- Email: [email protected]
Styrene polymerization on mineral filler surfaces, modified with organosilicon peroxides
~Polymer Science U.S.S.R. Vol. 28, No. 9, pp. 2122--2128, 1986
,Printed in Poland
0032-3950/86 $10.00+.00 O 1987Pergamon Journals Ltd.
STYRENE POLYMERIZATION ON MINERAL FILLER SURFACES, MODIFIED WITH ORGANOSILICON PEROXIDES* N. V. YABLOKOVA,Yu. A. ALEKSANDROVand O. M. TITOVA Chemical Research Institute of the N. I. Lobachevsky State University, Gorky
(Received 17 January 1985) Styrene polymerization on filler surfaces modified with organosilicon peroxides has been studied. It was showD that the amount of initiator grafted to the surface depends on the nature of the peroxide and of the filler. The kinetic parameters of breakdown of the initiators, grafted to the surface and the features o f styrene polymerization on modified fillers have been established. It was shown that vinyltri(tert-butylperoxy) silane is capable of ensuring the formation of polystyrene compositions with a grafted polymer, without previous modification of the filler surface. The effect of surface modification of the filler OD the properties of polystyrene samples, filled with Aerosil and A1203 was studied.
THE USE of fillers modified with a grafted initiator for preparing filled polymers is promising for the exploitation of composite materials with desired applicational properties [1-3]. At the same time, the effect of the graft is a complex and unexplained function of the nature of the filler, the modifier, the polymer and also the conditions of conducting tlae filled polymerization. In this work, the effect of modification of a filler surface by the following organosilicon peroxides: dimethyldi-(tert-butylperoxy)silane (I), methyltri-(tert-butylperoxy)silane (II), vinyltri(tert-butylperoxy)silane (III) and tetra(tert-butylperoxy)silane IV, on the chemical and physico-mechanical properties of filled polystyrenes was studied. T h e 7 form of A12Oa, Aerosil, Tie2 and chemically precipitated CaCO3 (Table 1) were used as the fillers. The initiators I - I V were grafted to filler surfaces, with not less than 98 ~. of base material, as described in references [4, 5]. The kinetics of thermal breakdown of the grafted peroxides were studied by an ampoule method, without solvent, placing in each ampoule the precise amount of modified filler. The concentration of undecomposed peroxide in each ampoule was determined iodometrically. The rate of styrene polymerization on the filler surface was studied by an ampoule method, the residual styrene being measured by a method suggested by Martin [6]. The filled polystyrene samples were prepared by pouring into a suspension of modified or unmodified filler and polymerizing the samples at 70-750 for 16 hr. Benzoyl peroxide was the initiator for polymerization on the unmodified fillers. The hardness of the samples was determined by U.S.S.R. specification 4670-77 and the impact resistance by specification 4647-80.
The initiator was grafted to the filler in a diethyl ether medium at 20--25°, by interaction of the active OH groups on the filler surface with the Me3COO group of the * Vysokomol. soyed. A28: No. 9, 1908-1913, 1986. 2122
2123
Styrene polymerization on mineral filler surfaces
above peroxides to form a grafted peroxide of structure -]-OSi(OOCMea)RIR2, where RI=CH3(Me), C H 2 = C H , Me3COO, R2=Me, Me3COO. The amount of the grafted peroxide was determined by iodometry. The effect of the type of peroxide and the filler on the content of grafted peroxide groups in the treated filler is shown in Table 1. The thermal decomposition of the grafted peroxide was investigated over the 70100° range (see Tables 2 and 3). The grafted initiator caused an increase in the peroxide thermal decomposition rate compared with that of the same compound in the liquid phase (Table 2). The kinetic curves, plotted with log Co/C-time coordinates (Co and C are initial and flow peroxide concentrations) are represented by systems of lines with a single (50yo decomposition) or 2 (35 and 709/00decomposition) inflexions, due to subsequent decomposition of some peroxide groups in the surface peroxides. A similar phenomenon was noted during the decomposition of organosilicon peroxides in the liquid phase [7]. TABLE 1.
EFFECT OF NATURE OF PEROXIDE AND OF FILLER ON CONTENT OF GRAFTED PEROXIDE GROUPS ON THE FILLER
Filler
Specific surface, m2/g
Grafted peroxide
A12Oa (y-form)
90
SiO2 (Aerosil)
175-200
IV llI IV III II
I
TiO2 C a C O a (chemically precipitated) TABLE 2.
0-6 0"4 0-5 0'4 0"2 0"I 0"2 0"03
I
100 L
Maximum content of O - O groups on the surface, wt. %
IV III
3
K I N E T I C AND ACTIVATION PARAMETERS FOR DECOMPOSITION OF THE FIRST PEROXIDE G R O U P
'OF ORGANOSILICON PEROXIDES, GRAFTED TO AN AEROSIL SURFACE AND THEIR ANALOGUES IN SOLUTION
Peroxide - - OSi(OOCMe3) 3 MeSi (OOCMe3) a - - OSi(Vi) (OOCMe3)2 * MeSi (Vi) (OOCMe~) 2 - - OSi(Me) (OOCMe3) a MezSi (OOCMe3) 2 - - OSi (Me) zOOCMea MeaSiOOCMea
Filler or solvent SiC2 Anisole SiC2 Nonane SiC2 Anisole SiC2 Nonane
k14o x 105, see- t
Ea, kJ/mole
log ko
21"1 6"3 22"5 8'83 9"8 0-47 7"5 0.007
101±3 133+4 73+3 109±2 110±4 149±5 149±4 172±5
9"2±0-9 12"6±0"7 5'5±0'8 9"7±0'6 9"9±0"8 13"5±0"7 14"5±0"7 14"5±0-7
* Vie~ C H = CH2. Note: kt4o is the decomposition rate constant o f the first peroxide group o f organosillcon peroxides at 140 ° in soc- t ko is the prc-exponcntiai factor in,the A r r h ~ i u s equation, k f k o e -zlar in ~ c -~.
2124
N.V. YAmLOgOVAet
TABLE 3.
KINETIC AND ACTIVATION P
~
aL
FOR DECOMPOSITION OF FIRST Pm~ON]DE GROUP 11~
PEROXID~IV AND III, GRAFTEDON TO AN Al2Os SUI~AC'B Peroxide IV
III
--O-Ogroups o n surface, wt. 0'6
T° 110 120 130 140 70 80 90 100 110 110 120 120
0"4
0"14 0.4 0.14 0"4
k x 103, sec -1 1"17 1"81 2.82 4"32 1.36 1-67
Ea, kJ/mole
log ko
57+3
4'8±0"8
50+3
3"56 5"63 8"50 8"55 12"6 12.7
t
4.8±0.~
A study of the influence of the nature of the peroxide on its decomposition on surfaces of A1203 and SiO2 (Tables 2 and 3) showed that as the number of peroxy fragments in the peroxide increase, the rate of decomposition of the first peroxy g r o u p increases. The rate increase is also observed when a methyl section in the grafted peroxide is replaced by vinyl. This is related to the fact that the spatial effects of the Me3COO and CH2 = C H groups increase the energy level of the base state of the peroxide and stabilization of the radical-like particles in the peroxide state reduces its energy level, compared with the energy state of the methyl substituted derivative. This leads to a reduction in the activation energy of radical formation and an increase in the decomposition rate constant k of the peroxide which has Me3COO and C H 2 = C H substituents (see Table 2). A change in the surface concentration of peroxide III, grafted on to A1203, does not affect the k for peroxide thermal decomposition (see Table 3). The effect of the nature of the filler on the decomposition rate of peroxide I I I on a surface was investigated. Substitution of Si in the surface layer of the filler by A1, Ti or Ca atoms leads to decrease in thermal stability of peroxide grafted to the surface (see Table 4). One should seek the reason in the electronic effects of the E - O group o f the surface peroxide.
1
l
I
I
~E--O--SiOOCMe.~,where E = S i , Ti,'AI, Ca.
During polymerization in presence of a filler on the surface of which an initiator system is attached, an appreciable increase in the initial reaction rate is observed. The reason for this consists not only in the fact that thermal polymerization is supplemented by initiated polymerization due to the grafted initiator, but that in the presence of"
Styrene polymerization on mineral filler surfaces
2125
a filler, there is ~ definite orientation of the monomer molecule on the surface layer accompanied by formation of coordinate links and leading to a kinetically more advantageous arrangement of the monomer molecules [8] which participate in the free radical polymerization chain. The homolytic decomposition of a peroxide, attached to a filler surface, is accompanied by the formation of two radicals I .~ --OSiR(OOCMe3)2 --, ~ - - 0 8 i - - 0 " + "OCMe3,
I
OOCMez TABLE 4.
E F F E C T OF N A T U R E OF FILLER ON DECOMPOSITION OF PEROXIDE
Ill,
GRAFTED TO THE SURFACE
(120 °) Peroxide grafted to the surface, wt. %
Filler
i:
k x 10 3 , sec -1
0"4 0.2
A1203 TiO2
1260 30
Filler
Peroxide ! grafted to the surface, wt. %
CaCo3
0"03 0"2
SiO2
k×
10 3, s e c - 1
20 7"4
one of which is chemically bonded to the surface and initiates the formation of grafted polymer. The other may escape into the bulk and undergo either further radical decomposition or initiate homopolymerization. o:,%
(:]~7
7
I00
q 60
q zo o
i
5
3
60
120 180 Time, min FIG. 1
200
0
60
120 180 Time ~min
200
FIG. 2
FiG. 1. Dependence of yield ~, of polystyrene on Al2Oa surface (60 wt. %), modified with peroxide III on polymerization time ( - O - O concentration on surface, 0.4 wt.%). / - t o t a l product; 2 - t h e r m a l polymer; 3 - g r a f t polymer; 4 - h o m o p o l y m e r (without thermal polymer); 5, 6 - t o t a l product curves obtained at an - O - O concentration on the surface of 0.13 and 0-3 wt. %, re-. spectively. Here and in Fig. 2, T= 120 °. Flo. 2. Influence of nature of modifier on grafted polystyrene yield on a n A I 2 O a surface (60 wt. ~o)° Peroxid es: I - III, 2 - I I I , not previously attached to the Ai2Oa surface; 3 - IV, 4 - I , 5 - l I . Active oxygen concentration on the surface, 0"4 wt. ~o.
N . V . YABLOKOVA e t aL
2126
The polymerization o f styrene was studied on an A1203 surface (60 wt. ~ ) modified with peroxide H I (0.4 wt. ~o o f O - O ) at 120°C, the amount of grafted polymer and h o m o p o l y m e r (Fig. 1) being determined. For comparison, the kinetics of styrene thermal polymerization in presence of unmodified aerosil was investigated (Fig. 1, curve 2). F r o m the results obtained, the consumption of peroxide attached to the A1203 surface can be assumed and conclusions drawn on the necessary quantity of the latter to secure greater m o n o m e r conversion. As follows f r o m Fig. 1 at conversions of up to c a 30 Yo, the polymerization rate does not depend on the surface concentration of peroxide. To secure complete styrene conversion at 120°C into polymer filled with A1203, it is necessary that the optimum surface concentration of peroxide I I I should be 0.4-0.5 wt.% of - O - O group (or 2 wt. ~o of styrene taken). Much lower surface initiator concentrations (0.14 and 0.3 wt.~o of - O - O - , see Fig. 1, curves 5 and 6) do not ensure 100Yo conversion to polymer. The kinetic and activation parameters given in Table 5 were determined f o r t h e overall polymerization reaction o f styrene (40 wt. Yo on an A1203 surface (60 wt. ~ ) , modified by peroxide I I I (0.4 wt. % of - O - O - ) . To follow the kinetics of graft polymer formation, one must remove h o m o p o l y m e r and unreacted monomer. This was done by the repeated extraction in a Soxhlet apparatus of the samples of filled polymers, using boiling toluene for 8 hr and subsequent determination of the amount of grafted polymer by weighing (see Fig. 1, curve 3). Al~O3 S U ~ A C Z (60 wt. %), MODIFIEDWITHPEROXIDEIII (0"4 wt. ~o - O - O - ) AND IN P~eNO~ OF NON-GRA~ PEROXIDBllI (0.6 wt. ~. - O - O - oN SrVRE~m)
TABLE 5. KINETIC AND ACTIVATION PARAMETERS FOR STYRENE POLYMERIZATION ON AN
T° 80 90 100
v × 104, mole/l.sec non-grafted grafted peroxide HI peroxide HI m
9"44 15.2
5"37 7"01 8'46
T° 120 130
v x 104, mole/1.sec grafted non-grafted peroxide III peroxide Ill 26"7 14"8 37"8
Note: E. equals 32.7 kJ/mole for grafted peroxide III, 28'5 kJ/mole for non-grafted III. The portion cut off from the line logv~logvo-E./4"575.2", which was used to calculate E. and logvo is 1'73 for the grafted and 1.0 for the non-grafted peroxide.
TABt~ 6. P~SICO-ME~CAt. CHARACr-~tSTICS OF POLYSTYRENE FILLED BY AERO$IL Modifier -
III IV
Impact strength (kJ/m2) with an Aerosil content (wt. ~) of 0 1 5 6"9 I0 5"6 4"4 4"2 4"0 3"6 5.6 5.4 5.4 5"2 5"0 5.8 5-6 5.6 5"6 5.2
Brinel hardness (MPa) for an Aerosil content (wt. ~) of 0 1 5 10 138 140 135 132 138 135 135 135 135 135 140 145
Styrene polymerization on mineral filler surfaces
2127
It appeared that 10-20~o of polymer is grafted on to the failer surface, depending o n the nature of the surface peroxide groups which participate in graft polymerization
(see Fig. 2). It was shown that formation of grafted product takes place, not only when the peroxide is previously attached to the A1203 surface but also when an organosilicon polyperoxide is introduced in a pure state into the filler-monomer system. A comparison of the kinetic and activation parameters for styrene polymerization, initiated by grafted peroxide III and this same peroxide not previously attached to the surface, shows that these parameters are close to one another (see Table 5). This indicates that the main part of the peroxide III, dissolved in the styrene, becomes grafted to the surface during the polymerization and ensures grafting of the same amount of polymer, as in the case where the same peroxide is previously attached to the filler surface (Fig. 2, curves 1 and 2). The highest graft polymerization rate and maximum graft polymer yield is observed when peroxide III, which has 2 functional groups, is used as modifier. Grafting. is achieved not only because of polymerization on to the silyloxy radical CH=CH2 A~_OSliO" 27 CH2=CHPh ---, AI--OSiOCH2--~HPh, ~ i OOCMe3 but also due to the vinyl section of the peroxide, grafted to the surface /'\/~/\ AI--OSi--cH=cH2+ AI--OSi--CH2--~ti2 27 ~t t 27CH.a=CHPh . >
j,,/'\ Polymer
--*
Polymer radical
AI--O-- S i - CII2-- Ctlz+- CH2--12HPb
In this work, certain physico-mechanical characteristics (resilience and BrineI hardness) of polystyrene compositions, filled with Aerosil and modified by the peroxides III and IV were studied. When the content of unmodified Aerosil is increased in the polymer, the strength of the filled samples is decreased (see Table 6, first line). The modification of the Aerosil by peroxides III and IV caused an increase in impact strength of 1.3-1.4 times, compared with that of samples filled by the unmodified analogues. The hardness of the polystyrene samples is practically unchanged by introducing modified fillers. Similar regularities were obtained with samples, filled with A1203 which was modifed with peroxides III and IV. Translated by C. W. CAPP
2128
V . S . SKAZKA et aIo
REFERENCES
1. S. S. IVANCHEV and A. V. DMITRENKO, Uspekhi khimii 51: 1178, 1982 2. H. Y. DEKKING, J. Polymer Sci. 9: 541, 1965; 11: 26, 1967 3. V. A. POPOV, A. N. GRISHIN, Yu. A. ZVEREVA, T. V. PALAYEVA, V. A. FOMIN and S. S. IVANCHEV, Vysokomol. soyed. A25: 760, 1984 (Translated in Polymer Sei. U.S.S.R. 25: 4, 883, 1984) 4. E. BUNCEL and A. DAVIES, J. Chem. Soc., 6, 1550, 1958 5. A. K. LITKOVETS, Avtoref. dis. na soiskaniye uch. st. kand. khim. nauk (Discn. on thesis, candidate in chemistry). 24 pp., L'vov politekhn, in-t, L'vov, 1984 6. R. V. MARTIN, Analyt. Chem. 21: 921, 1949 7. N.P. SLUCHEVSKAYA, V. A. YABLOKOV,N. V. YABLOKOVAand Yn. A. ALEK~ANDROV, Zhurn. obshch, khimii 46: 1640, 1976 8. Ye. M. MOROZOVA, L. A. TRAVNIKOVA and V. I. YELISEYEVA, Mekhanika kompozit. materialov, 5, 924, 1980
Polymer Science U.S.S.R, Vol. 28, No. 9, pp. 2128-2135, 1986 Printed in Poland
0032-3950/86 $10.00+.00 O 1987 Pergamon Journals Ltd.
PHYSICAL PROPERTIES OF THE SYSTEM POLY(ETHYLENE OXIDE)-RESORCINOL* V. S. ~KAZKA, V. YA. NIKOLAYEV,YE. A. BEKTUROV,S. KUDAIBERGENOV, K. D. PETRENKOand V. P. PRIVALKO 50th U.S.S.R. Anniversary Syktyrkarsk State University Institute of Chemical Sciences, Kaz.S.S.R. Academy of Sciences Institute of Macromoleeular Chemistry, Ukr.S.S.R. Academy of Sciences
(Received22 January 1985) Physical properties of the system poly(ethylene oxide)-resorcinol have been investigated by X-ray diffraction, small-angle light scattering, polarization microscopy with crossed Nicols, and differential scanning calorimetry. Formation of a molecular complex is accompanied by changes in the crystalline and supermolecular spherulitic structure. Temperatures and heats of phase transformations have been determined. THE SYSTEM poly(ethylene oxide) (PEO)-resorcinol represents a suitable model object for studying the formation of molecular complexes stabilized by hydrogen bonds between a macromolecular and a low-molecular-weight compound. The frequent occurfence in nature of molecular complexes that involve a polymeric constituent and their considerable practical importance lie behind the continuing interest in such systems. As already shown [I, 2], the phase diagram of the system PEO--resorcinol features an * Vysokomol. soyed. A28: No. 9, 1914-1919, 1986.
,Printed in Poland
0032-3950/86 $10.00+.00 O 1987Pergamon Journals Ltd.
STYRENE POLYMERIZATION ON MINERAL FILLER SURFACES, MODIFIED WITH ORGANOSILICON PEROXIDES* N. V. YABLOKOVA,Yu. A. ALEKSANDROVand O. M. TITOVA Chemical Research Institute of the N. I. Lobachevsky State University, Gorky
(Received 17 January 1985) Styrene polymerization on filler surfaces modified with organosilicon peroxides has been studied. It was showD that the amount of initiator grafted to the surface depends on the nature of the peroxide and of the filler. The kinetic parameters of breakdown of the initiators, grafted to the surface and the features o f styrene polymerization on modified fillers have been established. It was shown that vinyltri(tert-butylperoxy) silane is capable of ensuring the formation of polystyrene compositions with a grafted polymer, without previous modification of the filler surface. The effect of surface modification of the filler OD the properties of polystyrene samples, filled with Aerosil and A1203 was studied.
THE USE of fillers modified with a grafted initiator for preparing filled polymers is promising for the exploitation of composite materials with desired applicational properties [1-3]. At the same time, the effect of the graft is a complex and unexplained function of the nature of the filler, the modifier, the polymer and also the conditions of conducting tlae filled polymerization. In this work, the effect of modification of a filler surface by the following organosilicon peroxides: dimethyldi-(tert-butylperoxy)silane (I), methyltri-(tert-butylperoxy)silane (II), vinyltri(tert-butylperoxy)silane (III) and tetra(tert-butylperoxy)silane IV, on the chemical and physico-mechanical properties of filled polystyrenes was studied. T h e 7 form of A12Oa, Aerosil, Tie2 and chemically precipitated CaCO3 (Table 1) were used as the fillers. The initiators I - I V were grafted to filler surfaces, with not less than 98 ~. of base material, as described in references [4, 5]. The kinetics of thermal breakdown of the grafted peroxides were studied by an ampoule method, without solvent, placing in each ampoule the precise amount of modified filler. The concentration of undecomposed peroxide in each ampoule was determined iodometrically. The rate of styrene polymerization on the filler surface was studied by an ampoule method, the residual styrene being measured by a method suggested by Martin [6]. The filled polystyrene samples were prepared by pouring into a suspension of modified or unmodified filler and polymerizing the samples at 70-750 for 16 hr. Benzoyl peroxide was the initiator for polymerization on the unmodified fillers. The hardness of the samples was determined by U.S.S.R. specification 4670-77 and the impact resistance by specification 4647-80.
The initiator was grafted to the filler in a diethyl ether medium at 20--25°, by interaction of the active OH groups on the filler surface with the Me3COO group of the * Vysokomol. soyed. A28: No. 9, 1908-1913, 1986. 2122
2123
Styrene polymerization on mineral filler surfaces
above peroxides to form a grafted peroxide of structure -]-OSi(OOCMea)RIR2, where RI=CH3(Me), C H 2 = C H , Me3COO, R2=Me, Me3COO. The amount of the grafted peroxide was determined by iodometry. The effect of the type of peroxide and the filler on the content of grafted peroxide groups in the treated filler is shown in Table 1. The thermal decomposition of the grafted peroxide was investigated over the 70100° range (see Tables 2 and 3). The grafted initiator caused an increase in the peroxide thermal decomposition rate compared with that of the same compound in the liquid phase (Table 2). The kinetic curves, plotted with log Co/C-time coordinates (Co and C are initial and flow peroxide concentrations) are represented by systems of lines with a single (50yo decomposition) or 2 (35 and 709/00decomposition) inflexions, due to subsequent decomposition of some peroxide groups in the surface peroxides. A similar phenomenon was noted during the decomposition of organosilicon peroxides in the liquid phase [7]. TABLE 1.
EFFECT OF NATURE OF PEROXIDE AND OF FILLER ON CONTENT OF GRAFTED PEROXIDE GROUPS ON THE FILLER
Filler
Specific surface, m2/g
Grafted peroxide
A12Oa (y-form)
90
SiO2 (Aerosil)
175-200
IV llI IV III II
I
TiO2 C a C O a (chemically precipitated) TABLE 2.
0-6 0"4 0-5 0'4 0"2 0"I 0"2 0"03
I
100 L
Maximum content of O - O groups on the surface, wt. %
IV III
3
K I N E T I C AND ACTIVATION PARAMETERS FOR DECOMPOSITION OF THE FIRST PEROXIDE G R O U P
'OF ORGANOSILICON PEROXIDES, GRAFTED TO AN AEROSIL SURFACE AND THEIR ANALOGUES IN SOLUTION
Peroxide - - OSi(OOCMe3) 3 MeSi (OOCMe3) a - - OSi(Vi) (OOCMe3)2 * MeSi (Vi) (OOCMe~) 2 - - OSi(Me) (OOCMe3) a MezSi (OOCMe3) 2 - - OSi (Me) zOOCMea MeaSiOOCMea
Filler or solvent SiC2 Anisole SiC2 Nonane SiC2 Anisole SiC2 Nonane
k14o x 105, see- t
Ea, kJ/mole
log ko
21"1 6"3 22"5 8'83 9"8 0-47 7"5 0.007
101±3 133+4 73+3 109±2 110±4 149±5 149±4 172±5
9"2±0-9 12"6±0"7 5'5±0'8 9"7±0'6 9"9±0"8 13"5±0"7 14"5±0"7 14"5±0-7
* Vie~ C H = CH2. Note: kt4o is the decomposition rate constant o f the first peroxide group o f organosillcon peroxides at 140 ° in soc- t ko is the prc-exponcntiai factor in,the A r r h ~ i u s equation, k f k o e -zlar in ~ c -~.
2124
N.V. YAmLOgOVAet
TABLE 3.
KINETIC AND ACTIVATION P
~
aL
FOR DECOMPOSITION OF FIRST Pm~ON]DE GROUP 11~
PEROXID~IV AND III, GRAFTEDON TO AN Al2Os SUI~AC'B Peroxide IV
III
--O-Ogroups o n surface, wt. 0'6
T° 110 120 130 140 70 80 90 100 110 110 120 120
0"4
0"14 0.4 0.14 0"4
k x 103, sec -1 1"17 1"81 2.82 4"32 1.36 1-67
Ea, kJ/mole
log ko
57+3
4'8±0"8
50+3
3"56 5"63 8"50 8"55 12"6 12.7
t
4.8±0.~
A study of the influence of the nature of the peroxide on its decomposition on surfaces of A1203 and SiO2 (Tables 2 and 3) showed that as the number of peroxy fragments in the peroxide increase, the rate of decomposition of the first peroxy g r o u p increases. The rate increase is also observed when a methyl section in the grafted peroxide is replaced by vinyl. This is related to the fact that the spatial effects of the Me3COO and CH2 = C H groups increase the energy level of the base state of the peroxide and stabilization of the radical-like particles in the peroxide state reduces its energy level, compared with the energy state of the methyl substituted derivative. This leads to a reduction in the activation energy of radical formation and an increase in the decomposition rate constant k of the peroxide which has Me3COO and C H 2 = C H substituents (see Table 2). A change in the surface concentration of peroxide III, grafted on to A1203, does not affect the k for peroxide thermal decomposition (see Table 3). The effect of the nature of the filler on the decomposition rate of peroxide I I I on a surface was investigated. Substitution of Si in the surface layer of the filler by A1, Ti or Ca atoms leads to decrease in thermal stability of peroxide grafted to the surface (see Table 4). One should seek the reason in the electronic effects of the E - O group o f the surface peroxide.
1
l
I
I
~E--O--SiOOCMe.~,where E = S i , Ti,'AI, Ca.
During polymerization in presence of a filler on the surface of which an initiator system is attached, an appreciable increase in the initial reaction rate is observed. The reason for this consists not only in the fact that thermal polymerization is supplemented by initiated polymerization due to the grafted initiator, but that in the presence of"
Styrene polymerization on mineral filler surfaces
2125
a filler, there is ~ definite orientation of the monomer molecule on the surface layer accompanied by formation of coordinate links and leading to a kinetically more advantageous arrangement of the monomer molecules [8] which participate in the free radical polymerization chain. The homolytic decomposition of a peroxide, attached to a filler surface, is accompanied by the formation of two radicals I .~ --OSiR(OOCMe3)2 --, ~ - - 0 8 i - - 0 " + "OCMe3,
I
OOCMez TABLE 4.
E F F E C T OF N A T U R E OF FILLER ON DECOMPOSITION OF PEROXIDE
Ill,
GRAFTED TO THE SURFACE
(120 °) Peroxide grafted to the surface, wt. %
Filler
i:
k x 10 3 , sec -1
0"4 0.2
A1203 TiO2
1260 30
Filler
Peroxide ! grafted to the surface, wt. %
CaCo3
0"03 0"2
SiO2
k×
10 3, s e c - 1
20 7"4
one of which is chemically bonded to the surface and initiates the formation of grafted polymer. The other may escape into the bulk and undergo either further radical decomposition or initiate homopolymerization. o:,%
(:]~7
7
I00
q 60
q zo o
i
5
3
60
120 180 Time, min FIG. 1
200
0
60
120 180 Time ~min
200
FIG. 2
FiG. 1. Dependence of yield ~, of polystyrene on Al2Oa surface (60 wt. %), modified with peroxide III on polymerization time ( - O - O concentration on surface, 0.4 wt.%). / - t o t a l product; 2 - t h e r m a l polymer; 3 - g r a f t polymer; 4 - h o m o p o l y m e r (without thermal polymer); 5, 6 - t o t a l product curves obtained at an - O - O concentration on the surface of 0.13 and 0-3 wt. %, re-. spectively. Here and in Fig. 2, T= 120 °. Flo. 2. Influence of nature of modifier on grafted polystyrene yield on a n A I 2 O a surface (60 wt. ~o)° Peroxid es: I - III, 2 - I I I , not previously attached to the Ai2Oa surface; 3 - IV, 4 - I , 5 - l I . Active oxygen concentration on the surface, 0"4 wt. ~o.
N . V . YABLOKOVA e t aL
2126
The polymerization o f styrene was studied on an A1203 surface (60 wt. ~ ) modified with peroxide H I (0.4 wt. ~o o f O - O ) at 120°C, the amount of grafted polymer and h o m o p o l y m e r (Fig. 1) being determined. For comparison, the kinetics of styrene thermal polymerization in presence of unmodified aerosil was investigated (Fig. 1, curve 2). F r o m the results obtained, the consumption of peroxide attached to the A1203 surface can be assumed and conclusions drawn on the necessary quantity of the latter to secure greater m o n o m e r conversion. As follows f r o m Fig. 1 at conversions of up to c a 30 Yo, the polymerization rate does not depend on the surface concentration of peroxide. To secure complete styrene conversion at 120°C into polymer filled with A1203, it is necessary that the optimum surface concentration of peroxide I I I should be 0.4-0.5 wt.% of - O - O group (or 2 wt. ~o of styrene taken). Much lower surface initiator concentrations (0.14 and 0.3 wt.~o of - O - O - , see Fig. 1, curves 5 and 6) do not ensure 100Yo conversion to polymer. The kinetic and activation parameters given in Table 5 were determined f o r t h e overall polymerization reaction o f styrene (40 wt. Yo on an A1203 surface (60 wt. ~ ) , modified by peroxide I I I (0.4 wt. % of - O - O - ) . To follow the kinetics of graft polymer formation, one must remove h o m o p o l y m e r and unreacted monomer. This was done by the repeated extraction in a Soxhlet apparatus of the samples of filled polymers, using boiling toluene for 8 hr and subsequent determination of the amount of grafted polymer by weighing (see Fig. 1, curve 3). Al~O3 S U ~ A C Z (60 wt. %), MODIFIEDWITHPEROXIDEIII (0"4 wt. ~o - O - O - ) AND IN P~eNO~ OF NON-GRA~ PEROXIDBllI (0.6 wt. ~. - O - O - oN SrVRE~m)
TABLE 5. KINETIC AND ACTIVATION PARAMETERS FOR STYRENE POLYMERIZATION ON AN
T° 80 90 100
v × 104, mole/l.sec non-grafted grafted peroxide HI peroxide HI m
9"44 15.2
5"37 7"01 8'46
T° 120 130
v x 104, mole/1.sec grafted non-grafted peroxide III peroxide Ill 26"7 14"8 37"8
Note: E. equals 32.7 kJ/mole for grafted peroxide III, 28'5 kJ/mole for non-grafted III. The portion cut off from the line logv~logvo-E./4"575.2", which was used to calculate E. and logvo is 1'73 for the grafted and 1.0 for the non-grafted peroxide.
TABt~ 6. P~SICO-ME~CAt. CHARACr-~tSTICS OF POLYSTYRENE FILLED BY AERO$IL Modifier -
III IV
Impact strength (kJ/m2) with an Aerosil content (wt. ~) of 0 1 5 6"9 I0 5"6 4"4 4"2 4"0 3"6 5.6 5.4 5.4 5"2 5"0 5.8 5-6 5.6 5"6 5.2
Brinel hardness (MPa) for an Aerosil content (wt. ~) of 0 1 5 10 138 140 135 132 138 135 135 135 135 135 140 145
Styrene polymerization on mineral filler surfaces
2127
It appeared that 10-20~o of polymer is grafted on to the failer surface, depending o n the nature of the surface peroxide groups which participate in graft polymerization
(see Fig. 2). It was shown that formation of grafted product takes place, not only when the peroxide is previously attached to the A1203 surface but also when an organosilicon polyperoxide is introduced in a pure state into the filler-monomer system. A comparison of the kinetic and activation parameters for styrene polymerization, initiated by grafted peroxide III and this same peroxide not previously attached to the surface, shows that these parameters are close to one another (see Table 5). This indicates that the main part of the peroxide III, dissolved in the styrene, becomes grafted to the surface during the polymerization and ensures grafting of the same amount of polymer, as in the case where the same peroxide is previously attached to the filler surface (Fig. 2, curves 1 and 2). The highest graft polymerization rate and maximum graft polymer yield is observed when peroxide III, which has 2 functional groups, is used as modifier. Grafting. is achieved not only because of polymerization on to the silyloxy radical CH=CH2 A~_OSliO" 27 CH2=CHPh ---, AI--OSiOCH2--~HPh, ~ i OOCMe3 but also due to the vinyl section of the peroxide, grafted to the surface /'\/~/\ AI--OSi--cH=cH2+ AI--OSi--CH2--~ti2 27 ~t t 27CH.a=CHPh . >
j,,/'\ Polymer
--*
Polymer radical
AI--O-- S i - CII2-- Ctlz+- CH2--12HPb
In this work, certain physico-mechanical characteristics (resilience and BrineI hardness) of polystyrene compositions, filled with Aerosil and modified by the peroxides III and IV were studied. When the content of unmodified Aerosil is increased in the polymer, the strength of the filled samples is decreased (see Table 6, first line). The modification of the Aerosil by peroxides III and IV caused an increase in impact strength of 1.3-1.4 times, compared with that of samples filled by the unmodified analogues. The hardness of the polystyrene samples is practically unchanged by introducing modified fillers. Similar regularities were obtained with samples, filled with A1203 which was modifed with peroxides III and IV. Translated by C. W. CAPP
2128
V . S . SKAZKA et aIo
REFERENCES
1. S. S. IVANCHEV and A. V. DMITRENKO, Uspekhi khimii 51: 1178, 1982 2. H. Y. DEKKING, J. Polymer Sci. 9: 541, 1965; 11: 26, 1967 3. V. A. POPOV, A. N. GRISHIN, Yu. A. ZVEREVA, T. V. PALAYEVA, V. A. FOMIN and S. S. IVANCHEV, Vysokomol. soyed. A25: 760, 1984 (Translated in Polymer Sei. U.S.S.R. 25: 4, 883, 1984) 4. E. BUNCEL and A. DAVIES, J. Chem. Soc., 6, 1550, 1958 5. A. K. LITKOVETS, Avtoref. dis. na soiskaniye uch. st. kand. khim. nauk (Discn. on thesis, candidate in chemistry). 24 pp., L'vov politekhn, in-t, L'vov, 1984 6. R. V. MARTIN, Analyt. Chem. 21: 921, 1949 7. N.P. SLUCHEVSKAYA, V. A. YABLOKOV,N. V. YABLOKOVAand Yn. A. ALEK~ANDROV, Zhurn. obshch, khimii 46: 1640, 1976 8. Ye. M. MOROZOVA, L. A. TRAVNIKOVA and V. I. YELISEYEVA, Mekhanika kompozit. materialov, 5, 924, 1980
Polymer Science U.S.S.R, Vol. 28, No. 9, pp. 2128-2135, 1986 Printed in Poland
0032-3950/86 $10.00+.00 O 1987 Pergamon Journals Ltd.
PHYSICAL PROPERTIES OF THE SYSTEM POLY(ETHYLENE OXIDE)-RESORCINOL* V. S. ~KAZKA, V. YA. NIKOLAYEV,YE. A. BEKTUROV,S. KUDAIBERGENOV, K. D. PETRENKOand V. P. PRIVALKO 50th U.S.S.R. Anniversary Syktyrkarsk State University Institute of Chemical Sciences, Kaz.S.S.R. Academy of Sciences Institute of Macromoleeular Chemistry, Ukr.S.S.R. Academy of Sciences
(Received22 January 1985) Physical properties of the system poly(ethylene oxide)-resorcinol have been investigated by X-ray diffraction, small-angle light scattering, polarization microscopy with crossed Nicols, and differential scanning calorimetry. Formation of a molecular complex is accompanied by changes in the crystalline and supermolecular spherulitic structure. Temperatures and heats of phase transformations have been determined. THE SYSTEM poly(ethylene oxide) (PEO)-resorcinol represents a suitable model object for studying the formation of molecular complexes stabilized by hydrogen bonds between a macromolecular and a low-molecular-weight compound. The frequent occurfence in nature of molecular complexes that involve a polymeric constituent and their considerable practical importance lie behind the continuing interest in such systems. As already shown [I, 2], the phase diagram of the system PEO--resorcinol features an * Vysokomol. soyed. A28: No. 9, 1914-1919, 1986.