Dynamic Monte Carlo Simulation for Chain‐Shuttling Polymerization of Olefin Block Copolymers in Continuous Stirred‐Tank Reactor

Abstract

consists of two catalysts with different α-olefin reactivity ratios and a chain shuttling agent (CSA). One of the catalysts with good α-olefin incorporation produces lowcrystallinity segments (soft blocks), while the other with poor α-olefin incorporation produces high-crystallinity segments (hard blocks). The CSA is added to "shuttle" growing chains between two catalysts, leading to statistical multiblock chain microstructures of OBCs. Due to their unique multiblock chain micro structures, OBCs have been reported to have several advantages, such as better end-use properties and processability, when compared to conventional polyolefin elastomers. [8-11] Since Zhang et al. [12] proposed the reaction mechanism, kinetic parameters, and reaction conditions for ethylene/1octene chain-shuttling polymerization, several mathematical models have been developed. [12-22] The model based on the method of moments for ethylene/1-octene chain-shuttling polymerization in continuous stirred-tank reactor (CSTR) was developed for the first time by Zhang et al. [12,13] Their model provides useful information on how the average microstructural properties of OBCs (i.e., average molecular weight, average copolymer composition, and average soft and hard block structures) vary with polymerization conditions. Unfortunately, this approach provides only the average microstructural properties of OBCs. To overcome the limitation of the previous approach, Anantawaraskul et al. [14-16] developed the static Monte Carlo (MC) model to provide detailed microstructural distribution of OBCs at the steady-state. The authors used the MC model to investigate the effect of polymerization parameters (i.e., chain-shuttling probability, propagation probability, transfer probability, catalyst ratio) on the chemical composition distribution (CCD), ethylene sequence distribution (ESD), and distribution of the number of blocks per chain. This approach, however, cannot describe the kinetics and microstructural evolution of OBCs. Recently, a dynamic MC model was developed to describe kinetics and microstructural evolution of OBCs during chainshuttling polymerization in a semibatch reactor. [17-22] Mohammadi et al. [17] introduced a dynamic MC model to discuss kinetics of chain-shuttling polymerization using dual catalysts based on the kinetics of coordinative chain transfer poly merization (a combining of living coordination poly merization with an A dynamic Monte Carlo model coupling with residence time distribution is developed to simulate chain microstructures of olefin block copolymers (OBCs) produced with the chain-shuttling polymerization in a continuous stirred-tank reactor (CSTR). The simulated results provide information on how polymer chain microstructures (i.e., average molecular weight, average comonomer content, and microstructural distributions) evolve in a CSTR system and show a good agreement with previously reported theoretical and experimental results. The model is also used to investigate effect of reaction conditions (i.e., catalyst feed compo...

Synthesis and characterization of polyolefin thermoplastic elastomers: A review

“…Tongtummachat et al further combined the dynamic Monte Carlo model with residence time distribution to predict the time evolution of the OBC chain microstructure synthesized by chain shuttling polymerization in a CSTR. [91] The simulation results were in good agreement with the experimental results prior to and during steady states. The model also provided insight into the transient response of the system caused by the residence time distribution, leading to a better understanding of the microstructure change in the OBCs during the polymerization.…”

Coordinative Chain Transfer and Chain Shuttling Polymerization

“…The evolution of the microstructure of OBC produced in a continuous stirred-tank reactor was also studied via a dynamic Monte Carlo method combined with residual time distribution, and a good agreement with experimental data was found. The increase of the amount of the Hf pyridylamido catalyst (incorporating more 1-octene) was found as expected to lead to an increase of the 1-alkene fraction in the copolymer together with a higher amount of soft block but also to a decrease of the 1-octene content in the soft block.…”

Toward Olefin Multiblock Copolymers with Tailored Properties: A Molecular Perspective

“…Compared to classical polyolefin synthesis, complexities of chain shuttling polymerization necessitate an advanced understanding of polymerization kinetics and evolution of microstructural indicators in the course of the polymerization. [14][15][16][17] The microstructural characteristics of OBCs can be classified into two categories: (i) topology-related molecular variables, including the number of linkage points per chain (LP), the average degree of polymerization of soft segments (DP SOFT n ), the average degree of polymerization of hard segments (DP HARD n ), ethylene sequence length of soft segments (ESL SOFT ), and ethylene sequence length of hard segments (ESL HARD ); and (ii) property-related molecular variables, including the comonomer content of the soft segments (C8% SOFT ), comonomer content of the hard segments (C8% HARD ), the average longest ethylene sequence length of the soft blocks (LES SOFT ), the average longest ethylene sequence length of the hard blocks (LES HARD ), and hard block percentage (HB%). [18] The topology-related characteristics were comprehensively discussed in a previous publication by patterning macromolecular landscape of OBCs.…”

“…Compared to classical polyolefin synthesis, complexities of chain shuttling polymerization necessitate an advanced understanding of polymerization kinetics and evolution of microstructural indicators in the course of the polymerization. [ 14–17 ]…”