Initiation Of Vinyl Polymerization Research Articles

Erratum to: Arenetricarbonylchromium Complexes in Polymerization Transformations by Radical Initiation of Vinyl Polymerization

Erratum to: Arenetricarbonylchromium Complexes in Polymerization Transformations by Radical Initiation of Vinyl Polymerization

Arenetricarbonylchromium Complexes in Polymerization Transformations by Radical Initiation of Vinyl Polymerization

The article is devoted to the systematization of investigations of arenetricarbonylchromium complexes in radical polymerization transformation at the initiation of vinyl polymerization. The presented data are shown that these compounds are promising and interesting model systems for the study of the phenomenon of the metal atom action on the reactivity of the monomer π-bond. The correlation between the structure of metal-containing monomers and polymerization parameters, as well as the molecular mass properties of the resulting polymers, are discussed.

Quenching of the triplet state of safranine-O by aliphatic amines in AOT reverse micelles studied by transient absorption spectroscopy

The photophysics of Safranine-O (3,6-diamino-2,7-dimethyl-5 phenyl phenazinium chloride) (SfH(+)Cl(-)) was investigated in reverse micelles (RMs) of AOT (sodium bis(2-ethylhexyl)sulfosuccinate) with special emphasis on the triplet state processes. The triplet is formed in its monoprotonated form, independently of the pH of the water used to prepare the RMs. While the intersystem crossing quantum yields in RMs are similar to those in organic solvents, the triplet lifetime is much longer. Since the pH in the water pool of AOT RMs is close to 5 and the triplet state of the dye is subjected to proton quenching, the long lifetime indicates that the dye resides in a region where it cannot be reached by protons during its lifetime. All the measurements indicate that the dye is localized in the interface, sensing a medium of micropolarity similar to EtOH : water (3:1) mixtures. The quenching by aliphatic amines was also investigated. While the quenching by the hydrophobic tributylamine is similar to that in methanol, the hydro-soluble triethanolamine is one order of magnitude more effective in RMs than in homogeneous solution. In the latter case the quenching process is interpreted by a very fast intramicellar quenching, the overall kinetics being controlled by the exchange of amine molecules between RMs. Semireduced dye is formed in the quenching process in RMs in the di-protonated state with a comparable quantum yield to the monoprotonated state formed in homogeneous solvents. The results point to the advantage of the reverse micellar system for the generation of active radicals for the initiation of vinyl polymerization, since a much lower concentration of amine can be employed with similar quantum yields.

Styrene polymerization with a macroinitiator having siloxane units

Block copolymers containing segments of poly(dimethylsiloxane) (PDMS) and polystyrene were synthesized. Dihydroxy terminated PDMS Mn 2500 g/mol, was reacted with an ali-phatic diisocyanate (isophorone diisocyanate) and an aliphatic hydroperxide (t-butyl hy-droperoxide). The resulting polymeric peroxycarbamate having siloxane units (a new mac-roinitiator) was used as free radical initiator for vinyl polymerization of styrene. Formation of block copolymers was illustrated by several characterization methods such as chemical and spectroscopic analysis, fractionation, and GPC. Mechanical and thermal characterization of the copolymers were made by stress–strain tests and DSC. The surface properties and the morphology of the block copolymers were investigated by contact angle measurements and SEM. © 1996 John Wiley & Sons, Inc.

Styrene polymerization with a macroinitiator having siloxane units

Block copolymers containing segments of poly(dimethylsiloxane) (PDMS) and polystyrene were synthesized. Dihydroxy terminated PDMS Mn 2500 g/mol, was reacted with an ali-phatic diisocyanate (isophorone diisocyanate) and an aliphatic hydroperxide (t-butyl hy-droperoxide). The resulting polymeric peroxycarbamate having siloxane units (a new mac-roinitiator) was used as free radical initiator for vinyl polymerization of styrene. Formation of block copolymers was illustrated by several characterization methods such as chemical and spectroscopic analysis, fractionation, and GPC. Mechanical and thermal characterization of the copolymers were made by stress–strain tests and DSC. The surface properties and the morphology of the block copolymers were investigated by contact angle measurements and SEM. © 1996 John Wiley & Sons, Inc.

Photoinduced Graft Copolymerization onto selected fibers

Abstract Although photopolymerization is one of the oldest methods for the initiation of vinyl polymerization, photografting is of recent origin. methods have been used for grafting vinyl monomers onto a large number of fibers by using a multitude of vinyI monomers with a view of improving some of the properties of the fibers to enhance better commercialization. The primary advantage of photoinitiated grafting compared to other methods, such as radiation or chemically initiated During the last three decades, various photoinitiating 91 grafting, is that some of the basic properties of the graft polymer can be imparted to the fiber without affecting its basic structure and morphology.

Polymerization of acrylamide initiated by the redox system Ce(IV)-4,4′-azobis (4-cyano pentanol)

Acrylamide was polymerized by eeric ion Ce (IV)-4,4′-azobis(4-cyano pentanol)(ACP) redox pair in aqueous nitric acid under nitrogen atmosphere. The rate of polymerization is proportional to [M]2,[ACP] and [Ce(IV)]−1. Termination mechanism which was exclusively linear offered one azo group per polymeric chain. The obtained polyacrylamide can be used as a water soluble initiator for vinyl polymerization.

Peroxo salts as initiators of vinyl polymerization—V. Polymerization of acrylonitrile initiated by the peroxomonosulphate-thioglycolic acid system

Aqueous thermal polymerization of acrylonitrile (AN) initiated by peroxomonosulphate (HSO 5 −, PMS)-thioglycolic acid (TGA) redox system was studied in the temperature range 30–60°. The effects of [monomer], [initiator], [reducing agent], pH, ionic strength and temperature on rate of polymerization ( R p) were studied. R p was found to depend on [AN] 2.0, [HSO 5 −] 1.0 and [TGA] −1.0. The overall activation energy was found to be 23.0 kJ·mol −1. A reaction scheme involving initiation by RS ., SO 4 .− and OH and linear termination has been proposed to explain the kinetics.

Peroxo Salts as Initiators of Vinyl Polymerization IV. Polymerization of Acrylonitrile by the Peroxomonosulphate–Oxovanadium(IV) System

A detailed kinetic study of the aqueous polymerization of acrylonitrile (AN) initiated by peroxomonosulphate (HSO5−, PMS)–oxovanadium(IV) redox system has been made in the temperature range 30°—60°C under dearated conditions at a constant ionic strength (μ=1.20). The effects of [monomer], [PMS], [oxovanadium(IV)], [H+], μ and temperature on rate of polymerization, Rp were investigated and the Rp was found to be proportional to [AN]1.5 [HSO5−]0.5 [oxovanadium(IV)]0.5. The kinetic and thermodynamic parameters were evaluated and are discussed. A suitable reaction scheme involving redox reaction of HSO5− and oxovanadium(IV) with mutual termination is proposed. The expression for degree of polymerization, Xn was obtained by molecular weight determination of the formed polymers. A comparison was also made with a similar redox system involving peroxodiphosphate.

The initiation of vinyl polymerization by tetrakis (trialkyl‐phosphite) nickel (o) derivatives

AbstractThe study of the polymerization of vinyl monomers initiated by zero‐valent nickel phosphite derivatives in the presence of organic halides has been extended to tetrakis (triethylphosphite) nickel (o) and tetrakis (tri 2‐chloroethylphosphite) nickel (o). A kinetic study with methyl methacrylate and carbon tetrachloride shows that the polymerization proceeds by a free radical process and that the mechanism of initiation resembles that previously reported for the corresponding triphenylphosphite and carbonyl derivatives. The primary process which becomes rate determining at sufficiently high carbon tetrachloride concentration is the nonreversible SN1 scission of an alkylphosphite ligand. These alkylphosphite initiators are considerably more active than the corresponding carbonyl derivatives, but are less active than the corresponding triphenyl‐phosphite derivative. The difference in activities between the aryl and alkylphosphite derivatives has been accounted for by differences in steric over‐crowding of these molecules.

Electrolytically initiated vinyl polymerization

AbstractAfter a short outline of the historic development of electroinitiated vinyl polymerization and a description of the early work in this field a survey is given on the most important initiation systems. The difficulties and problems which arise, in addition to conventional initiation of vinyl polymerization, are analyzed. Among others, these comprise the spatial heterogeneity of active particle production, the necessity of dissolving the electrolyte in the polymerization system, which preferably also should be a solvent for the polymer formed, the susceptibility of the electrode process to impurities, the eventual termination of the growing chains by the products of the process taking place at the counter‐electrode, and the possibility of simultaneous initiation of anionic and free radical polymerization at the cathode and of cationic and free radical polymerization at the anode. Some examples show that in spite of these numerous difficulties precise kinetic measurements are possible in some free radical as well as in some ionic initiation systems. While the initiation of free radical polymerization processes suffers from disappointingly low current yields (≈︁10−3), throughout which makes this initiation much inferior to any conventional one, there are some positive features inherent in the electroinitiation of ionic polymerization. Especially, it is the possibility to carry out cationic polymerization exclusively in presence and under control of such counterions which are known to have favorable polymerization characteristics (this is to lead to high rates and molecular weights), however, the corresponding anhydrous acids of which do not exist, by merely oxidizing the monomer in presence of salts of these counterions (e.g. AgSbF6). Due to the non‐availability of the corresponding anhydrous acid HSbF6 this cannot be accomplished in a direct manner by conventional techniques.

Peroxo salts as initiators of vinyl polymerization—III. Polymerization of acrylonitrile initiated by the peroxomonosulphate-Co(II) redox system

The kinetics of aqueous polymerization of acrylonitrile initiated by peroxomonosulphate Co(II) redox system have been investigated in the range 30–50°C under nitrogen at a fixed ionic strength of 0.30 mol · dm −3. The overall rate of polymerization, followed gravimetrically, was found to be proportional to [AN] 1.5[PMS] 1.0[Co(II)] 0.5. The activation energy was found to be 42 kJ · mol −1. An increase in ionic strength slightly decreased the rate of polymerization. Inhibition of polymerization was caused by the addition of sulphuric acid in the range of 0.05-0.50 mol · dm −3. The rate law for polymerization was fitted to a reaction mechanism involving all possible initiation reactions and termination by mutual combination.

Studies of the role of acetone triplets in the initiation of vinyl polymerization

Triplet acetone generated from the thermal decomposition of tetramethyl-1,2-dioxethane was shown to be incapable of initiating the free radical polymerization of methyl methacrylate and styrene. Triplet acetone is rapidly quenched by energy transfer to the monomer, but the excited state of the monomer so produced does not initiate polymerization. Acetone does not initiate polymerization when irradiated into its n−π ∗ singlet state with UV irradiation in the absence of a co-sensitizer, but is effective when photolysed in the presence of triethylamine which quenches the acetone, possibly by resulting in the efficient formation of ketyl radicals. In contrast, methyl tert-butyl ketone is an effective initiator because of the more rapid rate of formation of radicals by α-cleavage when one of the substituents gives rise to a tertiary alkyl radical.

Dual role of metallic lithium in the initiation of vinyl polymerization

Alkali-metal-initiated polymerization of dienes has been known since the 19109. Metallic sodium and potassium have been known as ionic initiators for quite some time.3 However, the designation of metallic lithium as an initiator has not always been unequivocal.

Hexakis(arylisocyano) derivatives of chromium(0) as initiators of vinyl polymerization: Steric effects

AbstractThe free radical polymerization of methyl methacrylate initiated by the hexakis (arylisocyano)chromium(0)‐CCl4 system has been studied for a number of derivatives in which both chlorine and methyl groups have been introduced into the benzene ring. It has been found that single substituents in the benzene ring, irrespective of position, have little effect on the activity of the system other than that which can be explained by the electronic effects of these substituents. However, where steric overcrowding occurs it has been shown that the rate of initiation is reduced considerably. This confirms the established mechanism of initiation for this type of derivative.

Peroxo salts as initiators of vinyl polymerization: Polymerization of acrolein initiated by potassium peroxodiphosphate

Kinetic studies were made on the polymerization of acrolein initated by potassium peroxodiphosphate (PP) in aqueous solution, in the presence and absence of Ag + ions. The rate of polymerization was found to depend on [ M] 3 2 (M = monomer) and was independent of both [PP] and [Ag +]. The overall activation energy was calculated to be 4.8 kcal mol −1. A mechanism involving termination by PO 2- 4 radicals is proposed and discussed.

Transition Metal Chelates as Initiators of Vinyl Polymerization

Abstract Recent information on the use of transition metal chelates as initiators of free radical polymerization of vinyl monomers is supplied. Chelates of various kinds and of various coordination numbers, derived from transition metal ions such as Mn(II), Mn(III), Co(II), Co(III), Fe(II), Fe(III), Cu(I), and Cu(II) with a multitude of both monomeric and polymeric ligands, are taken into consideration. The efficiency of the individual chelates toward radical polymerization of vinyl monomers under variable reaction conditions are discussed. The co-catalytic activity of some chelates in photopolymerization and peroxide initiated vinyl polymerization is accounted for. The kinetic results and spectroscopic evidence leading to the mechanistic details of individual paths of initiation of polymerization are discussed.

Peroxo Salts as Initiators of Vinyl Polymerization. 6. Kinetics of Polymerization of Acrylonitrile Initiated by Potassium Peroxodisulfate in Aqueous Medium-Ag+Catalysis

Abstract The kinetics of polymerization of acrylonitrile initiated by potassium peroxodisulfate in neutral and acid conditions was studied. Rp depended upon [S2O8 2-]1/2 and [monomer]3/2 both in neutral and acid solutions. The influence of ionic strength and the cata-lytic effect of Ag+ on the System are discussed. Suitable mech-anisms are proposed.

Peroxo salts as initiators of vinyl polymerization, 7. Kinetics of uncatalyzed and Ag(I) catalyzed polymerization of methacrylic acid initiated by potassium peroxodiphosphate in aqueous sulfuric acid solutions

Peroxo salts as initiators of vinyl polymerization, 7. Kinetics of uncatalyzed and Ag(I) catalyzed polymerization of methacrylic acid initiated by potassium peroxodiphosphate in aqueous sulfuric acid solutions

Peroxo salts as initiators of vinyl polymerization, 5. Kinetics of polymerization of N‐vinyl‐2‐pyrrolidone by peroxodisulfate in aqueous solution. Effect of Ag+ and Cu2+ ions

AbstractThe kinetics of the polymerization of N‐vinyl‐2‐pyrrolidone by peroxodisulfate ion in aqueous solution in the presence and absence of metal ions Ag+ and Cu2+ is studied. The rate laws for the polymerization are established and the kp/kt1/2 values computed. A negative salt effect is observed for the Ag+ catalysed process, indicating the formation of a complex of the type AgS2O8− (aq). Cu2+ ions, however, are found to reduce the rate of polymerization.