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.     

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 coordinated monomers VII. A kinetic study on the alternating copolymerization of methyl methacrylate with styrene using stannic chloride

The alternating copolymerization of methyl methacrylate with styrene in the presence of stannic chloride at ?50°C in toluene was kinetically investigated both under photoirradiation and with the tri-n-butylboron-benzoyl peroxide initiator. The concentrations of the binary and ternary molecular complexes in the copolymerization solution were estimated by use of the equilibrium constants. The rates are found to be proportional to the 1.5th and 1.0th orders of the concentration of the ternary molecular complex composed of stannic chloride, methyl methacrylate, and styrene, under photoirradiation and with initiator, respectively. The conversion increases proportionally with the polymerization time, while the degree of polymerization is constant irrespective of the time. The rates depend linearly upon the square root of the intensity of the incident light and upon the concentration of tri-n-butylboron, respectively. The alternating copolymerization is confirmed experimentally to precede the homopolymerization of the monomer charged in large excess both under photoirradiation and with initiator. The kinetic results indicate consistently that the alternating copolymerization proceeds through the homopolymerization of the ternary molecular complex in the steady state with a bimolecular termination. Both the conventional radical mechanism and the double complex mechanism are unsuitable for the present alternating copolymerization.     

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.     

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. XX. Ab initio molecular orbital study on the binary molecular complex composed of methyl methacrylate and boron trichloride

The stereo and the electronic structures of methyl methacrylate and the binary molecular complex composed of methyl methacrylate and boron trichloride are determined by quantum chemical calculations based on ab initio molecular orbital methods with the STO-3G basis set. The Stable structures of methyl methacrylate in the free state are a transoid from and a cisoid form. The transoid form is slightly (0.5 kcal/mol) more stable than the cisoid form. The total energy change accompanying binary molecular complex formation is calculated to be ?43 kcal/mol. The most stable structure of the binary molecular complex composed of methyl methacrylate and boron trichloride is a twisted form in which the dihedral angle between the vinyl group and the ester group is 19.7°. A large amount of electron transfer from methyl methacrylate to boron trichloride is calculated to occur on binary molecular complex formation. Mulliken's population analysis shows the electron transfer to be the origin of the twist of the binary molecular complex. The energy level of the lowest unoccupied molecular orbital is substantially lowered by the coordination of boron trichloride.     

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.     

Ferrocenyl-containing iron(ii) clathrochelate-benzoyl peroxide, a new initiating system for radical polymerization of methyl methacrylate

Radical polymerization of methyl methacrylate initiated by the benzoyl peroxide — macrobicyclic bis-ferrocenylboron-capped iron(ii) tris-1,2-cyclohexanedione dioximate system was studied. The ferrocenyl-containing macrobicyclic complex and benzoyl peroxide forms an efficient initiating system that allows one to perform the polymerization process at a high rate with substantially reduced amounts of the initiator and the metal complex component at 30–75 °C and to influence the molecular-weight characteristics of poly(methyl methacrylate) produced.     

Polymerization of coordinated monomers. XXI. Ab initio molecular orbital study on the binary molecular complex composed of methyl methacrylate and boron trifluoride

The stereo- and electronic structures of the binary molecular complex composed of methyl methacrylate and boron trifluoride are obtained by using an ab initio molecular orbital method with an STO-3G basis set. The total energy change on the binary molecular complex formation is ?1.3 X 10^?2 Hartree (?8.2 kcal/mol). The electron transfer from methyl methacrylate to boron trifluoride and the change in the energy level of the lowest unoccupied molecular orbital of methyl methacrylate on the complex formation with boron trifluoride are much smaller than those on the complex formation with boron trichloride. A twisted form in which the dihedral angle between the vinyl plane and the ester plane is 16.9° is the most stable structure of the binary molecular complex composed of methyl methacrylate and boron trifluoride. A strong bonding overlap population between a β-hydrogen of methyl methacrylate and a fluorine of boron trifluoride is found in this conformation. © 1992 John Wiley & Sons, Inc.     

Polymerization of coordinated monomers. XXII. Ab initio molecular orbital study on the binary radical complexes of 2-methoxycarbonyl propyl radical with boron trichloride and with boron trifluoride as a model of growing radical end

The geometrical and electronic structures of the binary radical complexes of 2-methoxycarbonyl propyl radical with boron trichloride and with boron trifluoride were determined by using an ab initio molecular orbital method. The 2-methoxycarbonyl propyl radical complex was a model of the growing radical end in the copolymerization of methyl methacrylate in the presence of boron halides. The most stable structure of the binary radical complex composed of 2-methoxycarbonyl propyl radical with boron trichloride was a twisted form in which the dihedral angle between the vinyl group and the ester group was 32°, while that of the binary radical complex composed of methyl methacrylate radical with boron trifluoride was a planar form as the free radical. The frontier orbital energy of 2-methoxycarbonyl propyl radical was lowered by 0.06 au by the coordination of boron trichloride, while that was lowered only by 0.02 au by the coordination of boron trifluoride. The polymerization mechanism was elucidated on the basis of these predictions. © 1993 John Wiley & Sons, Inc.     

Effect of heterocyclic derivatives of ferrocene on free-radical polymerization of methyl methacrylate and styrene

The free-radical bulk homopolymerization of methyl methacrylate and styrene initiated by benzoyl peroxide or AIBN in the presence of heterocyclic derivatives of ferrocene is studied. It is shown that, in the case of the peroxide initiator, ferrocene derivatives form highly efficient initiation systems, which make it possible to polymerize methyl methacrylate at a high rate, to reduce the molecular mass of polymers, and to synthesize polymers with a high content of syndiotactic triads, while in the case of AIBN, such systems are not formed.     

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. 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.     

Reverse Atom‐Transfer Radical Polymerization at Room Temperature

This paper aims at reporting on the “living”/controlled radical polymerization of methyl methacrylate initiated with the benzoyl peroxide (BPO)/Cu^IX (X=Br,Cl)/2,2'‐bipyridine (bpy) redox system at room temperature. No control is observed for the polymerization conducted in bulk and in toluene, whereas a polymer with predetermined molecular weight and rather narrow molecular weight distribution is formed in butanone. The solvent has thus a decisive effect on the reverse atom‐transfer radical polymerization of methyl methacrylate initiated with the BPO/Cu^IX (X = Br,Cl)/bpy ternary system at 25°C.     

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.     

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. 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.     

Effects of chlorophosphines on the radical polymerization of methyl methacrylate

The effect of chlorophosphines (phosphorus trichloride, dichlorophenylphosphine, chlorodiphenylphosphine) on the radical polymerization of methyl methacrylate was investigated in benzene solution. The polymerization was carried out at 50°C by the standard solution method, α,α′-azobisisobutyronitrile being used as an initiator. These chlorophosphines accelerated the polymerization of methyl methacrylate but did not affect the rate of decomposition of α,α′-azobisisobutyronitrile. Ultraviolet and infrared spectral data suggested that the acceleration effect was due to the complex formation of methyl methacrylate with each chlorophosphine. From the result of a copolymerization with styrene, it was found that the reactivity of methyl methacrylate monomer increased in the presence of dichlorophenylphosphine.     

Determination of rate constants of benzoyl peroxide and azobisisobutyronitrile dissociation via polymerization kinetics

A linear expression is derived from Tobolsky's equation related to the dead-end polymerization method to determine the rate constant for the initiator dissociation. This novel graphical method applies remarkably well to the kinetic data collected by dilatometry from the polymerization of methyl methacrylate initiated by 2,2′-azobisisobutyronitrile and benzoyl peroxide in toluene at 60°C. Results obtained for these two initiators are consistent with those published in the literature. Applicability of the method is confined to at least 5% and at most 13% decomposition of initiator. However, these limiting values are sensitive to the experimental techniques employed. The effects of induced decomposition of benzoyl peroxide and thermal polymerization of methyl methacrylate are shown to be negligible in the present investigations.