Copolymerization of acrylamide and styrene. II. Reactivity ratios with unperturbed acrylamide

It was reported earlier that the copolymerization of acrylamide and styrene is strongly affected by the copolymerization medium. The effect was attributed to a change in the polarity of the ethylenic bond in the acrylamide monomer due to hydrogen bonding and/or dipole—dipole interaction, depending on the medium. In view of those findings, it was suggested that absolute values for the reactivity ratios for the copolymerization of these two monomers might be obtained only when the acrylamide monomer is unperturbed. Copolymerizations of these monomers at a number of ratios, therefore, were done in benzene, which does not undergo hydrogen bonding and has no dipole moment, at high dilution, when amide—amide interactions between acrylamide molecules should be essentially eliminated. The values of r₁ and r₂(M₁ = acrylamide) were 9.14 ± 0.27 and 0.67 ± 0.08, respectively. There appears to be some indication in this system that high dilution adversely affects the reactivity of the acrylamide monomer while enhancing that of styrene. This aspect requires more study.     

STUDY ON COPOLYMERIZATION OF ACRYLAMIDE WITH STYRENE INITIATED BY METHYL ETHYL KETONE AND ITS DERIVATIVES IN COMPARISON WITH CONVENTIONAL RADICAL INITIATOR

Copolymerization of acrylamide (AAm) with styrene (St) was carried out in the presence of methyl ethyl ketone (MEK), methyl isopropyl ketone (MIK) and t-butyl methyl ketone (tBMK) without any conventional initiator in tetrahydrofuran (THF) at 60°C. The copolymerization of AAm with St proceeded readily in the presence of the MEK, MIK, and tBMK, while no copolymerization of AAm with St proceeded in the absence of these ketones under the same conditions and no homo-polymerization of St proceeded even in the presence of the ketones. The reactivity ratio of monomer AAm (r₁) is smaller than that of St (r₂) in all of the copolymerization systems, and increases as the order: MEK < MIK < tBMK. The conversion of the copolymerizations increases as the same order described above. The interaction between AAm and the ketones with hydrogen bonding was estimated by the shifts of the absorption bands of the amide carbonyl and N-H groups in the infrared spectra. From the results of the copolymerization between AAm and St, the greater the shift in the N-H absorption, the higher the amount of AAm found in the copolymer.     

Influence des solvants sur la copolymérisation de l'acrylamide avec l'acrylonitrile

The copolymerization of acrylamide with acrylonitrile was investigated in various solvents, which can be put into three groups according to their influence on molecular associations; (1) solvents autoassociated by hydrogen- bonds (acetic acid, methanol, water, dimethylformamide); (2) polar solvents which can associate with the NH group of acrylamide (acetonitrile, dioxane, acetone); (3) inert solvents (toluene, benzene, hexane). The reaction kinetics and the compositions of the copolymers are different for each group of solvents. The composition of copolymers formed in solvents of group 1 vary widely, depend- ing on the solvent. Copolymers formed in all solvents of group 2 have the same composition which is that of copolymers formed in bulk. The amount of acrylamide is highest in copolymers formed in inert solvents of group 3. Such parameters as the degree of conversion, the reaction temperature, the mode of initiation and the extent of dilution only slightly affect the composition of copolymers. Homopolymerizations of acrylamide and acrylonitrile were investigated in all solvent used.The results suggest that the effects of solvents on the copolymerization of acrylamide with acrylonitrile are consequences of the various modes of molecular association of acrylamide. The solvents affect the equilibrium between auto- association of acrylamide and its association with solvent and thereby affect the reactivity of the monomer.     

Effect of solvent on the copolymerization of ethylene and vinyl acetate

The ethylene (M₁)–vinyl acetate (M₂) copolymerization at 62°C and 35 kg/cm² with α,α′-azo-bisisobutyronitrile as initiator has been studied in four different solvents, viz., tert-butyl alcohol, isopropyl alcohol, benzene, and N,N-dimethylformamide. The experimental method used was based on frequent measurement of the composition of the reaction mixture throughout the copolymerization reaction by means of quantitative gas chromatographic analysis. Highly accurate monomer reactivity ratios have been calculated by means of the curve-fitting I procedure. The observed dependence of the r values on the nature of the solvent is surprisingly large and can be correlated with the volume changes (= excess volumes) observed on mixing vinyl acetate (VAc) with the relevant solvent. An increased hydrogen bonding or dipole–dipole interaction through the carbonyl moiety of the acetate side group of VAc, induces a decreased electron density on the vinyl group of VAc, which in turn leads to a decreased VAc reactivity. The differences among the overall rates of copolymerization in the various solvents can be interpreted in terms of a variable chain transfer to solvent and the rate of the subsequent reinitiation by the solvent radical. In the case of benzene, complex formation is believed to play an important part.     

Polymerization of coordinated monomers. XVIII. Sequence distribution in methyl acrylate–styrene copolymers prepared in the presence of zinc chloride

Methyl acrylate and styrene have been copolymerized in the presence of zinc chloride either by photoinitiation or spontaneously. The copolymerization mechanism is investigated by analyses of copolymers composition and monomer sequence distribution. The resulting copolymers are not always alternating, their composition being dependent especially on the monomer feed ratio. Appreciable deviation to higher methyl acrylate unit content from an equimolar composition occurs at monomer feed fractions of methyl acrylate over 0.7. The larger deviation is induced by higher temperature, by photoirradiation, and by greater dilution of the reaction mixture with toluene. The ¹³C-NMR spectrum of the alternating copolymer shows a sharp singlet at the carbonyl region, whereas the spectra of random copolymers prepared by benzoyl peroxide initiation at 60°C show a triplet splitting at the carbonyl carbon region, irrespective of copolymer composition. The relative intensities of the triplet peaks for the random copolymers are in good correspondence to the contents of triad sequences calculated by means of conventional radical copolymerization theory. These results clearly indicate that the carbonyl splitting is caused predominantly by variation of the monomer sequence and not by variation of the stereosequence. The monomer sequence distribution in the copolymers is thus directly and quantitatively measured from the split carbonyl resonance. Although the same triplet splitting appears in the spectra of methyl acrylate–rich copolymers prepared in the presence of zinc chloride at high feed ratios (>0.7) of methyl acrylate, the relative intensities of the split peaks do not fit the sequence distributions of random copolymers calculated by means of the Lewis–Mayo equation. The copolymerization yielding these peculiar sequences and the alternating sequence in the presence of zinc chloride is fully comprehended by a copolymerization mechanism proceeding between two active coordinated monomers, i.e., the ternary molecular complex composed of zinc chloride, methyl methacrylate, and styrene, and the binary molecular complex composed of zinc chloride and methyl methacrylate.     

Monomer reactivity ratios in graft copolymerization

This paper discusses monomer reactivity ratios in various radiation- and redox-initiated graft copolymerizations. The polymers studied were polyethylene, cellulose acetate, poly(vinyl chloride), polytetrafluoroethylene, poly(vinyl alcohol), and poly(methyl methacrylate); the comonomer mixtures were styrene–acrylonitrile, methyl acrylate–styrene, acrylonitrile–methyl acrylate, and vinyl acetate–acrylonitrile. The polymer–comonomer mixture systems were so chosen as to permit study of both homogeneous and heterogeneous systems. The homogeneous systems included systems of low and high viscosity. The heterogeneous systems included both polymers swollen by the comonomer mixture and polymers not swollen by the comonomer mixture. None of the homogeneous grafting systems studied showed deviations from the normal copolymerization behavior under a variety of experimental conditions. Monomer reactivity ratios in graft copolymerization were the same as the values in nongraft copolymerization. The heterogeneous systems in which the polymer was swollen by the comonomer mixture yielded grafted copolymer compositions which were the same as those in nongraft copolymerization. The heterogeneous grafting system polytetrafluoroethylene/styrene–acrylonitrile showed deviations from normal copolymerization behavior at low degrees of grafting when the reaction was only on the polymer surface. The behavior became normal at higher degrees of grafting when the system approaches that in which the polymer is swollen by the comonomers. In all reaction systems, it was found that the use of radiation to initiate the reaction does not in any way affect the copolymerization behavior of the two monomers in a comonomer pair.     

Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. III. Effect of salt on cationic copolymerization of styrene derivatives with vinyl ethers by acetyl perchlorate

A common-ion salt, tetra-n-butylammonium perchlorate, was found to affect the monomer reactivity ratios in the cationic copolymerization by acetyl perchlorate of styrene with p-methylstyrene and of 2-chloroethyl vinyl ether with p-methylstyrene, but not those for the copolymerization of 2-chloroethyl vinyl ether with isobutyl vinyl ether. In the copolymerization of p-methylstyrene with styrene or with 2-chloroethyl vinyl ether, the addition of the common-ion salt in a polar solvent shifted the monomer reactivity ratios to those in a less polar solvent. The molecular weight distribution analysis of the copolymer suggested that the addition of the common-ion salt depresses the dissociation of propagating species. Therefore, it was concluded that a propagating species with a different degree of dissociation shows a different relative reactivity towards two monomers. The nature of propagating species was also discussed on the basis of the common-ion effect on the monomer reactivity ratios in various solvents.     

Dispersion copolymerization of styrene and other vinyl monomers in polar solvents

Dispersion polymerization is a very attractive method for preparing micrometer‐size monodisperse polymer particles. The applications of microspheres have been greatly expanded by the use of copolymers. Here, the dispersion copolymerization of styrene and seven other vinyl monomers was carried out in polar solvents. The effect of the different comonomers on the particle size was systematically investigated. The particle size first decreased and then increased with an increasing fraction of acrylamide in the monomer feed, and at a higher fraction of such a comonomer, only a gel‐like polymer was obtained. The particle size also increased with the increase in the contents of the hydrophilic comonomers in the monomer mixtures, and the copolymer molecular weight decreased meanwhile. Although the amount of the hydrophobic comonomer in the monomer mixture changed, the particle size was hardly affected. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 555–561, 2001     

Effects of solvent as an electron-pair acceptor on propagation reactions during radical polymerization and copolymerization of polar vinyl monomers

We carried out radical homopolymerization and copolymerization in various kinds of solvents at 60°C by using diisopropyl fumarate (DiPF) and methyl methacrylate (MMA) as electron-accepting polar monomers and styrene (St) and vinyl benzoate (VB) as electron-donating monomers. The highest polymerization rate was observed in the polar and electron-pair accepting solvents, such as 2,2,2-trifluoroethanol for the homopolymerization and copolymerization of these monomers. It has been revealed that the polymerization rate is correlated to the electron-pair–accepting property of the solvent used, rather than the polarity in the linear free energy relationship. We have demonstrated the validity of the acceptor number as the index for interpreting the interaction of the solvent with the monomer and the propagating chain end. The monomer reactivity ratios were determined for the St–DiPF, VB–DiPF, and St–MMA copolymerizations. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2803–2814, 1999     

Copolymérisations de l'acrylonitrile. XII. Phénomènes de solvatation préférentielle et effet de conversion dans la copolymérisation (acrylonitrile–styrène)

Kinetic deviations with the conversion observed in free-radical-initiated [acrylonitrile (A)–styrene (S)] copolymerization carried out in DMF solution have been interpreted in terms of preferential solvation of the polymer by one of the monomers or the solvent. First it is well established that the initial styrene content of the PAS copolymer increases if a slight amount of polymer is introduced before the beginning of polymerization. Next the preferential solvation has been studied and characterized in various solvents (toluene or DMF) from the results of differential refractometry at dialysis equilibrium of the ternary solution (solvent–monomer–polymer) versus its solvent mixture. It was found that the most polar monomer, acrylonitrile, is already adsorbed by the polymer, mostly in copolymerizations carried out in DMF, from initially rich acrylonitrile mixtures. It is suggested that this phenomenon implies a heterogeneous repartition of the monomer mixture in the solution, which may affect the kinetic copolymerization when the conversion increases.     

Statistical radical copolymerization of styrene and methyl methacrylate in a room temperature ionic liquid

Use of a room temperature ionic liquid as the medium for conventional free radical copolymerization of styrene and methyl methacrylate resulted in reactivity ratios that were significantly different from those obtained in conventional organic solvents or in bulk, demonstrating that polymerization in this alternative medium offers potential to create copolymers having new monomer sequences.     

Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. I. Propagation and initiation of the copolymerization of acrylonitrile with styrene copolymer

Copolymerization of acrylonitrile with styrene spontaneously occurred on addition of zinc chloride without addition of any other radical initiator. The composition of the copolymer approached that of strictly alternating copolymer as zinc chloride added to the copolymerization system increased. The significance of the apparent monomer reactivity ratios of this copolymerization system was studied from a kinetic point of view, and it was shown that the monomer sequence distribution is indicated by the apparent monomer reactivity ratios. Further, equations which represent the relation between the apparent monomer reactivity ratios and Q,e values at a given salt concentration were derived. These equations reasonably accounted for the decrease of the apparent monomer reactivity ratios of the copolymerization of acrylonitrile with styrene in the presence of zinc chloride and the behavior of the other acrylonitrile copolymerization systems in the presence of zinc chloride. The initiation step of the spontaneous radical copolymerization of acrylonitrile with styrene in the presence of zinc chloride was explained by a cross-initiation mechanism.     

HEMA—NVP—St三元共聚体系中单体的表观竞聚率

本文采用计算机数字积分和单纯形调优法根据Alfrey-Goldfinger共聚方程微分式,从HEMA-NVP—St三元共聚高转化率体系的转化率一组成数据,直接求算了各单体的表观竞聚率,用求得的表观竞聚率计算的转化率一组成曲线,与实验值符合很好。讨论了单体部分互溶对表观竞聚率的影响。发现在此三元共聚体系中,引入少量的均化剂,可以明显改善St与其它单体的互溶程度,使相应的表观竞聚率显著降低。     

Coupling of intramolecular hydrogen bonding to the cis-to-trans isomerization of a proline imide bond of small model peptides

A relationship between intramolecular hydrogen bonding and the cis-trans isomerization of a proline imide bond for proline-containing short peptides were studied by proton NMR and infrared spectroscopy using DMSO-d6/CDCl3 mixed solvents. The percentage of the trans form increases with increasing fraction of CDCl3 in the mixed solvents except for compounds without possibility of intramolecular hydrogen bonding. Chemical shift variations of amide protons with solvent mixing ratios were found to be useful for judging whether the amide protons take part in the intramolecular hydrogen bonding to a considerable degree or not. These results and infrared spectra were used to specify intramolecularly hydrogen bonded structures of the peptides. Formation of the 10-membered or 13-membered hydrogen bonded ring which includes the carbonyl group precedent to the prolyl residue facilitates the cis-to-trans isomerization and these hydrogen bonded rings are strong enough to restrict the proline imide bond to the trans form in CDCl3 solution. On the other hand, a 7-membered hydrogen bonded ring is not so effective in restricting the proline imide bond.     

Effects of solvent on the free-radical copolymerizabilities of pyridazinones with styrene

Free-radical copolymerizations of N-methylpyridazinone (I) and N-phenylpyridazinone (II) with styrene (M₁) were carried out in various solvents. The copolymerization rates were found to increase linearly with increasing viscosities of the reaction mixtures. Monomer reactivity ratios were strongly affected by the reaction media. This might be due to solvation of the carbonyl group of the pyridazinone ring, because linear relationships between log 1/r1 and vc=o of the pyridazinones were obtained. It was also found that monomer concentration influences these copolymerizabilities.     

Kinetics and mechanism of the polymerization of styrene–acrylonitrile in the presence of polybutadiene

The mechanism of free radical grafting of styrene–acrylonitrile with polybutadiene was studied. By assuming a copolymerization mechanism an equation that related the amount of homopolymer formed and its molecular weight to a reactivity ratio and the charged ratio of monomer to polydiene was derived. Polymerizations that contained a variety of ratios of monomer to polybutadiene, two different catalysts, and variable amounts of a mercaptan modifier were studied. The weight fraction of homopolymer and its molecular weight were determined by high-speed GPC. The results were analyzed by the new equation and all showed a constant value of the reactivity ratio, which strongly suggests that the mechanism of the grafting reaction is copolymerization. Evidence that suggests that none of the grafting is a result of a hydrogen abstraction mechanism is also presented.     

4-乙烯基吡啶-氯化锌络合物与电子给体单体光照下共聚合研究

受电子单体4-乙烯基吡啶-氯化锌络合物(4-VP)_2ZnCl_2(M_1)可以和电子给体单体如苯乙烯(M_2)在365nm光照下共聚合。聚合是二者形成的基态电荷转移复合物(CTC)吸收光后产生自由基引发的。测得竞聚率为r_1=2.04,r_2=0.23。对溶剂极性的影响和(4-VP)_2Znal_2与其它电子给体单体光照下共聚合也作了研究。     

Hydrogen‐bonding Structures and Energetics of Acrylamide Isomers,Tautomers, and Dimers: An ab initio Study and Spectral Analysis

Hydrogen‐bonding patterns and energetic profiles of acrylamide isomers (syn‐ and skew‐), tautomers (amide and imidic acid forms) and 13 stable dimers have been studied using the second‐order Møller–Plesset perturbation theory with basis sets up to aug‐cc‐pVTZ. Syn‐acrylamide is the most stable monomer with a reaction barrier of 4.15 kcal/mol for the syn–skew isomerization reaction. The direct amide–imidic acid tautomerization reaction is separated by too high a barrier to surpass. The most stable dimer corresponds to the planar double‐hydrogen‐bonded configuration, indicating its crucial role in determining the stability of the formed complex. Moreover, hydrogen bonds have significant effects on the infrared spectral features, which can be consistently explained solely based on the acrylamide dimeric structures and energetics without monomeric and dimeric tautomer forms. The results are useful for studying the stability of the acrylamide clusters in condensed‐phase samples such as those in food chemistry studies.     

Water-Soluble imide-amide copolymers. III. Preparation and characterization of poly (acrylamide-co-N,N-diallylaniline) and poly (acrylamide-co-sodium N,N-diallylsulfanilate)

N,N-diallylaniline monomer was prepared in good yields, for use in preparation of homopolymer and for copolymerization with acrylamide. Functionalized N,N-diallylaniline monomer, as sodium N,N-diallylsulfanilate, was also prepared in good yields for copolymerization with acrylamide. Both monomers were fully characterized by elemental analysis, IR, and NMR. Poly (N,N-diallylaniline) was obtained by polymerization of a strongly acidic aqueous solution of N,N-diallylaniline initiated with hydrogen peroxide. Spectroscopic data from this homopolymer was used to facilitate spectral assignments of the new copolymers. Copolymers of acrylamide with N,N-diallylamine were prepared at monomer feed ratios of 10, 20, and 30 mol % amine and gave 3.5, 7.4, and 8.9 mol % incorporation, respectively. Similar diallyl monomer incorporation rates were obtained for the copolymerization of sodium N,N-diallylsulfanilate with acrylamide. With 10, 30, and 50 mol % of the sodium salt relative to acrylamide, 3.9, 8.4, and 19.2 mol % incorporation of the diallyl monomer was obtained.     

新型阴离子型温敏水凝胶

新型阴离子型温敏水凝胶王昌华,曹维孝（北京大学化学与分子工程学院,北京,１００８７１）关键词温敏水凝胶,溶胀比,Ｎ－异丙基丙烯酰胺１９８４年Ｔａｎａｋａ等人［１］发现Ｎ－异丙基丙烯酰胺（ＮＩＰＡ）与Ｎ,Ｎ－亚甲基双丙烯酰胺（ＭＢＡ）的微交联共聚体,在...