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Synthesis and characterisation of some new photografted polycarbonates
Polymer Photochemistry 4 (1984) 13-20
Synthesis and Characterisation of Some New Photografled Polycarbonates
T. M. I b r a h i m , K. G . A 1 - L a m e e a n d G e o r g i u s A . A d a m * Chemistry Department, College of Science, Basrah University, Iraq (Received: 6 October, 1982)
ABSTRACT Several copolycarbonates of bisphenol-A (I) and 1,1,l-trichloro-2,2bis(4-hydroxyphenyl ethane) (II) containing different percentages of H have been prepared. Acrylonitrile monomer has been successfully grafted on these copolymers via the chlorinated group (-CCl3) by photochemical reaction using Mn2( CO )xo as a catalyst in the presence o[ U V light. The grafted copolymers were then purified by reprecipitation and extraction, and have been characterised by various techniques. The grafted copolymers show better thermal stability as measured thermogravimetrically ( T G A ). The solubility of the prepolymers decreases significantly after grafting, and the grafted copolymers also become more brittle. INTRODUCTION In a previous study 1 we synthesised and examined new copolycarbonates containing different molar ratios of (II) in the hope of improving the solvent stress cracking resistance of the commercial bisphenol-A polycarbonates. U n f o r t u n a t e l y these copolymers did not show any i m p r o v e m e n t in this respect. D u e to the outstanding resistance of A B S rubber toward solvents and oils 2 we decided to t To whom correspondence should be addressed. 13
Polymer Photochemistry 0144-2880/84/$3.00 (~) Elsevier Applied Science Publishers Ltd, England, 1984. Printed in Northern Ireland
14
7". M. Ibrahim, K. G. Al-Lamee, Georgius A. Adam
graft acrylonitrile monomer on the above copolycarbonates by a photochemical reaction which has already been described by Bamford et al. 3 By this reaction block, graft and network polymers based on initiating systems typically composed of an organic halide and an organometallic derivative of a transition metal in a low oxidation state were prepared; polymers with enhanced thermal stability are prepared through this route.
EXPERIMENTAL
Materials Acrylonitrile was supplied by B D H and was purified by fractional vacuum distillation. Mn2(CO)10 was supplied by Fluka and was purified by sublimation at 40°C under reduced pressure (0.1 mm Hg4). Dimethyl formamide (DMF) supplied by Fluka was purified by fractional vacuum distillation. T h e prepolymers
The copolymers of I and II were prepared following the procedure used in reference 1. Several copolymers containing different percentages of II were prepared, purified and analysed, then used in the present study. The other reagents and solvents were used as supplied.
Polymerisation procedure The reaction vessel was charged with: acrylonitrile (0.189mol), Mn2(CO)10 (10 -4 mol), DMF (10 cm 3) and prepolymer (10 -2 mol). The vessel was evacuated from atmospheric oxygen through a vacuum line by freezing and thawing cycles; after repeating this procedure several times the vessel was sealed under vacuum. The reaction mixture was exposed to U V light using a high pressure mercury lamp (SP 200 Bausch and Lomb) for a period of 4 h. The reaction mixture was then poured, with mixing, into 250 cm 3 of distilled water.
15
Synthesis of some new photografted polycarbonates
Purification of the grafted polymers T h e cr u d e r eac t i on p r o d u c t was refluxed with c h l o r o f o r m to extract the u n g r a f t e d p r e p o l y m e r , f ol l ow e d by refluxing with a s a t u r a t e d solution of K S C N t o extract t he h o m o p o l y a c r y l o n i t r i l e5. Finally t h e p o l y m e r s w e r e d e s o l v e d in D M F and r e p r e c i p i t a t e d with distilled water. T h e p o l y m e r s w e r e dried u n d e r v a c u u m at 80 °C overnight.
Chmcterisation of the polymers P o l y m e r analysis T h e p r e p o l y m e r s and grafted c o p o l y m e r s w e r e analysed by el em ent al analysis, an d i nf r a - r e d a nd N M R spectroscopy. T h e analyses w ere carried o u t at the A l f r e B e r n h a r d t Mikroanalytisches L a b o r a t o r i u m (Elbach iiber Engelskirchen, W e s t G e r m a n y ) . T h e elemental analysis d a t a f o r th e p r e p o l y m e r s and grafted c o p o l y m e r s are shown in T a b l e l.
TABLE 1 The Elemental Analysis Results for the Prepolymers and Grafted Copolymers
% calculated
Grafted copolymers % found
% found
Prepolymers*
5 7 11 13 95
C
H
Cl
C
H
Cl
C
74-05 73.45 72-20 71-70 53"30
5-32 5- 25 5-10 5.02 2-73
2'43 2"86 4"44 5.20 29.88
74-26 71"50 71-26 69"13 52-67
5.72 5"32 5"13 4"94 2.87
2-47 2-76 4-39 5"07 29.63
66"89 67-41 67-88 66.94 65"29
H
Cl
5"64 0"16 5-69 0"21 5-71 0-14 5.60 0.18 5"31 0"28
N 21-67 20-39 23-40 22.66 22-83
* Percentage of II in the prepolymer calculated from the elemental analysis results.
Viscometry Using a U b b e l o h d e s u s p e n d e d level v i s c o m e t e r at 3 0 ± 0 - 0 1 °C, the solvents used w e r e c h l o r o f o r m and D M F for t he p r e p o l y m e r s and g raf ted c o p o l y m e r s , respectively. T h e m e a s u r e d intrinsic viscosities are shown in T a b l e 2.
16
T. M. Ibrahim, K. G. A l - L a m e e , Georgius A . A d a m TABLE
2
Some Characteristics of the Prepolymers and Grafted Copolymers [,rl] cm 3 g-1 Prepolymer
5 7 11 13 95
Xn * Prepolymer
Grafted copolymer
88 58 76 38 **
126 133 215 270 208
4-14 3.97 4.78 4-75 27"80
*The average degree of polymerisation for polyacrylonitrile in the grafted chain. **The intrinsic viscosity was not measurable (too low).
Thermal analysis The thermogravimetric analyses were carried out on a M O M derivatograph thermoanalyser. The measurements were obtained: (1) isothermally at 160 °C following the procedure used in reference 6, (2) by raising the temperature of the sample at a steady rate, 10 °C min -1, until the polymers were substantially decomposed (Figs. 1001 /f
. , . .........................
/
BC / I"
o 6c 7=
,f.--,iL . . . . . . . . . . . . ! / / /
i
._~
f'
4c
/
f"
.~'_..
2C
ix
I
..
•
*" ."
.
il px
j"
J /
.. ."
• ,,....,,." """
0
~..--L:_~:-;'~" 200
I T~mperature
400
I
600 (°C)
Fig. la. Thermogravimetric analysis curves . . . . .
I
800
1000
95% grafted copolymer; - - - , polyacrylonitrile;---, 95% prepolymer.
Synthesis of some new photografted polycarbonates
17
100
,
80 /"
/..///.... ...........................
/" l~,f,;" .../
/ /,;4. //'/;,"
o 60-
/...- /
/I
•
40--
.: . ....... 20--
....... 200
400 Ternpcratur¢
600 (*C)
800
1000
Fig. lb. Thermogravimetric analysis curves for the grafted copolymers. -.-, 5%; ,7%; -.. , 1 1 % ; - - - , 13%;...,95%.
l a and lb). All the measurements were carried out against standard ot-A1203 in the presence of air.
RESULTS A N D DISCUSSION The elemental analysis results shown in Table 1 confirm that the grafting of acrylonitrile by a photochemical reaction is successful. In grafted copolymers the percentage of chlorine decreases while there is a substantial increase in the percentage of nitrogen. The other evidence which confirms grafting is the drastic change in the intrinsic viscosity of the prepolymers and grafted copolymers in addition to the spectroscopic evidence, i.e. an absorption band was observed at 2240 cm -1 due to the nitrile group vibration. The thermogravimetric curves for the grafted copolymers (Fig. lb) also confirm the occurrence of grafting. The decomposition process takes place in two stages: the first stage at 260 °C losing HCN from the grafted portions, then the final decomposition at temperatures above 550 °C (Table 3). Several other thermal characteristics were obtained from the thermograms, i.e. decomposition temperature (DT), rate of decomposition and the activation energy of the decomposition process (see Table 3).
18
T. M. Ibrahim, K. G. Al-Lamee, Georgius A. Adam TABLE 3 The Thermal Stability Characteristics of the Prepolymers and Grafted Copolymers
Decomposition temperature (°C)
dw/dt*
Activation energy (kJ tool -~)
Prepolymer
5 7 11 13 95
a
b
a
b
a
b
550 565 540 580 460
580 680 700 700 680
0.04 0.10 0.07 0.06 0.05
0.03 0.02 0-02 0-02 0.02
75 80 70 90 45
76 85 64 151 80
* Rate of decomposition at decomposition temperature as % weight loss min -t. a = prepolymer. b = grafted copolymer.
The thermal analysis results show that the thermal stability increases with an increase in the degree of grafting. The grafted copolymers were more stable than the prepolymers, because the prepolymers undergo thermal decomposition at 150 °C losing HC1 as follows: CC13
C~12
Such a route is not possible in the case of the grafted copolymers; instead they lose HCN at 260 °C. On the other hand the improved thermal stability of the grafted copolymers could be due to the stronger intermolecular forces caused by the presence of polar nitrile groups. In the isothermal study at 160 °C the grafted copolymers were superior in their thermal stability and typical graphs are shown in Fig. 2. From the instantaneous slopes of the thermograms at different temperatures, the energy of activation for the decomposition process over an initial 20% weight loss was calculated and the results
Synthesis of some new photografted polycarbonates
19
1.995
1"991
/0
1.983
I
25
0
Fig. 2.
I
50 Time (rain)
I
75
Isothermal weight loss at 160 °C. O, 5% grafted copolymer; A, 7% grafted copolymer;O, 11% grafted copolymer;I , 13% grafted copolymer.
obtained for the different polymers are shown in Table 3. The mechanism of photografting is displayed in the following scheme: Initiation step Mn2(CO) 10
) Mn(CO)4 4- Mn(CO)6
CC13
iO
Mn(CO)4 + ~ ~ H ~ - O - - - C - - O
-----* O
C.Cl~ Mn(CO)4C1 + CO 2Mn(CO)6
, Mn(CO)sC1
, Mn(CO)xo + 2CO
20
T. M. Ibrahim, K. G. AI-Lamee, Georgius A. Adam o
CC12
CC12 X'~NC. H C H 2 Propagation ~
C
H
-
~
+ nCH2~------CHCN
'
CC12 \ CNC.H - - C H 2
CN
CN
Termination The termination reactions could be either by coupling, disproportionation and/or by chain transfer to m o n o m e r , solvent or to the polymer chains. REFERENCES 1. AI-Faiz, M. M. and Adam, Georgius A., Polymer Journal, 12(4) (1980) 225. 2. Morton, M., (ed.), Rubber technology, 2nd edn., Reinhold Co., New York, 1973. 3. Bamford, C. H., Eastmond, G. C., Whittle, D. and Dyson, R. W., J. Polym. Sci. (c), 16 (1967) 2425; Polymer, 10 (1969) 759; Polymer, 10 (1969) 885; Polymer, 10 (1969) 771. 4. Bamford, C. H., Eastmond, G. G. and Robinson, V. J., Trans. Faraday Soc., 60 (1964) 751. 5. Corosa, R. J., Polymer, 1 (1960) 477. 6. Baktash, A. and Adam, Georgius A., Thermochimica Acta, 53 (1982) 149.
Synthesis and Characterisation of Some New Photografled Polycarbonates
T. M. I b r a h i m , K. G . A 1 - L a m e e a n d G e o r g i u s A . A d a m * Chemistry Department, College of Science, Basrah University, Iraq (Received: 6 October, 1982)
ABSTRACT Several copolycarbonates of bisphenol-A (I) and 1,1,l-trichloro-2,2bis(4-hydroxyphenyl ethane) (II) containing different percentages of H have been prepared. Acrylonitrile monomer has been successfully grafted on these copolymers via the chlorinated group (-CCl3) by photochemical reaction using Mn2( CO )xo as a catalyst in the presence o[ U V light. The grafted copolymers were then purified by reprecipitation and extraction, and have been characterised by various techniques. The grafted copolymers show better thermal stability as measured thermogravimetrically ( T G A ). The solubility of the prepolymers decreases significantly after grafting, and the grafted copolymers also become more brittle. INTRODUCTION In a previous study 1 we synthesised and examined new copolycarbonates containing different molar ratios of (II) in the hope of improving the solvent stress cracking resistance of the commercial bisphenol-A polycarbonates. U n f o r t u n a t e l y these copolymers did not show any i m p r o v e m e n t in this respect. D u e to the outstanding resistance of A B S rubber toward solvents and oils 2 we decided to t To whom correspondence should be addressed. 13
Polymer Photochemistry 0144-2880/84/$3.00 (~) Elsevier Applied Science Publishers Ltd, England, 1984. Printed in Northern Ireland
14
7". M. Ibrahim, K. G. Al-Lamee, Georgius A. Adam
graft acrylonitrile monomer on the above copolycarbonates by a photochemical reaction which has already been described by Bamford et al. 3 By this reaction block, graft and network polymers based on initiating systems typically composed of an organic halide and an organometallic derivative of a transition metal in a low oxidation state were prepared; polymers with enhanced thermal stability are prepared through this route.
EXPERIMENTAL
Materials Acrylonitrile was supplied by B D H and was purified by fractional vacuum distillation. Mn2(CO)10 was supplied by Fluka and was purified by sublimation at 40°C under reduced pressure (0.1 mm Hg4). Dimethyl formamide (DMF) supplied by Fluka was purified by fractional vacuum distillation. T h e prepolymers
The copolymers of I and II were prepared following the procedure used in reference 1. Several copolymers containing different percentages of II were prepared, purified and analysed, then used in the present study. The other reagents and solvents were used as supplied.
Polymerisation procedure The reaction vessel was charged with: acrylonitrile (0.189mol), Mn2(CO)10 (10 -4 mol), DMF (10 cm 3) and prepolymer (10 -2 mol). The vessel was evacuated from atmospheric oxygen through a vacuum line by freezing and thawing cycles; after repeating this procedure several times the vessel was sealed under vacuum. The reaction mixture was exposed to U V light using a high pressure mercury lamp (SP 200 Bausch and Lomb) for a period of 4 h. The reaction mixture was then poured, with mixing, into 250 cm 3 of distilled water.
15
Synthesis of some new photografted polycarbonates
Purification of the grafted polymers T h e cr u d e r eac t i on p r o d u c t was refluxed with c h l o r o f o r m to extract the u n g r a f t e d p r e p o l y m e r , f ol l ow e d by refluxing with a s a t u r a t e d solution of K S C N t o extract t he h o m o p o l y a c r y l o n i t r i l e5. Finally t h e p o l y m e r s w e r e d e s o l v e d in D M F and r e p r e c i p i t a t e d with distilled water. T h e p o l y m e r s w e r e dried u n d e r v a c u u m at 80 °C overnight.
Chmcterisation of the polymers P o l y m e r analysis T h e p r e p o l y m e r s and grafted c o p o l y m e r s w e r e analysed by el em ent al analysis, an d i nf r a - r e d a nd N M R spectroscopy. T h e analyses w ere carried o u t at the A l f r e B e r n h a r d t Mikroanalytisches L a b o r a t o r i u m (Elbach iiber Engelskirchen, W e s t G e r m a n y ) . T h e elemental analysis d a t a f o r th e p r e p o l y m e r s and grafted c o p o l y m e r s are shown in T a b l e l.
TABLE 1 The Elemental Analysis Results for the Prepolymers and Grafted Copolymers
% calculated
Grafted copolymers % found
% found
Prepolymers*
5 7 11 13 95
C
H
Cl
C
H
Cl
C
74-05 73.45 72-20 71-70 53"30
5-32 5- 25 5-10 5.02 2-73
2'43 2"86 4"44 5.20 29.88
74-26 71"50 71-26 69"13 52-67
5.72 5"32 5"13 4"94 2.87
2-47 2-76 4-39 5"07 29.63
66"89 67-41 67-88 66.94 65"29
H
Cl
5"64 0"16 5-69 0"21 5-71 0-14 5.60 0.18 5"31 0"28
N 21-67 20-39 23-40 22.66 22-83
* Percentage of II in the prepolymer calculated from the elemental analysis results.
Viscometry Using a U b b e l o h d e s u s p e n d e d level v i s c o m e t e r at 3 0 ± 0 - 0 1 °C, the solvents used w e r e c h l o r o f o r m and D M F for t he p r e p o l y m e r s and g raf ted c o p o l y m e r s , respectively. T h e m e a s u r e d intrinsic viscosities are shown in T a b l e 2.
16
T. M. Ibrahim, K. G. A l - L a m e e , Georgius A . A d a m TABLE
2
Some Characteristics of the Prepolymers and Grafted Copolymers [,rl] cm 3 g-1 Prepolymer
5 7 11 13 95
Xn * Prepolymer
Grafted copolymer
88 58 76 38 **
126 133 215 270 208
4-14 3.97 4.78 4-75 27"80
*The average degree of polymerisation for polyacrylonitrile in the grafted chain. **The intrinsic viscosity was not measurable (too low).
Thermal analysis The thermogravimetric analyses were carried out on a M O M derivatograph thermoanalyser. The measurements were obtained: (1) isothermally at 160 °C following the procedure used in reference 6, (2) by raising the temperature of the sample at a steady rate, 10 °C min -1, until the polymers were substantially decomposed (Figs. 1001 /f
. , . .........................
/
BC / I"
o 6c 7=
,f.--,iL . . . . . . . . . . . . ! / / /
i
._~
f'
4c
/
f"
.~'_..
2C
ix
I
..
•
*" ."
.
il px
j"
J /
.. ."
• ,,....,,." """
0
~..--L:_~:-;'~" 200
I T~mperature
400
I
600 (°C)
Fig. la. Thermogravimetric analysis curves . . . . .
I
800
1000
95% grafted copolymer; - - - , polyacrylonitrile;---, 95% prepolymer.
Synthesis of some new photografted polycarbonates
17
100
,
80 /"
/..///.... ...........................
/" l~,f,;" .../
/ /,;4. //'/;,"
o 60-
/...- /
/I
•
40--
.: . ....... 20--
....... 200
400 Ternpcratur¢
600 (*C)
800
1000
Fig. lb. Thermogravimetric analysis curves for the grafted copolymers. -.-, 5%; ,7%; -.. , 1 1 % ; - - - , 13%;...,95%.
l a and lb). All the measurements were carried out against standard ot-A1203 in the presence of air.
RESULTS A N D DISCUSSION The elemental analysis results shown in Table 1 confirm that the grafting of acrylonitrile by a photochemical reaction is successful. In grafted copolymers the percentage of chlorine decreases while there is a substantial increase in the percentage of nitrogen. The other evidence which confirms grafting is the drastic change in the intrinsic viscosity of the prepolymers and grafted copolymers in addition to the spectroscopic evidence, i.e. an absorption band was observed at 2240 cm -1 due to the nitrile group vibration. The thermogravimetric curves for the grafted copolymers (Fig. lb) also confirm the occurrence of grafting. The decomposition process takes place in two stages: the first stage at 260 °C losing HCN from the grafted portions, then the final decomposition at temperatures above 550 °C (Table 3). Several other thermal characteristics were obtained from the thermograms, i.e. decomposition temperature (DT), rate of decomposition and the activation energy of the decomposition process (see Table 3).
18
T. M. Ibrahim, K. G. Al-Lamee, Georgius A. Adam TABLE 3 The Thermal Stability Characteristics of the Prepolymers and Grafted Copolymers
Decomposition temperature (°C)
dw/dt*
Activation energy (kJ tool -~)
Prepolymer
5 7 11 13 95
a
b
a
b
a
b
550 565 540 580 460
580 680 700 700 680
0.04 0.10 0.07 0.06 0.05
0.03 0.02 0-02 0-02 0.02
75 80 70 90 45
76 85 64 151 80
* Rate of decomposition at decomposition temperature as % weight loss min -t. a = prepolymer. b = grafted copolymer.
The thermal analysis results show that the thermal stability increases with an increase in the degree of grafting. The grafted copolymers were more stable than the prepolymers, because the prepolymers undergo thermal decomposition at 150 °C losing HC1 as follows: CC13
C~12
Such a route is not possible in the case of the grafted copolymers; instead they lose HCN at 260 °C. On the other hand the improved thermal stability of the grafted copolymers could be due to the stronger intermolecular forces caused by the presence of polar nitrile groups. In the isothermal study at 160 °C the grafted copolymers were superior in their thermal stability and typical graphs are shown in Fig. 2. From the instantaneous slopes of the thermograms at different temperatures, the energy of activation for the decomposition process over an initial 20% weight loss was calculated and the results
Synthesis of some new photografted polycarbonates
19
1.995
1"991
/0
1.983
I
25
0
Fig. 2.
I
50 Time (rain)
I
75
Isothermal weight loss at 160 °C. O, 5% grafted copolymer; A, 7% grafted copolymer;O, 11% grafted copolymer;I , 13% grafted copolymer.
obtained for the different polymers are shown in Table 3. The mechanism of photografting is displayed in the following scheme: Initiation step Mn2(CO) 10
) Mn(CO)4 4- Mn(CO)6
CC13
iO
Mn(CO)4 + ~ ~ H ~ - O - - - C - - O
-----* O
C.Cl~ Mn(CO)4C1 + CO 2Mn(CO)6
, Mn(CO)sC1
, Mn(CO)xo + 2CO
20
T. M. Ibrahim, K. G. AI-Lamee, Georgius A. Adam o
CC12
CC12 X'~NC. H C H 2 Propagation ~
C
H
-
~
+ nCH2~------CHCN
'
CC12 \ CNC.H - - C H 2
CN
CN
Termination The termination reactions could be either by coupling, disproportionation and/or by chain transfer to m o n o m e r , solvent or to the polymer chains. REFERENCES 1. AI-Faiz, M. M. and Adam, Georgius A., Polymer Journal, 12(4) (1980) 225. 2. Morton, M., (ed.), Rubber technology, 2nd edn., Reinhold Co., New York, 1973. 3. Bamford, C. H., Eastmond, G. C., Whittle, D. and Dyson, R. W., J. Polym. Sci. (c), 16 (1967) 2425; Polymer, 10 (1969) 759; Polymer, 10 (1969) 885; Polymer, 10 (1969) 771. 4. Bamford, C. H., Eastmond, G. G. and Robinson, V. J., Trans. Faraday Soc., 60 (1964) 751. 5. Corosa, R. J., Polymer, 1 (1960) 477. 6. Baktash, A. and Adam, Georgius A., Thermochimica Acta, 53 (1982) 149.