Simultaneous enhancement in processability and mechanical properties of polyethylenes via tuning the molecular weight distribution from unimodal to bimodal shape

Long, Chuanjiang; Dong, Zhen; Liu, Xiaoqing; Yu, Feng; Shang, Yuxuan; Wang, Keqiang; Feng, Sitong; Hou, Xunan; He, Chaobin; Chen, Zhong‐Ren

doi:10.1016/j.polymer.2022.125287

Cited by 18 publications

(12 citation statements)

References 88 publications

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“…Many factors such as molecular weight, molecular weight distribution, and branching content strongly in uence the miscibility of polyole n blends, which is crucial to realizing desired properties for multimodal polyole ns. [30][31][32][33][34][35] As expected, good miscibility is di cult to achieve for mixtures of linear and branched polyole ns. 36,37 This poor miscibility is exponentially ampli ed for the above-mentioned bimodal polar functionalized polyole ns, since the low-molecular-weight fraction is both more branched and more polar than the high-molecular-weight fraction.…”

Section: Introductionmentioning

confidence: 55%

A Co-Anchoring Strategy for the Synthesis of Polar Bimodal Polyethylene

Chen

Zou

Wang

et al. 2022

Preprint

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Since polar groups can poison the metal centers in catalysts, the incorporation of polar comonomers usually comes at the expense of catalytic activity and polymer molecular weight. In this contribution, we demonstrate polar bimodal polyethylene as a potential solution to this trade-off. The more-polar/more-branched low-molecular-weight fraction provided polarity and processability, while the less-polar/less-branched high-molecular-weight fraction provided mechanical and melt properties. To achieve high miscibility between these two fractions, three synthetic routes were investigated: mixtures of homogeneous catalysts, separately supported heterogeneous catalysts, and a co-anchoring strategy (CAS) to heterogenize different homogeneous catalysts on one solid support. The CAS route was the only viable strategy for the synthesis of polar bimodal polyethylene with good molecular level entanglement and minimal phase separation. This produced polyolefin materials with excellent mechanical properties, surface/dyeing properties, gas barrier properties, as well as extrudability and 3D-printability.

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Section: Introductionmentioning

confidence: 55%

A Co-Anchoring Strategy for the Synthesis of Polar Bimodal Polyethylene

Chen

Zou

Wang

et al. 2022

Preprint

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“…A series of linear unimodal and bimodal PEs were synthesized by the chain transfer polymerization method using a FI-Ti catalyst in the presence of diethyl zinc (ZnEt 2 ). The synthetic method was described in our recent work . The details of polymerization are provided in the Supporting Information…”

Section: Methodsmentioning

confidence: 99%

“…For example, adding small quantities of long chains to the short chain matrix significantly enhances the shear-induced crystallization of polymers. − Besides, the addition of long chains provides more tie molecules connecting adjacent lamellae, which could enhance the strength of polymer blends . Recently, we have reported that the modulation of molecular weight distribution (MWD) from unimodal to bimodal shape simultaneously enhances the processability, stiffness, and tensile strength of PEs without sacrificing ductility . Therefore, the understanding of the crystallization kinetics of polymers with bimodal MWD shapes is of great importance.…”

Section: Introductionmentioning

confidence: 99%

“…Tremendous methods have been developed to prepare bimodal polymers. − Compared with the physical blending method, the chemical synthetic method could prepare bimodal PEs with good miscibility due to synthesizing LMW and HMW chains in situ. In our previous work, well-defined linear unimodal and bimodal PEs with controllable molecular weights have been synthesized by a chain transfer polymerization method . Linear PE is a fine model polymer which eliminates the impact of chain branching and tacticity. , In this work, a similar method has been used to synthesize a series of unimodal and bimodal PEs.…”

Section: Introductionmentioning

confidence: 99%

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Molecular Weight Distribution Shape Dependence of the Crystallization Kinetics of Semicrystalline Polymers Based on Linear Unimodal and Bimodal Polyethylenes

Long

Dong

et al. 2023

ACS Appl. Polym. Mater.

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The manipulation of the crystallization kinetics and crystallinity of polymers without altering their chemical composition, chain structure, or average molecular weight is challenging, while little attention is paid to the role of molecular weight distribution (MWD) shape. In this work, a series of well-defined linear unimodal and bimodal polyethylenes (PEs) with molecular weights ranging from 300 k to 1200 k g/mol were synthesized to serve as a model system to study the impact of bimodal MWD shape on the crystallization kinetics of semicrystalline polymers in comparison with unimodal MWD shape at the same weight-average molecular weight (M w). It is shown that PEs with a bimodal shape exhibit a faster nucleation rate and crystallization rate with a smaller lamellar width at low isothermal temperatures. A higher crystallization enthalpy of bimodal PEs is shown in non-isothermal experiments. The mechanism behind this is elucidated, which suggests that MWD shapes mainly affect the small-scale nucleation process without altering the large-scale growth process. This first systematic comparative study on the crystallization kinetics of linear unimodal and bimodal PEs gives insight into tailoring the crystallization behavior of semicrystalline polymers from an MWD shape perspective.

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“…Many factors such as molecular weight, molecular weight distribution, and branching content strongly influence the miscibility of polyolefin blends, which is crucial to realizing desired properties for multimodal polyolefins [30][31][32][33][34][35] . As expected, good miscibility is difficult to achieve for mixtures of linear and branched polyolefins 36,37 .…”

mentioning

confidence: 99%

A co-anchoring strategy for the synthesis of polar bimodal polyethylene

Zou

Wang

et al. 2023

Nat Commun

View full text Add to dashboard Cite

Since polar groups can poison the metal centers in catalysts, the incorporation of polar comonomers usually comes at the expense of catalytic activity and polymer molecular weight. In this contribution, we demonstrate polar bimodal polyethylene as a potential solution to this trade-off. The more-polar/more-branched low-molecular-weight fraction provides polarity and processability, while the less-polar/less-branched high-molecular-weight fraction provides mechanical and melt properties. To achieve high miscibility between these two fractions, three synthetic routes are investigated: mixtures of homogeneous catalysts, separately supported heterogeneous catalysts, and a co-anchoring strategy (CAS) to heterogenize different homogeneous catalysts on one solid support. The CAS route is the only viable strategy for the synthesis of polar bimodal polyethylene with good molecular level entanglement and minimal phase separation. This produces polyolefin materials with excellent mechanical properties, surface/dyeing properties, gas barrier properties, as well as extrudability and 3D-printability.

show abstract

Simultaneous enhancement in processability and mechanical properties of polyethylenes via tuning the molecular weight distribution from unimodal to bimodal shape

Cited by 18 publications

References 88 publications

A Co-Anchoring Strategy for the Synthesis of Polar Bimodal Polyethylene

A Co-Anchoring Strategy for the Synthesis of Polar Bimodal Polyethylene

Molecular Weight Distribution Shape Dependence of the Crystallization Kinetics of Semicrystalline Polymers Based on Linear Unimodal and Bimodal Polyethylenes

A co-anchoring strategy for the synthesis of polar bimodal polyethylene

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