Effect of electron donors on 1,3‐butadiene polymerization by a Ziegler–Natta catalyst based on neodymium

High‐cis polybutadiene produced by catalyst systems based on a rare earth is an elastomer used to produce green tires. This type of tire presents lower rolling resistance, which allows higher fuel economy, and thus fewer chemical compounds are discharged into the atmosphere. In this work, the influence of electron donors [tetrahydrofuran (THF) and tetramethylethylenediamine (TMEDA)] present in the polymerization solvent on the microstructure and molecular weight characteristics of the polybutadiene produced by neodymium catalysts was studied. The catalyst synthesis was carried out in glass bottles for 1 h at a temperature between 5 and 10°C. The catalyst components were diisobutylaluminum hydride, neodymium versatate, and tert‐butyl chloride. The polymerization reaction was carried out for 2 h. The reaction temperature was kept at 70± 3°C. The addition of TMEDA or THF above a determined concentration reduced the catalytic activity, molecular weight, and concentration of cis‐1,4 units (<96%), whereas the polydispersity increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2539–2543, 2005     

Gas phase polymerization of 1,3‐butadiene with supported neodymium‐based catalyst: Investigation of molecular weight

The gas phase polymerization of 1,3‐butadiene (Bd), with supported catalyst Nd(naph)₃/Al₂Et₃Cl₃/Al(i‐Bu)₃ or/and Al(i‐Bu)₂H, was investigated. The polymerization of Bd with neodymium‐based catalysts yielded cis‐1,4 (97.2–98.9%) polybutadiene with controllable molecular weight (MW varying from 40 to 80 × 10⁴ g mol^?1). The effects of reaction temperature, reaction time, Nd(naph)₃/Al(i‐Bu)₃ molar ratio, and cocatalyst component on the catalytic activity and molecular weight of polymers were examined. It was found that there are two kinds of active sites in the catalyst system, which mainly influenced the MW and molecular weight distribution of polybutadiene. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1945–1949, 2004     

Polymerization of 1,3‐butadiene using neodymium chloride tripentanolate–triethyl aluminum catalyst systems

Neodymium chloride tripentanolate catalysts of the general formula NdCl₃ × nL with n = 3, L = 1‐pentanol (II), 2‐pentanol (III), and 3‐pentanol (IV) were prepared by an alcohol interchange reaction between neodymium chloride n isopropanolate (I) with pentanols. These NdCl₃ tripentanolates (II–IV) were characterized by gravimetric and elemental analysis. They were evaluated for homopolymerization of 1,3‐butadiene using triethyl aluminum as cocatalyst in cyclohexane solvent. The role of positional isomers of pentanols (1, 2, and 3) in catalytic activity on conversion, intrinsic viscosity, and microstructure was studied. The neodymium chloride tripentanolate‐2 (III) has high catalytic activity followed by (II) and (IV). The conversions were increased with increases in catalyst, cocatalyst concentrations, and temperature, and decreases in intrinsic viscosity values. The microstructure was determined by Fourier transform‐infrared spectroscopy (FTIR) and found to have a predominantly cis‐1,4 structure (>99%), which was marginally influenced by variation in cocatalyst concentration and temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 595–602, 1999     

1,3‐butadiene polymerization using Co/Nd‐based Ziegler/Natta catalyst: Microstructures and properties of butadiene rubber

Among Ziegler‐Natta catalysts used for 1,3‐butadiene (1,3‐BD) polymerization, the advantage of a neodymium (Nd)‐based catalyst is that it provides butadiene rubber (BR) with a high content of cis?1,4 configuration and a low amount of vinyl?1,2 units. Whereas, a cobalt (Co)‐based catalyst can produce BR with a low content of trans?1,4 configuration. Thus, this research was aimed to prepare BR containing a high content of cis?1,4 configuration with low amounts of both trans?1,4 and vinyl?1,2 units using a combination of Nd‐ and Co‐based Ziegler/Natta catalysts with triethyl aluminum (TEAL) and diethyl aluminum chloride (DEAC) acting as a co‐catalyst and a chlorinating agent, respectively. The effects of the molar Co/Nd ratio, TEAL concentration, DEAC loading, 1,3‐BD content, solvent type, and reaction temperature on % conversion, microstructures, molecular weight, and molecular weight distribution of the obtained BR (Co/Nd‐BR) were evaluated. The Co/Nd‐BR having >97% of cis?1,4 configuration, <2% of trans?1,4 structure, and <1% of vinyl?1,2 unit with >80% conversion was achieved when 3.01 M of 1,3‐BD concentration was treated in a toluene/cyclohexane mixture (7/3 [w/w]). The Co/Nd‐BR exhibited no gel formation with high mechanical performance, which was equivalent to commercial BR produced from a Nd‐based catalyst system. POLYM. ENG. SCI., 55:14–21, 2015. © 2014 Society of Plastics Engineers     

Dimethylsilylbis(1‐indenyl) zirconium dichloride/methylaluminoxane catalyst supported on nanosized silica for propylene polymerization

A dimethylsilylene‐bridged metallocene complex, (CH₃)₂Si(Ind)₂ZrCl₂, was supported on a nanosized silica particle, whose surface area was mostly external. The resulting catalyst was used to catalyze the polymerization of propylene to polypropylene. Under identical reaction conditions, a nanosized catalyst exhibited much better polymerization activity than a microsized catalyst. At the optimum polymerization temperature of 55°C, the former had 80% higher activity than the latter. In addition, the nanosized catalyst produced a polymer with a greater molecular weight, a narrower molecular weight distribution, and a higher melting point in comparison with the microsized catalyst. The nanosized catalyst's superiority was ascribed to the higher monomer concentration at its external active sites (which were free from internal diffusion resistance) and was also attributed to its much larger surface area. Electron microscopy results showed that the nanosized catalyst produced polymer particles of similar sizes and shapes, indicating that each nanosized catalyst particle had uniform polymerization activity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Syndiospecific polymerization of styrene based on dichlorobis(1,3‐diketonato)titanium/methylaluminoxane catalyst system: effects of substituents on catalyst activity

Dichlorobis(substituted‐1,3‐diketonato)titanium complexes 4a–e have been synthesized and were combined with methylaluminoxane as cocatalyst to be employed in the polymerization of styrene. The polystyrenes produced have high syndiotacticities of 94.0–98.2%. The substituents at either 2‐ or 1,3‐positions of 1,3‐diketones can noticeably influence catalyst activities. The catalytic activities of 4a–c bearing 2‐substituents and 4e bearing 1,3‐diphenyl groups are tenfold higher than that of 4d bearing 1,3‐dimethyl groups. The effects of polymerization conditions on the catalyst activities and the syndiotacticities of the polystyrene produced have been examined. © 2000 Society of Chemical Industry     

Polymerization of 1,3‐butadiene with VO(P204)2 activated by methylaluminoxane,purified methylaluminoxane,and trimethylaluminum

The effect of different aluminum‐based cocatalysts (MAO, pMAO, and TMA) on butadiene (Bd) polymerization catalyzed by VO(P204)2 was investigated. The bimodal dependence of the polymer yield on the [MAO]/[V] molar ratio was revealed, and an highest polymer yield was achieved at a rather low [MAO]/[V] molar ratio ([MAO]/[V] = 13). The microstructures of the resulting poly(Bd)s were also significantly influenced by the ratio. In the TMA or pMAO system, the polymer yields were also very sensitive to the [Al]/[V] molar ratio. However, the microstructures of the resulting poly(Bd)s were almost independent of the ratio. In relation to the microstructures of poly(Bd)s obtained by the MAO and TMA systems at various temperatures, the 1,2‐unit contents were found to be the most abundant microstructure for both systems. In the pMAO system, the trans‐1,4‐units were the most abundant. The results of the additions of Lewis bases (THF and TPP) into Bd polyerization system comfirmed the existing of the two types of the reactions of VO(P₂₀₄)₂‐MAO catalyst and had the polymerization process controlled to some extent. The different thermal behaviors of these catalytic systems also show that multiple types of active centers were formed during the reaction between VO(P₂₀₄)₂ and MAO. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Butadiene polymerization in the presence of VOCl3–dialkylmagnesium catalytic system

The butadiene polymerization in toluene at 25°C on VOCl₃? (n‐C₄H₉)Mg(iso‐C₈H₁₇) catalytic system was investigated. The kinetic parameters of polymerization and molecular characteristics of polybutadiene were determined. It was shown that substitution of traditional organoaluminum cocatalysts in trans‐regulating vanadium systems does not have an effect on its stereospecificity, but significantly influences on the active centers reaction ability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 596–600, 2003     

The effect of initiator‐to‐monomer ratio on the properties of the polybutadiene‐ol synthesized by free radical solution polymerization of 1,3‐butadiene

Polybutadiene‐ol was synthesized by solution radical polymerization of 1,3‐butadiene in the presence of hydrogen peroxide as initiator and 2‐propanol as solvent. The ratio of initiator to monomer molar concentration, [I₀]/[M₀], was varied while temperature, reaction time and the type and amount of solvent were kept constant. The effects on the M_n; M_w; M_v; PDI, OH‐number and functionality of the synthesized polyols were studied. By taking several samples during a polymerization batch and analyzing them, the time of reaction was chosen as 100 min, after which the PDI changed dramatically. M_n decreased exponentially with increasing [I₀]/[M₀] according to the relationship M_n = 565.55 ([I₀]/[M₀])^?0.7553. The decrease observed in M_w gradually levelled off with increasing [I₀]/[M₀] and molecular weight distribution broadened at larger values of [I₀]/[M₀]. The OH‐number increases with [I₀]/[M₀]. In addition to the number‐average molecular weight, functionality is dependent on the number of hydroxyl‐terminated chain radicals in the reaction medium. Copyright © 2003 Society of Chemical Industry     

Maghnite‐H+, a solid catalyst for the cationic polymerization of α‐methylstyrene

The polymerization of α‐methylstyrene (AMS) catalyzed by Maghnite‐H⁺ (Mag‐H) was investigated. Mag‐H is a montmorillonite sheet silicate clay, exchanged with protons. It was found that the cationic polymerization of AMS is initiated by Mag‐H at ambient temperature in bulk and in solution. The effect of the amount of Mag‐H, the temperature, and the solvent was studied. The polymerization rate increased with increase in the temperature and the proportion of catalyst, and it was larger in nonpolar solvents. These results indicated the cationic nature of the polymerization. It may be suggested that the polymerization is initiated by proton addition to monomer from Mag‐H. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Cationic polymerization of 1,3‐pentadiene coinitiated by zinc halides

Technology of industrial production of liquid rubber under trademark “SKOP” is based on the cationic polymerization of 1,3‐penadiene (piperylene) in the presence of TiCl₄ or AlCl₃‐based catalytic systems. The disadvantage of these catalytic systems is the high probability of formation of branched and insoluble fractions due to the chain transfer to polymer. This deteriorates the useful qualities of SKOP. Here we propose the new initiating systems for the cationic polymerization of 1,3‐pentadiene based on the homogeneous (dissolved in a minimal amount of diethyl ether) zinc halides (ZnCl₂ and ZnBr₂) as coinitiators and hydrochloric acid, tert‐butyl chloride or trichloroacetic acid as initiators. These initiating systems allow to synthesize fully soluble low molecular weight (M_n = 1000–3000 g mol^?1) poly(1,3‐pentadiene)s with relatively narrow molecular weight distribution (M_w/M_n < 2.0), which do not contain any high molecular weight and insoluble fractions in the whole range of monomer conversion. The polymers synthesized in the presence of zinc halides possess the same microstructure that those prepared with TiCl₄ as coinitiator. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polymerization of butadiene and isoprene with the NdCl3 · 3TBP-TIBA catalyst system

The isoprene and butadiene polymerization processes with the NdCl₃ · 3TBP-TIBA catalyst system (TBP: tributylphosphate, TIBA: triisobutylaluminium) are studied in detail using an original and very accurate experimental technique. The influences of the initial monomer concentration, the polymerization temperature and the catalyst and cocatalyst concentrations on the conversion, the average molar masses, the polydispersity and the microstructure of the polymers are discussed and explained considering the allylic complexes formed between the neodymium atom and the last monomer unit in the macromolecular chain. A first-order reaction with respect to the monomer was obtained. The calculated value of the activation energy (25.58 kJ mol^?1) is lower than for classical Ziegler-Natta catalysts, thus demonstrating the higher catalytic activity of the NdCl₃ · 3TBP-TIBA catalyst system used. Two types of active centers are possible, as confirmed by GPC data. One of them, which includes aluminium, is more stable and favors the transformation from “anti” allylic units to “syn” allylic units. Thus, the 1,4-cis unit content of the prepared polymers is mainly determined by the TIBA concentration. The catalyst does not react by transfer reactions as TIBA does. The obtained conversions are always higher for butadiene than for isoprene due to a higher tendency of the former to complexate with the neodymium atom and forming allylic complexes.     

Cationic polymerization of 2,3‐dihydro‐4H‐pyran using 12‐tungstophosphoric acid as a solid acid catalyst

The bulk polymerization of 2,3‐dihydro‐4H‐pyran catalyzed by 12‐tungstophosphoric acid was investigated. The effects of the time, temperature, and amount of the catalyst on the polymerization reaction were studied. The propagation exclusively involved C?C bonds. Propagation by ring opening was not observed. The total polymerization time and the melting temperature decreased as the proportion of the catalyst and the temperature were increased because of the increase in the number of active centers and the chain‐transfer reaction, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polymerization of 1,3‐dienes containing functional groups: 8. Free‐radical polymerization of 2‐triethoxysilyl‐ 1,3‐butadiene

The presence of a bulky substituent at the 2‐position of 1,3‐butadiene derivatives is known to affect the polymerization behavior and microstructure of the resulting polymers. Free‐radical polymerization of 2‐triethoxysilyl‐1,3‐butadiene ( 1 ) was carried out under various conditions, and its polymerization behavior was compared with that of 2‐triethoxymethyl‐ and other silyl‐substituted butadienes. A sticky polymer of high 1,4‐structure ( ) was obtained in moderate yield by 2,2′‐azobisisobutyronitrile (AIBN)‐initiated polymerization. A smaller amount of Diels–Alder dimer was formed compared with the case of other silyl‐substituted butadienes. The rate of polymerization (R_p) was found to be R_p = k[AIBN]^0.5[ 1 ]^1.2, and the overall activation energy for polymerization was determined to be 117 kJ mol^?1. The monomer reactivity ratios in copolymerization with styrene were r ₁ = 2.65 and r_st = 0.26. The glass transition temperature of the polymer of 1 was found to be ?78 °C. Free‐radical polymerization of 1 proceeded smoothly to give the corresponding 1,4‐polydiene. The 1,4‐E content of the polymer was less compared with that of poly(2‐triethoxymethyl‐1,3‐butadiene) and poly(2‐triisopropoxysilyl‐1,3‐butadiene) prepared under similar conditions. Copyright © 2010 Society of Chemical Industry     

Methylaluminoxane‐activated neodymium chloride tributylphosphate catalyst for isoprene polymerization

The polymerization of isoprene was examined by using a novel binary catalyst system composed of neodymium chloride tributylphosphate (NdCl₃·3TBP) and methylaluminoxane (MAO). The NdCl₃·3TBP/MAO catalyst worked effectively in a low MAO level ([Al]/[Nd] = 50) to afford polymers with high molecular weight (M_n ～10⁵), narrow molecular weight distribution (M_w/M_n = 1.4–1.6), and high cis‐1,4 stereoregularity (> 96%). The catalytic activity increased with an increasing [Al]/[Nd] ratio from 30 to 100 and polymerization temperature from 0 to 50°C, while the M_n of polymer decreased. The presence of free TBP resulted in low polymer yield. Polymerization solvent remarkably affected the polymerization behaviors; the polymerizations in aliphatic solvents (cyclohexane and hexane) gave polymer in higher yield than that in toluene. The M_w/M_n ratio of the producing polymer remained around 1.5 and the gel permeation chromatographic curve was always unimodal, indicating the presence of a single active site in the polymerization system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40153.     

MgCl2‐supported Ziegler–Natta catalyst containing dibenzoyl sulfide donor for propylene polymerization

Polypropylene (PP) was synthesized in the presence of Ziegler–Natta catalysts composed of MgCl₂‐TiCl₄‐internal donor/AlR₃‐external donor. Diisobutyl phthalate is a well‐known internal donor in current PP production. Nevertheless, phthalates are often blamed as endocrine disruptors. The objective is to find an ecofriendly internal donor producing PP with maintaining its physical properties. When using dibenzoyl sulfide, synthesized PP shows the superiority to diisobutyl phthalate in the activity of catalyst (40 vs. 22 kg PP/g catalyst), the isotacticity of polymer (99.5 vs. 98.0 wt % of heptane insolubles), and the molecular weight distribution of PP product (M_w/M_n = 4.8 vs. 4). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40743.     

In Situ Preparation of a Compatibilized Poly(cis‐1,4‐butadiene)/Poly(ε‐caprolactone) Blend

The ternary Ziegler‐Natta‐type catalyst system based on neodymium versatate (NdV), diisobutylaluminium hydride (DIBAH) and ethylaluminium sesquichloride (EASC) was used for the in situ preparation of a compatibilized blend consisting of poly(cis‐1,4‐butadiene) (BR = butadiene rubber) and poly(ε‐caprolactone) (PCL). Poly(cis‐1,4‐butadiene)‐block‐poly(ε‐caprolactone) which acts as compatibilizer for the two immiscible polymers BR and PCL was obtained by a two step sequential polymerization with the preparation of a living cis‐1,4‐BR building block in the first stage and the subsequent polymerization of CL during the second stage. This preparation method resulted in a polymer blend comprising the homopolymers BR and PCL as well as the block copolymer BR‐block‐PCL. For detailed characterization the block copolymer was separated from the respective homopolymers BR and PCL by means of fractionation with the binary solvent mixture dimethylformamide/methylcyclohexane (DMF/MCH) which mixes well at elevated temperature and exhibits phase separation at ambient temperature. ¹H NMR, IR, SEC and TEM were used for characterization of the block copolymer.

TEM of BR‐block‐PCL.     

Zinc‐based catalyst for the ring‐opening polymerization of cyclic esters

A zinc‐based catalyst zinc bis[bis(trimethylsilyl)amide] was used for the polymerization of cyclic esters including L ‐lactide (L ‐LA) and 2‐methyl‐2‐carboxyl‐propylene carbonate (MBC). The polymerization of L ‐lactide in THF could be carried out successfully under mild conditions in very short time by using the zinc catalyst and alcohols as the initiators. Kinetic study in solution polymerization prooved the polymerization has high monomer conversion degree close to 100% and the molecular weight of the resulting polyester has linear increase with the increase of [M]₀ /[I] (molar ratio of monomer to initiator). Sequential polymerization of L ‐LA and MBC in THF also showed high MBC conversion of 94% with a narrow molecualr weight maintained, indicating a living nature of this polymerization. The zinc catalyst system has also been used for the L ‐LA bulk polymerization with a high monomer conversion. ¹³C NMR indicated the polymer possesses high regioregularity and the minor regioirregular component was owing to the D ‐LA in the monomer inserted into the polymer mainchain during the transesterifcation. Interaction between monomer and zinc catalyst has been found to be a key factor to sustain a homogenous solution during the initiating procedure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Seaweed‐derived κ‐carrageenan: Modified κ‐carrageenan as a recyclable green catalyst in the multicomponent synthesis of aminophosphonates and polyhydroquinolines

A seaweed‐derived biopolymer, κ‐carrageenan (KCAR), with a slight modification was assumed as an organosulfonic‐type Bronsted acid in the catalysis of polyhydroquinoline and α‐aminophosphonate syntheses through one‐pot multicomponent reaction procedures under aqueous conditions. In this investigation, KCAR was found to be an efficient, heterogeneous and homogeneous, recyclable, economical, and green catalyst. Moreover, biocompatibility, ease of separation, high chemoselectivity, and lower reaction time were other aspects of this catalyst. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43190.     

Nano‐sized silica supported Me2Si(Ind)2ZrCl2/MAO catalyst for ethylene polymerization

Nano‐sized and micro‐sized silica particles were used to support a zirconocene catalyst [racemic‐dimethylsilbis(1‐indenyl)zirconium dichloride], with methylaluminoxane as a cocatalyst. The resulting catalyst was used to catalyze the polymerization of ethylene in the temperature range of 40–70°C. Polyethylene samples produced were characterized with scanning electron microscopy (SEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). Nano‐sized catalyst exhibited better ethylene polymerization activity than micro‐sized catalyst. At the optimum temperature of 60°C, nano‐sized catalyst's activity was two times the micro‐sized catalyst's activity. Polymers obtained with nano‐sized catalyst had higher molecular weight (based on GPC measurements) and higher crystallinity (based on XRD and DSC measurements) than those obtained with micro‐sized catalyst. The better performances of nano‐sized catalyst were attributed to its large external surface area and its absence of internal diffusion resistance. SEM indicated that polymer morphology contained discrete tiny particles with thin long fiberous interlamellar links. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011