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).     

Vinylhydroquinone. III. Copolymerization of vinylhydroquinone and vinyl monomers by tri-n-butylborane

The copolymerization of vinylhydroquinone (VHQ) and vinyl monomers, e.g., methyl methacrylate (MMA), 4-vinyl-pyridine (4VP), acrylamide (AA), and vinyl acetate (VAc), by tri-n-butylborane (TBB) was investigated in cyclohexanone at 30°C under nitrogen. VHQ is assumed to copolymerize with MMA, 4VP, and AA by vinyl polymerization. The following monomer reactivity ratios were obtained (VHQ = M₂): for MMA/VHQ/TBB, r₁ = 0.62, r₂ = 0.17; for 4VP/VHQ/TBB, r₁ = 0.57, r₂ = 0.05; for AA/VHQ/TBB, r₁ = 0.35, r₂ = 0.08. The Q and e values of VHQ were estimated on the basis of these reactivity ratios as Q = 1.4 and e = ?;1.1, which are similar to those of styrene. This suggests that VHQ behaves like styrene rather than as an inhibitor in the TBB-initiated copolymerization. No homopolymerization was observed either under nitrogen or in the presence of oxygen. The reaction mechanism is discussed.     

Copolymerization of Vinyl Chloride and Sulfur Dioxide. II. Copolymerization Rates and Copolymer Compositions

The rate of copolymerization of vinyl chloride (VC) with sulfur dioxide and the composition of the poly (vinyl chloride sulfone) formed have been measured for comonomer liquid mixtures with X_VC = 0.1 to 1.0 and over the temperature range -95 to +46°C.

Polymerization was initiated by γ-irradiation (-95 to +46°C) and with the t-butyl hydroperoxide/SO₂/methanol redox system (-95 to -18°C). The copolymerization rates and copolymer compositions indicated two distinct temperature regions, with a change in mechanism around 0°C. For radiation initiation below 0°C, the rate versus comonomer composition relationship showed a maximum at an x_VC value which increased with increasing temperature. Above 0°C, the rate decreased with increasing temperature and was greatly retarded by SO₂. No high molecular weight copolymer or VC homopolymer was formed on irradiation of comonomer mixtures above ～55°C.     

Synthesis of Graft Polymers by Copolymerization of Macromonomers. II. Copolymerization Kinetics of Styrene-and Methacrylate-Terminatedpoly(2-Acetoxyethyl Methacrylate) Macromonomers

Styrene-terminated poly(2-acetoxyethyl methacrylate) macromonomer (EBA), methacrylate-terminated poly(2-acetoxyethyl methacrylate) macromonomer (MPA), and methacrylate-terminated poly(methyl methacrylate) macromonomer (MPM) were synthesized and subjected to polymerization and copolymerization by a free-radical polymerization initiator (AIBN). EBA and MPA were homopolymerized at various concentrations. EBA exhibited higher reactivity than styrene. The reactivity of MPA, however, was almost equal to that of glycidyl methacrylate. Cumulative copolymer compositions were determined by GPC analysis of copolymerization products. The reactivity ratios estimated were r_a = 0.95 and r_b , = 0.90 for EBA macromonomer (a)-methyl methacrylate (b) copolymerization. These values were not consistent with literature values for the styrene-methyl methacrylate and p-methoxy-styrene-methyl methacrylate systems. The reactivity ratios estimated for MPA and 2-bromoethyl methacrylate were r_a - 0.95 and r_b , = 0.98; equal to the glycidyl methacrylate-2-bromoethyl methacrylate system. MPA or MPM was also copolymerized with styrene, and the reactivity ratios were r_a = 0.40, r_a = 0.60 and r_a = 0.39, r_a = 0.58, respectively. These estimates were in good agreement with the reactivity ratios for glycidyl methacrylate and styrene. Thus, no effect of molecular weight was observed for both copolymerization systems.     

Copolymerization of Vinyl Chloride and Sulfur Dioxide. III. Evaluation of the Copolymerization Mechanism

The mechanism of copolymerization of vinyl chloride (V) with sulfur dioxide (S) to form a variable composition polysulfone with average V:S molar ratio n ≥ 1 is examined. The copolymerization deviates from Lewis-Mayo behavior above -78°C. Alternative models for propagation involving (1) penultimate and pen-penultimate unit effects, (2) complex participation, and (3) depropagation are considered quantitatively by comparison of calculated and experimental copolymer/comonomer composition relationships and comonomer sequence distributions. Our theoretical modeling of the copolymerization shows that it is difficult to discriminate convincingly between alternative mechanisms. The penultimate and pen-penultimate effect models can account for the copolymer compositions, but not for the dilution effects which were observed provided the diluent is truly inert. The complex participation model can account for experimental behavior from -78 to -18°C by the assumption of addition of SV complexes, but it becomes rapidly less satisfactory at higher temperatures. Depropagation is the only model which can account for the compositions and dilution effects above 0°C. Progressive depropagation, with increasing temperature, of chains ending in the triad sequences ～SVS?, ～VVS?, and ～VSV? can explain the observed behavior over the entire comonomer composition and temperature range, but involvement of comonomer complexes in the propagation reactions is highly likely below 0°C.     

Radiation-Induced Copolymerization of Tetrafluoroethylene and Propylene. 2. Copolymerization in Solution

Copolymerization of tetrafluoroethylene and propylene in chlorofluorohydrocarbon solvents was carried out below room temperature with γ-rays from a ⁶⁰Co source. A remarkable rate-accerelating effect was observed in these solution systems, although the activation energies and the compositions of copolymers were almost the same as those in bulk system. The most effective solvent was found to be trichlorotrifluoroethane. Kinetic results of the copolymerization in trichlorotrifluoroethane solution system revealed the role of solvent to be complicated, with the possibility of affecting almost all reaction steps of the polymerization.     

Vinyl Chloride Copolymerization. Penultimate Effects with Conjugated Comonomer

A kinetic study of the radical copolymerization of vinyl chloride with acrylonitrile, methyl methacrylate, or styrene, using the chromatographic method, shows that penultimate effects are observed in all cases, chiefly for the acrylonitrile case (r_cc = 0.03, r_ac = 3.0). The conjugated monomer induces a stronger penultimate effect than the unconjugated vinyl chloride; this effect might be correlated with the e values of the Q-e scheme. A strong antepenultimate effect is observed on the styrene ended radicals (r_sss = 3.0, r_css = 20.0, r_scs = 18.5, r_ccs = 2.7), which might be related to a steric effect.     

Copolymerization of vinylsilanes with styrene

New vinylsilanes (M₂), i. e. phenylvinylsilane (I), allylmethylsilane (II), allylphenylsilane (III), and p-vinylphenylmethylsilane (IV), were prepared and copolymerized with styrene (M₁). The monomer reactivity ratios were r₁ = 5.7 and r₂ = 0, r₁ = 36 and r₂ = 0, r₁ = 29 and r₂ = 0₁, and r₁ = 0.91 and r₂ = 1.1, respectively. From the results of infrared and NMR spectra it was indicated that the vinylsilanes participated in copolymerization in the form of a vinyl type of polymerization and not in the form of a hydrogen-transfer type of polymerization. The reaction of copolymer with alcohols and methyl methacrylate and appropriate catalysts was investigated.     

Donor-Acceptor Complexes in Copolymerization. LIX. Alternating Diene-Dienophile Copolymers. 13. Copolymerization of Dicyclopentadiene and Maleic Anhydride

The solution and bulk copolymerization of dicyclopentadiene (DCP) and maleic anhydride (MAH) occurs over the temperature range 80–240°C, upon the addition of a free-radical catalyst which has a short half-life at the reaction temperature. An unsaturated 1/1 MAH/DCP copolymer, derived from the copolymerization of MAH with the norbornene double bond, followed by a Wagner-Meerwein rearrangement, is obtained in the presence of a large excess of DCP at 80° C, while a saturated 2/1 MAH/ DCP copolymer, derived from the cyclocopolymerization of the residual cyclopentene unsaturation, is obtained at higher temperatures or in the presence of excess MAH. The copolymers prepared under other conditions with intermediate MAH/DCP mole ratios contain both 1/1 and 2/1 repeating units. The copolymer obtained from bulk copolymerization above 170° C contains units derived from cyclopentadiene-MAH cyclocopolymerization as well as DCP-MAH copolymerization.     

Copolymerization of acrylonitrile. III. Copolymerization with α-cyanocinnamamide

Acrylonitrile was copolymerized in solution with α-cyanocinnamamide up to low conversions. The conventional scheme of copolymerization fitted this copolymer. The basic properties, such as solubility, viscosity, and thermal behavior, of the copolymer prepared in bulk and in solution were determined.     

Copolymerization of styrene. V. Copolymerization with α-cyanocinnamamide

Copolymers of styrene with α-cyanocinnamamide were prepared by free radical initiation in bulk and in DMF solution and also by thermal initiation in bulk. The copolymerization parameters were determined by the conventional scheme of copolymerization and by an improved scheme taking into account the penultimate unit. Different values of the copolymerization parameters were obtained at the above mentioned different polymerization conditions, indicating the existence of a solvent effect. The influence of the comonomer on some of the basic properties, like intrinsic viscosity, solubility, melting range, and glass transition temperature and on some mechanical and behavior properties of the copolymers was studied in comparison with homopolystyrene.     

Kinetics of Free Radical Copolymerization. V. Copolymerization of Ethyl Acrylate with Styrene. Composition of Copolymers

The composition of copolymers formed at 50°C in ethyl acrylate/ styrene/azo-bis-isobutyronitrile/benzene systems of different composition was investigated. The experimental composition data (based on the elementary analysis of copolymers) were evaluated by the η-ζ transformation method. Finite monomer conversions were taken into account. The classical composition equation was found to describe the system under investigation. The reactivity ratios are p ₁ = 0.152 ± 0.006; p ₂ = 0.787 ± 0.023. The free radical copolymerization of ethyl acrylate and styrene has been investigated in benzene solution at 50°C. Our results on the initiation kinetics were disclosed in our recent publication [1]. Now we are reporting on our studies concerning the composition of ethyl acrylate/styrene copolymers.     

Kinetics of Radical Copolymerization. XV. Absolute Rate Constants in the Copolymerization System Styrene-Ethyl Acrylate-Benzene

Abstract

With the use of rate data of the system St-EA-AIBN-Bz-50°C measured earlier, the parameters of the rate equation derived in terms of the hot radical theory were determined. The reason for the reevaluation of experimental data was that the absolute values of propagation and termination rate constants could be determined in the homopolymerization of both monomers with the improved rotating sector method elaborated for nonsteady-state kinetic investigations. This enabled us to determine the rate constants of the elementary reactions and deactivation parameters (γ₁₂ and γ₂₁) of the copolymerization. The rate data calculated with the new parameter set are in good agreement with the measured ones, proving the applicability of the hot radical theory. The results are represented by a steric coordination system in order to call attention to the importance of the simultaneous study of composition-and dilution-dependence in copolymerization.     

Donor-Acceptor Complexes in Copolymerization. III. Conjugated Diene-Acrylonitrile Copolymerization in the Presence of Metal Halides

The copolymerization of isoprene or butadiene with acrylonitrile in the presence of zinc chloride or ethylaluminum sesquichloride, in the presence or absence of a free radical catalyst, at 30-70°C yields an equimolar, diene-acrylonitrile alternating copolymer containing more than 90% trans-1,4 unsaturation, irrespective of monomer charge. The copolymer results from the homopolymerization of a diene-acrylonitrile…metal halide transoid charge transfer complex. When ZnCl₂ is the electron-accepting metal halide and the polymerization is carried out at temperatures of 50°C and higher or to high conversions, the equimolar copolymer is accompanied by a high acrylonitrile polymer, and in the presence of a radical catalyst, by a normal radical copolymer. In the presence of the organoaluminum halide and in the absence of a radical catalyst, the alternating copolymer is the only product, irrespective of monomer charge. However, in the presence of a radical catalyst and at high acrylonitrile monomer charges, e.g., D/AN = 10/90, the alternating copolymer is accompanied by a normal radical copolymer. The formation of equimolar, alternating copolymer at all monomer ratios and in the absence or presence of a radical catalyst indicates that the (D-AN…MX) charge transfer complex readily undergoes homopolymerization and does not copolymerize with free diene or acrylonitrile or with the AN-AN…MX complex.     

Block Copolymerization of Vinyl Monomers with Macroiniferer

Abstract

Block copolymers composed of a polyether, such as poly(oxytetra-methylene), and vinyl polymers, such as polystyrene, poly(methyl methacrylate), poly(butyl acrylate), and poly(vinyl acetate), were prepared by photopolymerizations of vinyl monomers initiated with a polyether macroiniferter, α - (diethyldithiocarbamylacetyl) - ω - (diethyldithiocar-bamylacetoxy)-poly(oxytetramethylene). ESR spectroscopy and end-group analysis of diethyldithiocarbamyl indicated that block copolymers should be predominantly ABA-type copolymers. The block copolymers were characterized in detail by NMR, GPC, and DSC analysis.     

Solvent Effect in Binary Copolymerization

Recently published experimental data concerning the solvent effect in binary copolymerization are re‐analyzed. Newer, more accurate, reactivity ratios were calculated using a non‐linear method (PROCOP), which involves all experimental data, conversion values included. The differences between the reactivity ratios provided by the recalculated values are discussed in terms of solvent effect. Based on the existing experimental data, the solvent effect was identified only for a few binary copolymerization systems.     

Studies in cyclocopolymerization. III. Copolymerization of divinyl ether with certain nitrogen-containing alkenes

The copolymerization of divinyl ether with fumaronitrile (A), tetracyanoethylene (B), and 4-vinylpyridine (C) has been studied, azobisisobutyronitrile being used as initiator. The compositions of the copolymers were calculated from their nitrogen and unsaturation content. Over a wide range of initial monomer composition, the mole fraction of A in the copolymers lies in the range 0.55–0.63, and the copolymers contained only 2–3% unsaturation, indicating a high degree of cyclization. The composition of the copolymers of B indicated that cyclization occurred to only a small extent, as the copolymers contained rather high unsaturation content. The values of r₁ = 0.23 and r₂ = 0.12 were obtained. The mole fraction of C in the copolymers lies between 0.85 and 0.998. If the assumption is made that r₁ ? r_c ? 0 and there is predominant cyclization, r₂ = 32.0 in this case. The difference in the composition of the copolymers is attributed to the difference between the electron density of the double bonds in A, B, and C.     

Acrylonitrile Copolymerizations. IV. Butadiene Copolymerization

The kinetics of the acrylonitrile–butadiene radical copolymerization, carried out in solution at 60°C, have been followed using gas chromatographic analysis. Remote units effects are observed only on the butadiene-ended radicals but they seem to involve a quite long sequence of butadiene units. The following values of the reactivity ratios are proposed: r_A = 0.067, r_AB = 0.70, r_ABB = 0.66, rABB = ^0.17,rBi → 001 to 0-06 for large values of L The results are discussed in terms of either polarity effects, or differences in reactivities between 1,4- or 1,2-butadiene radicals, or finally of charge transfer complexes between the monomers.     

过硫酸铵-尿素引发丙烯酸甲酯与明胶接枝共聚

接枝共聚合反应;过硫酸铵-尿素引发丙烯酸甲酯与明胶接枝共聚