Solvent and kinetic penultimate unit effects in the copolymerization of acrylonitrile with itaconic acid

Copolymerization of acrylonitrile (AN) with itaconic acid (IA) in dimethylformamide (DMF) and DMF/water mixture was investigated at enhanced concentrations of the latter. Analysis of the copolymer composition revealed the existence of a marked penultimate unit effect with respect to radicals terminated in AN. The reactivity of IA was considerably less than that of AN, manifested as a negative reactivity ratio for the former. The r_IA values ranging from −0.28 to −0.50 and r_AN values ranging from 0.53 to 0.70, were obtained by Kelen-Tudo's (KT) and extended KT methods. The penultimate reactivity ratios were determined by both linear and non-linear methods. The values ranged from r₁=0.009 to 0.01, r₁^′=0.0015 to 0.0043, r₂=0.54 to 0.69 and r₂^′=0.9 to 1.03. The reactivity of AN radical towards IA decreased about twofold when the latter formed the penultimate group. The penultimate model explained an acceptable rational feed-copolymer composition profile for the whole composition range. Addition of water decreased the reactivity of IA slightly. IA caused a decrease in the apparent copolymerization rate in agreement with the observed trends in the reactivity ratios; presence of water caused a further decrease in the rate of polymerization. A statistical prediction of monomer sequences based on reactivity ratios implied that IA existed as a lone monomer unit between the long sequences of AN units.     

Terminal and Penultimate Reactivity Ratios in the Styrene-Acrylonitrile Free-Radical Copolymerization System in Bulk

ABSTRACT

The terminal and penultimate model reactivity ratios for the styrene-acrylonitrile monomer system in bulk have been investigated by the simplex and scanning method. It has been shown that Mayo-Lewis equation has an unique solution when determining the reactivity ratios according to the terminal model while for the penultimate model the non-uniqueness in determination of the reactivity ratios has been found. The numerical values of the penultimate r-parameters calculated with the simplex method depend on the initial guess for r-parameters.

Several sets of penultimate reactivity ratios for the styrene-acrylonitrile system in bulk have been found to be equal from mathematical point of view. The reactivity ratios with comparable standard deviation have an equivalent graphical representation on the copolymerization diagragm. It has been also confirmed that the penultimate model is a more appropriate of the models considered to describe the variation of the copolymer composition with the monomer feed. Taking into account previous results for the styrene-methyl methacrylate system in bulk it is thereby assumed that the occurrence non-uniqueness in determination of the penultimate model reactivity ratios does not depend on the monomer system.     

Application of the monomer reactivity ratios to the kinetic‐model discrimination and the solvent‐effect determination for the styrene/acrylonitrile monomer system

The impact of reactivity ratios determined with the Nelder and Mead simplex method on the kinetic‐model discrimination and the solvent‐effect determination for the styrene/acrylonitrile monomer system was investigated. For the monomer system, the penultimate unit effect was inversely proportional to the polarity of the solvent: acetonitrile < N,N‐dimethylformamide < methyl ethyl ketone < toluene. Quantitatively, the penultimate unit effect could be correlated with an absolute value of the difference between the standard deviation of the reactivity ratios determined for the terminal and penultimate models. By application of the F test, the penultimate model was justified for copolymerization in toluene. The conclusion was less certain for polymerization in methyl ethyl ketone. With a scanning procedure based on the simplex method, it was found that an equivalent representation of the copolymer‐composition data could be achieved with multiple sets of penultimate‐model reactivity ratios. However, the relationship between the triad‐sequence distribution and copolymer composition depended on the reactivity‐ratio set chosen for the microstructure determination. The microstructure calculated with the penultimate‐model reactivity ratios determined with the simplex method from the initial guess (r₁₁ = r₁, r₂₁ = 1/r₂, r₂₂ = r₂, r₁₂ = 1/r₁) did not obey the general “bootstrap effect” rule. This observation still requires some theoretical interpretation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 846–854, 2000     

Fortran IV programs for the penultimate copolymerization model

Three programs have been written for calculations involving use of the penultimate copolymerization model. The first computes the penultimate reactivity ratios from composition-conversion data, without constraints, at any conversion. A nonlinear leastsquares technique using Marquardt's algorithm is employed. The second program computes the four optimum starting monomer feed ratios, M₁⁰/M₂⁰ which should be used by the experimenter from the penultimate reactivity ratios. These optimum feed ratios are obtained by choosing the conditions necessary to minimize the determinant of the variance-covariance matrix. The input for the first program includes estimates of known values of the penultimate reactivity ratios. By using these two programs sequentially the experimenter has an optimized experimental approach toward evaluating penultimate reactivity ratios at any conversion. Finally, a program has been provided to calculate composition–conversion data, given penultimate reactivity ratios.     

Copolymerization and Copolymers of 2,4,5-Tribromostyrene with Styrene and Acrylonitrile

Abstract

2,4,5-Tribromostyrene (TBSt) was copolymerized with styrene (St) or acrylonitrile (AN) in toluene solution using 2,2′-azobisisobutyronitrile as free radical initiator. The copolymerization reactivity ratios were found to be for the system TBSt/St r ₁ = 1.035 ± 0.164 (TBSt) and r ₂ = 0.150 ± 0.057 (St), and for the system TBSt/AN r ₁ = 2.445 ± 0.270 (TBSt) and r ₂ = 0.133 ± 0.054 (AN). The e and Q values were also calculated. The initial copolymerization rate, R _p, for both systems linearly increases as the content of TBSt in the monomer mixture increases. However, these values are somewhat higher when AN was used as a comonomer. A similar behavior has also been established for the course of the copolymerization reactions to high conversion. The resulting copolymers and TBSt-homopolymer show similar thermal stabilities of polystyrene. However, the glass transition temperature increases markedly with increasing TBSt content.     

Styrene—Acrylonitrile Copolymerization: Effect of Remote Units on the Reactivity of the Styrene-Ended Radicals

Application of the gas-liquid chromatographic method to the analysis of the process of styrene-acrylonitrile radical copolymerization, especially with a monomer mixture rich in styrene, provided evidence for penultimate and antepenultimate effects. Methods are given for the determination of the corresponding reactivity ratios:

r _A ≈ 0, r _AS = 0.55, r _ASS = 0.50, r _SSS = 0.25     

N-vinylpyrrolidone and 4-vinyl Benzylchloride Copolymers: Synthesis,Characterization and Reactivity Ratios

The copolymers prepared in this study by free radical copolymerization of N-vinylpyrrolidone (M ₂) with 4-vinylbenzylchloride (M ₁) using 2,2′-azobisisobutyronotrile (AIBN) initiator in 1,4-dioxane solvent at 70°C were characterized by FTIR, ¹H-NMR and ¹³C-NMR techniques. Polymer solubility was tested in both polar and nonpolar solvents. The thermal properties were studied by thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). Copolymer compositions were established by H¹-NMR spectra, while reactivity ratios of the monomers were computed using the linearization methods viz., Fineman-Ross (FR) (r ₁ = 1.67 and r ₂ = 0.67), Kelen-Tudos (KT) (r ₁ = 1.77 and r ₂ = 0.65) and extended Kelen-Tudos (EK-T) (r ₁ = 1.72 and r ₂ = 0.63) methods at lower conversion. Furthermore, reactivity ratios in nonlinear error-in-variables method (RREVM) also compute the reactivity ratios (r ₁ = 1.76 and r ₂ = 0.66); these are found to be in good agreement with each other. The distribution of monomer sequence along the copolymer chain was calculated using a statistical method based on the calculated reactivity ratios.     

Reactivity ratios for copolymerization of vinyl chloride with 2-methylpentyl vinyl brassylate by computerized linearization

A computerized version of the Fineman-Ross linearization procedure was used to determine reactivity ratios for copolymerization of vinyl chloride (monomer 1) and 2-methylpentyl vinyl brassylate (monomer 2). From differential refractometry data for the products of low-conversion copolymerization, the procedure gave r₁ = 1.06 and r₂ = 0.234. The ratios computed from chlorine contents of the same products were r₁ = 1.10 and r₂ = 0.239. The polarity factor (e₂) and general monomer reactivity (Q₂) calculated for monomer 2 from these ratios were, respectively, ?0.95 to ?0.98 and 0.032–0.033. The interquartile range for the copolymerization of a mixture of 60% monomer 1 and 40% monomer 2 was 1.4%. These values suggest that from suitable proportions of reactants, sufficiently homogeneous distribution of monomers can be achieved in copolymers of vinyl chloride and 2-methylpentyl vinyl brassylate to offer the possibility of effective internal plasticization.     

Radical copolymerization of acrylonitrile with 2,2,2‐trifluoroethyl acrylate for dielectric materials: Structure and characterization

Radical copolymerization based on acrylonitrile (AN) and 2,2,2‐Trifluoroethyl acrylate (ATRIF) initited by AIBN was investigated in acetonitrile solution. The resulting poly(AN‐co‐ATRIF) copolymers were characterized by ¹H, ¹³C, and ¹⁹F NMR and IR spectroscopy, and size exclusion chromatography (SEC). Their compositions were assessed by ¹H NMR. The kinetics of radical copolymerization of AN with ATRIF was investigated from sereval experiments achieved at 70 °C from initial [AN]₀/[ATRIF]₀ molar ratios ranging between 20/80 and 80/20 and was enabled to determine the reactivity ratios of both comonomers. From the monomer—polymer copolymerization curve, the Fineman–Ross and Kelen–Tüdos laws enabled to assess the reactivity ratios (r_AN= r₁ = 1.25 ± 0.04 and r_ATRIF = r₂ = 0.93 ± 0.05 at 70 °C) while the revised patterns scheme led to r₁₂ = r_AN = 1.03, and r₂₁ = r_ATRIF = 0.78 at 70 °C. In all cases, r_AN x r_ATRIF product was close to unity, which indicates that poly(AN‐co‐ATRIF) copolymers exhibit a random structure. This was also confirmed by the Igarashi's and Pyun's laws which revealed the presence of AN‐ATRIF, AN‐AN, and ATRIF‐ATRIF dyads. The Q and e values for ATRIF were also assessed (Q₂ = 0.62 and e₂ = 0.93). The glass transition temperature values, T_g, of these copolymers increased from 17 to 61 °C as the molar percentage of ATRIF decreased from 77 to 16% in the copolymer. Thermogravimetry analysis of poly(AN‐co‐ATRIF) copolymers showed a good thermal stability compared to that of poly(ATRIF) homopolymer due to incorporation of AN comonomer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3856–3866     

Non-uniqueness in determination of terminal and penultimate model reactivity ratios in the styrene-methyl methacrylate free-radical copolymerization system

The terminal and penultimate model reactivity ratios in the free-radical copolymerization of styrene and methyl methacrylate in bulk at 40°C were calculated by means of the simplex and scanning methods. Calculations showed that for the terminal model r₁ and r₂ vary in comparatively narrow ranges of 0.548–0.552 and 0.480–0.483, respectively. For the penultimate model, the most accurate reactivity ratios calculated by the simplex method, which were r₁₁ = 0.727, r₂₂ = 0.490, r₂₁ = 2.890, r₁₂ = 4.583, are surrounded with sets of reactivity ratio values of equal accuracy. The ranges of variation were found to be 0.711–0.746, 0.487–0.492, 2.810–2.970 and 4.213–5.049, respectively. Numerical values of the penultimate r-parameters calculated with the simplex method depend, due to the structure of the multidimensional space (r₁₁, r₂₂, r₂₁, r₁₂, σ), on the initial guess for the r-parameters. Use of the covariance matrix for the estimation of the indetermination ranges is discussed.     

Copolymerization of Diethyl Vinyl Phosphate with Vinyl Acetate and Acrylonitrile

Free radical-initiated copolymerization of diethyl vinyl phosphate (DEVPA) with vinyl acetate (VAc) and acrylonitrile (AN) was studied. The monomer reactivity ratios for the monomer pairs, determined at 60°C using benzoyl peroxide as an initiator, are: r₁(VAc) = 0.95, r₂(DEVPA) = 0.93; r₁(AN) = 6.6, r₂(DEVPA) = 0.049. The values of the Alfrey-Price constants, Q and e, for DEVPA were calculated to be 0.025 and 0.13, respectively, from the VAc system, and 0.026 and 0.14, respectively, from the AN/DEVPA pair. These results indicate that the general reactivity of DEVPA is almost the same as that of VAc and that the diethylphosphate group is a stronger electron-attracting group than the acetoxy group. The intrinsic viscosity and number-average molecular weight of copolymers decreased as their content of DEVPA units increased, indicating a high degree of chain transfer caused by DEVPA.     

Silyl enol ethers as monomer. III. Radical polymerization and copolymerizations of 2-trimethylsilyloxy-1,3-butadiene and desilylation of the resulting polymers

2-Trimethylsilyloxy-1,3-butadiene (TMSBD), the silyl enol ether of methyl vinyl ketone, was homopolymerized with a radical initiator to afford polymers with a molecular weight of ca. 10⁴. Radical copolymerizations of TMSBD with styrene (ST) and acrylonitrile (AN) in bulk or dioxane at 60°C gave the following monomer reactivity ratios: r₁ = 0.64 and r₂ = 1.20 for the ST (M₁)–TMSBD (M₂) system and r₁ = 0.036 and r₂ = 0.065 for the AN (M₁)–TMSBD (M₂) system. The Q and e values of TMSBD determined from the reactivity ratios for the former copolymerization system were 2.34 and ?1.31, respectively. The resulting polymer and copolymers were readily desilylated with hydrochloric acid or tetrabutylammonium fluoride as catalyst to yield analogous polymers having carbonyl groups in the polymer chains.     

Effects of temperature on styrene–methacrylonitrile copolymerization

The free-radical copolymerization of styrene and methacrylonitrile was studied in toluene solution at 60, 90, and 120°C. Copolymer composition was estimated from gas-chromatographic measurement of unreacted monomer concentrations. Reactions were carried to about 20% conversion to minimize analytical errors. Reactivity ratios were calculated by using an integrated form of the Mayo-Lewis simple copolymerization equation. Reactivity ratios were not sensitive to reaction temperature. The values at 90°C are r₁ = 0.41 (methacrylonitrile) and r₂ = 0.37 (styrene). The r₁ values are higher than those reported by other workers, presumably because of advantages in the present analytical technique and calculation method. The negligible temperature dependence of reactivity ratios is in accord with theory. If monomer pairs exhibit pronounced dependence of reactivity ratios on polymerization temperature, this may indicate a change in mode of placement of units in the polymer chain.     

Effect of reaction medium on copolymerization of acrylonitrile and methyl acrylate

The copolymerization of acrylonitrile (AN) with methyl acrylate (MEA) has been investigated in three types of polymerization, i.e., emulsion polymerization in water with a water-soluble initiator, suspension polymerization in water with an oil-soluble and water-insoluble initiator, and solution polymerization in dimethyl sulfoxide (DMSO). Monomer reactivity ratios at 50°C. for AN and MEA are found to be r₁ = 0.78 ± 0.02, r₂ = 1.04 ± 0.02 in emulsion polymerization; r₁ = 1.02 ± 0.02, r₂ = 0.70 ± 0.02 in DMSO solution polymerization; r₁ = 0.75 ± 0.05, r₂ = 1.54 ± 0.05 in suspension polymerization. The large differences found in the reactivity ratios may be attributed to the different ratio of concentration of two monomers in the loci of polymerization. Chemically, AN is somewhat more reactive than MEA as shown by the reactivity ratios in DMSO. In the case of the suspension polymerization, the MEA/AN ratio in the polymer particles in which polymerization occurs may be higher than that in the total phase. Experimental results of the emulsion polymerization show that the emulsion polymerization of AN occurs both in the particles and in water. In addition, rates of the copolymerization of AN with MEA have also been investigated.     

Free Radical Copolymerization of N‐Cyclohexylmaleimide with Cyclohexene

The radical copolymerization of cyclohexene (M₁) and N‐cyclohexylmaleimide (M₂) was carried out with 2,2′‐azobis(isobutyronitrile) as an initiator in various solvents at 55°C. The copolymerization of cyclohexene with N‐cyclohexylmaleimide in chloroform, dioxane and benzene proceeded in a homogeneous system to give an alternating copolymer when the monomer of cyclohexene was over 40 mol% in the feed. It was found that the initial rate of the copolymerization (R_p), as well as the number‐average molecular weight of copolymers, were dependent on the monomer composition and was at maximum at about 30 mol% of cyclohexene in the feed. The effects of solvents on the R_p and reactivity ratios were also investigated in this copolymerization system. The copolymerization in dioxane produced a higher R_p than that in chloroform and benzene, and the monomer reactivity ratios were found to be r₁=0, r₂=0.032 in chloroform; r₁=0, r₂=0.065 in benzene and r₁=0, r₂=0.14 in dioxane, respectively.     

Reversible addition-fragmentation chain transfer radical copolymerization of β-pinene and methyl acrylate

The feasibility of radical copolymerization of β-pinene and methyl acrylate (MA) was clarified for the first time. The monomer reactivity ratios were evaluated by Fineman-Ross, Kelen-Tudos and non-linear methods, respectively. The obtained values were r_β-pinene ∼ 0 and r_MA ∼ 1.3, indicating that the copolymerization led to polymers rich in methyl acrylate units and randomly alternated by single β-pinene unit. The addition of Lewis acid Et₂AlCl to the AIBN-initiated copolymerization enhanced the incorporation of β-pinene. Furthermore, the possible controlled copolymerization of β-pinene and MA was then attempted via the reversible addition-fragmentation transfer (RAFT) technique. The copolymerization (f_β-pinene = 0.1) using 1-methoxycarbonyl ethyl dithiobenzoate (MEDB) as a RAFT agent gave copolymers with lower molecular weight and narrower molecular weight distribution. However, the presence of MEDB strongly retarded the copolymerization. Thus a new RAFT agent 1-methoxycarbonyl ethyl phenyldithioacetate (MEPD), which gives a less stable macroradical intermediate than MEDB, was synthesized and introduced to the copolymerization. As anticipated, a much smaller retardation was observed. Moreover, the copolymerization displayed a somewhat controlled features within a certain overall conversion (<∼40%).     

Radical copolymerization of crotonyl compounds with styrene

The monomer reactivity ratios for the radical copolymerization of crotononitrile (CN), methyl crotonate (MC), and n-propenyl methyl ketone (PMK) with styrene (St) were measured at 60°C. in benzene and little penultimate unit effect was shown for these systems. The values obtained were: St–CN, r₁ = 24.0, r₂ = 0; St–MC, r₁ = 26.0, r₂ = 0.01; St–PMK, r₁ = 13.7, r₂ = 0.01. The rate of copolymerization and the viscosity of the copolymer decreased markedly as the molar fraction of the crotonyl compound in the monomer mixture increased. The Q–e values were also calculated to be as follows: CN, e = 1.13, Q = 0.009; MC, e = 0.36, Q = 0.015; PMK, e = 0.61, Q = 0.024. A linear relationship was obtained between the e values of the crotonyl compounds and their Hammett constants σ_m.     

二乙基二烯丙基氯化铵均聚及其与丙烯酰胺或丙烯酸共聚动力学研究

采用膨胀计法研究了以过硫酸铵为引发剂,二乙基二烯丙基氯化铵(DEDAAC)在水溶液中的均聚及其与丙烯酰胺(AM)和丙烯酸(AA)共聚动力学,测定了相应的聚合表观活化能;采用元素分析法测定了DEDAAC分别与AM和AA在低转化率下共聚物的组成,并采用氯离子选择性电极法测定了DEDAAC-AM共聚物中的氯离子含量,按Kelen-Tudos方法求得了相应的竞聚率.结果表明,DEDAAC均聚速率方程为RP=k[M]0.99[I]0.76,表观活化能Ea=77.00kJ/mol,说明链终止为单基终止和双基终止并存,引发过程与单体浓度无关;DEDAAC与AM在摩尔比为4∶1时,共聚动力学方程为RP=[M]2.53[I]0.90,表观活化能Ea=67.06kJ/mol,单体竞聚率为rDE=0.31±0.02、rAM=5.27±0.53;DEDAAC与AA在摩尔比为4∶1时,共聚动力学方程为RP=k[M]2.94[I]0.83,表观活化能Ea=70.07kJ/mol,竞聚率为rDE=0.28±0.03、rAA=5.15±0.28;DEDAAC与AM和AA等共聚为非理想共聚,得到的产物均为无规共聚物.