Showing papers on "Ionic polymerization published in 1969"

Kinetics of dispersion polymerization of soluble monomers. I. Methyl methacrylate

Abstract: The kinetics of the free-radical-initiated polymerization of methyl methacrylate in n-dodecane to produce dispersions of polymer stabilized with a steric barrier of soluble polymer chains have been determined by thermal analysis. The mode of the polymerization can be described in terms of a bulk polymerization within the monomerswollen polymer particles. A theoretical expression has been derived on the basis of a reaction scheme in which all the radicals produced in the diluent phase are transferred immediately to the polymer particles, monomer swells the polymer particles in partition equilibrium with monomer in the diluent, and polymerization proceeds within the polymer particle according to the kinetics of bulk polymerization, taking into account Trommsdorff acceleration and plasticization effects.

Alkyllithium and alkali metal tert‐butoxide as polymerization initiator

Abstract: We have shown that the presence of other alkali metal alkoxides in the alkyllithium-initiated polymerization drastically increases the rate of polymerization and vinyl unsaturation in polybutadiene. Mechanistically, the propagating center is the dynamic equilibriums between carbon–metal bonds and oxygen–metal bonds. With potassium, rubidium, and cesium salts it reaches a limiting anionic behavior.

Chain transfer in anionic polymerization. Determination of chain-transfer constants by using carbon-14-labeled chain transfer agents

Abstract: A method is described in which 14C-labeled chain-transfer agents are employed to measure chain-transfer constants in anionic polymerization as low as 10−6. Each chain-transfer step incorporates one molecule of the chain-transfer agent into the polymer so that measurement of the activity and conversion allows evaluation of the chain-transfer constant. This method is independent of the initiator concentration and efficiency, making the technique especially useful when problems with the initiator are encountered. The experimental procedure is described in detail for the case of chain transfer to toluene in the n-butyllithium-initiated polymerization of styrene, where CRH was found to be 5 × 10−6. A mathematical treatment is given showing the relationship between the degree of polymerization (DPn) and chain transfer.

Polymerization of coordinated monomers. I. Stereoregulation in the free‐radical polymerization of methyl methacrylate‐zinc chloride or methyl methacrylate–stannic chloride complexes

Abstract: Stereoregulation in free-radical polymerization was studied for the polymerization of the 2:1 or 1:1 complex of methyl methacrylate with ZnCl2 or SnCl4. The complexes were polymerized with the use of a free-radical initiator or γ-ray irradiation either in the liquid or solid state at various temperatures ranging from −196 to 110°C, and the tacticities of the resulting polymers were determined by NMR spectroscopy. The polymers had different and characteristic values of tacticities depending upon the complex species, i.e., the kind of metal chloride and the stoichiometry. The tacticities were found to be independent of the polymerization temperature in both the liquid and solid states, in contrast with the fact that tacticities of the polymer from pure monomer changed markedly with the temperature. A temperature dependence appeared in the polymerization system, which contained more monomer than that corresponding to the 2:1 complex. The effect of the viscosity or the solid phase on the stereoregulation was examined in comparison with the polymerization of a mixture of methyl methacrylate and liquid paraffin. Two possible explanations regarding the stereoregulation mechanism are offered in relation to the structures of the complexes.

Radical polymerization of N‐vinylcaprolactam in homogeneous solution. II

Abstract: The polymerization of N-vinylcaprolactam in toluene, dioxane, chlorobenzene, dimethylformamide, and ethylene carbonate with various peroxides, perbenzoates and azobisisobutyronitrile as initiators at 60–80°C, was studied. Under these conditions azobisisobutyronitrile and tert-butyl perbenzoate have satisfactory activity as initiators. Under these conditions N-vinylcaprolactam polymerization in homogeneous solution is first order towards the monomer and 0.5 order towards the initiators.

Olefin Polymerizations and Copolymerizations with Aluminum Alkyl-Cocatalyst Systems. IV. The Polymerization of Styrene

Abstract: The mechanism of cationic styrene polymerization with the AlEt2Cl/RCl (R = alkyl or aryl) catalyst-cocatalyst system has been investigated. Polymerization initiation, i.e., cocatalyst efficiency, is apparently determined by the relative stability and/or concentration of the initiating carbonium ions provided by the cocatalyst RCl. Whereas n-butyl, isopropyl, and sec-butyl chlorides exhibit low cocatalyst efficiencies because of low ion concentrations, triphenyl methyl chloride is a poor cocatalyst because the stability of the derivative triphenyl methyl ion is much higher than that of the propagating styryl ion. Alkyl halides that give ions of intermediate stability are efficient cocatalysts. Isobutyl chloride and benzyl chloride seem to be exceptions and the reasons for this are discussed. A general simple scheme of the polymerization mechanism is proposed.

Process for the anionic polymerization of unsaturated hydrocarbon monomers

Abstract: THE DISCLOSURE IS CONCERNED WITH A NEW METHOD OF EFFECTING THE ANIONIC PO/LYMERIZATION OF POLYMERIZABLE UNSATURATED HYDROCARBON MONOMERS, WHEREIN A CATALYSTCOCATALYST COMBINATION IS USED. THE CATALYST-COCATALYST COMBINATION CONSISTS OF (A) AN ANIONIC CATALYST OF A GROUP I-A OR II-A METAL, AND (B) A COMPOUND OF A GROUP III-A ELEMENT AS THE COCATALYST.

Vinyl polymerization with Fe(III)-thiourea as initiator system. Part I. General features and kinetics of Fe(ClO4)3-thiourea reaction†

Abstract: Initiation of polymerization of methyl methacrylate, styrene, and acrylonitrile with the redox system Fe(III)—thiourea has been examined. For the heterophase polymerization any of the ferric salts, such as FeCl3, Fe2(SO4)3, and Fe(ClO4)3 can be used as oxidant, but there is no polymerization in the homogeneous phase when FeCl3 is used as oxidant. It was also observed that Fe(ClO4)3 retards the radical polymerization of styrene, though this salt has hardly any effect on the radical polymerization of methyl methacrylate. Further, the reaction between Fe(ClO4)3 and thiourea was found to be kinetically of second order. The rate is largely influenced by the nature of the solvent. It is concluded that apart from the dielectric constant of the solvents, specific effects like complex formation of Fe(III) with solvents should have a marked influence on the rate of this reaction.

Polymerization of coordinated monomers. II. Stereoregulation in the free‐radical polymerization of methacrylonitrile–zinc chloride or methacrylonitrile–stannic chloride complexes

Abstract: The effect of complex formation on stereoregulation in free-radical polymerization was studied. Complexes of methacrylonitrile with ZnCl2 and SnCl4 were prepared and their properties and structures examined. The complexes were polymerized by initiation of α,α′-azobisisobutyronitrile or by irradiation with γ-rays from a60Co source or ultraviolet rays either in solution or in bulk at various temperatures ranging from −78 to 100°C. The triad tacticities of the resulting polymethacrylonitrile were determined by converting it to poly(methyl methacrylate) for NMR spectroscopy. The radicals in complexed forms were studied by ESR spectroscopy with the polymerization system in toluene irradiated with ultraviolet rays at −120°C. The tacticities of the resulting polymers and their dependencies on the polymerization temperature were found to be characteristic of the complex species, i.e., the kind of metal chloride and the stoichiometry, being different from the tacticities and the dependencies, respectively, of the polymer obtained with pure methacrylonitrile. The 2:1 and the 1:1 complexes with SnCl4 were found to give an eleven-line and a nine-line spectrum, respectively. On the basis of the results of both the tacticities and the ESR spectra, it was estimated that the proportion of the intracomplex reaction was 40%, and that the probabilities of isotactic diad addition of intra- and intercomplex reaction were 0.70 and 0.48, respectively.

Polymerization and copolymerization of diolefins

Abstract: DIOLEFINS ARE POLYMERIZED AND COPOLYMERIZED IN THE PRESENCE OF A CATALYST WHICH IS OBTAINED BY REACTING A TRANSITION METAL COMPOUND WITH A SOLID COMPOUND OF A BIVALENT METAL CONTAINING HYDROXYL AND/OR OXYGEN GROUPS OR WITH A POLYMER WHICH CONTAINS ELECTRON DONOR GROUPS AND THEN ACTIVATING THE THUS OBTAINED PRODUCE WITH AN ORGANOMETALLIC COMPOUNDS.

Polymerization by transition metal derivatives XI. Stereospecific polymerization of butadiene in the presence of π-allyl nickel halogenoacetates

Abstract: The catalytic properties of a series of π-allyl nickel halogenoacetates are reported for the cis-1,4 polymerization of butadiene. Correlations between the catalytic activity of the complexes and the electron-with-drawing properties of their counter-anions were made.

Cationic polymerization behavior of hydroxystyrenes

Abstract: Solution polymerizations of o-, m- and p-hydroxystyrene with boron trifluoride etherate were investigated. The results of infrared and ultraviolet spectroscopic investigations of the polymers thus obtained indicate that p-hydroxystyrene polymer consisted mainly of the structure formed through the normal vinyl polymerization mechanism, whereas o- and m-hydroxystyrene polymers contained considerable portions of the structures due to the reaction of the vinyl group with the phenol nucleus. The rate of polymerization and the intrinsic viscosity of the polymer decreased in the order p-hydroxystyrene ≫ o-hydroxystyrene > m-hydroxystyrene. It was of interest that on the cationic polymerization only p-hydroxystyrene gave polymer of high molecular weight. Plausible polymerization mechanisms were considered. Solid-state polymerization of p-hydroxystyrene at solid carbon dioxide temperature with the use of boron trifluoride etherate was also investigated. Appreciable polymerization occurred only at fairly high catalyst concentrations.

Monomer‐isomerization polymerization. V. Effects of transition metal compounds on monomer‐isomerization polymerizations of butene‐2 and pentene‐2

Abstract: In order to clarify the correlation between polymerization and monomer isomerization in the monomer-isomerization polymerization of β-olefins, the effects of some transition metal compounds which have been known to catalyze olefin isomerizations on the polymerizations of butene-2 and pentene-2 with Al(C2H5)3–TiCl3 or Al(C2H5)3–VCl3 catalyst have been investigated. It was found that some transition metal compounds such as acetylacetonates of Fe(III), Co(II), and Cr(III) or nickel dimethylglyoxime remarkably accelerate these polymerizations with Al(C2H5)3–TiCl3 catalyst at 80°C. All the polymers from butene-2 were high molecular weight polybutene-1. With Al(C2H5)3–VCl3 catalyst, which polymerizes α-olefins but does not catalyze polymerization of β-olefins, no monomer-isomerization polymerizations of butene-2 and pentene-2 were observed. When Fe(III) acetylacetonate was added to this catalyst system, however, polymerization occurred. These results strongly indicate that two independent active centers for the olefin isomerization and the polymerizations of α-olefins were necessary for the monomer-isomerization polymerizations of β-olefins.