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     

以新癸酸钕/正丁基锂/氯化二乙基铝催化体系合成聚丁二烯

以新癸酸钕(简称Nd)/正丁基锂(简称Li)/氯化二乙基铝(简称Al)为催化剂进行丁二烯聚合,考察了聚合温度、催化剂配制时c(Li)/c(Nd)和c(Al)/c(Nd)以及烷基铝种类对丁二烯聚合的影响。结果表明,在c(Li)/c(Nd)为12、c(Al)/c(Nd)为15左右时催化剂具有最高的催化活性,聚合物收率可达100%。在0℃,c(Li)/c(Nd)为12、c(Al)/c(Nd)为15的条件下,可以得到具有高顺式-1,4-结构(摩尔含量97.6%)、窄分子量分布(分子量分布指数1.23)的聚合物。随聚合温度升高,催化体系的活性提高,所得聚合物的相对分子质量和顺式-1,4-结构摩尔含量降低。     

Polymerization of butadiene and copolymerization of butadiene with styrene using neodymium amide catalysts

The polymerization of butadiene was performed with catalysts based on the complex Nd{N(SiMe₃)₂}₃ (1). This amide complex in combination with methyaluminoxane or with a boron compound ([HNMe₂Ph][B(C₆F₅)₄], [CPh₃][B(C₆F₅)₄] or B(C₆F₅)₃) and Al(iBu)₃ showed high activity and stereospecificity in polymerization of butadiene. The cationic complex [Nd{N(SiMe₃)₂}₂(THF)₂][B(C₆F₅)₄] (2) was prepared by reaction of 1 and [HNMe₂Ph][B(C₆F₅)₄]. The catalyst 2/Al(iBu)₃ (ratio Al/Nd: 10/1) was highly active for butadiene polymerization. Copolymerization of butadiene and styrene was performed with the catalytic system Nd{N(SiMe₃)₂}₃/[HNMe₂Ph][B(C₆F₅)₄]/Al(iBu)₃ (3). Copyright © 2004 Society of Chemical Industry     

Preparation and swelling properties of solution crosslinked poly(cis‐1,4‐butadiene) gels

Poly(cis‐1,4‐butadiene) (PCB) gels were prepared by the crosslinking polymerization of 4‐tert‐butylstyrene (tBS) and divinylbenzene (DVB) onto unvulcanized butadiene rubber with a solution polymerization technique with benzoyl peroxide (BPO) as an initiator. The effects of the reaction conditions, such as the amount of the solvent, the amount of DVB and tBS, and the initiator (BPO), on the equilibrium swelling ratio (Q_e) were also investigated. The highest oil absorbencies of crosslinked gels in xylene and cyclohexane were 51.35 and 32.98 g/g, respectively. A swelling kinetic equation was proposed for this system: Q_t = Q_e ? {Kt + [1/(Q_e ? Q₀)]}^?1, where Q_t is the swelling ratio at time t, Q₀ is the initial swelling ratio, and K is the swelling kinetic constant. This equation fit the experimental results quite well. The diffusion of organic solvents in PCB gels was Fickian. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2241–2245, 2003     

Synthesis of high molecular weight copolymer of styrene and butadiene bearing high 1,4‐cis butadiene unit from copolymerization with CpTiCl3/methylaluminoxane catalyst

Copolymerization of styrene (St) and butadiene (Bd) with CpTiCl₃/methylaluminoxane (MAO) catalyst in the presence or absence of chloranil (CA) was investigated. The CpTiCl₃/MAO catalyst showed a high activity for the copolymerization of St with Bd. The 1,4‐cis contents in the Bd units for the copolymerization of St and Bd with the CpTiCl₃/MAO catalyst was observed, and the 1,4‐cis content was optimum at a MAO/Ti mole ratio of around 225. The effect of the polymerization temperature on the copolymerization was noted, as was the effect of the 1,4‐cis microstructure in the Bd units for the copolymerization of St and Bd. The addition of CA to the CpTiCl₃/MAO catalyst was found to influence the molecular weight of the copolymer. The high weight‐average molecular weight copolymer (M_w = ca. 50 × 10⁴) consisting of mainly a 1,4‐cis microstructure of Bd units (1,4‐cis = 80.0%) was obtained from the copolymerization with the CpTiCl₃/MAO catalyst in the presence of CA (CA/Ti mole ratio = 1) at 0°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2942–2946, 2003     

1,2‐Polymerization of 1,3‐butadiene with Cr(acac)3‐alkylaluminum catalysts

The polymerization of butadiene (Bd) with chromium(III) acetylacetonato [Cr(acac)₃]‐trialkylaluminum (AlR₃) or methylaluminoxane (MAO) catalysts was investigated for the synthesis of 1,2‐poly(Bd). The polymerization of Bd was found to proceed with Cr(acac)₃‐AlR₃ (R‐Me, Et, i‐Bu) catalysts to give poly(Bd) with a high 1,2‐vinyl content, but highly isotactic 1,2‐poly(Bd) was not synthesized. The Cr(acac)₃‐MAO catalyst gave a polymer consisting of low 1,2 units. The effects of the Al/Cr mole ratios on the polymerization of Bd with the Cr(acac)₃‐AlR₃ catalysts were observed. With an increase of Al/Cr mole ratios, the isotactic (mm) content of the polymer increased but the 1,2‐vinyl contents decreased. The effects of the aging time and temperatures of the catalysts on the polymerization of Bd with the Cr(acac)₃‐AlR₃ catalysts were also observed, and the lower polymerization temperature and the prolonged aging time were favored to produce the 1,2‐vinyl structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1621–1627, 2000     

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 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     

Highly trans‐1,4‐specific polymerization of 1,3‐butadiene catalyzed by [2,6‐bis{(4S)‐ (−)‐isopropyl‐2‐oxazolin‐2‐yl}pyridine] chromium complex activated with modified methylaluminoxane

Chromium complexes with N,N,N‐tridentate ligands, LCrCl₃ (L = 2,6‐bis{(4S)‐(?)‐isopropyl‐2‐oxazolin‐2‐yl}pyridine ( 1 ), 2,2′:6′,2″‐terpyridine ( 2 ), and 4,4′,4″‐tri‐tert‐butyl‐2,2′:6′,2″‐terpyridine ( 3 )), were prepared. The structures of 1 and 2 were determined by X‐ray crystallography. Upon activation with modified methylaluminoxane (MMAO), 1 catalyzed the polymerization of 1,3‐butadiene, while 2 and 3 was inactive. The obtained poly(1,3‐butadiene) obtained with 1 ‐MMAO was found to have completely trans‐1,4 structure. The 1 ‐MMAO system also showed catalytic activity for the polymerization of isoprene to give polyisoprene with trans‐1,4 (68%) and cis‐1,4 (32%) structure. Copyright © 2011 Society of Chemical Industry     

Binary copolymerization of 4‐methyl‐1,3‐pentadiene with styrene,butadiene and isoprene catalysed by a titanium [OSSO]‐type catalyst

Binary copolymerization of 4‐methyl‐1,3‐pentadiene (4MPD) with styrene, butadiene and isoprene promoted by the titanium complex dichloro{1,4‐dithiabutanediyl‐2,2′‐bis[4,6‐bis(2‐phenyl‐2‐propyl)phenoxy]}titanium activated by methylaluminoxane is reported. All the copolymers are obtained in a wide range of composition and the molecular weight distributions obtained from gel permeation chromatographic analysis of the copolymers are coherent with the materials being copolymeric in nature. The copolymer microstructure was fully elucidated by means of ¹H NMR and ¹³C NMR spectroscopy. Differential scanning calorimetry shows an increase of glass transition temperature (T_g) with the amount of 4MPD in the copolymers with butadiene and isoprene, while in the copolymers with styrene T_g is increased on increasing the amount of styrene. © 2016 Society of Chemical Industry     

Blends of polypropylene with poly(cis‐butadiene) rubber. III. Study on the phase structure and morphology of incompatible blends of polypropylene with poly(cis‐butadiene) rubber

Scanning electron microscopy (SEM) was used to study the structure and morphology of partly compatible binary blends of polypropylene with poly(cis‐butadiene) rubber. The SEM images were transformed by digital image process software designed by our group, and binarized images were obtained. The size (mean diameters d_p and characteristic lengths L) of phases was calculated using binarized images. Small‐angle light scattering was employed to study the structure and morphology of phases in the blends. The structural parameters, including correlation distance a_c, average chord lengths l , and mean diameter D_S to describe the structure and morphology of phases in binary blends, were calculated based on the corresponding theory. The variation of correlation distance a_c, average chord length l , and mean diameter D_S were the same as that of mean diameters d_p and characteristic length L. At the same time, the distribution of sizes of the dispersed phase in binary blends was calculated with graph transition technique, which possessed log‐normal distribution characterization. The power spectrum images corresponding to small‐angle light scattering images were obtained by two‐dimensional fourier transformation of binary images. The correlation distances a_cf and average chord length l _f have been calculated by intensity of power spectrum images and that was the same as a_c and l . © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4900–4909, 2006     

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     

Mechanical and flame‐retarding properties of styrene–butadiene rubber filled with nano‐CaCO3 as a filler and linseed oil as an extender

A nanosize CaCO₃ filler was synthesized by an in situ deposition technique, and its size was confirmed by X‐ray diffraction. CaCO₃ was prepared in three different sizes (21, 15, and 9 nm). Styrene–butadiene rubber (SBR) was filled with 2–10 wt % nano‐CaCO₃ with 2% linseed oil as an extender. Nano‐CaCO₃–SBR rubber composites were compounded on a two‐roll mill and molded on a compression‐molding machine. Properties such as the specific gravity, swelling index, hardness, tensile strength, abrasion resistance, modulus at 300% elongation, flame retardancy, and elongation at break were measured. Because of the reduction in the nanosize of CaCO₃, drastic improvements in the mechanical properties were found. The size of 9 nm showed the highest increase in the tensile strength (3.89 MPa) in comparison with commercial CaCO₃ and the two other sizes of nano‐CaCO₃ up to an 8 wt % loading in SBR. The elongation at break also increased up to 824% for the 9‐nm size in comparison with commercial CaCO₃ and the two other sizes of nano‐CaCO₃. Also, these results were compared with nano‐CaCO₃‐filled SBR without linseed oil as an extender. The modulus at 300% elongation, hardness, specific gravity, and flame‐retarding properties increased with a reduction in the nanosize with linseed oil as an extender, which helped with the uniform dispersion of nano‐CaCO₃ in the rubber matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2563–2571, 2005     

Performance study of modified ZSM‐5 as support for bimetallic chromium–copper catalysts for VOC combustion

The catalytic performance of bimetallic chromium–copper supported over untreated ZSM‐5 (Cr? Cu/Z), ZSM‐5 treated with silicon tetrachloride (Cr–Cu/SiCl₄‐Z) and ZSM‐5 treated with steam (Cr–Cu/H₂O‐Z) is reported. The activity is based on the combustion of ethyl ethanoate and benzene at a feed concentration of 2000 ppm and a gas hourly space velocity (GHSV) of 32 000 h^?1. Due to higher reactivity and larger molecular size compared with that of water molecules, SiCl₄ reacted at the external surface of ZSM‐5 crystals. Cr–Cu/SiCl₄‐Z and Cr–Cu/H₂O‐Z both gave slightly lower conversion and carbon dioxide yield compared with Cr–Cu/Z. This was attributed to larger active metal crystallites formed in the mesopores and narrowing pore mouth and pore intersection by extraframework species. Cr–Cu/SiCl₄‐Z and Cr–Cu/H₂O‐Z both had reduced concentration and strength of acid sites, thus making them less susceptible to deactivation by coking. The coke accumulated by these two catalysts was relatively softer and more easily decomposed in oxygen during catalyst regeneration. Copyright © 2004 Society of Chemical Industry     

Copolymerization of butadiene with styrene using a rare‐earth metal compound – dialkylmagnesium – halohydrocarbon catalytic system

Copolymerizations of butadiene (Bd) with styrene (St) were carried out with catalytic systems composed of a rare‐earth compound, Mg(n‐Bu)₂ (di‐n‐butyl magnesium) and halohydrocarbon. Of all the rare earth catalysts examined, Nd(P₅₀₇)₃–Mg(n‐Bu)₂–CHCl₃ showed a high activity in the copolymerization under certain conditions: [Bd] = [St] = 1.8 mol l^?1, [Nd] = 6.0 × 10^?3 mol l^?1, Mg/Nd = 10, Cl/Nd = 10 (molar ratio), ageing for 2 h, copolymerization at 50 °C for 6–20 h. The copolymer of butadiene and styrene obtained has a relatively high styrene content (10–30 mol%), cis‐1,4 content in butadiene unit (85–90%), and molecular weight ([η] = 0.8–1 dL g^?1). Monomer reactivity ratios were estimated to be r_Bd = 36 and r_St = 0.36 in the copolymerization. © 2002 Society of Chemical Industry     

Performance of silicon‐carbide foams as supports for Pd‐based methane combustion catalysts

BACKGROUND: Cellular foam materials are a new type of catalyst support that provides improved mass and heat transport characteristics and similar pressure drops to other well‐established structured supports such as monoliths. RESULTS: A Pd‐based catalyst has been prepared using a moderate surface area (25 m² g^?1) β‐SiC foam support without further washcoating. The stability of this catalyst has been tested for methane combustion at lean conditions, showing a small decrease of activity during the first 10 h followed by stable performance. Characterization of fresh and aged catalyst shows no significant changes. The influence of the most important reaction conditions, such as reactor loading (0.25–1 g), temperature (300–550 °C) and inlet methane concentration (833 and 1724 ppm), was studied in a fixed‐bed reactor. The results were fitted to three kinetic models: Mars‐van Krevelen; Langmuir‐Hinselwood; power‐law kinetics. CONCLUSIONS: The Pd/β‐SiC foam catalyst, prepared without the previous addition of a washcoating has been demonstrated to be stable for the combustion of methane‐air lean mixtures. A Mars‐van Krevelen kinetic model provides the best fit to the results obtained. Copyright © 2011 Society of Chemical Industry     

Mechanical properties and thermal aging behavior of styrene‐butadiene rubbers vulcanized using liquid diene polymers as the plasticizer

The mechanical properties of styrene‐butadiene rubber (SBR) vulcanizates prepared using various plasticizers including liquid polybutadiene and styrene‐butadiene copolymers were investigated. The effect of the liquid polymers as the plasticizers on the mechanical properties of the polymers, such as the hardness, tensile storage modulus, tanδ, and the modulus at 100% elongation values, were determined before and after the thermal aging. As a result, it was revealed that the use of these liquid polymers gave less amount of change in the measurement values for the mechanical properties during the aging. The crosslinking density and the amount of free polymers were also determined on the basis of the swelling and extraction data, respectively, using several organic solvents. These results support the fact that the added liquid polymers are fixed to the SBR networks. We revealed the superiority of the liquid styrene‐butadiene copolymers as the plasticizer, which provides sufficient mechanical properties after vulcanization and the excellent maintenance of the properties during the thermal aging process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Sulphonation of polystyrene‐butadiene rubber with chlorosulphonic acid for proton exchange membrane: Kinetic study

Proton exchange membrane for fuel cell application was synthesized from a hydrophobic polystyrene‐butadiene rubber (PSBR) via sulphonation at different temperatures (22, 35, 55, 65, and 75°C) and varying time with chlorosulphonic acid. Infra‐red spectroscopy (IR) and proton nuclear magnetic resonance (¹H‐NMR) were used to confirm the occurrence of sulphonation. Sulphonation occurred only on the phenyl ring with a maximum degree of sulphonation of 70.96 mole percent. Consequently, 10^?3–10^?2 S/cm proton conductivity was achieved. Two models for the reaction kinetics were investigated: first‐order reversible and first‐order irreversible, respectively. However, the reaction kinetic was found to obey the first‐order reversible model. The activation energy (E_a) of the reaction was calculated to be 41.56 kJ/mol of PSBR repeat unit, which is an indication that the reaction is nonspontaneous. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010