temperature of transition I in SKI is linked to its Tz by the equation T * = Ts+ 110 °, which is higher than the "liquid-liquid" transition temperature [22, 23]. Authors of an earlier paper [23~ assume that transition T* is explained by the loss of the fundamental property of macromolecular c h a i n s - c o o p e r a t i v e property. However, above this transition (T*) three further transitions are observed which, according to data obtained by the diffusion method, result in more intense rearrangement of the elastomer matrix. It is interesting that the temperature of transition III is higher than temperatures of transition I (by ,,~ 50°). A similar pattern was observed in the case of PS, polymethylaerylate, P M M A , PVC and poylisobutylene [24]. According to the classification of Boyer transitions this is the so-called T*-transition. The form of variation of Do and Co in PI and N R suggests that transition III may only be regarded as transition of the system to a structureless liquid, while in the temperature range below transition II sufficiently extended ordered microregion are present in the elastomer matrix, consisting of helical coiled macrochain fragments.
Translated by E. SEMERF REFERENCES 1. Fizicheskiye svoistva elastomerov, edited by A. I. Marei, p. 48, Khimiya, Moscow, 1975 2. B. S. GRISHIN, I. A. T U T O R S K I I and Ye. E. POTAPOV, Vysokomol. soyed. A16: 130~ 1974 (Translated in Polymer Sci. U.S.S.R. 16." 1, 156, 1974) 3. F. F. S U K H O V and N. A. SI.X)VOKHOTOVA, Zh. prikl, spektroskopii 9: 11, 167, 1968 4. E. M A E K A W A , R. C. M A H C K E and J. D. FERRY, J. Chem. Phys. 69: 281, 1965 5. D. J. PLAZEK, J. Polymer Sci. A-2, 4: 745, 1966 6. G. M. BARTENEV and J . V. ZELENEV, Plaste und Kautschuk 23: 166, 1977 7. M. G. BARTENEV and M. N. LJOLIN, Plaste und Kautschuk 24: 741, 1976 8. V. A. VOLGIN, Yu. A. L A Z A R E V and I. A. TUTORSKII, (book): Tez. dokl. Vses. nauchnotekhn, konf. Yaroslavl' (Proc. of the All-Union Sci.-Techn. Conf. Yaroslavl') p. 205, 198~ 9. L. V. SOKOLOVA, O. A. CHESNOKOVA, O. A. NIKOLAYEVA and V. A. SHERSHNEV~ Vysokomol. soyed. A27: 352, 1985 (Translated in Polymer Sci. U.S.S.R. 27: 2, 392, 1985) I0. L. V. SOKOLOVA, O. A. CHESNOKOVA, O. A. NIKOLAYEVA and V. A. SHERSHNEV,. (book): Tez. dokl. VIII Vses. konf. po koUoidnoi khimii i fizikokhim, mekhanike (Proceedings of the VIIIth All-Union Conf. on Colloid Chemistry and Physico-Chemical Meth-ods). p. 80, Tashkent, 1983 11. L. V. SOKOLOVA, O. A. C H E S N O K O V A and V. A. S H E R S H N E V , Vysokomol. soyed.. A22: 2305, 1980 (Translated in Polymer Sci. U.S.S.R. 22: 10, 2529, 1980)
Determining the size of drops of dispersed phase during polycondensation
997
12. L. V. SOKOLOVA, O. A. CHESNOKOVA and V. A. SHERSHNEV, Vysokomol. soyed. A26: 314, 1984 (Translated in Polymer Sci. U.S.S.R. 26: 2, 346, 1984) 13. R. BAHULE, K. HAJEK and J. NEDBAL, Polymer Bull. 4: 399, 1981 14. I. DEKHANT, R. DANTS, V. KIMMER and R. SHMOL'KE, IK spektroskopiya polimerov, p. 252, Khimiya, Moscow, 1976 15. V. N. NIKITIN and B. Z. VOLCHEK, Zh. prikl, spektroskopii 4: 546, 1966 16. M.V. VOL'KENSHTEIN, Konfiguratsionnaya statistika makromolekul, p. 138, Izd. AN SSSR, Moscow-Leningrad, 1959 17. I. A. TUTORSKII, L. V. SOKOLOVA and B. A. DOGADKIN, Kolloidn. zh. 32: 590, 1970 18. I. A. TUTORSKII, L. V. SOKOLOVA, A. L. IZYUMNIKOV, V. M. KHARLAMOV and B. A. DOGADKIN, Vysokomol. soyed. AI5: 1587, 1973 (Translated in Polymer Sci. U.S.S.R. 15: 7, 1777, 1973) 19. L. V. SOKOLOVA, Dis. na soiskaniye uch. st. kand. khim. nauk, p. 175, MITKHT, Moscow, 1970 20. E. FETTES, Khimicheskiye reaktsii polimerov, vol. 1, p. 177, Mir, Moscow 1967 21. M. F. BUKHINA, Kristallizatsiya kauchukov i rezin, p. 150, Khimiya, Moscow, 1973 22. R. F. BOYER, J. Appl. Polymer Sci. 20: 1245, 1976 23. A. M. LOBANOV and S. Ya. FRENKEL', Vysokomol. soyed. A22: 1045, 1980 (Translated in Polymer Sci. U.S.S.R. 22: 5, 1150, 1980) 24. J. B. ENNS and R. F. BOYER, Polymer Preprints 18: 475, 1977
Polymer Science U.S.S.R. Vol. 27, No. 4, pp. 997-1000, 1985 Printed in Poland
0032-3950/85 $10.00+.00 © 1986PergamonPress Ltd.
M E T H O D S FOR DETERMINING THE SIZE OF D R O P S OF THE D I S P E R S E D P H A S E DURING H E T E R O P H A S E POLYCONDENSATION * A. E. HOLLAND, O. S. MATYUKHINA, M. I. SILING, N. I. GEL'PERIN, L. A. KARPENKO a n d G. 1. FAIDEL' Scientific Industrial Association "Plastics"
(Received 23 March 1984) Methods are proposed for determining the interface during heterophase polycondensation, which are based on the recovery of drops of the dispersed phase. It was shown by heterophase synthesis of polycarbonate that these methods enable the interface to be determined during synthesis with an accuracy of + 13 ~ , one measurement taking 10--15 min. MANY polymers are synthesized in liquid heterophase systems. The structure of the emulsion formed and the interface (IF) may have a considerable effect on process rate and the composition of the products formed. Similar dependences are typical of reactions in the diffusion range, which take place * Vysokomol. soyed. A27: No. 4, 884--886, 1985.