Bulk polymerization of acrylonitrile. I. An experimental investigation of the kinetics of the bulk polymerization of acrylonitrile

A comprehensive experimental investigation is reported of the bulk polymerization of acrylonitrile (AN) to limiting conversion using 2,2′-azobisisobutyronitrile (AIBN) as initiator at 40°, 60°, and 80°C. Molecular weight development was followed by gel permeation chromatography (GPC).     

Polyelectrolyte behaviour of acrylonitrile methallylsulphonate copolymers in dimethylformamide

The properties in organic solvent (DMF) of two ionic copolymers are investigated and compared to those of polyelectrolytes in aqueous solutions. First, the viscometric behaviour is disccussed: it is demonstrated that [η] varies linearly with $\text{C}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}{}_{\mathrm{T}}$, where C_T is the ionic concentration of the solution. At infinite salt concentration we obtain data in agreement with unperturbed dimensions. Using isoionic dilution, we deduce ø_p, the osmotic coefficient. From osmometry, the dependence of ø_p on the concentration is obtained and compared to the theoretical value. In the presence of neutral salt, the osmotic pressure is determined as a function of salt and polymer concentrations. The results are interpreted in terms of a Donnan equilibrium.     

Micellar effect on the kinetics of ceric ion-initiated polymerization of acrylonitrile in the presence of organic substrate

The micellar effect on the kinetics of ceric ion-initiated polymerization of acrylonitrile (AN) in the presence of N-acetylglycine has been studied in the temperature range 30–50°C. The neutral emulsifier (Triton X-100) has no effect on the R_p, whereas both anionic (NaLS) and cationic (NCTAB) emulsifiers accelerate the rate of polymerization appreciably. Comparison of the effect of different organic substrates on the rate of polymerization has been made. Various effects such as the concentration of metal ion, surfactant, monomer, sulfuric acid, organic solvents, and inorganic salts on R_p have also been investigated. The most remarkable feature of the investigation involves the enhancement of R_p in the presence of micelles. A suitable mechanism for the derivation of the rate expression for the above system is proposed along with the calculation of activation energy and prediction of optimum conditions. © 1994 John Wiley & Sons, Inc.     

NO2-initiated polymerization of acrylonitrile

The polymerization of acrylonitrile initiated with NO₂ in dimethyl sulfoxide has been studied. The kinetics of polymerization was followed gravimetrically. The effect of monomer, initiator, and temperature on the rate of polymerization has been given. The overall activation energy was found to be 18.06 kcal.mol^?1. The polymerization with NO₂ appears to be initiated by a free-radical mechanism.     

A DSC study of the polymerization of 2-Vinylpyridine in dimethylformamide

The polymerization of 2-vinylpyridine (2VP) in dimethylformamide (DMF) with azobisisobutyronitrile (AIBN) as initiator was studied with a differential scanning calorimeter. By taking an appropriate amount of AIBN and after correction for its decomposition, the following values could be obtained: Heat of polymerization ΔH_p,o = ?68 ± 4 kJ/mol; overall Arrhenius activation parameters E_a = 90.0 ± 4 kJ/mol and ln A = 24 ± 1.0 (A = 2.6 × 10¹⁰ dm^3/2/mol^1/2. s).     

Graft polymerization of acrylonitrile onto wheat straw

Acrylonitrile was graft polymerized onto ground, water-washed wheat straw using Fe²⁺-H₂O₂ as initiator. Reaction conditions were selected to minimize homopolymer formation and maximize the amount of polyacrylonitrile (PAN) grafted to straw. Polymerizations typically yielded straw-g-PAN containing 30–35% PAN. A two-step fractionation scheme was developed for determining the relative amounts of PAN grafted to cellulose, hemicellulose, and lignin. This scheme involved (1) delignification of straw-g-PAN with sodium chlorite followed by removal of lignin-grafted PAN by extraction with dimethylformamide (DMF), and (2) hydrolysis of the hemicellulose component with 1 N trifluoroacetic acid followed by DMF extraction of hemicellulose-grafted PAN. Product remaining after these two treatments was assumed to be cellulose-g-PAN. When relative amounts of PAN grafted to cellulose, hemicellulose, and lignin were compared with relative percentages of these components present in wheat straw, the percentage of total PAN grafted to lignin was less than its relative percentage in straw, whereas that grafted to hemicellulose was considerably more. Although the use of Ce⁴⁺ as initiator gave little or no polymer with whole, water-washed straw, grafted polymerization occurred when delignified straw was used as substrate. Relative amounts of PAN grafted to cellulose and hemicellulose were not greatly different from those observed with Fe²⁺-H₂O₂ initiation onto whole straw.     

Electrochemical polymerization of acrylonitrile with quaternary salts

The electrochemical polymerization of acrylonitrile was carried out in the solutions of tetrabutylammonium bromide and tetrabutylphosphonium bromide in N,N-dimethylformamide in a divided electrolytic cell. The formation of polyacrylonitrile of high molecular weight (7.6 × 10⁴) took place in the cathode compartment. The kinetics of the polymerization was investigated for different initial monomer concentrations, current levels, and electrode materials. The polymerization mechanism is anionic.     

Effect of organized anionic surfactant system on the kinetics of V(V)-organic substrate-initiated polymerization of acrylonitrile

The kinetics of polymerization of acyrlonitrile (AN) initiated by a V(V)-cyclohexanone redox system in the presence of a surfactant was studied over a temperature range of 30–50°C in acidic medium. The anionic surfactant sodium dodecyl sulfate (SDS) enhances the rate of polymerization (R_p) as well as rate of V(V) consumption (−R_v). The cationic surfactant, cetyltrimethylammonium bromide (CTAB), decreases both R_p and −R_v, while the nonionic surfactant, Triton-X-100, has no effect on the rate. The change of concentration of the surfactant, monomer, acid, and cosolvent on the rate of polymerization were examined. Both R_p and −R_v are computed in the presence of different organic substrates, i.e., cyclohexanone, cyclopentanone, glycerol, and citric acid. The viscosity-average molecular weight (M_v) of the polycrylonitrile, obtained at different [SDS], was determined using the Mark-Howink relationship. A suitable mechanistic scheme was proposed for the process. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1825–1833, 1997     

Polymer structure formed in radiation-induced graft polymerization

Methacrylic acid (MAA) and methyl methacrylate (MMA) were grafted onto nylon 6, cellulose triacetate, cotton, viscose rayon, and polyester fibers, and the stereoregularities of the grafted polymers were determined. The graft polymerization was carried out with preirradiation techniques using γ-rays from a Co 60 source. The grafted copolymers were then separated from the homopolymers by Soxhlet extraction. The grafted (branch) polymers were isolated from the trunk polymers by acid hydrolysis and their stereoregularity was determined with a 100 MHz NMR spectrometer. The stereo-regularity of PMAA or PMMA grafted onto viscose rayon or cotton fiber was different from that of the polymers formed in ordinary radical polymerization.     

超声辐射丙烯腈的无皂乳液聚合

以过硫酸铵为引发剂,用超声波引发丙烯腈单体进行无皂乳液聚合,研究了单体浓度、引发剂浓度、反应时间对单体转化率的影响情况,并对聚合物进行了IR、TEM表征,结果显示聚丙烯腈乳胶粒尺寸均匀,约为50nm。     

Effect of sodium lauryl sulfate on the polymerization of acrylonitrile

Micellar catalyzed polymerization of acrylonitrile using ceric(IV)–glycerol redox system in aqueous sulfuric acid solution in the presence of sodium lauryl sulfate (NaLS) has been studied. The polymerization experiments were conducted between 15°C and 25°C, under conditions where no oxidation of sodium lauryl sulfate by ceric ion would we expected. The rate of polymerization (R_p) increases with increasing concentration of NaLS. The rate of monomer (AN) disappearance was proportional to [AN]^1.5 and [glycerol]^0.5, but, however, R_p changes in a nonlinear manner with increase in Ce(IV) concentration in the presence of the surfactant. The rate of Ce(IV) disappearance was not proportional to its original concentration. The chain length of the polymer could not be determined viscometrically, as the polymer obtained in presence of NaLS was insoluble in organic solvents. The activation energy of this polymerization process was calculated by conducting the experiment at different temperatures. The infrared spectra of the polymers in the presence and absence of surfactant have also been examined.     

The redox aqueous polymerization of acrylonitrile under pressure

Effect of pressure (atmospheric to 20 X 10⁶ Pa) on the K₂S₂O₈–Na₂S₂O₄ initiated aqueous polymerization of acrylonitrile has been studied at 25°C. The conversion and rate of the polymerization tend to rise initially with increase of pressure and fall subsequently to a limiting value. The initial rise in the rate is consistent with an increase of k_p or a decrease in k_t due to high pressure. The ultimate tendency of the rate to fall is possibly due to a decrease in the diffusion rate of the monomer from the aqueous phase to the growing polymer radical site. The molecular weight shows a more or less similar trend except that the fall in the molecular weight begins at a lower pressure range than the same in the rate or conversion. This is explained on the basis of enhanced monomer transfer reaction. These observed kinetic characteristics are not sensitive to the appearance of heterogeneity in the system due to insoluble polymer phase in as much as homogeneous reaction systems in DMF or DMSO essentially exhibit the same features. The rate is proportional to the square root of the product of [K₂S₂O₈] and [Na₂S₂O₄] and varies linearly as the first power of the monomer concentration.     

Ceric ion-induced redox polymerization of acrylonitrile on cellulose

The ceric ion-cellulose redox system has been studied for grafting acrylonitrile on cotton fibers. Grafting yields are very high as compared to the persulfate-thiosulfate redox system reported earlier. Traces of copper sulfate in the reaction mixture do not increase grafting yields, unlike the persulfate-thiosulfate system. The high polymerization rate on cotton fibers is shown to be due to the reducing action of cellulose and not to the large surface area of cotton fibers. The Ce⁺⁴ consumption during grafting is higher than during oxidation of cellulose, indicating formation of homopolymer during the grafting reaction. Studies on the consumption of Ce⁺⁴ by model compounds such as D-glucose and α-methyl-D -glucoside show that the hemiacetal group in D -glucose is responsible for a faster rate of Ce⁺⁴ consumption. Formation of a Ce⁺⁴-alcohol complex also contributes to the initial fast rate of Ce⁺⁴ consumption. Studies on the oxidation of cellulose by Ce⁺⁴ indicate that the initial oxidative attack occurs on carbon atom 2, with the formation of a >C?O group. On further oxidation, cleavage of the C₂-C₃ bond occurs as shown by the presence of glycol aldehyde determined chromatographically. Cellulose-polyacrylonitrile grafts have been isolated by an acetolysis treatment followed by extraction with dimethylformamide. Number-average molecular weights of the isolated fractions are approximately 50,000–55,000. A theoretical method to calculate the number-average molecular weights, based on the PAN and the COOH contents of the grafted cellulose, is described.     

Water-superabsorbent polymers through gamma radiation-induced graft-copolymerization of acrylonitrile on guargum

Superabsorbent polymers based on guargum have been prepared through a graft-copolymerization reaction using acrylonitrile as the monomer by a gamma ray-induced irradiation technique. Various grafting parameters have been studied. The grafted products have been characterized using infrared spectroscopy, thermogravimetric, and differential thermal analysis. The thermograms reveal the superior thermal stability of the grafted product over the control at all stages of its degradative cycle. The maximum absorbency obtained of the superabsorbent product was around 300 g/g.     

丁二烯丙烯腈聚合过程中间产物性能研究

采用兰州石化公司生产的丁腈橡胶N41乳液聚合配方,考察了聚合反应单体转化率随反应时间的变化,测定了生胶的结合丙烯腈含量、分子质量及其分布、玻璃化转变温度、微凝胶含量和门尼黏度等性能,结果表明:随着转化率的升高,生胶结合丙烯腈含量降低,耐寒性能变好,门尼黏度、相对分子质量及其分布指数升高,当转化率达到86%时,生胶的门尼黏度达到产品指标上限。     

Group transfer polymerization of acrylonitrile in bulk at ambient temperature

Summary Group transfer polymerization of acrylonitrile was conducted in bulk at room temperature with 1,1,3-trimethyl-5-methylen-2, 6-dioxa-1-silacyclohexen (TMDSCH) as the initiator and tetrabutylammonium bibenzoate (TBABB) as the catalyst. The experimental results showed that the new GTP initiator gave polyacrylonitrile in fairly good yields with well control of the molecular weight and polydispersity.