Studies of Radical Alternating Copolymerization. III. Kinetics of the Copolymerization of Citraconic Anhydride and Vinyl Acetate: A New Method of Evaluating the Kinetics Constant

We show that the copolymerization of citraconic anhydride and vinyl acetate is an alternating one. The two monomers form a charge transfer complex, and we propose a new strategy to determine the value of the velocity constants β₁ = K_AC/K_AD and β₂ = K_DC/K_DA involving the acceptor A, the donor D, and their charge transfer complex C. We obtained β₁ = 9.9 and β₂ = 3.6. The complex exhibits a greater reactivity than the monomer in the propagation reactions.     

Spontaneous Alternating Copolymerization via Zwitterion Intermediates

This article describes a new concept of copolymerization which occurs spontaneously without any added catalyst. A nucleophilic monomer (M_N) combines with an electrophilic one (M_E) to generate a zwitterion ^[+]M_N—M, which is responsible for the initiation and propagation of copolymerization. Twenty-three novel copolymerizations have been explored on the basis of the new concept. M_N monomers which have been investigated are five- and six-membered cyclic imino ethers, dihydro-2(3H)-furanimine, an azetidine, a cyclic phosphinic acid ester and a Schiff base; the M_E monomers include β-propiolactone, a cyclic dicarboxylic acid anhydride, a sultone, acrylic acid, acrylamide, a β-hydroxyalkyl acrylate and ethylenesulfonamide. In most combinations, alternating 1 : 1 copolymers were produced. In addition to the above-mentioned combinations, the alternating 1 : 1 copolymerization of cyclic phosphite with α-keto acid was discovered.     

Alternating Copolymerization of Styrene and N-(4-Bromophenyl)Maleimide

Abstract

Free radical copolymerization of styrene (St) and N(4-bro-mophenyl)maleimide (4BPMI) in dioxane solution gave an alternating copolymer in all proportions of feed comonomer compositions. The monomer reactivity ratios were found to be r ₁, = 0.0218 ± 0.0064 (St) and r ₂, = 0.0232 ± 0.0112 (4BPMI), and the activation energy of the copolymerization reaction for the equimolar ratios of comonomer was E _a, = 51.1 kJ/mol. The molecular weights of the copolymers obtained are relatively high, the T _g's showed similar values (490 K), and the thermal stability is higher than that of polystyrene. The initial rate of copolymerization depends on the total concentration of the comonomers and the maximum occurred at higher 4BPMI mol fractions; however, the overall conversion is highest at equimolar comonomer composition. It has been shown that a charge-transfer complex participates in the process of copolymerization. The initial reaction rate was measured as a function of the monomer molar ratios, and the participation of the charge-transfer complex monomer and the free monomers was quantitatively estimated.     

Copolymerization of methyl vinyl ketone with styrene in the presence of cobalt(II) nitrate

Copolymerization of methyl vinyl ketone (MVK) with styrene was carried out at 50°C in the presence of cobalt(II) nitrate. The resulting monomer reactivity ratios decreased with an increasing concentration of the cobalt salt. This finding suggests that the metal salt participates in the propagation step of the copolymerization. Absolute copolymerization parameters were determined by assuming a three-component system as free MVK (M₁), MVK complexed with cobalt(II) nitrate (M₂), and styrene (M₃): k₁₁/k₁₂ = 0.184, k₁₁/k₁₃ = 0.235, k₂₂/k₂₁ = 7.18 × 10⁻², k₂₂/k₂₃ = 6.79 × 10⁻⁴, k₃₃/k₃₁ = 0.380, and k₃₃/k₃₂ = 2.77 × 10⁻³, and Q₂ = 19.65 and e₂ = 2.83. The complexed MVK monomer is more reactive to the polymer radical with the terminal styrene unit than the free MVK. Very small values for the monomer reactivity ratios, k₂₂/k₂₃ and k₃₃/k₃₂, show the marked alternating tendency for the copolymerization of the complexed monomer with styrene. In practice, however, alternating copolymer could not be obtained because of the poor solubility of cobalt(II) nitrate.     

Donor-Acceptor Complexes in Copolymerization. IV. Alternating Tendency in Free Radical Copolymerization. NMR Analyses of Alternating and Random Copolymers

An NMR investigation was carried out on variable composition, random and equimolar, alternating copolymers of acrylonitrile (A) with styrene (S), isoprene (I), and butadiene (B). The NMR spectra of the SA copolymers contained peaks at 3 τ (aromatic ring protons), 7.2-7.5 τ (CH protons of A), and 8.1 -8.5 τ (CH and CH₂ protons of S and CH₂ protons of A). All NM R peaks of the alternating SA copolymer were shifted to the higher field due to the shielding effect of S. The NMR spectra of the IA copolymers contained peaks at 4.72-4.91 τ (?CH protons of I), 7.27-7.4 τ (CH protons of A), 7.71-7.93 τ (CH₂ protons of I), and 8.35 τ (CH₃ protons of I and CH₂ protons of A). The peaks at 4.72 τ (?CH) and 7.72 τ (CH₂) were assigned to I in the I-A diad and the peaks at 4.91 τ (?CH) and 7.93 τ (CH₂) were assigned to I in the I-I diad. The NMR spectra of the BA copolymers contained peaks at 4.4-4.6 τ (?CH protons of B), 7.2-7.5 τ (CH protons of A), 7.71-7.97 T (CH₂ protons of B), and 8.0-8.4 τ (CH₂ protons of A). The peaks at 4.42 τ (?CH) and 7.71 τ (CH₂) were assigned to B in the B-A diad and the peaks at 4.6 τ (?CH) and 7.9 τ(CH₂) were assigned to B in the B-B diad. The alternating structure of the copolymers prepared through metal halide-activated complexes was confirmed by NMR analysis. The random copolymers prepared by free radical initiation contain a high concentration of alternating sequences, as anticipated from the values of r₁ and r₂ where r₁(S, I, and B) is 6-10 times higher than r₂ (A).     

Mechanism of Donor-Acceptor Alternating Copolymerization

The alternating copolymerization of butadiene and an acrylic compound in the presence of ethyl aluminum dichloride and vanadium oxychloride as complexing agents was studied kinetically for the comparison of two mechanisms, i. e., one involving an intermediate of a ternary complex of butadieneacrylic monomer-EtAIClz and the other without the complex formation. The rate of propagation was found to attain a maximum at a definite monomer composition, and this composition is not varied by changing the amount of EtAICl₂ but decreased with increasing the concentration of total monomer. This fact is explained only by the mechanism of the ternary complex intermediate. In relation to the mechanism, NMR study of the ternary complex, ESR study of the growing radical NMR study of the regularity of the copolymer, and the elementary reaction of the propagation are reviewed with discuss ion.     

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     

Synthesis of Copolymers by Living Carbanionic Alternating Copolymerization

The synthesis and characterization of copolymers from styrene and 1,3‐pentadiene (two isomers) are reported. Styrene/1,3‐pentadiene (1:1) copolymerization with carbanion initiator yield living, well‐defined, alternating (r₁ = 0.037, r₂ = 0.056), and highly stereoregular copolymers with 90%–100% trans‐1,4 units, designed M_ns and low Ð_Ms (1.07–1.17). The first‐order kinetic resolution and NMR spectra demonstrate that the copolymers obtained possess strictly alternating structure containing both 1,4‐ and 4,1‐enchaiments. Also a series of copolymers with varying degrees of alternation are synthesized from para‐alkyl substituted styrene derivatives and 1,3‐pentadiene. The degree of alternation is strongly dependent on the polarity of solvent, reaction temperature, type of trans‐cis isomer of 1,3‐pentadiene and para‐substituted group in styrene. The macro zwitterion forms (SPC) through the distribution of electronic charges from the donor (1,3‐pentadiene) to the acceptor (styrenes) are proposed to interpret the carbanion alternating copolymerization mechanism. Owing to the versatility of the carbanion‐initiating reaction, the present alternating strategy based on 1,3‐pentadiene (especially cis isomer) can serve as a powerful tool for precise control of polymer chain microstructure, architecture, and functionalities in one‐pot polymerization.

     

Radical Copolymerization of Acrylonitrile with Methyl Acrylate Complexed by Zinc Chloride

Abstract

The kinetics of the radical copolymerization of acrylonitrile with methyl acrylate complexed by zinc chloride (ZnCl₂) in dimethylformamide (DMF) was investigated at 60, 65, and 70°C. The kinetic data revealed that R_p was an inverse function of ZnCl₂ concentration and directly related to monomers concentration. The increase in the activation energy from 11.85 to 19.25 kJ·mol^?1 and the decrease in the value of the ratio of the propagation to termination rate constants (k_p ²/k_t ) from 0.08 to 0.06 L·mol^?1·s^?1 on the addition of ZnCl₂ indicated its retarding effect. The chain transfer constant of DMF for the system was 16.25 × 10^?4, accordingly the degree of polymerization decreased. The structure and composition of the copolymers determined by ¹H-NMR and elemental analysis was found to be alternating. The nonideal behavior of the glass transition temperatures determined by DSC also favors the alternation of monomer units in the copolymer. The reaction proceeds via a cross-propagation mechanism.     

Alternating copolymerization of maleic anhydride with allyl chloroacetate

Some regularities of radical alternating copolymerization of maleic anhydride with allyl chloroacetate are studied. The formation of donor–acceptor complexes between comonomers with complexing constant K_c = 0.052 L/mol is found using ¹H NMR spectroscopy. The kinetic parameters for this copolymerization reaction are found and the quantitative contribution of monomer complexes to chain-growth radical reactions is calculated. It is shown that either a “free-monomer” mechanism (dilute solutions) or a “mixed” mechanism (concentrated solutions) prevails for chain growth during radical copolymerization depending on total monomer concentration. It is found that inhibition of degradative chain transfer in the course of the reaction studied takes place owing to the presence of α-chlorine atom in the allyl chloracetate molecule and formation of charge transfer complex.     

Alternating copolymer of butadiene and ethylene. I. Copolymerization by TiCl4–R3Al catalyst systems

Alternating copolymerization of butadiene and ethylene was investigated by the TiCl₄?R₃Al system as catalyst with the use of toluene solutions of monomers of various compositions or by introducing a 1:1 gaseous mixture of both monomers into the reaction system. It was found that the copolymer composition is much influenced by the monomer composition or by the flow rate of monomer. Copolymers containing sequences of alternating monomer arrangement are formed by the polymerization of a monomer mixture having a butadiene: ethylene ratio of 4:1. A suitable catalyst for the alternating copolymerization was found to consist of R₃Al?TiCl₄ at a ratio of 2. The addition of amine was found to modify the catalyst to favor the alternating copolymerization but was accompanied by a decrease in catalyst activity.     

Alternating Ring-Opening Metathesis Copolymerization of Norborn-2-ene with cis-Cyclooctene and Cyclopentene

Ru-alkylidenes based on unsymmetrical imidazolin-2-ylidenes, were used for the alternating copolymerization of norborn-2-ene (NBE) with cis-cyclooctene (COE) and cyclopentene (CPE), respectively. Alternating copolymers, i.e., poly(NBE-alt-COE)_n and poly(NBE-alt-CPE)_n containing up to 97 and 91% alternating diads, respectively, were obtained. The copolymerization parameters of the alternating copolymerization of NBE with CPE under the action of different initiators were determined using a first order Markov model. Hydrogenation of poly(NBE-alt-COE)_n yielded a fully saturated, hydrocarbon-based polymer.     

Copolymerization of 2,3-Dihydropyran and Ethyl Vinyl Ether with Maleic Anhydride

2,3-Dihydropyran (DHP) and ethyl vinyl ether (EVE) were co-polymerized with maleic anhydride (MA) with benzoyl peroxide at 60°C, and 1:1 alternating copolymers were obtained. The rates were maximum at 1:1 monomer composition. Spontaneous copolymerization and solvent effect on the rate were observed in the copolymerization of DHP with MA, in which initial rates were slower in more polar solvents. Participation of charge transfer complex was considered. EVE copolymerized rapidly with MA, reaching the theoretical limiting conversion of 1:1 alternating copolymerization. Although DHP-MA comonomer pair and EVE-MA comonomer pair formed similar 1:1 charge transfer complexes, DHP copolymerized slowly with MA to produce a low molecular weight copolymer, and the limiting conversion was much lower than the theoretical one. To explain these, degradative chain transfer to DHP monomer is proposed as the initial rate of DHP-MA copolymerization is proportional to the initiator concentration to the power 1.1. Q and e values of DHP were calculated to be 0.013 and -0.93, respectively, from the monomer reactivity ratios of copolymerization of DHP with acrylonitrile [r₁ (DHP)=0.003 ± 0.006 and r₂ (AN)=3.6 ± 0.3].     

Metal-Ylide Complex-Initiated Radical Copolymerization of Methylmethacrylate and Styrene

Abstract

Phenacyl dimethylsulfonium ylide complex of mercuric chloride (PDSY-HgCl₂)-initiated radical copolymerization of styrene with methylmethacrylate (MMA) at 85 ± 0.1°C using dioxane as an inert solvent yields random copolymers as evidenced by NMR spectroscopy. The kinetic equation for the present system was R_p α [PDSY-HgCl₂]^0.5 [Sty]^1.0 [MMA]^1.0. The values of energy of activation (ΔE) and k² _p/k₁ were 48.0 kJ mol^?1 and 8.6 × 10^?4 L mol^?1 s^?1, respectively. The mechanism of the reaction has also been proposed for the present system. The properties of copolymer were studied in the form of film. The film was highly absorptive for nitric acid but less absorptive for acetic acid. The film was water impermeable.     

Copolymerization of methyl 2-acetamidoacrylate and styrene in the presence of stannic chloride

Continuous variation method in UV revealed that methyl N-acetylaminoacrylate (MNA) and SnCl₄ formed the 1:1 complex. The copolymerization of MNA with styrene in tetrahydrofuran was carried out at 50 °C in the presence of SnCl₄. The resulting monomer reactivity ratios decreased with an increasing concentration of SnCl₄ added. This finding suggests that SnCl₄ participates in the propagation step of the copolymerization. Therefore, the copolymerization was analyzed by assuming terpolymerization of free MNA (M₁), complexed MNA (M₂), and styrene (M₃). The absolute copolymerization parameters were obtained as follows: k₁₁/k₁₂=0.165, k₁₁/k₁₃=3.04, k₂₂/k₂₁=0.32, k₂₂/k₂₃=0.103, k₃₃/k₃₁=0.058, k₃₃/k₃₂=0.001, Q₁=6.03, e₁=0.52, Q₂=88.57, and e₂=2.23. The complexed MNA is more reactive to polymer radicals with free MNA and styrene as the terminal unit than the free MNA. Very small values of k₂₂/k₂₃ and k₃₃/k₃₂ suggests that the copolymerization of the complexed MNA and styrene proceeds alternatingly.     

Alternating copolymerization of carbon dioxide and epoxide catalyzed by an aluminum Schiff base–ammonium salt system

The alternating copolymerization of carbon dioxide (CO₂) and cyclohexene oxide (CHO) with an aluminum Schiff base complex in conjunction with an appropriate additive as a novel initiator is demonstrated. A typical example is the copolymerization of CO₂ and CHO with the (Salophen)AlMe ( 1a )–tetraethylammonium acetate (Et₄NOAc) system. When a mixture of the 1a –Et₄NOAc system and CHO was pressurized by CO₂ (50 atm) at 80 °C in CH₂Cl₂, the copolymerization of CO₂ and CHO took place smoothly and produced a high polymer yield in 24 h. From the IR and NMR spectra, the product was characterized to be a copolymer of CO₂ and CHO with an almost perfect alternating structure. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis indicated that an unfavorable reaction between Et₄NOAc and CH₂Cl₂ and a possible chain‐transfer reaction with concomitant water occurred, and this resulted in the bimodal distribution of the obtained copolymer. With carefully predried reagents and apparatus, the alternating copolymerization in toluene gave a copolymer with a unimodal and narrower molecular weight distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4172–4186, 2005     

Chemoselective Alternating Copolymerization of Limonene Dioxide and Carbon Dioxide: A New Highly Functional Aliphatic Epoxy Polycarbonate

The alternating copolymerization of biorenewable limonene dioxide with carbon dioxide (CO₂) catalyzed by a zinc β‐diiminate complex is reported. The chemoselective reaction results in linear amorphous polycarbonates that carry pendent methyloxiranes and exhibit glass transition temperatures (T_g) up to 135 °C. These polycarbonates can be efficiently modified by thiols or carboxylic acids in combination with lithium hydroxide or tetrabutylphosphonium bromide as catalysts, respectively, without destruction of the main chain. Moreover, polycarbonates bearing pendent cyclic carbonates can be quantitatively prepared by CO₂ insertion catalyzed by lithium bromide.     

Alternating Copolymerization of Propylene Oxide with Biorenewable Terpene‐Based Cyclic Anhydrides: A Sustainable Route to Aliphatic Polyesters with High Glass Transition Temperatures

The alternating copolymerization of propylene oxide with terpene‐based cyclic anhydrides catalyzed by chromium, cobalt, and aluminum salen complexes is reported. The use of the Diels–Alder adduct of α‐terpinene and maleic anhydride as the cyclic anhydride comonomer results in amorphous polyesters that exhibit glass transition temperatures (T_g) of up to 109 °C. The polymerization conditions and choice of catalyst have a dramatic impact on the molecular weight distribution, the relative stereochemistry of the diester units along the polymer chain, and ultimately the T_g of the resulting polymer. The aluminum salen complex exhibits exceptional selectivity for copolymerization without transesterification or epimerization side reactions. The resulting polyesters are highly alternating and have high molecular weights and narrow polydispersities.     

Mechanism of Alternating Copolymerization of Vinyl Acetate and Maleic Anhydride

Vinyl acetate and maleic anhydride are known to give 1:1 alternating copolymerization regardless of the monomer feed composition. The existence of a charge transfer complex between the comonomers has been shown and its equilibrium constant determined.

The mechanism has been discussed, starting from a study of the copolymerization rate when varying the solvent, the temperature, and the concentration of comonomers.