Polymerization of coordinated monomers. X. Kinetic study of alternating copolymerization of methyl methacrylate and styrene with stannic chloride in dichloroethane

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.     

Ternary Molecular Complex in the Alternating Copolymerization of Methyl Methacrylate with Styrene Using Stannic Chloride

The equimolar alternating copolymerization of methyl methacrylate (MMA) with styrene (St) in the presence of stannic chloride in toluene (Tl) is investigated kinetically. The concentrations of the ternary molecular complexes, [SnCl₄-MMA … St] and [SnCl₄-MMA … T1], are calculated by use of the formation constants of the ternary molecular complexes. The rates of copolymerization under photo-irradiation and with tri-n-butyl boron-benzoyl peroxide as an initiator are proportional to the 1.5th order and 1. Oth order, respectively, of the concentration of the ternary molecular complex [SnCl₄ · MMA … St]. The alternating copolymerization precedes the homopolymerization of the methyl methacrylate charged in excess. The alternating regulation of the copolymerization is ascribed to the homopolymerization of the ternary molecular complex from the kinetic results. The magnitudes of the shifts for     

Polymerization of coordinated monomers. XII. Alternating copolymerization of γ-crotonolactone with styrene with the use of stannic chloride

γ-Crotonolactone and styrene copolymerize alternately in the presence of stannic chloride at -10°C under photoirradiation. The intrinsic viscosity of the resulting copolymer is in the range of 0.6–0.8 dl/g at 30°C in chloroform. The equilibrium constants for the complex formation between stannic chloride and γ-crotonolactone were determined in 1,2-dichloroethane-toluene solution at 0 and ?20°C by use of absorption band at 350 nm. Continuous variation plots based on the ¹H-chemical shift show a 1:1 interaction between styrene and the γ-crotonolactone coordinated to stannic chloride. The equilibrium constants for the ternary molecular complex formation between the coordinated γ-crotonolactone and styrene were determined in 1,2-dichloroethane in the temperature range from ?20 to 0°C. The equilibrium constants, derived independently from the measurements of the nonequivalent protons in γ-crotonolactone, are equal to each other within the experimental error. The mechanism of the alternating copolymerization of γ-crotonolactone and styrene in the presence of stannic chloride is discussed in terms of the homopolymerization of the ternary molecular complex.     

Polymerization of coordinated monomers. VI. Molecular complex formation of methyl methacrylate coordinated to stannic chloride with styrene or toluene

The equilibrium constants for the complex formation between stannic chloride and methyl methacrylate were determined in n-hexane–toluene solution at 0, ?20, and ?30°C by using the absorption band at 350 nm. Continuous variation plots at ?20°C in n-hexane based on the ¹H-chemical shifts definitely show a 1:1 interaction between the coordinated methyl methacrylate and styrene or toluene. The magnitudes of the shifts for the four groups of protons in methyl methacrylate are found to be in a specific ratio in common with the 1:2 complex–styrene or -toluene system. The equilibrium constants for the ternary molecular complex formation between the 1:2 complex and styrene or toluene were determined in n-hexane in the temperature range ?50 to +20°C by use of the chemical shifts. The concentrations of the complex species in the alternating copolymerization solutions were estimated by use of the equilibrium constants. There is a linear relationship between the enthalpy and the entropy changes for the ternary molecular complex formation, which is governed by the enthalpy factor. The specificity of the interactions indicates a specific time-averaged orientation of benzene ring to the coordinated methyl methacrylate. The effects of the coordination of methyl methacrylate to stannic chloride were discussed on the basis of results of ¹³C-NMR spectroscopy.     

Polymerization of coordinated monomers. XIX. Kinetic study of the alternating copolymerization of methyl methacrylate with styrene by boron trichloride

Alternating copolymerizations of methyl methacrylate with styrene in the presence of boron trichloride at 0°C in 1,2-dichloroethane were carried out by using benzoyl peroxide as an initiator. Conversion increased proportionally with polymerization time, whereas the degree of polymerization was constant irrespective of time. The rate depended linearly on the square root of the concentration of benzoyl peroxide. The equilibrium constants for the formation of the ternary molecular complex composed of methyl methacrylate, styrene, and boron trichloride in 1,2-dichloroethane at ?20, ?10, and +4°C were determined by ¹H-NMR spectroscopy. The concentrations of the ternary molecular complex in the polymerization mixtures were evaluated from the equilibrium constant of the formation. The rate of the alternating copolymerization was proportional to the first order of the concentration of the ternary molecular complex. The distribution of methyl methacrylate-centered triads in the alternating copolymer was different from that of styrene-centered triads. These results can be explained by a mechanism involving the homopolymerization of a ternary molecular complex.     

Polymerization of coordinated monomers. XIV. Systematic deviations from alternating regulation in copolymerization of methyl methacrylate with styrene in the presence of metal halides

Methyl methacrylate (MMA) and styrene (St) copolymerize in the presence of zinc chloride at 3°C under photoirradiation. The contents of methyl methacrylate in the copolymers obtained at a [ZnCl₂]/[MMA] molar ratio of 0.4 are systematically larger than 53 mole %, which is the limiting value at a small feed ratio of methyl methacrylate. The resulting copolymers are confirmed as the sole products and not the mixtures by thin layer chromatography. The effect of dilution of the monomer feed mixture with toluene on copolymer composition suggests that it depends chiefly on the feed concentration of styrene and hardly at all on monomer feed ratios. Copolymerizations are also conducted in the presence of stannic chloride at ?17°C under photoirradiation and in the presence of ethylaluminium sesquichloride at 0°C with spontaneous initiation. The contents of methyl methacrylate in both copolymers obtained at feed ratios lower than 60 mole % almost correspond to the 1:1 alternating copolymer and increase systematically with higher feed ratios. The systematic deviations of copolymer composition obtained in the presence of metal halides are reasonably interpreted by the participation of the binary molecular complex composed of metal halide and methyl methacrylate in the polymerization of the ternary molecular complex composed of metal halide, methyl methacrylate, and styrene.     

Polymerization of coordinated monomers. XVI. Stereoregulation in the alternating copolymerization of methyl methacrylate with styrene in the presence of metal halides

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.     

Block copolymerization with trapped radicals

Acrylonitrile–styrene, vinyl chloride–styrene and vinyl chloride–methyl methacrylate block copolymers were obtained by employing trapped radicals in polyacrylonitrile or poly(vinyl chloride) formed in a heterogeneous system by tri-n-butylboron in air as initiator. The trapped polymer radicals were activated on addition of dimethylformamide as solvent. Confirmation of block copolymers was carried out with solvent extractions, elementary analysis, and turbidimetry. In block copolymerization, the polyacrylonitrile trapped radical was more active than the poly(vinyl chloride) radical. Results of kinetic studies were used to consider the mechanism of polymerization.     

Polymerization of coordinated monomers. XVIII. Sequence distribution in methyl acrylate–styrene copolymers prepared in the presence of zinc chloride

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.     

Polymerization of coordinated monomers. III. Copolymerization of acrylonitrile–zinc chloride,methacrylonitrile–zinc chloride or methyl methacrylate–zinc chloride complex with styrene

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.     

Kinetic study of the alternating copolymerization of butadiene and methyl methacrylate

A kinetic investigation of the alternating copolymerization of butadiene and methyl methacrylate with the use of a system of ethylaluminum dichloride and vanadyl chloride as a catalyst was undertaken. The relation between the polymer yield and the molar fraction of methyl methacrylate in the feed was examined by continuous variation of butadiene and methyl methacrylate, the concentrations of total monomer, ethylaluminum dichloride, and vanadyl chloride being kept constant. This continuous variation method revealed that the polymer yield attains its maximum value with a monomer feed containing less than the 0.5 molar fraction of methyl methacrylate. This value of the molar fraction of methyl methacrylate affording the maximum polymer yield decreased on increasing the total monomer concentration but was not changed on varying the concentration of ethylaluminum dichloride. The number of active species estimated from the relation between yield and molecular weight of the polymer was almost constant, regardless of the molar fraction of methyl methacrylate in the feed. Consequently, it can be said that the maximum polymer yield depends mainly on the propagation reaction, not on the initiation reaction or the termination reaction. Three types of the mechanism have been discussed for this alternating copolymerization: polymerization via alternating addition of butadiene and methyl methacrylate complexed with ethylaluminum dichloride by the Lewis-Mayo scheme; polymerization via the ternary intermediate of butadiene, methyl methacrylate, and ethylaluminum dichloride; polymerization via the complex formation of butadiene and methyl methacrylate complexed with ethylaluminum dichloride occurring only at the growing polymer radical. From the kinetic results obtained, it was shown that the first and third schemes are excluded, and polymerization by way of the ternary intermediate is compatible with the data.     

Polymerization of coordinated monomers. IX. Charge-transfer spectrum of the system composed of metal halide,polar vinyl monomer,and electron-donating monomer

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.     

Further Studies on Homo- and Copolymerization of Styrene through Metallocenic Initiator Systems

Summary: Binary metallocene-MAO and ternary diphenylzinc-metallocene-MAO initiator systems have been tested as initiators in the homopolymerization of styrene and also in its copolymerization with several diverse comonomers including substituted styrenes, styrene derivatives, α-olefins and dienes. Various titanocenes and zirconocenes and some exploratory experiment with hafnocene were carried out. The results indicate that titanocenes were more effective than zirconocenes in the homopolymerization of styrene while zirconocenes did better in α-olefin polymerization. It was found that titanocenes generated mainly syndiotactic polystyrene, s-PS, while zirconocenes yielded atactic polystyrene or, depending on the zirconocene, a low percentage of s-PS. For these types of initiators the polymerization process depends largely on the inductive effect of the substituents linked to the benzene ring of styrene and on its position (ortho, meta or para). Substituent multiplicity reduced markedly the effectiveness of these initiator systems. Styrene/isoprene polymerization was also studied using binary zirconocene-MAO initiator systems that yielded low conversions and also low molecular weight polymers.     

Vinylhydroquinone. IV. Preparation and polymerization behavior of 2-methyl-5-vinylhydroquinone derivatives

As in the case of vinylhydroquinone (I), its alkyl-substituted derivative, 2-methyl-5-vinylhydroquinone (II) was found to copolymerize with methyl methacrylate by tri-n-butylborane in cyclohexanone at 30°C. II was prepared from the O,O′-bisether compound, 2-methyl-5-vinyl-O,O′-bis(1′-ethoxyethyl)hydroquinone (III). The monomer reactivity ratios (M₂ = II) were determined to be r₁ = 0.37 and r₂ = 0. No homopolymerization proceeded under the same conditions. Ordinary free-radical initiators, such as azobisisobutyronitrile and benzoyl peroxide, were not effective in the homopolymerization of II. 1:1 Copolymers were obtained from II and maleic anhydride by using tri-n-butylborane as an initiator. The copolymers exhibited no definite melting range and decomposed at 370–375°C endothermally (DSC). The polymerization behavior of III was also investigated. Although tri-n-butylborane did not initiate the homopolymerization of the monomer, azobisisobutyronitrile was capable of initiating the homopolymerization and copolymerization of III. The monomer reactivity ratios (M₁ = styrene) were determined to be r₁ = 0.83 and r₂ = 0.18. The ratios gave the following Q and e values; Q = 0.15 and e = ?2.2.     

Free-radical polymerization of vinyl ferrocene

The results of quantitative studies of the rates of free-radical polymerization of vinyl ferrocene indicate that the latter has polymerization characteristics similar to those of styrene. The rates of homopolymerization of these two monomers in benzene at 70°C. were measured with the use of azobisisobutyronitrile as catalyst. The rate constants (k = R_p/[M][I]^1/2) are k_VF = (1.1 ? 1.8) × 10^?4, k_STY = 1.65 × 10^?4. Small amounts of vinyl ferrocene and styrene have similar effects on the rates of polymerizations of methyl methacrylate and ethyl acrylate and on the molecular weights of the resulting polymer. Polystyrene and poly(vinyl ferrocene) with similar molecular weights are isolated from polymerizations carried out under identical conditions. The rates of copolymerization of vinyl ferrocene—methyl methacrylate, vinyl ferrocene—styrene, and styrene—methyl methacrylate were determined by following the disappearance of monomers by means of gas chromatographic analyses. The relative reactivity for vinyl ferrocene is slightly lower than that for styrene.     

Copolymerization and homopolymerization reactions in systems containing electron-donor monomer,electron-acceptor monomer,and lewis acid

Investigations of the copolymerization of acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, acrylic acid, acryloyl chloride, methyl vinyl ketone, and acrolein with styrene, and of acrylonitrile with acenaphthylene and 1,3-cyclopentadiene in the presence of Lewis acids as catalysts have been carried out. It was found that the free-radical alternating copolymerization and ionic copolymerization or homopolymerization reactions can proceed in these systems. The yield of the competitive free-radical and ionic reactions was related to the type of monomers and strength of the Lewis acid. The mechanism of the catalytic effect of Lewis acids in the reactions studied is discussed.     

Alternating copolymerization of benzofuran and acrylic monomers in the presence of organoaluminum compounds

The copolymerization of benzofuran and acrylic monomers, such as acrylonitrile, methacrylonitrile, methyl acrylate, and methyl methacrylate, was investigated in the presence of aluminum compounds as complexing agents for acrylic monomers. Among the various kinds of aluminum compound, ethylaluminum sesquichloride is the most suitable for alternating copolymerization, whereas ethoxyaluminum compounds of low acidity allow the incorporation of excess acrylic monomer and dichloride of strong acidity is likely to induce cationic homopolymerization of benzofuran as a side reaction. The equimolar amount of sesquichloride with respect to acrylic monomer is necessary for alternating copolymerization. Azobisisobutylonitrile (AIBN) is an effective initiator but benzoyl peroxide is not. Nuclear magnetic resonance (NMR) of the copolymer indicates that the copolymer is essentially alternating, although some block sequences of acrylic monomer sometimes exist. As a mechanism the copolymerization via a ternary complex of acrylic monomer, aluminum compound, and benzofuran is considered. Free acrylic monomer participates in copolymerization when the amount or acidity of the complexing agent is insufficient. A quantitative relation between monomer and copolymer composition is derived from a scheme based on the copolymerization of the donor monomer-acceptor monomer complex with free acrylic monomer.     

Polymerization of coordinated monomers. XVII. Alternating copolymerization of methyl methacrylate with styrene by boron compounds

By the use of various boron compounds methyl methacrylate and styrene were copolymerized under photoirradiations at ?20°C. The alternately regulating activities of the boron compounds in the copolymerizations were in the following order: boron trichloride > ethylboron dichloride > boron trifluoride > diethylboron chloride ? triethylboron (?0). Boron trichloride and ethylboron dichloride exhibited such high regulating activities that their presence in 1 mol% in the charged methyl methacrylate was sufficient to complete equimolar alternating copolymerization. The alternating copolymerization proceeded in the steady state. The copolymerization rates decreased in the following order: boron trichloride ? ethylboron dichloride > diethylboron chloride ? triethylboron (?0). The cotacticities of methyl methacrylate-centered triads in the resulting copolymers were identical to those prepared with boron trichloride, ethylboron dichloride, and diethylboron chloride. The mechanism of the alternating copolymerization is discussed.     

Polymerization of methyl methacrylate by the binary system of the copper–amine complex type resin and carbon tetrachloride

The polymerization of vinyl monomers initiated by binary initiator systems composed of a copper–amine complex type resin and organic halides has been studied. These binary systems initiated the polymerization of various vinyl monomers. A kinetic study of the polymerization of methyl methacrylate initiated by the copper–amine complex resin–CCl₄ system was carried out, and it was found that the polymerization proceeds by way of a radical mechanism. This fact was also supported by the copolymerization of methyl methacrylate with styrene. The overall activation energy of the polymerization of methyl methacrylate was estimated as 8.4 kcal/mole. The activity of the initiator systems was greatly dependent upon the dissociation energy of carbon–halogen bonds in the organic halides. A possible initiation mechanism with the binary systems is proposed and discussed.     

4-甲基丙烯酸-2,2,6,6-四甲基哌啶醇酯自由基聚合的研究

<正> 带受阻胺基团的聚合物是一类新型光稳定剂,这类聚合物的合成研究已有一些报道,但是关于单体分子中的亚胺基对自由基聚合影响报道各不相同。 本文用偶氮二异丁腈(AIBN)为引发剂,对4-甲基丙烯酸-2,2,6,6-四甲基哌啶醇酯(MTMP)的均聚及其与苯乙烯(St)的共聚合进行了研究,同时也考察了MTMP的母体化合物4-羟基-2,2,6,6-四甲基哌啶(TMP)对St及甲基丙烯酸甲酯(MMA)聚合的影响,并对St-MTMP共聚合体系中介质的影响进行了初步探讨。