Polymerization of acrylamide and methacrylamide photoinitiated by azidopentamminecobalt(III) chloride

The kinetics of polymerization of acrylamide and methacrylamide, photoinitiated by azidopentamminecobalt(III) chloride in homogeneous aqueous acid medium was studied systematically. Monochromatic wavelengths 365, 405, and 435 mμ were employed for irradiation. Polymerization proceeded without any induction period, and the reaction was followed by measurements of rate of monomer disappearance (bromometrically), rate of complex disappearance (spectrophotometrically), and the chain lengths of the polymer formed (viscometrically). The dependences of the rate of polymerization on variables like light intensity, light absorption fraction by the complex, wavelength, monomer concentration, hydrogen ion concentration, nature of the acid used (HClO₄, HNO₃, and H₂SO₄), etc., were studied. The rate of polymerization of acrylamide depended on the unit power of monomer concentration and on the square root of light absorption fraction k_ε and light intensity I. The rate of methacrylamide polymerization was proportional to the unit power of monomer concentration and fractional powers of 0.25 and 0.30 of k_ε and I, respectively. A kinetic reaction scheme is proposed and discussed in the light of the experimental results, and it has been concluded that (1) the primary photochemical act is an electron transfer reaction from the azide ion to Co(III) in the complex, (2) initiation of polymerization is by azide radical, (3) termination is by mutual destruction of polymer radicals.     

Noncoordinating anions in carbocationic polymerization

The initiation and catalysis of isobutylene polymerization from several new metallocene and nonmetallocene initiator-catalysts that contain the noncoordinating anions (NCA), B(C₆F₅)₄⁻ and RB(C₆F₆)₃⁻, is reported. Application of these initiator-catalysts is extended to styrenics and vinyl ethers. The NCA does not contribute to termination and can be used in low concentrations compared with conventional Lewis acids. These qualities provide for isobutylene polymerizations that yield low M_n oligomers or high M_n polymer, dependent upon the initiator and polymerization conditions. Mechanistic aspects of initiation, transfer and termination as well as the participation of adventitious water are considered for each class of initiator-catalyst. The influence of the NCA on the stereoregularity of cationic styrene polymerization is also considered. NCAs do not cause the stereospecific carbocationic polymerization of styrene. We suggest that under conditions not conducive to carbocationic polymerization, NCA/metallocenes mediate the coordination polymerization of styrene. © 1997 John Wiley & Sons, Inc.     

Kinetic study of the crosslinking reaction of 1,2‐polybutadiene with dicumyl peroxide in the absence and presence of vinyl acetate

The crosslinking reaction of 1,2-polybutadiene (1,2-PB) with dicumyl peroxide (DCPO) in dioxane was kinetically studied by means of Fourier transform near-infrared spectroscopy (FTNIR). The crosslinking reaction was followed in situ by the monitoring of the disappearance of the pendant vinyl group of 1,2-PB with FTNIR. The initial disappearance rate (R₀) of the vinyl group was expressed by R₀ = k[DCPO]^0.8[vinyl group]^−0.2 (120 °C). The overall activation energy of the reaction was estimated to be 38.3 kcal/mol. The unusual rate equation was explained in terms of the polymerization of the pendant vinyl group as an allyl monomer involving degradative chain transfer to the monomer. The reaction mixture involved electron spin resonance (ESR)-observable polymer radicals, of which the concentration rapidly increased with time owing to a progress of crosslinking after an induction period of 200 min. The crosslinking reaction of 1,2-PB with DCPO was also examined in the presence of vinyl acetate (VAc), which was regarded as a copolymerization of the vinyl group with VAc. The vinyl group of 1,2-PB was found to show a reactivity much higher than 1-octene and 3-methyl-1-hexene as model compounds in the copolymerization with VAc. This unexpectedly high reactivity of the vinyl group suggested that an intramolecular polymerization process proceeds between the pendant vinyl groups located on the same polymer chain, possibly leading to the formation of block-like polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4437–4447, 2004     

Controlled/living polymerization of MMA promoted by heterogeneous initiation system (EPN‐X–CuX–bpy)

The polymerization of methyl methacrylate (MMA) promoted by heterogeneous initiation system (ethyl‐2‐halopropionate (EPN‐X)–CuX–2,2′‐bipyridyl (bpy), where X = Br or Cl) is studied in detail. The results show that ethyl‐2‐bromopropionate (EPN‐Br) is an efficient initiator as expected, and that CuCl–bpy, instead of CuBr–bpy, is a better catalyst for the controlled polymerization of MMA. The solvents with a high value of dielectric constant (ε) will lead to fast initiation and narrow molecular weight distribution (MWD). As a result, the controlled, living polymerization of MMA with EPN‐Br–CuCl–bpy can be got in ethyl acetate (EAc) at 100°C and in acetonitrile at 80°C. All results suggest that the initiation reaction is a controlling step in the controlled polymerization of MMA. The relationship between the UV spectra of CuCl–bpy and the performances of the polymerization in EAc or acetonitrile suggest that the formation of bis‐bpy complex, [Cubpy₂]X⁻, will lead to fast initiation and good control of the polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1255–1263, 1999     

Polymerization of acrolein and methyl vinyl ketone induced by amine–water and pyridine–phenol systems

It was reported that acrolein (AL) in tetrahydrofuran (THF) polymerizes at temperatures below 0°C in the presence of pyridine (Py) and water. To clarify this polymerization mechanism the polymerization of AL and methyl vinyl ketone (MVK) by an initiation system such as Py–water, triethylamine (Et₃N)–water, or Py–phenol(Ph) was carried out. The polymerization rate (R_p) of MVK in the Et₃N–water system was expressed by the same equation, R_p = k [Et₃N] [H₂O] [MVK]², used for AL in the Py–water system. Meanwhile, β-hydroxypropionaldehyde, β-phenoxypropionaldehyde, γ-ketobutanol, and β-phenoxy-1-methylpropionketone were obtained as the initial addition products. The polymer of AL obtained was composed of polymer units of vinyl and aldehyde polymerization, but the structure of MVK polymer obtained by the Py–water system was composed of only vinyl polymerization units. The polymerization of MVK by the Py–Ph system did not occur, however. These results were discussed in terms of the initiation and propagation mechanisms.     

Living cationic polymerization of vinyl ethers and styrene derivatives: Design of initiating systems based on added salts with halogen anions

This paper overviews three living cationic polymerization systems (for styrene, p-methoxystyrene, and isobutyl vinyl ether) that are, in common, featured by: (i) specifically in nonpolar solvents, the use of the hydrogen halide/metal halide initiating systems (HX/MX_n; X: I, Br, Cl; MX_n: ZnX₂, SnCl₄), which generate a living growing carbocation stabilized by a nucleophilic counteranion (X⁻…MX_n); (ii) specifically in polar solvents, the use of externally added ammonium salts (nBu₄N⁺Y⁻; Y⁻: I⁻, Br⁻, Cl⁻), which permit the generation of living species from HX/MX_n by providing nucleophilic halogen anions Y⁻, either the same as or different from the halogen X⁻ in HX.     

Polymerization of α-methylstyrene by living polymer in tetrahydrofuran

Kinetics of polymerization of α-methylstyrene by poly-α-methylstyrylsodium (a “living” polymer) has been studied in tetrahydrofuran at ?78°C. Complex dependences were established: that of the conversion X on reduced time φ and that of the apparent rate constant for the polymer chain propagation on conversion X and on the concentration of living polymers and monomer. The experimental data obtained were explained by assuming a coordination mechanism of anionic polymerization including the following elementary reaction: (a) generation of active polymerization centers (K₁) by interaction of the living polymer with the monomer; (b) propagation of the polymer chains (K₂); (c) monomolecular (K₃₁) and bimolecular (K₃₂) reactions of isomerization of active centers resulting in the formation of high molecular weight living polymers capable of again becoming active centers of polymerization. Approximate derivation of kinetic equation was carried out and the constants of elementary reactions were determined (K₁ = 0.15, K₂ = 24, K₃₂ = 14.1./mole-min and K₃₁ = 0.05 min^?1). The coincidence of the expected dependencies X = F(τ; φ) K_p = F(X; n₀^?1/2); dx/dτ = F(n₀) with the experimental ones was followed with the aid of computers. The expected change in the values of X and K_p depending on the contribution of each elementary reaction to the overall polymerization process was analyzed.     

Neodymium Catalyst for the Polymerization of Dienes and Polar Vinyl Monomers

Ziegler–Natta catalysts have played a major role in industry for the polymerization of dienes and vinyl monomers. However, due to the deactivation of the catalyst, this system fails to polymerize polar vinyl monomers such as vinyl acetate, methyl methacrylate, and methyl acrylate. Herein, a catalytic system composed of NdCl₃⋅3TEP/TIBA is reported, which promotes a quasi‐living polymerization of dienes and is also active for the homopolymerization of polar vinyl monomers. Additionally, this catalytic system generates polymyrcene‐b‐polyisoprene and poly(myrcene)‐b‐poly(methyl methacrylate) diblock copolymers by sequential monomer addition. To encourage the replacement of petroleum‐based polymers by environmentally benign biobased polymers, polymerization of β‐myrcene is demonstrated with a catalytic activity of ≈106 kg polymer mol Nd⁻¹ h⁻¹.     

Kinetics of polymerization of acrylic acid initiated by Mn3+–isobutyric acid redox system. II

The kinetics of redox -initiated polymerization of acrylic acid (AA) by the systerm Mn³⁺-isobutyric acid (IBA) in sulfuric acid was studied in the temperature range of 35–50°C. The overall rates of polymerization (R_p), disappearance of manganic ion (?R_m), and degree of polymerization (X _n), were measured with variation in [monomer], [Mn³⁺], [IBA], H⁺, μ, [Mn²⁺], and temperature. The polymerization is initiated by the organic free radical that develops from the Mn³⁺-isobutyric acid oxidation reaction. Two types of termination reactions, one by the metal ion (Mn³⁺) and the other by the MN³⁺-isobutyric acid complex are proposed to explain the kinetic results. The various rate parameters were evaluated an discussed.     

Synthesis of ionic polymers by free radical polymerization using aprotic trimethylsilylmethyl-substituted monomers

Aprotic ionic polymers containing trimethylsilylmethyl-substituted imidazolium structures are synthesized using free radical polymerization of monomers comprising a vinyl group either at the cation or at the anion. Bulk polymerization is used for the room temperature ionic liquid monomer 1-trimethylsilylmethyl-3-vinylimidazolium bis(trifluoromethylsulfonyl)imide. In contrast to this, solution polymerization is applied for 1-trimethylsilylmethyl-3-methylimidazolium p-styrene sulfonate because this monomer undergoes self-polymerization during melting at a higher temperature than selected for bulk polymerization. Glass transition temperature (T _g) of the ionic polymers and intrinsic viscosity measurements indicate differences between these polymers, which are composed either of a polycation with a trimethylsilylmethyl substituent at each vinylimidazolium segment of the polymer chain and mobile bis(trifluoromethylsulfonyl)imide (NTf₂⁻) anions or a polyanion containing p-styrene sulfonate segments and mobile 1-trimethylsilylmethyl-3-methylimidazolium cations. The new aprotic ionic polymers containing trimethylsilylmethyl substituents may be interesting for application in adhesive, interlayer and membrane manufacturing.     

Benzoin type photoinitiator for free radical polymerization

Benzoin, a popular photoinitiator for free radical polymerization of vinyl monomers, was improved by introduction of two methyl thioether substituents. This new benzoin derivative showed an about 50 times higher light absorption in the near‐UV spectral region and performed better than the unsubstituted benzoin in polymerization experiments in bulk solutions or films of acrylate monomers when low initiator concentrations are used. Laser flash photolysis, low temperature luminescence experiments and photoproduct studies by mass spectrometry suggest that a slow α‐cleavage mechanism (k_α = 2.2 × 10⁵ s^?1) from the electronic triplet state with a quantum yield of 0.1 is the primary photoreaction to generate the initiating free radicals. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Syntheses and properties of photochromic polymers of the azobenzene and thiazine series

Photochromic polymers of the azobenzene and thiazine series were synthesized via two routes: (1) synthesis of vinyl photochromic monomers and subsequent polymerization and (2) chemical reactions of the substrate polymers with photochromic components. Polyvinylaminoazobenzenes, polyvinylhydroxyazobenzenes, polyacrylamidomethylaminoazobenzenes, and polyacrylamidomethylthionine were thus prepared and their photochromic behavior investigated. In the case of azobenzene polymers, irradiations from a 100-W projection lamp are enough to induced reversible changes in absorption spectra both in benzene solutions and film states, their absorption maxima being located around 400 mμ in the dark. Better results are obtained for some polymers as compared with the corresponding low molecular weight compounds; in the case of the thionine polymer (absorption maximum, ca. 600 mμ), the presence of ferrous ion remarkably enhances the photosensitivity in aqueous solutions, but incorporation of some polymers containing hydroxyl groups, such as poly(vinyl alcohol), are preferable for film states.     

Polymerized ionic liquids: Effects of counter‐anions on ion conduction and polymerization kinetics

A novel imidazolium‐containing monomer, 1‐[ω‐methacryloyloxydecyl]‐3‐(n‐butyl)‐imidazolium (1BDIMA), was synthesized and polymerized using free radical and controlled free radical polymerization followed by post‐polymerization ion exchange with bromide (Br), tetrafluoroborate (BF₄), hexafluorophosphate (PF₆), or bis(trifluoromethylsulfonyl)imide (Tf₂N). The thermal properties and ionic conductivity of the polymers showed a strong dependence on the counter‐ions and had glass transition temperatures (T_g) and ion conductivities at room temperature ranging from 10 °C to −42 °C and 2.09 × 10⁻⁷ S cm⁻¹ to 2.45 × 10⁻⁵ S cm⁻¹. In particular, PILs with Tf₂N counter‐ions showed excellent ion conductivity of 2.45 × 10⁻⁵ S cm⁻¹ at room temperature without additional ionic liquids (ILs) being added to the system, making them suitable for further study as electro‐responsive materials. In addition to the counter‐ions, solvent was found to have a significant effect on the reversible addition‐fragmentation chain‐transfer polymerization (RAFT) for 1BDIMA with different counter‐ions. For example, 1BDIMATf₂N would not polymerize in acetonitrile (MeCN) at 65 °C and only achieved low monomer conversion (< 5%) at 75 °C. However, 1BDIMA‐Tf₂N proceeded to high conversion in dimethylformamide (DMF) at 65 °C and 1BDIMABr polymerized significantly faster in DMF compared to MeCN. NMR diffusometry was used to investigate the kinetic differences by probing the diffusion coefficients for each monomer and counter‐ion in MeCN and DMF. These results indicate that the reaction rates are not diffusion limited, and point to a need for deeper understanding of the role electrostatics plays in the kinetics of free radical polymerizations. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1346–1357     

Studies of the reactions of thiocyanate ion with chloropentammine Ru(III) dichloride and bromopentammine Ru(III) dibromide and iodopentammine Ru(III) diiodide at various temperatures

New mono-, di- and trinuclear, cationic and anionic species of Ru(III) complexes containing ammonia, thiocyanate and halide ions have been prepared by the reaction of NH₄SCN on[Ru(NH₃)₅X]X₂ (X = Cl⁻, Br⁻, I⁻) at various temperatures. A polynuclear species of RU(II) is also described. The reaction products are temperature dependent. All the compounds have been characterised by chemical analyses, spectral (IR, UV and visible), magnetic susceptibility, polarographic, cyclic voltammetry, conductivity and ion exchange studies. Interconversion among various products has also been described. New acids of Ru(III), H[Ru(NH₃)₂X₃(NCS)] (X = Cl⁻, Br⁻, I⁻) have been isolated and their properties have been studied.     

Uranyl ion-sensitized polymerization of acrylamide and methacrylamide in aqueous solution

The kinetics of polymerization of the vinyl monomers, acrylamide and methacrylamide, photosensitized by uranyl ions in homogeneous aqueous acid medium was studied systematically. Monochromatic radiation of wavelengths 365, 405, and 436 mμ was used for irradiation. Uranyl perchlorate in aqueous perchloric acid (pH = 0–2) was used as the sensitizer to ensure that only uncomplexed UO₂²⁺ ions existed in the solution. Polymerization was found to proceed without any induction period, the steady state being attained in about 10–20 min., and was followed by the measurement of the rate of monomer disappearance by bromine addition method. The chain lengths of the polymers were determined by viscometry. It was observed that there was no change in the initiator concentration, [UO₂²⁺], during polymerization. The dependence of the rate of polymerization on variables like light intensity, light absorption fraction by the active species, wavelength, monomer concentration, hydrogen ion concentration, temperature, nature of the acid used (HClO₄ and H₂SO₄), viscosity of the medium etc., were studied. A kinetic reaction scheme is proposed and discussed in the light of the experimental results. Certain rate parameters were calculated. The mechanism of photosensitization by uranyl ions with specific reference to primary photochemical act, initiation of polymerization etc., are discussed.     

A New Radical Initiator of the Binary System of Cupric Methoxide and Carbon Monoxide

Under carbon monoxide pressure, cupric alkoxides such as cupric methoxide, Cu(OCH₃)₂, and cupric acetylacetonate methoxide, Cu(acac)(OCH₃), initiate the polymerization of vinyl monomers. The microstructure of polybutadiene and the composition of styrene-methacrylate copolymer by these catalyst systems have indicated a free radical mechanism. The mechanism of the initiation was examined by the end group of product polymer and the analysis of the reaction between the catalyst components. Reduction of Cu(OCH₃)₂ and Cu(acac)(OCH₃) with carbon monoxide to Cu(OCH₃) and Cu(acac), respectively, was responsible for the initiating activity. The decomposition of these unstable cuprous species produces methoxyl and acetylacetonyl radicals which initiate the polymerization.     

The carbenium ion - oxonium ion exchange processes related to vinyl and ring-opening polymerization

It has previously been proposed (Ref. 1) that in the cationic vinyl polymerizations, proceeding with termination due to the collapse of ion pairs, addition of bases increases “livingness”, because of the fast convertion of the otherwise dead (within the time of polymerization) covalent species into the onium ions; these, in turn, fast convert into carbenium ions, the actually propagating species. Equilibria between carbenium ions (CH₃OCH₂⁺A⁻ has been used as a model) and their onium counterparts ((CH₃)₂O taken as a model base) as well as between covalent species (CH₃OCH₂OSO₂CF₃) and the corresponding oxonium ion (with a (CH₃)₂O ligand) have been studied by dynamic ¹H and ¹⁹F NMR. Total ionization of methoxymethyl triflate (CH₃OCH₂OSO₂CF₃) has been shown to increase indeed from 10⁴ (-10°C) to 10⁶ (-70°C) times when 1,0 mol·L⁻¹ of (CH₃)₂O is added. Although this model system better describes polymerization of cyclic acetals than that of vinyl ethers, it shows at least qualitatively the importance of bases in ionization of covalent species, which may be responsible for reinitiation in the cationic polymerization of vinyl ethers.     

Effects of cosolvents on helical substituted polyacetylene particles prepared through suspension polymerization

Acetylenic monomers undergo aqueous suspension polymerization providing particles constructed by helical substituted polyacetylene. Different from suspension polymerization of vinyl monomers, a cosolvent is indispensable to dissolve Rh catalyst and solid acetylenic monomers. The cosolvent is found to play essential roles in monomers' polymerization and the particles' formation. To systemically explore the effects of cosolvents, three monomers, M1 (achiral, liquid), M2 (achiral, solid), and M3 (chiral, solid), and six cosolvents (divided into two groups by their miscibility with water) are used for performing suspension polymerization in aqueous media at 30 °C, with Rh⁺B^– (C₆H₅)₄ as catalyst and polyvinylpyrrolidone as stabilizer. FTIR spectra and gel permeation chromatography confirm the occurrence of polymerization. Raman spectra demonstrate the high cis contents of the polymer chains. Scanning electron microscope images show that the polymer particles obtained under optimal conditions are in spherical morphology. Circular dichroism and UV‐vis spectroscopy demonstrate the helical structures of the polymer chains forming the chiral particles. Dynamic light scattering characterization is carried out to characterize the nanoparticles. The type and amount of the cosolvent affect the polymerization remarkably. Cosolvents with higher polarity lead to smaller polymer particles, while lower polar cosolvents provide larger ones. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2670–2678     

Solid-state initiation of polymerization of N-vinylcarbazole by gases

Chlorine gas has been shown by previous investigators to initiate the polymerization of solid N-vinylcarbazole at room temperature, giving a maximum yield of 66% polymer after 18 hr. This initiation of polymerization of N-vinylcarbazole without the application of heat, by a gas, is the only solid-state initiation other than those that are radiation-induced known to us. This study was undertaken in order to determine both the scope and the mechanism of the room-temperature solid-state initiation of vinyl polymerization of N-vinylcarbazole by gases. The gases (HCl, Cl₂, and N₂O₄) were absorbed by solid N-vinylcarbazole, giving very rapid exothermic polymerization: HCl, 37% polymer yield, M?_n 2500; Cl₂, 50% polymer yield, M?_n 4703; N₂O₄, 91% polymer yield, M?_n 7073. The gases NOCl, BF₃, and HBr were not absorbed by N-vinylcarbazole and did not initiate polymerization. The N₂O₄-initiated polymerization, which gave a high yield of polymer, was complete within 5 min. after introduction of gas. This polymerization method and the resulting polymer compared favorably with conventional peroxide-initiated melt polymerization and the polymer obtained thereform. The mechanism of gas-initiated polymerization, which was studied with introduction of inhibitors, appears to be classically cationic in nature.