Polymerization of butadiene under the action of lithium containing initiating system

Polymerization of butadiene under the action of n-butyl lithium modified by of alkali and alkaline earth metal alkoxides was researched. Microstructure and molecular characteristics of the samples of polybutadiene synthesized were determined. The influence of polymerization conditions on the properties of the resulting polymer was examined.     

Polymerization of butadiene with titanium-magnesium nanocatalysts

The suspension polymerization of butadiene in the presence of titanium-magnesium nanocatalysts combined with triisobutylaluminum is studied. The resulting polybutadiene is shown to contain up to 99% trans-1,4-units. The dependences of polymer microstructure on temperature and the Al-to-Ti ratio are investigated. The kinetic parameters of the process and the properties of trans-1,4-polybutadiene are examined.     

Polymerization of butadiene sulfone

Polymerization of butadiene sulfone (BdSO₂) by various catalysts was studied. Azobisisobutyronitrile (AIBN), butyllithium, tri-n-butylborn (n-Bu)₃B, boron trifluoride etherate, Ziegler catalyst, and γ-radiation were used as catalysts. Butadiene sulfone did not polymerize with these catalysts at low temperatures (below 60°C.), but polymers were obtained at high temperature with AIBN or (n-Bu)₃B. The polymerization of BdSO₂ initiated by AIBN in benzene at 80–140°C. was studied in detail. The obtained polymers were white, rubberlike materials and insoluble in organic solvents. The polymer composition was independent of monomer and initiator concentrations and reaction time. The sulfur content in polymer decreased with increasing polymerization temperature. The polymers prepared at 80 and 140°C. have the compositions (C₄H₆)_1.55- (SO₂) and (C₄H₆)_3.14(SO₂), respectively, and have double bonds. These polymers were not alternating copolymers of butadiene with sulfur dioxide. The polymerization mechanism was discussed from polymerization rate, polymer composition, and decomposition rate of BdSO₂. From these results, the polymerization was thought to be “decomposition polymerization,” i.e., butadiene and sulfur dioxide, formed by the thermal decomposition of BdSO₂, copolymerized.     

Polymerization of (meth)acrylates with aluminum-based initiators

<正>A simple and effective way to prepare poly(acrylate)s,such as poly(methacrylate),poly(butyl acrylate) and poly(butyl methacrylate),has been achieved by using the single component aluminum-based compounds,such as modified methylaluminoxane(MMAO),triisobutylaluminium(TIBA) and triethylaluminium(TEA) as initiators.Effective initiations and high molecular weight polymers with unimodal molecular weight distributions could be easily obtained by varying the reaction parameters of systems under mild conditions.Although these aluminum compounds were inefficient initiators for methyl methacrylate(MMA) polymerization,they exhibited remarkable catalytic activity for butyl methacrylate(BMA) polymerization,affording high molecular weight poly(BMA)s.     

Polymerization of epoxide with hydroxylamides as thermally latent initiators

A new class of thermally latent initiators for the ring‐opening polymerization of epoxides has been developed. The latent initiators developed herein were the hydroxylamides 1a , 1b , and 1c , which were synthesized from phthalide, 3‐isochromanone, and cis‐cyclohexahydrophthalide, respectively, by their ring‐opening reactions with pyrrolidine. These hydroxylamides were designed so that their hydroxyl groups could attack the amide moiety intramolecularly upon heating, leading to ring closure and formation of the corresponding lactones while releasing pyrrolidine, the initiator for the anionic ring‐opening polymerization of an epoxide. The temperatures at which this thermal dissociation occurred were strongly dependent on the hydroxylamide molecular structure. When using the hydroxylamides as thermally latent initiators, the polymerizations of bisphenol‐A diglycidyl ether were investigated at various temperatures. This investigation clarified that the threshold temperature, that is, the temperature at which polymerization was initiated, increased in the order of 1a , 1b , and then 1c . © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2611–2617     

Polymerization of butadiene with the NiCl2‐methylaluminoxane catalyst

The polymerization of butadiene (Bd) with the soluble and insoluble parts of the NiCl₂‐methylaluminoxane (MAO) catalyst was investigated. Both parts initiate the polymerization of Bd to give a high molecular weight polymer consisting of mainly cis‐1,4‐structure. The activity of the soluble part for the polymerization is higher than that of the insoluble part. We presume that NiCl₂ reacts with MAO to give a soluble alkyl‐nickel complex that shows high activity for the polymerization of Bd.     

Polymerization of methyl methacrylate with ferric laurate in combination with various substituted amines as initiators

The effect of various substituted amines on the polymerization of methyl methacrylate initiated by ferric laurate—amine as the initiator system has been studied in carbon tetrachloride medium at 60°C. Amines used are n-butyl amine, di-n-butyl amine. The rate of polymerization is found to follow the order: tertiary > secondary > primary amine. From the detailed kinetic studies it was found that the overall polymerization rate can be expressed by the equation: The relative activity of the different amines has been found to be dependent on the relative electron-donating tendency of the substituents present in the amine. The mechanism of the polymerization is discussed on the basis of these results, and various kinetic constants are evaluated.     

Polymerization of butadiene by neodymium catalysts on oxide supports

The suspension polymerization of butadiene in hexane and toluene in the presence of catalysts composed of organoaluminum compounds and neodymium versatate applied on oxides (Al₂O₃, aluminum silicate A-14, Aerosil A-300, and white soot BS-200) has been studied. Triisobutylaluminum and its combination with ethylaluminum sesquichloride are used as organoaluminum compounds. The activity and stereospecificity of the catalysts has been found to depend strongly on the nature of supports. Catalysts based on Aerosil and white soot appear to be the most active. With the use of these catalysts, polybutadiene containing up to 97.5% 1,4-cis-units has been synthesized.     

Polymerization of butadiene by polybutadienyllithium in the presence of tetrahydrofuran

Polymerization of butadiene by polybutadienyllithium (PBLi) has been studied in THF for concentrations of PBLi between 10^?4 and 10^?2 mol/I in the range 20–70°, and also in a non-polar medium using THF as an added electron donor at various THF/PBLi ratios. The kinetic order with respect to PBLi in THF was 0.5 and the activation energies of the overall process and the propagation on free carbanions were 7.5 and 6.7 kcal/mol respectively. Rate constants for propagation on the free carbanions were calculated at three temperatures and rate constants for propagation on contact ion pairs were determined at two THF/PBLi ratios. Data on the kinetics of polymerization and the microstructure of the polymers suggest that contact ion pairs and free carbanions participate in propagation reactions.     

Block copolymerization. VI. Polymerization of pivalolactone with macromolecular initiators from polystyrene and polytetrahydrofuran

Polymerization of pivalolactone with polystyryl sodium or polystyryl ethoxysodium in tetrahydrofuran resulted in homopolymer mixtures. Block copolymers of pivalolactone and styrene were obtained by the polymerization of pivalolactone with sodium polystyrene carboxylate in tetrahydrofuran containing dimethyl sulfoxide. Block copolymers of pivalolactone and tetrahydrofuran were obtained by the polymerization of pivalolactone with polytetrahydrofuran containing carboxylate endgroups. The mechanism of the initiation reaction and various factors affecting block efficiency are discussed.     

Anionic polymerization of methacrylonitrile—II.: Polymerization with 1,1-diphenyl-n-hexyllithium and sec-butyllithium as initiators

The anionic polymerization of methacrylonitrile has been investigated at ?75° in toluene with 1,1-diphenyl-n-hexyllithium and sec-butyllithium as initiators. With both initiators, initiation was fast and no unreacted initiator was left. The efficiency was much higher for 1,1-diphenyl-n-hexyllithium than for sec-butyllithium probably for steric reasons. With both initiators, a second order dependence on initiator was found. To check that this is not an artifact resulting from measurements in a medium starting to gel at a point which is difficult to detect precisely, kinetic measurements were also carried out with 2-polystyryl-l,l-diphenylethyllithium as an initiator. Second order kinetics were again obtained; the propagation rate constants, taking into account the efficiencies of initiators, were the same within experimental error for all three initiators. Viscosity measurements performed on a methacrylonitrile “capped” 2-polystyryl-l,l-diphenylethyllithium initiator showed the living polymethacrylonitrile chains to be associated.     

Hindered lithium dialkylamide initiators for the living anionic polymerization of methacrylic esters

Lithium diisopropylamide is an efficient initiator for the anionic polymerization of methyl methacrylate in polar solvents at –78°C. Predictable molecular weights based on the initiator concentration were obtained, yields were quantitative, and molecular weight distributions were relatively narrow (<1.30). The presence of an amino end group and confirmation of the initiation mechanism were confirmed by potentiometric titration using HClO₄. Number-average molecular weights determined by titration agreed well with values determined by SEC. Other lithium dialkylamides that contain larger alkyl groups such as lithium diisobutylamide were less efficient initiators. This was attributed to the more nucleophilic anion due to less steric hindrance near the nitrogen atom. Molecular weight distributions were significantly broadened (>2.0), and molecular weight control was not achieved. However, polymer yields were quantitative. In all cases, PMMA stereochemistry was indicative of a solvent-separated lithium counterion, and triad compositions were identical to organolithium initiated homopolymers, i.e., 78% syndiotactic, 20% heterotactic, and 2% isotactic. © 1994 John Wiley & Sons, Inc.     

Polymerization of butadiene catalyzed by a cobalt-containing catalyst in aliphatic media

The polymerization of butadiene catalyzed by the preformed Co(2-ethylhexanoate)₂-Et₃Al₂Cl₃-isoprene (a molar ratio of 1: 20: 20) catalytic system in toluene, cyclohexane, and hexane has been studied. In toluene, the catalyst demonstrates high activity and stereospecificity and yields a high-molecular-mass polymer. In cyclohexane and hexane, the catalyst has a high activity but affords polymers with lower contents of 1,4-cis-units and reduced intrinsic viscosities. The addition of EtAlCl₂ and/or a decrease in the polymerization temperature make it possible to obtain polybutadiene containing more than 96% 1,4-cis-units and an acceptable intrinsic viscosity (2.0–2.8 dl/g) in the nonaromatic solvents as well.     

Polymerization of liposomes composed of diene-containing lipids by radical initiators. II. Polymerization of monodiene-type lipids as liposomes

1-Palmitoyl-2(2,4-octadecadienoyl)-sn-glycero-3-phosphocholine (POPC), a polymerizable lipid that contains one diene group in only a 2-acyl chain, was polymerized as liposome in an aqueous medium. Polymerization was initiated by water-insoluble azobisisobutyronitrile (AIBN), or water-soluble azobis(2-amidinopropane) dihydrochloride (AAPD). AIBN was mixed with monomeric lipids, and the mixture was dispersed in an aqueous medium by sonication to prepare AIBN-containing monomeric lipid liposomes. On the other hand, AAPD was simply added to the liposome suspension. The POPC liposomes were easily polymerized by the addition of AAPD, a water-soluble radical initiator, but few were polymerized by AIBN. The results suggested that the diene group in the 2-acyl chain was in an aqueous phase and, therefore, easily polymerized by a water-soluble radical initiator. The polymerized POPC liposomes were revealed to be more stable than those of monomeric ones because the scattered-light intensity from the polymerized POPC liposome suspension changed a little by the addition of Triton X-100. For only the polymerized ones, the liposome structure was confirmed by TEM after addition of an excess amount of Triton X-100.     

Anionic polymerization. III. Polymerization of butadiene with alkali metal alkoxide-modified alkali metal system

A high molecular weight polybutadiene was prepared in hexane solvent by using alkali metal (Li, Na, K) and metal tert-butoxide (Li, Na, K) as a polymerization initiator. The microstructure of polybutadiene varies, depending on the type of modifiers and polymerization and temperatures. The results and mechanistic implications of this study are discussed.