Polymerization Of Isoprene Research Articles

ИДЕНТИФИКАЦИЯ ПЕРЕМЕННЫХ ПАРАМЕТРОВ ДИНАМИКИ ХИМИЧЕСКОГО РЕАКТОРА ДЛЯ БЛОЧНОЙ ПОЛИМЕРИЗАЦИИ ИЗОПРЕНА

The dynamics of non-isothermal chemical batch reactor for isoprene polymerization process in bulk, i.e. the object with the distributed, and also the variable parameters, is considered. The identification procedure proposed makes it possible to describe the reactor dynamics with the help of a system of differential equations with constant coefficients in each of partial time intervals. The transfer functions for operating channel obtained are as follows: the reaction mixture temperature – the cold carrier temperature, and also the average conversion – the cold carrier temperature.

Isoprene Polymerization in the Presence of Phosphate Catalytic Systems Based on a Mixture of Neodymium and Gadolinium Salts

Coordination polymerization of isoprene in the presence of Ziegler–Natta catalytic systems based on a mixture of neodymium and gadolinium bis(2-ethylhexyl) phosphates at the neodymium/gadolinium molar ratios of 25/75, 50/50, and 75/25 was studied. These catalytic systems exhibit high catalytic activity in isoprene polymerization, equal to that of the catalytic system based on neodymium bis(2-ethylhexyl) phosphate. The influence of the Nd/Gd ratio on the molecular-mass characteristics and microstructure of the polymers obtained was examined. The kinetic parameters of the isoprene polymerization using catalytic systems based on a mixture of neodymium and gadolinium salts were determined. The possibility of using such systems in the synthesis of stereoregular cis-1,4-polyisoprene with the optimum level of molecular masses was demonstrated

Catalytic Behavior of Cobalt Complexes Bearing Pyridine-Oxime Ligands in Isoprene Polymerization.

Several cobalt(II) complexes Co1-Co3 bearing pyridine-oxime ligands (L1 = pyridine-2-aldoxime for Co1; L2 = 6-methylpyridine-2-aldoxime for Co2; L3 = phenyl-2-pyridylketoxime for Co3) and picolinaldehyde O-methyl oxime (L4)-supported Co4 were synthesized and well characterized by FT-IR, mass spectrum and elemental analysis. The single-crystal X-ray diffraction of complex Co2 reveals that the cobalt center of CoCl2 is coordinated with two 6-methylpyridine-2-aldoxime ligands binding with Npyridine and Noxime atoms, which feature a distorted octahedral structure. These Co complexes Co1-Co4 displayed extremely high activity toward isoprene polymerization upon activation with small amount of AlClEt2 in toluene, giving polyisoprene with high activity up to 16.3 × 105 (mol of Co)-1(h)-1. And, the generated polyisoprene displayed high molecular weights and narrow molecular distribution with a cis-1,4-enriched selectivity. The type of cobalt complexes, cocatalyst and reaction temperature all have effects on the polymerization activity but not on the microstructure of polymer.

Enhanced Control of Isoprene Polymerization with Trialkyl Rare Earth Metal Complexes through Neutral Donor Support.

The development of catalysts for stereospecific polymerization of 1,3-dienes is an area of interest due to the robust nature of poly(1,3-diene)s' physical and mechanical properties, as well as the material's versatility in many applications. Dialkyl rare earth metal complexes supported by a diverse cast of ligand frameworks are selective for the polymerization of 1,3-dienes and are an exciting option for examination. However, development in this area has been hampered by the focus on complex catalyst systems that are costly to make. In this study, we synthesize a series of simple homoleptic trialkyl rare earth metal precatalysts and highlight their efficacy for isoprene polymerization using 1 or 2 equiv of [Ph3C][B(C6F5)4] activator. We investigated the addition of commercially available in situ donors, leading to the identification of triphenylphosphine as an ideal support to enhance the dispersity control and prevent loss of catalyst activity. We demonstrated how the activation and reaction conditions, including the order/time of reagent addition and donor electronics, had a major impact on the rate, control, and selectivity for the polymerization of 1,3-dienes. Further interrogation of the catalyst system signals the crucial role of triphenylphosphine in providing enhanced stability and control in this living catalyst system.

Length effect of crosslinkers on the mechanical properties and dimensional stability of vitrimer elastomers with inhomogeneous networks

Inhomogeneous network construction is a useful strategy to solve the trade-off between mechanical strength and creep in vitrimer rubbers. But it is still lack of tools to tune the mechanical properties and network dynamics of this new system. In this paper, uneven distribution of functional groups was realized by sequential coordination polymerization of myrcene and isoprene and epoxidation. The following epoxidation and curing generated VMI-x samples with inhomogeneous network. Polyisoprene was used to prepare control samples called VPI-x with homogeneous network. Different lengths of dicarboxylic acid crosslinkers (SA = succinic acid, HA = heptanedioic acid, DA = decanedioic acid) were used to probe their effects on dynamic behaviors, mechanical properties and recyclability. Morphological test and nanomechanical mapping confirmed the inhomogeneous feature of VMI-x samples. For both inhomogeneous and homogeneous samples, SA and DA crosslinkers brought higher tensile strength and modulus, earlier SIC phenomenon and higher orientation percentage of amorphous molecular chains than those of HA, which are ascribed to extra permanent cross-linking existing in SA samples and transition entanglements existing in DA samples. However, the constrain effect of SA crosslinker is too strong in inhomogeneous network to sacrifice the extensibility, which is much smaller than those of HA and DA. SA and DA samples also present restricted segmental motion and superior creep resistant properties compared to HA samples according to the results of broadband dielectric spectroscopy and DMA test. Differently, at high temperature above 130 °C, the stress relaxation, topology freezing transition temperature (Tv) and recycling efficiency of strength are dominated by the crosslinker length monotonically, probably due to the disentanglement of DA crosslinkers. Compared to homogeneous network, inhomogeneous ones showed obvious enhanced mechanical properties, lower hysteresis, quicker segmental relaxation, lower creep and quicker network relaxation. This work demonstrates that crosslinker lengths could tune the vast aspects of vitrimer elastomers and is a non-negligible factor to determine their properties, especially for those with inhomogeneous networks.

Isoprene polymerization catalyzed by iron (II) and cobalt(II) complexes carrying 2,6‐bis(1H′‐allylbenzimidazolyl)pyridyl ligand

AbstractThe incorporation of cis‐1,4 and 3,4(+1,2) units is important to the overall properties of polyisoprene. Nevertheless, polymerization to prepare such polymer via coordinative‐insertion method has less reported. In the present study, 2,6‐bis(1H’‐allyl‐benzimidazolyl)pyridine has been installed onto the iron and cobalt prior to heterogeneous supporting. They are shown to be amenable to homogeneous polymerization of isoprene, affording 3,4(+1,2) units enriched polymer. The addition of disulfide carbon into cobalt catalyst is decisive for boosting productivity and elevating 3,4 (+1,2) insertion. Whereas, diethylphosphite external donor merely behaves as a chain transfer agent in iron catalyzed polymerization. The produced polymer with a controlled 3,4(+1,2) ratio and molar mass may find application as a single rubber, in polymer blends, composites, adhesives, and as a versatile platform for transforming to a wide range of functional polymer.Highlights Novel iron and cobalt complexes are made. High activities toward isoprene polymerization are achieved. 3,4(+1,2) incorporated polyisoprene is obtained.

Cycloheptyl-Fused Iminopyridine-Iron Catalysts for Isoprene Polymerization with Enhanced Activity and Thermal Stability

Cycloheptyl-Fused Iminopyridine-Iron Catalysts for Isoprene Polymerization with Enhanced Activity and Thermal Stability

Scandium and neodymium dichloride complexes supported by amido-imino ligands: synthesis, structure, reactivity, and catalytic activity in isoprene polymerization

Scandium and neodymium dichloride complexes supported by amido-imino ligands: synthesis, structure, reactivity, and catalytic activity in isoprene polymerization

Kinetics of Isoprene Polymerization in the Presence of a Gadolinium Catalyst: Effect of the Chemical Composition and Particle Size of the Isopropanol Solvate of Gadolinium Chloride

Kinetics of Isoprene Polymerization in the Presence of a Gadolinium Catalyst: Effect of the Chemical Composition and Particle Size of the Isopropanol Solvate of Gadolinium Chloride

Neodymium-Mediated Coordinative Chain Transfer Polymerization of Isoprene in the Presence of External Donors.

Nd-based polydiene elastomers, including NdIR and NdBR, are regarded as indispensable key raw materials in preparing green tires with excellent performance capabilities, but their wide application is still limited by the relative higher cost of Nd precatalysts. Nd-mediated coordinative chain transfer polymerization (CCTP) of diene provides an effective strategy to reduce the precatalyst cost, because this method involves very high atom economy, i.e., each Nd molecule can generate multiple polymer chains. Nevertheless, all possible factors that could influence such CCTP behaviors are still mostly unexplored to date. In this report, the basic chemistry on the influence of external donors on the overall CCTP behaviors of isoprene was established for the first time. It was found that increasing the amount of external donors had a negative influence on the chain transfer efficiencies, resulting in gradually decreasing atom economies. Catalyst addition order studies revealed that the coordination of donors with cationic Nd active species, rather than alkylaluminium CTAs, contributed mostly to such decreased efficiencies. Moreover, it was found that when the ratio of donors and Nd compounds was higher than 1.0, the CCTP behaviors were corrupted, resulting in polymers with broad distributions, as well as resulting in low atom economies; nevertheless, when the ratio was lower than 0.5, the system still displayed CCTP characteristics, implying that the critical ratio for maintaining the CCTP was 0.5. Additionally, when such a ratio was 0.01, the high atom economy was almost the same as donor-free CCTP systems. Detailed kinetic studies at such a ratio demonstrated that the donor-contained system proceeded in a well-controlled manner, as concluded from the good linear relationship between the Mn of the PIps against the polymer yields, as well as the good linearity between the Mn against the (IP)/(Nd) ratios. Such maintained CCTP properties also allowed for seeding two-step polymerizations to prepare diblock copolymers with precisely controlled molecular weights. Expanding the types of donors to more phosphine, oxygen, and nitrogen containing compounds showed that they also affected the CCTP behaviors depending on their steric and electronic properties.

Discrete Trivalent Lanthanide Isobutylaluminates in Isoprene Polymerization: Elucidation of Cationized Active Species

Discrete Trivalent Lanthanide Isobutylaluminates in Isoprene Polymerization: Elucidation of Cationized Active Species

Diethylaluminum chloride-co-initiated cationic polymerization of isoprene: dramatic effect of the nature of alkyl halide on the properties of synthesized polymers

The cationic polymerization of isoprene using alkyl halide/Et2AlCl initiating system (alkyl halide: tert-butyl chloride, tert-butyl bromide, 2-chloro-2-methylbutane and isopropyl chloride) at different temperatures has been studied. It was shown for the first time that using of tertiary alkyl halide in conjunction with Et2AlCl allowed to synthesize fully soluble solid thermoplastic polymers with reduced unsaturation (41–48 mol%) as well as relatively high glass transition temperature (52–60°С) and softening point (102–128°С). The substitution of tertiary alkyl halides on the secondary one (isopropyl chloride) results in the obtaining of cross-linked polymers due to the low activity of isopropyl chloride in chain transfer to alkyl halide. It was found that alkyl halide nature, the ratio of alkyl halide to Et2AlCl, duration and temperature of the polymerization of isoprene have dramatic effect on the unsaturation of synthesized polymers as well as their molecular weight, polydispersity, physical and chemical properties.

Polymerization of isoprene, myrcene, and butadiene catalyzed by cobalt complexes supported with 2‐acetyl‐6‐iminopyridine ligand

Cobalt complexes carrying 2‐acetyl‐6‐iminopyridine ligand are synthesized and characterized. Single‐crystal X‐ray diffraction reveals the cobalt ion is chelated with two nitrogen atoms and an acetyl oxygen atom additionally. A significant prolonged Co–O distance (2.3960(57) Å) is found, indicative of a labile character. Activated by diethylchloroaluminum, all complexes show high conversion rates for isoprene and myrcene polymerizations, affording cis‐1,4/3,4 regulated 1,3‐diene polymers. The polymerization of butadiene, interestingly, gives predominant cis‐1,4 selectivity (>99.2%) with moderate activity. The substituent at ortho‐position of arylimine plays a minor role in controlling activity and selectivity as well as the molecular weight of the resultant polymers. The properties of resultant poly(1,3‐diene)s are stable even in a wide range of operational conditions, such as [Al]/[Co] varied from 20 to 600, temperature spanning from 0°C to 60°C, and monomer–catalyst ratio from 1000 to 4000. These additional benefits of minimum fluctuation in catalytic performances may be suitable for industrial polymerization process.

Highly active and thermally robust pyridylbenzotriazole iron-based catalysts for preparation of polyisoprenes that feature high wet traction and low rolling resistance

A series of pyridylbenzotriazole iron (II) complexes with general formula (L2FeCl2) were synthesized and characterized by IR, ESI-MS, and elemental analysis. Determined by single-crystal X-ray crystallography, complex Fe1 adopts a distorted octahedral geometry. Upon activation with methylaluminoxane (MAO), the activity of the complex for isoprene polymerization decreased as the bulkiness of the substituent at 6-position of the pyridyl ring of the ligand increased. Notably, Fe1 exhibited excellent activity of 4.1 × 106 g/(mol (Fe)•h), affording polymers with ultra-high molecular weight (Mn = 2380 × 103 g/mol) and narrow distributions (Mw/Mn = 1.72). The resulting polyisoprenes possessed predominantly cis-1,4/3,4 alternating structure and short cis-1,4 and 3,4 sequences, irrespective of the reaction conditions, indicating high thermal stability of the catalyst. Moreover, the prepared polyisoprene composite showed higher mechanical properties compared to SSBR-2466 and SSBR-5025 which are the key components of current commercial tread rubber, and had comparable wet traction and superior rolling resistance.

Structurally Rigid (8-(Arylimino)-5,6,7-trihydroquinolin-2-yl)-methyl Acetate Cobalt Complex Catalysts for Isoprene Polymerization with High Activity and cis-1,4 Selectivity

A series of cobalt complexes bearing (8-(arylimino)-5,6,7-trihydroquinolin-2-yl)methyl acetate ligand framework were prepared using a one-pot synthesis method. These complexes were then extensively investigated for their catalytic performance in isoprene polymerization. In addition to the complexes being characterized via FT-IR spectrum and elemental analysis, the molecular structure of Co1 and Co5 was determined via X-ray diffraction analysis. The analysis revealed a chloride-bridged centrosymmetric binuclear species in which each cobalt center exhibited a distorted square pyramidal geometry. Among the prepared complexes, Co1 demonstrated the highest catalytic activity of 1.37 × 105 g (mol of Co)−1(h)−1, achieving complete monomer conversion and resultant polyisoprene showed high molecular weight (Mn ≥ 2.6 × 105 g/mol). All of the complexes showed preference for the cis-1,4 configuration ranging from 65% to 72%, while the 3,4 monomer insertion units constituted between 27% and 34% of the polymer structure. Moreover, extensive investigations were conducted to assess the impact of reaction parameters and ligand properties on the catalytic activities and microstructural characteristics of the resulting polymer.

Polymerization of butadiene and isoprene using α-diimine cobalt catalysts bearing electron donor at the N-aryl of imine

Cobalt dibromide supported by α-diimine ligand ortho-positioned with sulfur and oxygen donor are synthesized and characterized. Single X-ray diffraction result shown the oxygen donor is connected with the metal center in complex Co4, resulting in a triangle bipyramidal configuration. With AlEt2Cl as an activator, the formed catalysts are able to efficiently catalyze butadiene polymerization following in an essential cis-1,4 chemoselectivity at 1/2000–1/6000 catalyst feeding. These catalysts are more active and robust for isoprene polymerization under identical conditions, affording polyisoprene rich in cis-1,4 fraction randomly incorporated with 3,4 units. The number average molecular weights (Mns) of the formed polymers are determined to be 1.1–7.8 × 105, higher than those found for polybutadiene (0.4–9.3 × 104). The O-Me donor in the N-Aryl impacts positively on the activity and the molecular weight of the resultant polymer. The catalysts show a stable chemoselectivity despite the activator and catalyst feeding, applied temperature, even the catalyst structure are varied.

Star-Shaped Thermoplastic Elastomers Prepared via RAFT Polymerization.

Styrene-based thermoplastic elastomers (TPEs) demonstrate excellent overall performance and account for the largest industrial output. The traditional methods of preparation styrene-based thermoplastic elastomers mainly focused on anionic polymerization, and strict equipment conditions were required. In recent years, controlled/living radical polymerization (CRP) has developed rapidly, enabling the synthesis of polymers with various complex topologies while controlling their molecular weight. Herein, a series of core crosslinked star-shaped poly(styrene-b-isoprene-b-styrene)s (SISs) was synthesized for the first time via reversible addition-fragmentation chain transfer (RAFT) polymerization. Meanwhile, linear triblock SISs with a similar molecular weight were synthesized as a control. We achieved not only the controlled/living radical polymerization of isoprene but also investigated the factors influencing the star-forming process. By testing the mechanical and thermal properties and characterizing the microscopic fractional phase structure, we found that both the linear and star-shaped SISs possessed good tensile properties and a certain phase separation structure, demonstrating the characteristics of thermoplastic elastomers.

Rare-earth metal complexes supported by indolyl-based NCN-pincer ligand and their efficient catalysis for isoprene polymerization

Rare-earth metal dialkyl complexes [1-CH2N(CH3)2–3-CH2CH2N(CH3)2C8H4N]RE(CH2SiMe3)2 (RE = 1-Y, 2-Er, 3-Yb and 4-Lu) were synthesized by the well-designed indolyl-based proligand 1-CH2N(CH3)2–3-CH2CH2N(CH3)2C8H4NH with rare-earth metal trialkyl complexes (RE(CH2SiMe3)2(THF)2) underwent direct alkane elimination. Single-crystal X-ray analyses and the NMR spectroscopy revealed these dialkyl complexes were analogous mononuclear NCN-pincer geometry via CH activation of 2-sp2 indole. Employing these complexes, upon activation by aluminum alkyls and borate, initiated isoprene polymerization with high conversion and high stereoselectivity (98% conversion of 2000 equivalent of isoprene, 1,4-cis polymers up to 91.5%).

Divalent Lanthanide Tetraisobutylaluminates: Reactivity and Living Isoprene Polymerization.

Lanthanide (Ln) tetraisobutylaluminates constitute key components in commercial 1,3-diene polymerization catalysts, and likewise are the homogeneous rare-earth-metal catalysts of prime industrial importance. Discrete divalent rare-earth-metal complexes [Ln(AliBu4 )2 ] (Ln=Sm, Eu, Yb) reported here display the first structurally characterized homoleptic metal tetraisobutylaluminates. Treatment of [Ln(AliBu4 )2 ] with C2 Cl6 gives access to SmII /SmIII mixed-valence cluster [Sm6 Cl8 (AliBu4 )6 ] and the YbII cluster [Yb4 Cl4 (AliBu4 )4 ], respectively. Reaction with B(C6 F5 )3 leads to hydride abstraction and formation of arene-coordinated hydroborates such as [Sm{HB(C6 F5 )3 }2 (toluene)2 ]. Complexes [Ln(AliBu4 )2 ] engage in single-component isoprene polymerization, affording high cis-1,4 polyisoprenes with narrow molecular weight distributions. Binary [Yb(AliBu4 )2 ]/[HNPhMe2 ][B(C6 F5 )4 ] fabricates polyisoprene in a perfectly living manner. The catalytically active species are scrutinized by NMR spectroscopy.

3,4-Enhanced Polymerization of Isoprene Catalyzed by Side-Arm Tridentate Iminopyridine Iron Complex with High Activity: Optimization via Response Surface Methodology.

3,4-Enhanced polymerization of isoprene catalyzed by late transition metal with high activity remains one of the great challenges in synthetic rubber chemistry. Herein, a library of [N, N, X] tridentate iminopyridine iron chloride pre-catalysts (Fe 1-4) with the side arm were synthesized and confirmed by the element analysis and HRMS. All the iron compounds served as highly efficient pre-catalysts for 3,4-enhanced (up to 62%) isoprene polymerization when 500 equivalent MAOs were utilized as co-catalysts, delivering the corresponding high-performance polyisoprenes. Furthermore, optimization via single factor and response surface method, it was observed that the highest activity was obtained by complex Fe 2 with 4.0889 × 107 g·mol(Fe)-1·h-1 under the following conditions: Al/Fe = 683; IP/Fe = 7095; t = 0.52 min.