Fullerene as radical inhibitor in polymerization of acrylonitrile initiated by arsonium ylide

Kinetics of polymerization of acrylonitrile (AN) in presence of fullerene (C₆₀) has been studied using p-acetyl benzylidine triphenyl arsonium ylide as initiator in dioxane at 60 ± 0.1°C under the blanket of nitrogen. The rate of polymerization (R _p ) at low concentration of fullerene may be represented as R _p ?? [Ylide]^0.5[AN]^1.0 [Full]^?0.6, indicating inhibition effect of fullerene on the polymerization. The energy of activation for the polymerization was found to be 71.5 ± 0.5 kJ mol^?1. Fourier transform infrared spectroscopic analysis (FTIR) confirmed the insertion of fullerene in to the final polymer. The mechanism for the polymerization has also been proposed.     

Radical polymerization of 2-methacryloyloxyethyl phosphorylcholine in water: kinetics and salt effects

The homogeneous polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) as betaine monomer with potassium peroxydisulfate (KPS) was kinetically investigated in water by means of FT-near IR spectroscopy. The overall activation energy of the polymerization was estimated to be 12.8 kcal/mol. The initial polymerization rate (R_p) at 40 °C was given by R_p = k[KPS]^0.98[MPC]^1.9. The presence of alkaline metal halides accelerated the polymerization. The larger the radius of metal cation or halide ion was, the larger the accelerating effect was. The accelerating salt effect was explained by interactions of salt ions with ionic moieties of the propagating polymer radical and/or the MPC monomer. A kinetic study was also performed on the polymerization of MPC with KPS in water in the presence of NaCl of 2.5 mol/l. R_p at 40 °C was expressed by R_p = k[KPS]^0.6[MPC]^1.6. A very low value of 4.7 kcal/mol was obtained as the overall activation energy of the polymerization.     

Studies on the cationic polymerization of o-methylstyrene

The polymerization of o-methylstyrene by H₂SO₄, AlBr₃, or BF₃,Et₂O gave polymers showing i.r. spectra identical to that of a polymer formed by thermal polymerization. It follows that the cationic polymerization of this monomer proceeds normally, i.e. without isomerization, as is the case for the cationic polymerizations of p-methyl-, p-isopropyl-, and o-isopropylstyrenes.     

Photopolymerization of methyl methacrylate in the presence of the tri-n-butyl boron—p-quinone system

The photopolymerization of methyl methacrylate in the presence of tri-n-butyl boron and a number of p-quinones is studied in a wide concentration range. It is shown that the rate of polymerization and the molecular-mass characteristics of the polymers depend on the structure and concentration of p-quinone. PMMA isolated at various conversions initiates the secondary polymerization of methyl methacrylate. The activity of the macroinitator depends on the structure of p-quinone.     

Oxidative polymerization of p-phenylenediamine

Oxidative polymerization of p-phenylenediamine in a hydrochloric acid solution yields not a polyquinoxaline polymer as described in the literature but a modified poly(1,4-benzoquinonediimine-N,N′-diyl-1,4-phenylene) analogous to polyaniline known as pernigraniline. A new scheme of oxidative polymerization of p-phenylenediamine was suggested.     

Pseudo-living radical polymerization using triarylmethane as the thermal iniferter

Triphenylmethane (TPM) was used as the initiator-transfer-terminator agent (iniferter) for the pseudo-living radical polymerization of methyl methacrylate (MMA) in cyclohexanone (CHO) for the first time. The pseudo-living radical polymerization of styrene is also investigated for comparison. The polymerizations both exhibit a linear increase of number molecular weight (M_n) with conversion and the obtained polymer can be utilized as a macroinitiator for the successful chain extension. Other factors such as polymerization temperature and the molar ratio of monomer-to-iniferter were investigated and the polymerization results also showed pseudo-living characteristics. Furthermore, other triarylmethanes with substituents, such as tris-(p-acetylphenyl) methane (TAcPM) and tris-(p-carboxyphenyl) methane (TCOPM), were also employed. The results further confirmed that the other compounds with similar structure can also be used as the iniferter.     

Isomerisation et polymerisation du cis-pentadiene-1,3

Cis-1,3-pentadiene can be polymerized in benzene solution by a catalyst formed from triethylaluminium and n-butylorthotitanate. When the molar ration Al/Ti is below 6, polymerization proceeds through a previous cis-trans isomerization of the diene. It has been possible to measure the two rate constants (k_t and k_p) which characterize the isomerization and the polymerization steps, respectively. The first one reaches its highest value when Al/Ti equals 2·6 and k_p is maximum when Al/Ti equals 6. Chloroform, which is a very efficient inhibitor for the polymerization, does not affect isomerization. Data are given on the microstructures of the polydienes so obtained.     

Metallocene monomers and polymers. Ferrocenyl and ferrocenylene derivatives

The synthesis and study of some polyenes, polýiminoimides and Schiff polybases with ferrocene obtained by either polymerization or polycondensation are reported.The following monomers were used: ethynylferrocene, 1-chloro-1′-ethynyl-ferrocene, α-chloro-β-formyl-p-ferrocenylstyrene, p-ferrocenylphenylacetylene, p-ferrocenylacetophenone, 1,1′-diacetylferrocene and 1,1′-bis[β-(2-furyl)acryloyl]ferrocene which were characterized by spectral and thermodifferential analyses and Hückel MO calculations. The polymerization was performed in the presence of benzoyl and lauroyl peroxides, triisopropylboron and complex catalysts of [P(C₆H₅)₃]₂ NiX₂ type. The ferrocene derivatives were polycondensed with biuret, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl thioether, 4,4′-diamino-2,2′-dinitrodiphenyl disulphide in the presence of metallic salts and p-toluene sulphonic acid as catalysts.Polymers with either linear or tridimensional structure showing good thermal stability and semiconducting properties have been obtained. Some polymers show catalytical activity in the polymerization of chloroformylated vinylic derivatives.     

Non-ideal polymerization. Treatment of non-ideality due to primary radical termination and degradative chain transfer

A method is proposed for analysing the problems associated with non-ideal polymerizations reflected mainly in the variability of R_p/[I]^0·5[M] where R_p is the rate of polymerization and [I] and [M] are the initiator and monomer concentrations, respectively. Primary radical termination and degradative chain transfer are treated jointly and the entirely different mathematical natures of the two processes are described. The method could dispense with the need to use the uninhibited rate of polymerization which does not lend itself to reliable measurements for many systems. It is found to be efficient in detecting the active species in a polymerization system that leads to non-ideality due to degradative chain transfer.This method is applied to vinyl chloride polymerization data from the literature, the values of constants obtained therefrom are found to agree well with the existing values.     

Radical polymerization behavior of 3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate in water

The homogeneous polymerization of 3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate (MDAPS) with potassium peroxydisulfate (KPS) was kinetically in situ investigated in water by means of FT-near IR spectroscopy. The overall activation energy of the polymerization was calculated to be 16.0 kcal/mol. The initial polymerization rate (R_p) at 40 °C was expressed by R_p=k[KPS]^0.65[MDAPS]^1.0. The presence of alkaline metal salts was observed to accelerate the polymerization. The order of acceleration at 40 °C was CsCl > KCl > NaCl > LiCl when the chloride salts were used. NaCl showed higher acceleration effect than NaF. NaBr and NaI exhibited retardation and inhibition effect, respectively, because of reduction of KPS and its primary radical with bromide and iodide ions. The polymerization of MDAPS with KPS in water in the presence of NaCl at 2.0 mol/l gave R_p=k[KPS]^0.70[MDAPS]^1.4 at 40 °C. The overall activation energy of the polymerization in the presence of NaCl was estimated to be 11.6 kcal/mol being considerably lower value compared with that in its absence. The syndiotacticity of poly(MDAPS) tended to increase with rising temperature and decrease in the presence of NaCl.     

Some aspects of nitroxide-mediated living radical polymerization of N-(p-vinylbenzyl)phthalimide

The free radical polymerization of N-(p-vinylbenzyl)phthalimide (VBP) “initiated” with the adduct of 2-benzoyloxy-1-phenylethyl and TEMPO (BS-TEMPO) or TEMPO-terminated polystyrene (PS-TEMPO) in N,N-dimethylformamide (DMF) at 125 °C was found to proceed in a living fashion, providing low-polydispersity PVBP and block copolymers of the type PS-b-PVBA, where TEMPO is 2,2,6,6-tetramethylpiperidinyl-1-oxy. Unlike TEMPO-mediated styrene polymerization, the polymerization rate slightly but distinctly depended on the adduct concentration, which was interpretable as a pre-stationary behavior. The hydrolysis of those polymers gave poly(p-aminomethylstyrene) (PAMS) and PS-b-PAMS, and further treatment of the block copolymer with hydrogen chloride provided an amphiphilic block copolymer. The polymeric amphiphile was used as an emulsifier in emulsion polymerization to produce a positively charged polymeric microsphere.     

Acidic peroxo salts: A new class of initiators for vinyl polymerization—II: Kinetics of polymerization of acrylonitrile initiated by potassium monopersulphate catalysed by Mn(II)

Kinetics of the polymerization of acrylonitrile initiated by an acidic peroxo salt (potassium monopersulphate) catalysed by Mn(II) have been investigated in aqueous systems over the range 30–50°. The rates of polymerization (R_p) have been studied for various concentrations of monomer and initiator. The efficiencies of various metal salts in catalysing the polymerization have been determined from the values of R_p. The effects of catalyst (MnSO₄), initiator, monomer and various aromatic and heterocyclic amines on R_p and conversion have been studied. The end-groups of the recovered polymers have been studied using standard methods. From the observed end-groups and kinetic results, a reaction scheme has been proposed, involving initiation by OH^. or S$\text{O}$₄^. radicals, generated by the interaction of the initiator with manganous sulphate, and termination by mutual combination.     

Highly stereospecific polymerization of isoprene with homogeneous binary Ziegler-Natta catalysts based on NCN-pincer neodymium precursor

The aryldiimine NCN-pincer stabilized neodymium dichloride combined with aluminum alkyls established a new type of homogeneous binary neutral Ziegler-Natta catalyst system. This system exhibited high activity and high cis-1,4 selectivity for the polymerization of isoprene (T _p = 20 °C, 98.2%; T _p = ?20 °C, > 99%). Such catalytic performances remained under a broad range of polymerization temperatures and monomer-to-neodymium ratios (from 500 to 8000), reaching high number-average molecular weight (M _n = 1582 kg/mol) and relatively narrow molecular weight distribution (PDI = 1.68), which was, however, influenced by the amount and bulkiness of aluminum alkyls. Dynamic investigation of the polymerization was performed, which showed the number-average molecular weight of the resultant polyisoprene had an almost linear correlation with the conversion, suggesting, in some degree, the polymerization with this catalytic system was controllable.     

Cinetique de polymerisation du styrene en presence de peroxyde de benzoyle p,p′ bis-bromomethyle synthese de polymeres peroxydes

The free radical polymerization of styrene has been studied by using p,p′-bisbromomethyl benzoyl peroxide as initiator containing a chain transfer group. The rate constant of decomposition (k_d) of this peroxide has been determined at various temperatures, as well as the efficiency factor f and the transfer constant to initiator C₁. At 60°, f = 0·70 ± 0·05 and C₁ = 0·5. Polystyrene containing peroxide groups has been prepared by using this initiator. The highest yield in polymeric peroxide has been obtained for polymerization in emulsion at 40°.     

Photopolymérisation de macromères multifonctionnels—I. Étude Cinétique

Highly crosslinked polymers have been obtained by photopolymerization of multiacrylate macromers under intense u.v. or laser irradiation. The marked inhibitory effect of O₂ was quantitatively evaluated by a kinetic study of these ultra-fast reactions by i.r. spectroscopy. The rate of polmerization (R_p) and the amount of residual unsaturation in the cured polymer were shown to depend primarily on the nature of the macromer chain and on the functionality of the monomer used as diluent. Despite the high rate of initiation, polymerization develops effectively, with large quantum yields: θ_p = 8300 polymerized units per photon absorbed for irradiations in N₂. The linear relationship between R_p and light-intensity strongly suggests a polymerization mechanism based on monomolecular termination.     

Polymerization of acrylamide in various solvents in the presence of Lewis acids

The radical polymerization of acrylamide in various solvents in the presence of Lewis acids has been investigated. Considerable effects of LiBr, LiCl and CaCl₂ on the total reaction rate and the values of k_p and k₁ for polymerization in DMSO or THF have been shown. For the polymerization of acrylamide in aqueous solution, addition of the salts does not affect the kinetic behaviour of the process. The observed effect of salts arises from complexation between the salt and the monomer and/or the propagating radicals.     

Low electrical percolation threshold in poly(ethylene terephthalate)/multi-walled carbon nanotube nanocomposites

Poly(ethylene terephthalate) (PET)/multi-walled carbon nanotube (MWCNT) nanocomposites were prepared by three different methods: in-situ polymerization technique (I-S), direct mixing in the melt (DM) and dilution of a 0.5 wt.% masterbatch, synthesized via in-situ polymerization, using melt mixing (MB). The morphology of the resulting nanocomposites was examined using scanning and transmission electron microscopy and their electrical properties were characterized by ac conductivity measurements. The I-S series of samples exhibited an extremely low electrical percolation threshold (p_c ≈ 0.06 wt.%), as compared to values of similar systems previously mentioned in literature. The MB series showed a comparable p_c value (p_c: 0.05-0.10 wt.%), whereas the investigation revealed a higher p_c in the DM series (p_c: 0.10-0.20 wt.%). Finally, selected concentrations of samples were prepared using OH-functionalized MWCNT, following the I-S procedure. The conductivity of these samples was found to be lower than that of samples with non-functionalized MWCNT.     

Investigation of the effect of epoxide structure on the initiation efficiency in isobutylene polymerizations initiated by epoxide/TiCl4 systems

The effect of the chemical structure of styrene-based epoxides, namely, styrene epoxide (SE), α-methylstyrene epoxide (MSE), p-methylstyrene epoxide (pM-SE) and α-methyl-p-methylstyrene epoxide (pM-MSE), in conjunction with TiCl₄, on the initiation efficiency (I_eff) in the carbocationic polymerization of isobutylene (IB) was investigated. SE yielded living polymerization, but the initiation efficiency was low when compared to MSE (I_eff=8% and 35%, respectively). pM-SE led to non-living IB polymerization, while pM-MSE revealed linear M_n-conversion plot and narrow MWD with a non-linear first order rate plot. Among the epoxides investigated, MSE was the best initiator to scale up the one-step synthesis of polyisobutylenes (PIBs) carrying one primary hydroxyl head group and one tertiary chloride end group. The hydroxyl functionality of these PIBs determined by ¹H-NMR was F_n=1.09±0.16 from 24 experiments.     

Radical polymerization behavior of vinyl phenylsufonylacetate

Vinyl phenylsulfonylacetate (VPSA) was prepared by the reaction of vinyl chloroacetate with sodium benzenesulfinate in acetone in the presence of a phase-transfer catalyst. VPSA showed a high radical homopolymerizability similar to vinyl acetate in spite of the fact that VPSA carries a phenyl group. The polymerization of VPSA with 2,2^′-azobisisobutyrate (MAIB) was kinetically investigated in acetone. The overall activation energy of the polymerization was 27.6 kcal/mol. The polymerization rate (R_p) at 50 °C was expressed by R_p=k[MAIB]^0.67[VPSA]^1.1. Poly(VPSA) showed exothermic (27 °C) and endothermic (57 °C) peaks in its DCS curve, corresponding to crystallization and melting. The tacticity of poly(VPSA) was estimated to be rr=29, mr=49, and mm=22.     

Comparative studies of chemically synthesized polyaniline and poly(o-toluidine) doped with p-toluene sulphonic acid

Polyaniline and poly(o-toluidine) doped with p-toluene sulphonic acid (p-TSA) were synthesized by in situ chemical polymerization method using ammonium per sulphate as an oxidizing agent. This is a novel polymerization process for the direct synthesis of emeraldine salt phase of the polymer. The polymers were characterized by using UV-Vis and FT-IR spectroscopy, SEM, elemental analyzer, TGA/DSC and conductivity measurements. Thermal analysis shows that poly(o-toluidine) is less thermally stable compared to polyaniline. The less conductivity in poly(o-toluidine) is due to the cumulative steric as well as electronic effect of the bulky methyl substituent present on the benzene ring. High temperature conductivity measurements show ‘thermal activated behavior’.