A unified picture of hard-soft segmental development along olefin chain shuttling copolymerization

Saeb, Mohammad Reza; Khorasani, Manouchehr; Ahmadi, Mostafa; Mohammadi, Yousef; Stadler, Florian J.

doi:10.1016/j.polymer.2015.08.059

Cited by 27 publications

(53 citation statements)

References 39 publications

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“…The equations provided here can be practically used to track the evolution of kinetics and microstructure during CSP, without necessitate derivation of complicated analytical expressions for the moments assigned to each of the monomeric units and blocks . In addition, results can be simply obtained and presented without the need for expensive calculations and elaborate data storage techniques …”

Section: Modelingmentioning

confidence: 99%

“…While direct assessment of multi‐block nature of OBCs using the existing conventional characterization methods is strictly limited, theoretical representation of microstructure based on modeling of CSP kinetics is an informative approach to establish structure properties relationship for OBCs and draw guidelines for developing new grades with special properties . Zhang et al have proposed a model based on the method of moments to predict the average chain and block structures especially in a continuous process .…”

Section: Introductionmentioning

confidence: 99%

“…Zhang et al have proposed a model based on the method of moments to predict the average chain and block structures especially in a continuous process . Mohammadi et al have suggested a model based on kinetic Monte Carlo (KMC) simulation which provides detailed image from distribution of microstructural features of chains and blocks at the molecular level . The former model considers two vector indices for monomers (ethylene and 1‐octene) and blocks (hard and soft) in addition to the indices correspond to the last monomeric unit, responsible for terminal model, and catalyst type, which makes the analytical derivation of consumption rates of the corresponding moments too complex .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Realistic Representation of Kinetics and Microstructure Development During Chain Shuttling Polymerization of Olefin Block Copolymers

Ahmadi

Nasresfahani

2015

Macro Theory & Simulations

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Olefin block copolymers (OBCs) are new class of thermoplastic elastomers having low glass transition temperature soft blocks and highly crystalline hard blocks synthesized by reversible chain shuttling between two catalysts with considerably different comonomer responses through a chain transfer agent. Theoretical representation of kinetics and microstructure evolution in chain shuttling polymerization (CSP) is of vital importance especially since the existing characterization tools have severe limitations in retrieving the blocky nature of OBCs. In this work, we correspondingly develop an effective model to represent CSP in practical conditions and compare our predictions to the existing experimental data. We illuminate kinetics and microstructure development in both OBC chains and individual blocks. We specifically clarify the effect of varying the reversibility of transfer reactions through tuning chain shuttling agent and hydrogen concentrations on OBC chains and blocks in terms of their corresponding molecular weight and chemical composition distribution and draw guidelines for achieving OBCs with desired properties.

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Section: Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Realistic Representation of Kinetics and Microstructure Development During Chain Shuttling Polymerization of Olefin Block Copolymers

Ahmadi

Nasresfahani

2015

Macro Theory & Simulations

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“…Microstructural distributions at the end-of-batch, such as the distribution of number of blocks per chain, block length distribution, chemical composition distribution (CCD), and ethylene sequence length distribution (ESLD), were also simulated. [ 18 ] The effects of processing parameters on the OBC microstructure at the end-of-batch, including chain shuttling agent (CSA) concentration, catalyst composition, and monomer ratio, were also studied by Ahmadi et al [ 19 ] These previous models provide useful guidelines for tailor-making OBCs, especially with respect to hard-and soft-block characteristics. However, detailed microstructures of OBC populations with different number of blocks and blocking structures (Scheme 1 ) and their contributions to the overall microstructural distributions have not yet been revealed in the open literature.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Formation of Linear Olefin Block Copolymers with Dynamic Monte Carlo Simulation

Tongtummachat

Anantawaraskul

Soares

2016

Macro Reaction Engineering

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low comonomer reactivity ratio and produces high-crystallinity blocks (hard-blocks), while the other catalyst has high comonomer reactivity ratio and makes low-crystallinity blocks (soft-blocks). The CSA is the special component because it shuttles living polymer chains between the two catalysts, making chains with alternating hard and soft blocks. [1][2][3][4][5][6][7] OBCs have higher heat and abrasion resistances, and better processability than conventional polyolefin elastomers. [8][9][10][11] Because OBC may have many blocks, mathematical models are needed to quantify how polymerization conditions affect their microstructures. A detailed mathematical model describes how the complex OBC microstructure evolves during polymerization, providing useful insights on how to control these microstructures. Models for chain-shuttling polymerization in continuous stirred-tank reactors (CSTRs) were first developed using the method of moments to describe polymerization kinetics and average chain microstructures. [12,13] Because this approach cannot generate detailed microstructural distributions, Monte Carlo (MC) models were later developed for OBCs made in CSTRs operated at steadystate. [14][15][16] Subsequently, Mohammadi et al. developed Chain-shuttling polymerization with dual catalysts has introduced a new class of polyolefins called olefin block copolymers (OBCs). A dynamic Monte Carlo model to describe the kinetics of chain-shuttling copolymerization in a semi-batch reactor is developed, and used it to study how the microstructure of OBCs with different numbers of blocks per chain evolves during polymerization. The model also describes how chain-shuttling rate constants and concentration of chain-shuttling agent affect populations of OBCs with different numbers of blocks per chain. These model predictions are useful to make OBCs with precisely designed microstructures.

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“…The introduction of long-chain branches in the main backbone using dual catalytic system with one catalyst producing the so-called macromer due to high rate of b-hydride elimination and the other being open to incorporate the bulky macromere in the growing chain belongs to this category as well [8,9]. Also, the recent discovery by Dow chemicals on production of olefinic multi-block copolymers (OBC) using a chain shuttling agent, transferring the growing chain between two catalysts with distinguishable difference in comonomer incorporation ability [10][11][12][13][14][15], can also be accounted. However, many of the dual catalytic systems simply benefit from catalysts that produce chains possessing different microstructures independently.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

Mortazavi

Jafarian

Ahmadi

et al. 2015

J Therm Anal Calorim

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Nickel diimine late transition metal (LTM) and Cp 2 TiCl 2 metallocene catalysts were supported on the TIBA-modified MgCl 2 ÁnEtOH adduct, separately and concurrently, at different ratios, to yield hybrid catalysts, where the catalytic precursors were activated in the ethylene polymerization with TEA as the cocatalyst. Polymerization activities revealed that supported LTM catalysts show very high levels of activity, in an adverse trend with polymerization temperature ranging from 30 to 70°C, in opposition to the activity of metallocene component. Consequently, the proportion of corresponding polymer fractions were tuned by changing reaction temperature as well as catalyst composition. Study of thermal properties confirmed that LTM component is responsible for production of less crystallizable branched chains, while metallocene fraction makes highly crystallizable linear chains. All samples showed noticeable thermorheological complexity due to coexistence of linear and branched microstructures. Interestingly, it was found that increase in metallocene fraction of the hybrid catalyst stalls the terminal relaxation of the produced polymers and increases the entanglement density by decreasing the extent of branching. Study of dynamic mechanical properties revealed that the intensity of b transition could be correlated with the branching level and catalyst composition accordingly.

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A unified picture of hard-soft segmental development along olefin chain shuttling copolymerization

Cited by 27 publications

References 39 publications

Realistic Representation of Kinetics and Microstructure Development During Chain Shuttling Polymerization of Olefin Block Copolymers

Realistic Representation of Kinetics and Microstructure Development During Chain Shuttling Polymerization of Olefin Block Copolymers

Understanding the Formation of Linear Olefin Block Copolymers with Dynamic Monte Carlo Simulation

Characteristics of linear/branched polyethylene reactor blends synthesized by metallocene/late transitional metal hybrid catalysts

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