High pressure copolymerization of styrene with maleic anhydride

The radical copolymerization of styrene with maleic anhydride was investigated in an acetone solution at 40°C under high pressure up to 4000 kg/cm². Effects of pressure on the monomer reactivity ratio considering the influence of the penultimate monomer unit were studied from kinetic data and IR spectra. It has been found that the radical copolymerization rate increases with pressure, especially concerning the reaction of maleic anhydride with a polymer chain possessing a maleic anhydride unit preceding the active styrene chain end.     

Kinetics of the copolymerization of styrene with maleic anhydride in ethyl methyl ketone

The copolymerization of styrene and maleic anhydride in ethyl methyl ketone as solvent and with benzoyl peroxide as initiator at 60–80°C in the entire feed composition range was studied. The resulting copolymers appear to have negative and positive deviations from alternation as determined by use of elemental analysis. The experimental data were found to fit a three-reactivity-ratio copolymer composition equation from the penultimate model. The inclusion of the reactivity ratio, k_SM (=k_SMM/k_SMS), in addition to r_SS (=k_SSS/k_SSM) and r_MS (=k_MSS/k_MSM), allows prediction of a positive deviation from the alternation, i.e. the mole fraction of maleic anhydride in the copolymer being higher than 0,5.     

Discussion on the mechanism of alternating copolymerization of styrene and maleic anhydride

To clear up the detailed mechanism of the alternating copolymerization of styrene (St) and maleic anhydride (MAn) concerning the initiation species, the propagation species, the tendency of the chain transfer reaction as well as the directional tendency of the reaction between copolymer radicals and monomer complexes, the role of the charge transfer complexes, characterization of end groups and additional donor effects were examined. The equilibrium constant of the St/MAn (1 : 1) complex was determined to be 0.31 by NMR spectroscopy, that suggested considerable amounts of complexes existing in the system. As expected, a small quantity of initiator (¹⁴C-azobisisobutyronitrile (AIBN)) was incorporated into the St/MAn copolymer. Chlorine atoms were scarcely incorporated into the copolymer synthesized in CCl₄ with AIBN or benzoyl peroxide (BPO) as an initiator. Hence the copolymerization was considered to be induced only by attacke of initiator radicals to the monomer or the complexes, contrary to the usual conception of telomerization. When the electron donor monomer was added to the system, the terpolymerization could be treated as a copolymerization of the two complexes, i.e., St/MAn and Donor/MAn. By adding naphthalene the rate maximum point shifted from higher concentration of MAn to the equivalent concentration of St and MAn. Degradative chain transfer to N.N-dimethylaniline was observed, confirming the existance of poly-MAn radicals. It was suggested from these results that the charge transfer complex and uncomplexed MAn took part in the copolymerization of St and MAn. This was proved kinetically. The whole mechanism was discussed.     

High conversion copolymerization, 1. Kinetics of the copolymerization of styrene and maleic anhydride

The copolymerization of styrene (S) with maleic anhydride (MAn) in 1,4-dioxane at 60, 70 and 80°C up to high conversion (≈ 98%) was followed by differential scanning calorimetry. The rate of copolymerization increases up to 20 – 40% conversion of both monomers and then gradually decreases to zero. The increase in the copolymerization rate is more pronounced for equimolar ratios [S]/[MAn] as compared to ratios with an excess of S. For a given mole ratio of S and MAn the copolymerization rate in 1,4-dioxane is higher at higher total monomer concentrations and/or at higher temperatures. The heat of copolymerization is 81,6 kj · mol^?1 for the equimolar [S]/[MAn] mixture. For mixtures with [S]/[MAn] > 1 the heat of reaction is between 70 and 80 kj · mol^?1. The limitingconversion of styrene for [S]/[MAn] = 1 is about 98%, and for [S]/[MAn] > 1 it is a function of the [S]/[MAn] ratio. Assuming exclusively the formation of an alternating S/MAn copolymer the following relation is derived. for the ratio of the apparent rate constants of propagation k?_p, and termination k?</_t.     

Solvent effect in radical copolymerization of styrene with p-aminostyrene

p-Aminostyrene ( 1 , M₁) and styrene (M₂) were radically copolymerized at 60°C in various solvents. There is a significant solvent effect on monomer reactivity ratios, especially on r₁, suggesting a specific interaction between the solvent and the polymer radical with the p-aminostyrene moiety at the terminal position. In order to clarify the solvent factor influencing the relative reactivity, the hydrogen-bond-accepting basicity of the solvent (β) was determined from enhanced UV shifts for 1 relative to N,N-dimethyl-p-aminostyrene. Regression analysis of r₁ with the solvatochromic parameters revealed that β is the major factor responsible for r₁-variations.     

Photo-induced copolymerization of cyclohexene with maleic anhydride

Kinetics and mechanism of photo-induced copolymerization of cyclohexene with maleic anhydride in chloroform were studied. The UV spectra suggested the formation of a chargetransfer complex between the comonomers. This complex was excited under irradiation and then underwent hydrogen abstraction to produce two kinds of radicals for initiation. The polymerization produces an alternating copolymer in the composition range of 25 to 75 mol-% of either comonomer. The chain-transfer role of cyclohexene was also investigated.     

High pressure copolymerization of cyclopentene with maleic anhydride

Radical copolymerization of cyclopentene with maleic anhydride was investigated under high pressure up to 6000 kg/cm² at 60°C. The rate of copolymerization increased markedly with pressure and the conversion at 6000 kg/cm² attained a maximum constant value in a few minutes. This behavior indicated very large absolute values for the activation volume compared with other vinyl polymerization systems. The copolymer composition was affected by pressure, for a given monomer feed the content of cyclopentene in the copolymer increased with pressure. This is an explanation for the penultimate effect due to cyclopentene. High pressure is presumed to be effective for eliminating the penultimate effect in copolymerization.     

The copolymerization of maleic anhydride with propene and isobutene

Alternating copolymers were obtained by radical copolymerization of propene (Pr) and isobutene (IB) with maleic anhydride. Both polymers (Pr and IB) do not homopolymerize under the applied reaction conditions. The copolymerization rates were determined.     

Alternative copolymerization of vinyl sulfides with maleic anhydride. III. Alternative copolymerization

Ethyl vinyl sulfide (EVS) and phenyl vinyl sulfide (PVS) were found to undergo alternative copolymerization with maleic anhydride (MAn) even in the absence of radical initiators. It is noted that both the rates and the reduced viscosities in these alternative copolymerization show a maximum at 50 mole-% comonomer mixture, anticipating that a 1 : 1 charge transfer complex is formed preceding polymerization. From spectroscopic studies, it was also observed that the formation of such a complex between vinyl sulfide and MAn was confirmed, but their equilibrium constants were quite small, i.e. 0.090 l./mole for PVS-MAn in CHCl₃ and 0.035 l./mole for EVS-MAn in CH₂Cl₂ at room temperature. The mechanism of these alternative copolymerizations is discussed.     

Application of the penultimate model in the copolymerization of styrene with maleic anhydride in ethyl methyl ketone at 50°C

Composition data for the copolymerization of styrene with maleic anhyride in ethyl methyl ketone at 50°C were obtained using a non-aqueous potentiometric direct titration method, and were analysed using a non-linear least squares optimization routine. Three variants of the penultimate model were fitted to the data: the four variable model (completely general), the three variable model (r_mm = 0,0) and the more usual two variable model (r_mm = r_sm = 0,0). Of these, the two variable model was adequate to describe the data. Best estimates of the reactivity ratios for data previously reported in the literature were calculated, and in one case the best values were markedly different to those originally given.     

Terpolymerization of maleic anhydride,styrene and electron-acceptor monomers

The free-radical terpolymerization of maleic anhydride, styrene, and acrylic monomers such as acrylonitrile, methyl acrylate and methyl methacrylate was studied. The alternating copolymerization of maleic anhydride with styrene was found to be favored in those systems. Contrary to theoretical predictions, maleic anhydride is more reactive than styrene in ternary systems. The relative reactivity of the acrylic monomers studied was found to decrease in the order: methyl methacrylate ≥ methyl acrylate > acrylonitrile. In the presence of a Lewis acid, such as ZnCl₂ or C₂H₅AlCl₂, the relative reactivity of acrylic monomers increases and at the respective complexing agent concentration the copropagation of the acrylic monomer with styrene can dominate. On the basis of the results obtained, some aspects of the mechanism of alternating propagation in systems comprising an electron-donor monomer and two electron-acceptor monomers are discussed.     

Cationic copolymerization of trioxane with styrene. II. Some factors effect on the copolymerization of trioxane with styrene

The homogeneous copolymerization of trioxane with styrene was carried out using various catalysts and solvents. The copolymerization rate increased with increase in the dielectric constant of the solvent used and decreased with increase In the acidity of the catalyst used. The reactivity of styrene increased and on the contrary, the reactivity of trioxane decreased with increase in the dielectric constant of the solvent.     

Photoinitiation, 8. Polymerization of methyl methacrylate and copolymerization of methyl methacrylate with maleic anhydride in the presence of zinc dichloride

The rate of photoinitiated (at wavelength λ = 365 nm) polymerization of methyl methacrylate (MMA) in acetone in the presence and/or absence of N,N-dimethylaniline is retarded by zinc dichloride and by maleic anhydride (MAn). The rate of photoinitiated copolymerization of MMA with MAn in acetone is greatly enhanced in the presence of ZnCl₂. The maximum copolymerization rate for a given ZnCl₂ concentration is obtained for 1:1 mole ratio of MMA and MAn in the feed. It was established that ZnCl₂ has no effect on the chemical composition of the MMA/MAn copolymer.     

The terpolymerisation of styrene,methyl methacrylate and maleic anhydride

Application of the Alfrey-Goldfinger equations to data from terpolymerisations of styrene, methyl methacrylate and maleic anhydride leads to values of the relative reactivity (R) of styrene and methyl methacrylate towards the maleic anhydride radical that are dependent upon the concentrations of the monomers in the feeds. It is shown that it is unlikely that this effect arises from the influence of maleic anhydride-comonomer complexes but may indicate the importance of a penultimate group effect involving styryl radicals.     

The mechanism of copolymerization of maleic anhydride with methyl methacrylate and with methyl acrylate

Composition diagrams for the copolymerization of maleic anhydride with methyl methacrylate and with methyl acrylate in ethyl methyl ketone at 50°C were determined using a non-aqueous potentiometric direct titration method. The data were analysed using non-linear least squares minimization procedures to test the applicability of terminal, penultimate and complex models for both systems. In both systems, the penultimate model was an improvement over the terminal model, though the penultimate effect was more pronounced in the methyl methacrylate system. No evidence could be found for complex participation in either system.     

Biological activity of maleic anhydride copolymers. I. Biocompatibility and antitumoural effects of maleic anhydride - vinyl acetate,maleic anhydride - methyl methacrylate and maleic anhydride- styrene copolymers

A series of maleic anhydride (MA)-vinyl acetate (VA), MA-methyl methacrylate (MM), and MA-styrene (S) copolymers were prepared and characterized. On employing various amounts of initiator, maleic anhydride-vinyl acetate, methyl methacrylate, and styrene copolymers with molecular weights ranging between 18000 and 200000 have been obtained. The in vivo and in vitro tests performed on K₅₆₂ cellular cultures (human chronic myeloid leukaemia) have shown that, as a function of the molecular weight, the synthesized copolymers demonstrate a 50% in vitro cytotoxicity and an average tumour regression of maximum 68%.     

Photoinitiation, 6. Copolymerization of styrene with maleic anhydride photoinitiated by the excited charge-transfer complex styrene-maleic anhydride

The kinetics of styrene (St) copolymerization with maleic anhydride (MA) initiated by light (at λ = 365 nm) was studied in acetone, acetonitrile, chloroform, and N,N-dimethyl formamide at 30°C. With the exception of the chloroform containing system, the copolymerizations took place in homogeneous reaction media. The copolymerization rate R_p = ?d([St] + [MA])/dt was found to be a function of the mole ratio of the comonomers in the reaction mixture. For a given ratio of comonomers R_p and the molecular weight of the resulting copolymer were found to be a function of the donor number of the solvent used for a given rate of initiation. Due to the dependence of R_p on the concentration of an equimolar mixture of both comonomers in acetone on [St] (at constant [MA]), and on [MA] (at constant [St]) the participation of the exciplex {St…acetone}^* in the initiation reaction can be expected. The ratio of the overall rate constants for the propagation (k?_p) and termination (k?_t) reactions, k?_p/2k?_t, determined by a rotating sector technique, was found to depend on the composition of the comonomer mixture. The copolymerization rate is proportional to the square root of the intensity of incident light, which, together with the observed inhibition effect of oxygen points to a radical mechanism of the photoinitiated copolymerization of St with MA. In the presence of the photosensitizer benzophenone in the system St/MA/acetone an increase in R_p was observed, accompanied by a decrease in molecular weight of the copolymer in comparison with the system without benzophenone.     

Application of spin trapping technique to radical polymerization, 11. Initiation and propagation mechanisms for alternating copolymerization of styrene with maleic anhydride

The initiation mechanism for spontaneous alternating copolymerization of styrene (St) with maleic anhydride (MAn) was investigated by means of spin trapping technique. using 2-methyl-2-nitrosopropane ( 7 ) as spin trapping agent. By means of ESR spectroscopy of the system St/MAn in ethylbenzene, a cyclic radical ( 13 ), produced via the Diels-Alder intermediate 25 , was detected as its aminyl oxide. A similar radical was also trapped from the system p-methyl-St/MAn and p-dimethylamino-St/MAn. It is formed faster in these systems than in the system St/MAn. In chloroform, however, two types of initiating radicals. 13 and the α-styryl radical ( 15 ), were trapped. This indicates that these radicals are produced via 25 and the charge transfer complex 27 , respectively. From these results an initiation mechanism is proposed. To clarify further the propagation mechanism, the spin trapping technique was applied to the system, which is initiated by tert-butoxyl radical formed from di-tert-butyl peroxalate ( 8 ). The effect of the concentration of 7 on the ESR spectrum of the system St/MAn/ 8 shows that 27 also participates in the propagation of this alternating copolymerization. Finally, the high reactivity of 27 , as compared with free monomers in alternating copolymerization systems, was attempted to be explained on the basis of the Evans-Polanyi theory.     

On the copolymerization of acrylonitrile with styrene in the presence of Lewis acid, 3. Photoinitiated copolymerization

The rate of the acrylonitrile (AN)-styrene (St) copolymerization (R_p) photoinitiated (λ=365 nm) by the St? AN? ZnCl₂ complex at 30°C is proportional to the square root of the intensity of radiation. The limiting viscosity number [η] of alternating copolymers increases with the intensity of radiation. The 1/[η] vs. R_p relationship for the St? AN copolymers is similar as has been found for the initiation of copolymerization by thermal decomposition of 2,2-azoisobutyronitrile. Provided benzophenone combined with 2-propanol is used as a photosensitizer, the rate of the St? AN copolymerization in acetone—at constant concentrations of both comonomers, zinc chloride, and benzophenone—decreases with 2-propanol concentration in the reaction mixture. If benzophenone alone (e.g. without 2-propanol) is used as a photosensitizer under equal conditions, the observed values of the rate of copolymerization are lower in comparison with the system where the ternary molecular complex is empolyed as a photosensitizer. Moreover, R_p decreases with increasing concentration of benzophenone in the system. These findings are interpreted as a result of the termination reactions of ketyl radicals (hydroxydiphenylmethyl radicals) with macroradicals of copolymer.