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1.
Tsuneaki Tanabe Hideomi Koinuma Hidefumi Hirai 《Journal of polymer science. Part A, Polymer chemistry》1981,19(12):3293-3306
Methyl acrylate and styrene have been copolymerized in the presence of zinc chloride either by photoinitiation or spontaneously. The copolymerization mechanism is investigated by analyses of copolymers composition and monomer sequence distribution. The resulting copolymers are not always alternating, their composition being dependent especially on the monomer feed ratio. Appreciable deviation to higher methyl acrylate unit content from an equimolar composition occurs at monomer feed fractions of methyl acrylate over 0.7. The larger deviation is induced by higher temperature, by photoirradiation, and by greater dilution of the reaction mixture with toluene. The 13C-NMR spectrum of the alternating copolymer shows a sharp singlet at the carbonyl region, whereas the spectra of random copolymers prepared by benzoyl peroxide initiation at 60°C show a triplet splitting at the carbonyl carbon region, irrespective of copolymer composition. The relative intensities of the triplet peaks for the random copolymers are in good correspondence to the contents of triad sequences calculated by means of conventional radical copolymerization theory. These results clearly indicate that the carbonyl splitting is caused predominantly by variation of the monomer sequence and not by variation of the stereosequence. The monomer sequence distribution in the copolymers is thus directly and quantitatively measured from the split carbonyl resonance. Although the same triplet splitting appears in the spectra of methyl acrylate–rich copolymers prepared in the presence of zinc chloride at high feed ratios (>0.7) of methyl acrylate, the relative intensities of the split peaks do not fit the sequence distributions of random copolymers calculated by means of the Lewis–Mayo equation. The copolymerization yielding these peculiar sequences and the alternating sequence in the presence of zinc chloride is fully comprehended by a copolymerization mechanism proceeding between two active coordinated monomers, i.e., the ternary molecular complex composed of zinc chloride, methyl methacrylate, and styrene, and the binary molecular complex composed of zinc chloride and methyl methacrylate. 相似文献
2.
Makoto Komiyama Hidefumi Hirai 《Journal of polymer science. Part A, Polymer chemistry》1976,14(1):183-194
The 1:2 stannic chloride–methyl methacrylate complex, the 1:2 stannic chloride–acrylonitrile complex, the ethylaluminum dichloride–methyl methacrylate complex, and the ethylaluminum dichloride–acrylonitrile complex exhibit charge-transfer absorption bands in the wavelength region longer than 300 nm with electron-donating compounds such as mesitylene, styrene, toluene, and butadiene. The absorption spectrum of the mixture of either methyl methacrylate or acrylonitrile with the electron-donating compound is, however, a superpostion of the spectra of the components without any additional absorption. Methyl isobutylate, 3-butenyl methyl ketone, and propionitrile show no charge-transfer absorption bands with the electron-donating compound, even in the presence of a metal halide. Both the presence of the C-C double bond conjugating with the polar group and the coordination of the polar group to a metal halide are essential for an electron-accepting monomer to exhibit a charge-transfer absorption with the electron-donating compound. Continuous variation plots with the use of the charge-transfer band definitely show a 1:1 interaction between the methyl methacrylate coordinated to stannic chloride and styrene, resulting in the determination of the equilibrium constants for the charge-transfer complex formation in methylene chloride: 0.21 l./mole at 25°C and 0.67 l./mole at ?50°C. The charge-transfer absorption is attributed to a ternary molecular complex composed of a metal halide, a polar vinyl monomer, and an electron-donating monomer. 相似文献
3.
The copolymerization of styrene with methyl methacrylate (S/MMA = 4/1) or acrylonitrile (S/AN = 1/1) in the presence of ethylaluminum sesquichloride (EASC) yields 1/1 copolymer in toluene or chlorobenzene. In chloroform the S-MMA-EASC polymerization yields 60/40 copolymer while the S-AN-EASC polymerization yields 1/1 copolymer. In the presence of EASC, styrene-α-chloroacrylonitrile yields 1/1 copolymer (DMF or DMSO), S-AN yields 1/1 copolymer (DMSO) or radical copolymer (DMF), S-MMA yields radical copolymer (DMF or DMSO), α-methylstyrene-AN yields radical copolymer (DMSO) or traces of copolymer (DMF), and α-MS-methacrylo-nitrile yields traces of copolymer (DMSO) or no copolymer (DMF). When zinc chloride is used as complexing agent in DMF or DMSO, none of the monomer pairs undergoes polymerization. However, radical catalyzed polymerization of isoprene-AN-ZnCl2 in DMF yields 1/1 alternating copolymer. The copolymerization of S/MMA in the presence of EASC yields 1/1 alternating copolymer up to 100°C, while the copolymerization of S/AN deviates from 1/1 alternating copolymer above 50°C. The copolymerization of S/MMA deviates from 1/1 copolymer at MMA/EASC mole ratios above 20 while the copolymerization of S/AN deviates from 1/1 copolymer at MMA/EASC ratios above 50. 相似文献
4.
Jos Luis de la Fuente Enrique Lpez Madruga 《Journal of polymer science. Part A, Polymer chemistry》1998,36(16):2913-2925
Free radical copolymerization of styrene/methyl methacrylate (S/MMA) and butyl acrylate/methyl methacrylate (BA/MMA) in the presence of n-dodecanthiol (DDT) has been studied at 60°C in a 3 mol/L benzene solution using 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. Overall chain transfer constant to DDT has been determined for both copolymerization systems, as a function of monomer feed composition using complete molecular weight distribution and the Mayo method. Overall transfer coefficients have values which are dependent on both monomer feed composition and individual comonomer transfer values. Composition, sequence distribution, and stereoregularity of copolymers obtained are, in our experimental conditions, independent of copolymer molecular weight. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2913–2925, 1998 相似文献
5.
Hidefumi Hirai Tsuneaki Tanabe Hideomi Koinuma 《Journal of polymer science. Part A, Polymer chemistry》1980,18(1):203-222
Triad cotacticities of alternating copolymers of methyl methacrylate with styrene prepared in the presence of zinc chloride, ethylaluminium sesquichloride, and ethylboron dichloride are investigated from the mechanistic point of view by means of 1H- and 13C-NMR. The cotacticities from 1H-NMR spectra are obtained accurately by using α-d-styrene in the place of styrene and by measuring the spectra on the copolymer in o-dichlorobenzene at 170°C. The relative intensities of three peaks of the splitting signal for the methoxy protons in the nonalternating copolymers obtained by the use of benzoyl peroxide in the absence of metal halides agree well with the cotacticity distribution calculated theoretically by the Lewis-Mayo mechanism with the stereoregulation following Bernoullian statistics. The splitting signals in the 1H- and 13C-NMR spectra of the alternating copolymers prepared in the presence of metal halides cannot be explained by the same mechanism. The relative intensities of three peaks of the splitting signals for the methoxy protons and for the carbonyl carbon in the methyl methacrylate unit (the contents of cotactic triads centered by the methyl methacrylate unit) are not equal to those for the aromatic C1 carbon in the styrene unit (the contents of cotactic triads centered by styrene unit). The value of f2Y - 4fxfz is not equal to zero, where fx, fy, and fz are the cosyndiotactic, coheterotactic, and coisotactic triad contents, respectively, in the alternating copolymer. Copolymers obtained in the presence of zinc chloride are not exactly equimolar alternating but always contain a methyl methacrylate unit in excess, and the relative intensities of the three peaks for the aromatic C1 carbon change with the copolymer composition. These results are explained by a proposed mechanism: the alternating copolymerization proceeds through the homopolymerization of a ternary molecular complex composed of a metal halide, methyl methacrylate, and styrene, accompanied with the stereoregulation following first-order Markovian statistics; the increase of methyl methacrylate content in the copolymer prepared in the presence of zinc chloride is caused by the participation of the binary molecular complex composed of a metal halide and methyl methacrylate in addition to the ternary molecular complex. 相似文献
6.
Tadashi Ikegami Hidefumi Hirai 《Journal of polymer science. Part A, Polymer chemistry》1970,8(1):195-208
The 1:1 or 2:1 complex of acrylonitrile, methacrylonitrile, or methyl methacrylate with ZnCl2 was copolymerized with styrene at the temperature of 0–30°C without any initiator. The structure of the copolymer from methyl methacrylate complex and styrene was examined by NMR spectroscopy. The complexes of acrylonitrile or methacrylonitrile with ZnCl2 gave a copolymer containing about 50 mole-% styrene units. The complexes of methyl methacrylate yielded an alternating copolymer when the feed molar ratio of methyl methacrylate to styrene was small, but with increasing feed molar ratio the resulting copolymer consisted of about 2 moles of methyl methacrylate per mole of styrene. The formation of a charge-transfer complex of styrene with a monomer coordinated to zinc atom was inferred from the ultraviolet spectra. The regulation of the copolymerization was considered to be effected by the charge-transfer complex. The copolymer resulting from the 2:1 methyl methacrylate–zinc chloride complex had no specific tacticity, whereas the copolymer from the 1:1 complex was richer in coisotacticity than in cosyndiotacticity. The change of the composition of the copolymer and its specific tacticity in the polymerization of the methyl methacrylate complex is related to the structure of the complex. 相似文献
7.
Wayne W. Y. Lau C. S. Lee S. Y. Lee S. H. Goh 《Journal of polymer science. Part A, Polymer chemistry》1993,31(6):1499-1503
Copolymers of 1,2,2,6,6-pentamethyl-4-piperidinyl m-isopropenyl-α,α-dimethylbenzyl carbamate (CB) with styrene (S) and with methyl methacrylate (MMA) were synthesized using AIBN as initiator. S–CB copolymers made from feed ranging from 0.45–0.94 mole fractions S and MMA-CB copolymers made from feed of 0.34–0.88 mole fractions MMA were used to determine the monomer reactivity ratios r1 and r2. The structure of S–CB copolymers was inferred to be mainly of a random nature and in the MMA–CB copolymerization system there is a stronger tendency to form alternating copolymers. © 1993 John Wiley & Sons, Inc. 相似文献
8.
C. S. Lee Wayne W. Y. Lau S. Y. Lee S. H. Goh 《Journal of polymer science. Part A, Polymer chemistry》1992,30(6):983-988
Copolymers of 2,2,6,6-tetramethylpiperidinyl methacrylate (TPMA) with styrene (S) and with methyl methacrylate (MMA) were synthesized using AIBN as initiator. S–TPMA copolymers from feed ranging from 0.10–0.80 mole fractions TPMA and MMA-TPMA copolymers from feed of 0.04–0.85 mole fractions TPMA were used in the determination of monomer reactivity ratios r1, r2. Four different methods were employed in the calculations of r1 and r2 and all calculated results were in good agreement with each other. The structure of S–TPMA copolymers was inferred to be of an alternating nature while that of MMA–TPMA copolymers was random. Both copolymers are potential hindered amine light stabilizers (HALS) and are expected to be less extractable from, and more compatible with, polystyrene and poly(methyl methacrylate) base polymers. 相似文献
9.
Tatsuro Ouchi Masaya Inaba Kohei Tadano Minoru Imoto 《Journal of polymer science. Part A, Polymer chemistry》1982,20(8):2089-2096
It was found that the copolymers of sodium acrylate (AA-Na) with styrene (St) and of sodium methacrylate (MAA-Na) with methyl methacrylate (MMA) could polymerize vinyl monomers in an aqueous phase without the usual initiator. Interestingly, there was a definite composition of the copolymer for the polymerization of a given monomer; for example, when poly(St-co-AA-Na) was used, St, MMA, vinyl acetate, ethyl acrylate, methyl acrylate, and acrylonitrile were polymerized by the copolymer having mole ratios of AA-Na:St of 0.61:0.29, 0.47:0.53, 0.38:0.62, 0.30:0.70, 0.24:0.76, and 1.00:0, respectively. The copolymers of various compositions can form hydrophobic areas (HAs) in the water phase. As has been repeatedly reported, the polymerization proceeds in the HAs, and the following new hypothesis was recently proposed that the hard (the less hydrophilic) HA prefers to incorporate the hard monomer and the soft (the less hydrophobic or the more hydrophilic) HA prefers to incorporate the soft monomer. The results mentioned above support this hypothesis. 相似文献
10.
Milan V. Patel Samir A. Patel Arabinda Ray Rajni M. Patel 《Journal of polymer science. Part A, Polymer chemistry》2004,42(20):5227-5234
Copolymers of monomers 2,4‐dichlorophenyl methacrylate (2,4‐DMA) and methyl methacrylate (MMA) were synthesized with different monomer feed ratios using toluene as a solvent and 2,2′‐azobisisobutyronitrile (AIBN) as an initiator at 70 °C. The copolymers were characterized by IR‐spectroscopy, and copolymer composition was determined with UV‐spectroscopy. The linearization method of Fineman–Ross was employed to obtain the monomer reactivity ratios. The molecular weights and polydispersity indexes were determined by gel permeation chromatography (GPC). Thermogravimetric analyses of polymers were carried out in nitrogen atmosphere. The homo‐ and copolymers were tested for their antimicrobial properties against selected microorganisms. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5227–5234, 2004 相似文献
11.
The methacrylate monomer, 2-[(5-methylisoxazol-3-yl)amino]-2-oxo-ethyl methacrylate (IAOEMA), was synthesized by reacting 2-chloro-N-(5-methylisoxazol)acetamide dissolved in acetonitrile with sodium methacrylate in the presence of triethylbenzylammoniumchloride (TEBAC). The free-radical-initiated copolymerization of IAOEMA, with styrene (ST) and methyl methacrylate (MMA) was carried out in dimethylsulphoxide (DMSO) solution at 65 °C using 2,2′-azobisisobutyronitrile (AIBN) as an initiator with different monomer-to-monomer ratios in the feed. The monomer (IAOEMA) and copolymers were characterized by FTIR, 1H- and 13C-NMR spectral studies. The copolymer composition was evaluated by nitrogen content in polymers led to the determination of reactivity ratios. The reactivity ratios of the monomers were determined by the application of Fineman-Ross and Kelen-Tüdös methods. The analysis of reactivity ratios revealed that ST and MMA are more reactive than IAOEMA, and copolymers formed are statisticalle in nature. The molecular weights (Mw and Mn) and polydispersity index of the polymers were determined using gel permeation chromagtography. Glass transition temperatures of the copolymers were found to increase with an increase in the mole fraction of IAOEMA in the copolymers. The apparent thermal decomposition activation energies (Ed) were calculated by Ozawa method using the SETARAM Labsys TGA thermobalance. 相似文献
12.
The copolymerization of isoprene or butadiene with acrylonitrile in the presence of zinc chloride or ethylaluminum sesquichloride, in the presence or absence of a free radical catalyst, at 30-70°C yields an equimolar, diene-acrylonitrile alternating copolymer containing more than 90% trans-1,4 unsaturation, irrespective of monomer charge. The copolymer results from the homopolymerization of a diene-acrylonitrile…metal halide transoid charge transfer complex. When ZnCl2 is the electron-accepting metal halide and the polymerization is carried out at temperatures of 50°C and higher or to high conversions, the equimolar copolymer is accompanied by a high acrylonitrile polymer, and in the presence of a radical catalyst, by a normal radical copolymer. In the presence of the organoaluminum halide and in the absence of a radical catalyst, the alternating copolymer is the only product, irrespective of monomer charge. However, in the presence of a radical catalyst and at high acrylonitrile monomer charges, e.g., D/AN = 10/90, the alternating copolymer is accompanied by a normal radical copolymer. The formation of equimolar, alternating copolymer at all monomer ratios and in the absence or presence of a radical catalyst indicates that the (D-AN…MX) charge transfer complex readily undergoes homopolymerization and does not copolymerize with free diene or acrylonitrile or with the AN-AN…MX complex. 相似文献
13.
Tadashi Ikegami Hidefumi Hirai 《Journal of polymer science. Part A, Polymer chemistry》1970,8(2):463-482
Complexes of methyl methacrylate and methacrylonitrile with Lewis acids (SnCl4, AlCl3, and BF3) were copolymerized with styrene at ?75°C under irradiation with a high-pressure mercury lamp in toluene solution. The resulting copolymers consisted of equimolar amount of methyl methacrylate or methacrylonitrile and styrene, regardless of the molar ratio of monomers in the feed. NMR spectroscopy showed the copolymers to have an alternate sequence. The tacticities of the copolymers varied with the complex to have an alternate sequence. The tacticities of the copolymers varied with the complex species: the copolymer from the SnCl4 complex system had a higher cosyndiotactieity, while those from the AlCl3 and the BF3 complex systems showed coisotacticity to predominate over cosyndiotacticity. NMR spectroscopic investigation of the copolymerization system indicated the presence of a charge-transfer complex between the styrene and the methyl methacrylate coordinated to SnCl4. The concentration of the charge-transfer complex was estimated to be about 30% of monomer pairs at ?78°C at a 1:1 molar ratio of feed. The growing end radicals were identified as a methyl methacrylate radical for the AlCl3 complex–styrene system and a styrene radical for the SnCl4 complex–styrene system by the measurement of the ESR spectra of the copolymerization systems under or after irradation with a high-pressure mercury lamp. The tacticity of the resulting polymer appears to be controlled by the structure of the charge transfer complex. In the case of the SnCl4 complex a certain interaction of SnCl4 with the growing end radical seems to be a factor controlling the polymer structure. These copolymerizations can be explained by an alternating charge-transfer complex copolymerization scheme. 相似文献
14.
Makoto Komiyama Hidefumi Hirai 《Journal of polymer science. Part A, Polymer chemistry》1976,14(2):307-318
The alternating copolymerization of methyl methacrylate with styrene with the use of stannic chloride was kinetically examined at ?20°C in 1,2-dichloroethane both under photoirradiation and with radical initiator (2:1 tri-n-butylboron-benzoyl peroxide system). At conversions lower than 7%, the conversion increases linearly to the polymerization time, whereas the degree of polymerization is constant irrespective of the polymerization time. The alternating copolymerizations are 1.5 order and the 1.0 order reactions with respect to the ternary molecular complex composed of stannic chloride, methyl methacrylate, and styrene, under photoirradiation and with initiator, respectively. The linear dependences of the rates upon the 0.5 order of the intensity of the incident light and upon the 1.0 order of the concentration of tri-n-butylboron indicate a bimolecular termination. The rate normalized by the 1.5 order of the concentration of the coordinated methyl methacrylate and the rate normalized by the concentration of the coordinated methyl methacrylate are proportional to the 1.5 and 1.0 orders of the charged concentration of styrene, for the copolymerizations under photoirradiation and with initiator, respectively. The kinetic results in the 1,2-dichloroethane solution are quite consistent with those in the toluene solution. The alternating copolymerization mechanism, in which the ternary molecular complex predominantly homopolymerizes as a monomer unit, is confirmed. 相似文献
15.
Yasushi Kamimura Osamu Haba Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2006,44(8):2448-2453
This article deals with the latent reactive polymers having isocyanate moiety obtained from the radical copolymerization of 2‐propenyl isocyanate ( 2PI ) with styrene, 2PI with methyl methacrylate ( MMA ), and 2‐methacryloyloxyethyl isocyanate ( MOI ) with styrene. The radical copolymerization was carried out in benzene (5.00 M by total monomer) in the presence of AIBN (3.00 mol % of total monomer) at 60 °C for 24 h. The isocyanate moiety in each copolymer was stable at room temperature for more than 6 months under aerobic atmosphere, because no change of the infrared absorption based on isocyanate group of the resulting copolymer at around 2250 cm?1 was observed. Isocyanate moiety of obtained copolymer (poly( 2PI ‐co‐ St )) reacted with excess diamines or diols at 80 °C in THF solution to afford the crosslinked polymer quantitatively. These results could demonstrate that isocyanate moiety in the copolymers showed thermal and reactive latency. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2448–2453, 2006 相似文献
16.
Abstract The copolymerization of chloroprene with methyl methacrylate was studied in the presence of Etn A1C13-n (n=1, 1.5, 2)-vanadium compounds. Monomer reactivity ratios in various catalyst concentrations were compared with that of a usual radical initiator. The apparent monomer reactivity ratio changed with the concentration of alkylaluminum halide. In this polymerization, alternating copolymer could not be prepared by the ordinary catalyst concentration by which the alternating copolymerization of chloroprene with acrylonitrile was carried out. The addition of more than 10 mole % of the alkylaluminum halide based on two monomers was required to prepare the copolymer which had equimolar composition irrespective of the feed monomer ratio. The configuration in the repeating unit of the copolymer was discussed by comparison with the NMR and IR spectra of the radical copolymer and the cyclic Diels-Alder adduct of chloroprene-methyl methacrylate. The high alternating tendency was clarified by ozonolysis of the copolymer which was prepared under the conditions which produced equimolar copolymer in various feed monomer ratios. The chloroprene unit of the copolymer was present in the 1, 4-trans structure in the copolymer prepared by the Etn A1C13-n -vanadium compound system. 相似文献
17.
A. K. Oultache B. Jasse L. Monnerie 《Journal of Polymer Science.Polymer Physics》1994,32(15):2539-2548
Orientation and relaxation behavior in uniaxially stretched styrene-co-methyl methacrylate random copolymers was investigated. When compared at a reference temperature T = Tg + constant, orientation of methyl methacrylate units (MMA) decreases while styrene units orientation increases with a decrease in the styrene percentage. This behavior can be related to intermolecular interactions between MMA units and to the stiffness of styrene-MMA units, which do not undergo conformational changes upon stretching. Both monomer units relax the same in a given copolymer and chain relaxation increases when the styrene percentage increases. Orientation relaxation of styrene and MMA units can be reduced to two general relaxation master curves whatever the blend composition, when the results are compared at same monomeric friction coefficient. © 1994 John Wiley & Sons, Inc. 相似文献
18.
The copolymers of methyl methacrylate (MMA) (or styrene (ST))/stearyl methacrylate (SMA) obtained from miniemulsion polymerization
were prepared and characterized. All the miniemulsions showed satisfactory colloidal stability upon aging due to the effectively
retarded Ostwald ripening by the reactive costabilizer SMA. In subsequent miniemulsion copolymerizations, monomer droplet
nucleation predominated in the particle formation process, but homogeneous nucleation could not be ruled out even at such
high levels of SMA (20–50 wt.%). The contact angle first increased rapidly and then leveled off when the SMA content increased
from 20 to 50 wt.% for both the copolymers of MMA/SMA and ST/SMA. At constant level of SMA, the copolymer of MMA/SMA with
a less hydrophobic composition showed a larger contact angle compared to the ST/SMA counterpart. The contact angle (103 ± 1°)
of the copolymer MMA/SMA (50/50 w/w) was comparable to that (104°) of PSMA. A schematic model was proposed to explain the experimental results. 相似文献
19.
Masaaki Hirooka Hiroshi Yabuuchi Jiro Iseki Yasuto Nakai 《Journal of polymer science. Part A, Polymer chemistry》1968,6(5):1381-1396
A vinyl monomer that has the nitrile or carbonyl group conjugated to the C?C double bond, such as acrylonitrile, methyl acrylate, and methyl methacrylate, forms a complex with an alkylaluminum halide, and the complex reacts spontaneously with a hydrocarbon monomer such as styrene, propylene, or ethylene, giving a high molecular weight copolymer. The copolymers always contain the two monomer units in 1:1 ratio. Thus styrene, copolymerized with methyl acrylate or methyl methacrylate in the presence of ethylaluminum sesquichloride in homogeneous toluene solution, gives such an equimolar copolymer regardless of the initial monomer compositions. The NMR spectra of these copolymers are distinctly different from those of the equimolar copolymers obtained with azobisisobutyronitrile as initiator and have simpler and well separated patterns. The copolymers and the corresponding radical copolymers appear to be amorphous, judged by their x-ray diffraction patterns and their differential thermal analyses. Their infrared spectra resemble each other very closely. Hence, the difference in the NMR spectra may be ascribed to the matter of the sequence distribution. The infrared spectrum of ethylene–methyl acrylate copolymer shows no absorption near 720 cm.?1 due to the methylene sequence arising from ethylene–ethylene linkage. These experimental data lead to the inference that the equimolar copolymers obtained in this work may have an alternating sequence. 相似文献
20.
Graft copolymers prepared by mastication of PVC in the presence of styrene or of a styrene/ methyl methacrylate mixture, have been studied by thermogravimetry, estimation of hydrogen chloride, thermal volatilization analysis, and flash pyrolysis/g.l.c. The degradation behaviour of PVC/ polystyrene mixtures, vinyl chloride/styrene random copolymers, a random copolymer of methyl methacrylate and styrene, and PVC/poly-α-methylstyrene mixtures has also been studied. The graft copolymers resemble the PVC/methacrylate graft copolymers previously studied in showing retardation of the dehydrochlorination reaction, but contrast with them in yielding chain fragments but no monomer during HCl production. Some stabilization of the second component at higher temperatures is also found. PVC/polystyrene mixtures behave in the same way as the corresponding graft copolymers, but vinyl chloride/styrene copolymers show reduced stability towards both dehydrochlorination and monomer production compared with the homopolymers. PVC/poly-α-methylstyrene mixtures yield some monomer concurrently with HCl loss, and display marked retardation of the latter reaction. Stabilization of the second polymer at higher temperatures is again observed. Many of these results add further strong support to the view that chlorine atoms are involved as chain carriers in the thermal dehydrochlorination of PVC. 相似文献