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The cationic polymerization of styrene by stannic chloride in the presence of carbon black
Letters
to the
irreversible sorption of methanol. The sorbed quantities are 0.40 and 0.61 cm’/g for fibers C and G, respectively. Though very high. these values are of the same order of magnitude as the pore volumes of ex-cellulose carbon fibers [9, IO]. -A part of 14Cfixed on fibers may result from the substitution of hydrogen atom from the C-H bond by methoxy groups ‘?X@. Such a reaction occurs with carbon black[l I]. J. LAHAYE A. PAsToR
Centre de Recherche~ far la PhysicoChrmre des Smjaces So~ides-CURS 24, acenae du Prkident Kennedy 68200 Mu/house. France
P
EHRBURGER E. PAPIRER
2. F. E. Bartell and E. J. Miller. J. Am Chea.
3. 4.
5. 6. 7.
Sot. 44. 1866 (1922). J. B. Donnet, Carbon 6. I61 (1968). E. Papirer. J. B. Donnet et V. T. Nguyen. Bull. Sec. C/rim. Fr. 4, II87 (1971). F. Kalberer and S. Rutscbmann. He/r. Gem. Acfa 44, 1956 (1961). J. Lahaye and I. P. Aubert, Fuel 56, 185119771. H. P. Boehm, Adc. Cat. 16, 179 (1966).
8. S. Zexel, ~oaa~sch. Chetn. 6,989 (1885): 7,406 (1886). 9. D. W. MCKee and V. J. Mimeault, Chemistry and Physics of Carbon. Vol. 8. p. 184. Marcel Dekker, New York (1965).
10. J. F. Molleyre, Dissertation Thesis, Nancy, France (1974). II E. Papirer. E Guyon and J. B. Donnet, Carbon 76, p,
REFERElNCFS I
Smith, Proc. Roy. Sot (London) A12. 424 (1863).
A.
If5
Editor
Baden-Baden
6/27-7/2
86.
(1976).
The cationic polymerizationof styrene by stannic chloride in the presenceof carbon black (Received 7 November The cationic polymerization of N-vinylcarbazole has been reported to be initiated by carbon black[l]. Although the reaction between carbon black and polymeric cations has been investigated~2~, little is known about the role of carbon black in the course of cationic polymerization. In this paper a study of cationic polymerization of styrene by stannic chloride in the presence of carbon black is reported. Carbon black used was Philblack 0 (N330, HAF), dried at 80°C in cacuo after Soxhlet extraction with benzene to remove the resinous substances on the surface. Guaranteed reagent grade stannic chloride from Wako Pure Chemical Ind., Ltd was used as catalyst. Styrene was made free of stabilizer by the usual method and distilled twice under reduced pressure prior to use. The polymerization reactton was carried out at 0°C in a solvent consisting of purified nitrobenzene and carbon tetrachloride. The reaetion mixture in a tOOml tear-drop type flask was stirred constantly with a magnetic stirrer The polymer containing carbon black was precipitated by methanol to separate it from solvent and residual monomer. Conversions were determined by the method reported previously[3]. The polymertc product was then examined by pyrolytic gas chromatography. The analytical procedure was similar to that reported previously[3]. The result of the polymerization in the presence of carbon black is shown in Fig. I, in which the effect of carbon black as a retarder in the course of the polymertzation is clearly shown.
60
PhilbhckO(gf SnC14iltYmol) CCL4 (ml) QN02 (ml)
83 28 30
1977)
However, the inhibition and the acceleration as in the case of thermal polymerization of styrene[4+5] were not observed The carbon black isolated after the polymerization reaction gave a stable dispersion in good solvents for polystyrene. such as toluene. Its pyrolytic gas chromatogram is shown in Fig 2. The peaks of the thermal decomposition products indicate that polystyrene was grafted onto the carbon black surface.
I
0
2
06 83 28 30
With an increase in the amount of carbon black, the rate polymerization decreased as we expected. The plots for initial rate of polymerization Rp against the reciprocal of amount of carbon black added l/[CB] are shown in Fig. 3. The basic processes of polymerization may be described follows:
$40 ji & $ U 20
Initiation: C+M---+M+
Fig. I. Cationic
I,
with the rate
/ 20
40 Time, rn11-1
polymerization of styrene by stannic the presence of Philblack 0 at 0°C
6
Fig. 2. Pyrolytic gas chromatogram of the surface of Philblack 0 reacted with the propagating polymeric cations. One gram of the carbon black was subjected to Soxhlet extraction with benzene for tO0 hr.
-LI D
0
4 mtn
Time.
r, =
60
UCIIMI.
Propagation: chloride
in
M + M,,” -%
M f, +,
of the the as
Letters to the Editor where [Cl, [Ml and jM+] represent the concen~ations of catalyst C, monomer M and propagating polymeric cation &f+, respectively. If the steady state where the initiation rate r, is equal to the termination rate r, is assumed, a constant concentration of M’ is given by
tM+l = ~~[Cl[~l/~*[CBl. so that the polymerization rate Rp is defined as follows:
0
2
1
‘/[c.
3
4
81 I s’
Fig. 3. Dependence of polymerization rate on the amount of carbon black. Five grams of styrene were polymerized in the presence of Philblaek 0 at 0°C using stannic chloride (8.3 x low4mol) in a solvent consisting of nitrobenzene (30ml) and carbon tetrachloride (28 ml).
Since this equation is consistent with the result shown in Fig. 3, it is reasonable to assume that the termination reaction occurrs on the surface of carbon black. The reaction sites on carbon black surface and the mechanism of grafting are being investigated in detail. Faculty of Engineering Niigata University Ga~o-cho l-2, ~ag~o~a Japan
(940)
KUMAKAZUOHKITA MASATO SHIMOMURA TERUYUKITSUHTA
REFERENCES
with the rate
I. K. Ohkita, N. Tsubokawa. M. Noda and M. Uchiyama, Carbon 15, 194(1977). 2. E. Papirer, J. C. Morawski and A. Vidal, Ang. Makromol, Chem. 42,91 (1975). 3. K. Ohkita, N. Tsubokawa, E. Saitoh, M. Noda and N. Takashina, Carbon 13,443 (1975). 4. J. W. Breitenbach and H. Preussler, J. Pdymer SC?. 4, 751 (1949). 5. G. Kraus, J. T. Gruver and K. W. Rollmann, J. Polymer Sci. 36, 564 (1959). 6. J. B. Donnet and G. Henrich, 1. Polymer Sci. 46,277 (1960).
rp = k,IMJ[M’]. Termination: M,+ + CB +
&
unreactive species
with the rate r, = k,[M+l[CB]
Solubiity of mesophasepitch (Received 4 November 1977) It is now well recognized that pitch is gradually transformed to a mesophase state during carbonization. The kinetics of mesophase formation has been correlated with the quality of mesophase and hence of the derived carbon. The anisotropic phase in mesophase pitch can be observed directly with the aid of a polarizing microscope, but it has become customary to monitor the extent of mesophase formation by measuring the change in solubility. The amount of insolubles in excellent pitch solvents, such as quinoline, pyridine, and anthracene oil has been equated to the mesophase content, and this relation has been adequate for mesophase pitches prepared by simple heat-treatment [l-8]. However, we wish to show in this communication that solubility cannot be used universally as a criterion for the amount of mesophase. The solubility of a particular mesophase pitch is related to the nature of the precursor, the mesophase prep~ation procedure, and to the specific solvent employed. Mesophase contents and solubility data were determined for mesophase pitches prepared with varying amounts of mesophase. The amount of mesophase was controlled by heat-treating for various periods of time at a fixed reaction tem~rature while sparging by bubbling inert gas through molten pitch to remove the volatiles. The mesophase content was computed by estimating the fraction of the area consisting of anisotropic phase in a vertical polished section of an entire sample of the pitch, Solubility data were determined in pyridine, toluene, and quinoline. The solubilities in pyridine and toluene were obtained by an exhaustive Soxhlet extraction of finely crushed pitch at the
boiling point of the respective solvents. The quinoline solubility was obtained by refluxing 0.5 g of pitch with 180ml of quinoline for 30 min and then filtering and weighing the insolubles. In Fig. 1, the percent of mesophase is plotted vs the per cent of pyridine insolubles for mesophase pitches made from two different precursors. Precursor A is a petroleum-derived pitch which forms large anisotropic mesophase domains while precursor B is an ethylene tar pitch which forms a more disordered carbon structure and gives a stringy coalesced and small-domain mesophase. A dotted line indicating the situation in which the percentage of insolubles would equal the mesophase content is also drawn on Fig. 1. It is apparent for both precursors that the amount of mesophase does become greater as the percentage of insolubles increases. However, there is not an exact correspondence between the amount of mesaphase and the insoluble content. For precursor B, the amount of insolubles is greater than the mesophase content up to about 75% PI, while for precursor A, the mesophase content is generally considerably higher than the amount of insolubles, The solubilities of pitches with different mesophase contents prepared from precursor A are shown in Fig. 2 for three solvents, quinoline, pyridine and toluene. The solubility is always highest in quinoline and lowest in toluene. The dotted line in Fig. 2 shows the relationship expected if the isotropic phase were totally soluble and the anisotropic phase were totally insoluble. The experimental data do not follow this line with any of the three solvents. Tofuene, the poorest solvent, does not even
to the
irreversible sorption of methanol. The sorbed quantities are 0.40 and 0.61 cm’/g for fibers C and G, respectively. Though very high. these values are of the same order of magnitude as the pore volumes of ex-cellulose carbon fibers [9, IO]. -A part of 14Cfixed on fibers may result from the substitution of hydrogen atom from the C-H bond by methoxy groups ‘?X@. Such a reaction occurs with carbon black[l I]. J. LAHAYE A. PAsToR
Centre de Recherche~ far la PhysicoChrmre des Smjaces So~ides-CURS 24, acenae du Prkident Kennedy 68200 Mu/house. France
P
EHRBURGER E. PAPIRER
2. F. E. Bartell and E. J. Miller. J. Am Chea.
3. 4.
5. 6. 7.
Sot. 44. 1866 (1922). J. B. Donnet, Carbon 6. I61 (1968). E. Papirer. J. B. Donnet et V. T. Nguyen. Bull. Sec. C/rim. Fr. 4, II87 (1971). F. Kalberer and S. Rutscbmann. He/r. Gem. Acfa 44, 1956 (1961). J. Lahaye and I. P. Aubert, Fuel 56, 185119771. H. P. Boehm, Adc. Cat. 16, 179 (1966).
8. S. Zexel, ~oaa~sch. Chetn. 6,989 (1885): 7,406 (1886). 9. D. W. MCKee and V. J. Mimeault, Chemistry and Physics of Carbon. Vol. 8. p. 184. Marcel Dekker, New York (1965).
10. J. F. Molleyre, Dissertation Thesis, Nancy, France (1974). II E. Papirer. E Guyon and J. B. Donnet, Carbon 76, p,
REFERElNCFS I
Smith, Proc. Roy. Sot (London) A12. 424 (1863).
A.
If5
Editor
Baden-Baden
6/27-7/2
86.
(1976).
The cationic polymerizationof styrene by stannic chloride in the presenceof carbon black (Received 7 November The cationic polymerization of N-vinylcarbazole has been reported to be initiated by carbon black[l]. Although the reaction between carbon black and polymeric cations has been investigated~2~, little is known about the role of carbon black in the course of cationic polymerization. In this paper a study of cationic polymerization of styrene by stannic chloride in the presence of carbon black is reported. Carbon black used was Philblack 0 (N330, HAF), dried at 80°C in cacuo after Soxhlet extraction with benzene to remove the resinous substances on the surface. Guaranteed reagent grade stannic chloride from Wako Pure Chemical Ind., Ltd was used as catalyst. Styrene was made free of stabilizer by the usual method and distilled twice under reduced pressure prior to use. The polymerization reactton was carried out at 0°C in a solvent consisting of purified nitrobenzene and carbon tetrachloride. The reaetion mixture in a tOOml tear-drop type flask was stirred constantly with a magnetic stirrer The polymer containing carbon black was precipitated by methanol to separate it from solvent and residual monomer. Conversions were determined by the method reported previously[3]. The polymertc product was then examined by pyrolytic gas chromatography. The analytical procedure was similar to that reported previously[3]. The result of the polymerization in the presence of carbon black is shown in Fig. I, in which the effect of carbon black as a retarder in the course of the polymertzation is clearly shown.
60
PhilbhckO(gf SnC14iltYmol) CCL4 (ml) QN02 (ml)
83 28 30
1977)
However, the inhibition and the acceleration as in the case of thermal polymerization of styrene[4+5] were not observed The carbon black isolated after the polymerization reaction gave a stable dispersion in good solvents for polystyrene. such as toluene. Its pyrolytic gas chromatogram is shown in Fig 2. The peaks of the thermal decomposition products indicate that polystyrene was grafted onto the carbon black surface.
I
0
2
06 83 28 30
With an increase in the amount of carbon black, the rate polymerization decreased as we expected. The plots for initial rate of polymerization Rp against the reciprocal of amount of carbon black added l/[CB] are shown in Fig. 3. The basic processes of polymerization may be described follows:
$40 ji & $ U 20
Initiation: C+M---+M+
Fig. I. Cationic
I,
with the rate
/ 20
40 Time, rn11-1
polymerization of styrene by stannic the presence of Philblack 0 at 0°C
6
Fig. 2. Pyrolytic gas chromatogram of the surface of Philblack 0 reacted with the propagating polymeric cations. One gram of the carbon black was subjected to Soxhlet extraction with benzene for tO0 hr.
-LI D
0
4 mtn
Time.
r, =
60
UCIIMI.
Propagation: chloride
in
M + M,,” -%
M f, +,
of the the as
Letters to the Editor where [Cl, [Ml and jM+] represent the concen~ations of catalyst C, monomer M and propagating polymeric cation &f+, respectively. If the steady state where the initiation rate r, is equal to the termination rate r, is assumed, a constant concentration of M’ is given by
tM+l = ~~[Cl[~l/~*[CBl. so that the polymerization rate Rp is defined as follows:
0
2
1
‘/[c.
3
4
81 I s’
Fig. 3. Dependence of polymerization rate on the amount of carbon black. Five grams of styrene were polymerized in the presence of Philblaek 0 at 0°C using stannic chloride (8.3 x low4mol) in a solvent consisting of nitrobenzene (30ml) and carbon tetrachloride (28 ml).
Since this equation is consistent with the result shown in Fig. 3, it is reasonable to assume that the termination reaction occurrs on the surface of carbon black. The reaction sites on carbon black surface and the mechanism of grafting are being investigated in detail. Faculty of Engineering Niigata University Ga~o-cho l-2, ~ag~o~a Japan
(940)
KUMAKAZUOHKITA MASATO SHIMOMURA TERUYUKITSUHTA
REFERENCES
with the rate
I. K. Ohkita, N. Tsubokawa. M. Noda and M. Uchiyama, Carbon 15, 194(1977). 2. E. Papirer, J. C. Morawski and A. Vidal, Ang. Makromol, Chem. 42,91 (1975). 3. K. Ohkita, N. Tsubokawa, E. Saitoh, M. Noda and N. Takashina, Carbon 13,443 (1975). 4. J. W. Breitenbach and H. Preussler, J. Pdymer SC?. 4, 751 (1949). 5. G. Kraus, J. T. Gruver and K. W. Rollmann, J. Polymer Sci. 36, 564 (1959). 6. J. B. Donnet and G. Henrich, 1. Polymer Sci. 46,277 (1960).
rp = k,IMJ[M’]. Termination: M,+ + CB +
&
unreactive species
with the rate r, = k,[M+l[CB]
Solubiity of mesophasepitch (Received 4 November 1977) It is now well recognized that pitch is gradually transformed to a mesophase state during carbonization. The kinetics of mesophase formation has been correlated with the quality of mesophase and hence of the derived carbon. The anisotropic phase in mesophase pitch can be observed directly with the aid of a polarizing microscope, but it has become customary to monitor the extent of mesophase formation by measuring the change in solubility. The amount of insolubles in excellent pitch solvents, such as quinoline, pyridine, and anthracene oil has been equated to the mesophase content, and this relation has been adequate for mesophase pitches prepared by simple heat-treatment [l-8]. However, we wish to show in this communication that solubility cannot be used universally as a criterion for the amount of mesophase. The solubility of a particular mesophase pitch is related to the nature of the precursor, the mesophase prep~ation procedure, and to the specific solvent employed. Mesophase contents and solubility data were determined for mesophase pitches prepared with varying amounts of mesophase. The amount of mesophase was controlled by heat-treating for various periods of time at a fixed reaction tem~rature while sparging by bubbling inert gas through molten pitch to remove the volatiles. The mesophase content was computed by estimating the fraction of the area consisting of anisotropic phase in a vertical polished section of an entire sample of the pitch, Solubility data were determined in pyridine, toluene, and quinoline. The solubilities in pyridine and toluene were obtained by an exhaustive Soxhlet extraction of finely crushed pitch at the
boiling point of the respective solvents. The quinoline solubility was obtained by refluxing 0.5 g of pitch with 180ml of quinoline for 30 min and then filtering and weighing the insolubles. In Fig. 1, the percent of mesophase is plotted vs the per cent of pyridine insolubles for mesophase pitches made from two different precursors. Precursor A is a petroleum-derived pitch which forms large anisotropic mesophase domains while precursor B is an ethylene tar pitch which forms a more disordered carbon structure and gives a stringy coalesced and small-domain mesophase. A dotted line indicating the situation in which the percentage of insolubles would equal the mesophase content is also drawn on Fig. 1. It is apparent for both precursors that the amount of mesophase does become greater as the percentage of insolubles increases. However, there is not an exact correspondence between the amount of mesaphase and the insoluble content. For precursor B, the amount of insolubles is greater than the mesophase content up to about 75% PI, while for precursor A, the mesophase content is generally considerably higher than the amount of insolubles, The solubilities of pitches with different mesophase contents prepared from precursor A are shown in Fig. 2 for three solvents, quinoline, pyridine and toluene. The solubility is always highest in quinoline and lowest in toluene. The dotted line in Fig. 2 shows the relationship expected if the isotropic phase were totally soluble and the anisotropic phase were totally insoluble. The experimental data do not follow this line with any of the three solvents. Tofuene, the poorest solvent, does not even