Branch Content of Metallocene Polyethylene

Ramachandran, Ramnath; Beaucage, Gregory; Kulkarni, Abhijit; McFaddin, Douglas; Merrick-Mack, Jean; Galiatsatos, Vassilios

doi:10.1021/ma900199t

Cited by 22 publications

(49 citation statements)

References 28 publications

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“…By a reverse application of the Mes DT theory, we calculate polymer segmental or blob sizes from experimental DT. These thermophoretically effective blob sizes are found to be in reasonable agreement with the persistence length of short chain branched polyethylenes 87 for linear samples and maximum blob sizes for higher branched samples in the range of blob sizes estimated in previous studies. 76 With this approach thus we demonstrate that the local stiffness of a polymer can be validated by thermal diffusion measurements.…”

Section: Discussionsupporting

confidence: 87%

“…For SCB-PE a persistence length ranging from 0.9 nm for high numbers of SCB to 0.6 nm for non-branched PE chains is reported. 87 Furthermore, the blob diameter of the cwPE with higher LCB is in agreement to the blob size of cwPE material originated from the same synthesis approach of about 8 -10 nm found by atomic force microscopy (AFM) and SANS and corresponding to a bottle-brush like conformation with a large thickness. 76 With regard to HT-ThFFF of regular polyolefins, a separation according to branching may most efficiently be performed in solutions of higher n-alkanes.…”

Section: Figuresupporting

confidence: 81%

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The Role of Solubility in Thermal Field-Flow Fractionation: A Revisited Theoretical Approach for Tuning the Separation of Chain Walking Polymerized Polyethylene

et al. 2020

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The influence of the polymer solubility on the separation efficiency in thermal field-flow fractionation (ThFFF) was investigated for a polymer model system of differently branched chain walking polyethylenes in five different solvents, which were selected depending on their physical parameters. The understanding of polymer thermal diffusion has been elucidated using a revisited approach based on the latest thermal diffusion prediction model by Mes, Kok and Tijssen combined with the Hansen solubility theory. Thereby, a significant improvement in the precision of the thermal diffusion prediction and the separation efficiency has been achieved by implementation of the temperature dependency on Hansen solubility parameters.In addition, we demonstrate a method for validation of the segmental size of polymer chains with varying topology by using the revisited thermal diffusion prediction approach in inverse mode and experimental thermal diffusion data.

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Section: Discussionsupporting

confidence: 87%

Section: Figuresupporting

confidence: 81%

The Role of Solubility in Thermal Field-Flow Fractionation: A Revisited Theoretical Approach for Tuning the Separation of Chain Walking Polymerized Polyethylene

et al. 2020

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“…In the study by Beaucage group, small‐angle neutron scattering (SANS) was applied to elucidate the LCB structure of metallocene‐catalyzed PE. A novel scaling approach was employed using SANS data to determine the polymer chain architecture and branching information, including the mole fraction branch content ( ϕ br ) of LCBs in PE, the average number of branch sites per chain ( n br ), the average number of branch sites per minimum path ( n br,p ), the average branch length ( z br ), and the number of inner segments ( n i ).…”

Section: Other Characterization Techniquesmentioning

confidence: 99%

A Comprehensive Review on Controlled Synthesis of Long‐Chain Branched Polyolefins: Part 3, Characterization of Long‐Chain Branched Polymers

Liu

Wang

et al. 2016

Macro Reaction Engineering

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Synthesis and characterization of long-chain branched polyolefins has been an important research topic for both academic and industrial researchers for many decades. This is particularly true since the discovery and successful commercialization of the constrained geometry catalyst systems in 1990s. The type of single site catalysts allows control in the synthesis and the precision in the characterization. Long-chain branched polyolefins exhibit improved melt processability, such as higher melt strength and better shear thinning, compared to their linear counterparts having the same molecular weight and distribution. In the previous papers, the catalyst systems and reaction conditions for the controlled synthesis of long-chain branched polyolefins have been reviewed. This paper aims at summarizing the literatures pertinent to the precise characterization of long-chain branched polyolefins. The major methods of long-chain branching characterization include: nuclear magnetic resonance, gel permeation chromatography, rheometry, dynamical mechanical analysis, differential scanning calorimetry, neutron scattering, and Fourier transform infrared spectroscopy. Recent progresses of these characterization methods, as well as their advantages and limitations, have been discussed in details.

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“…Equation (21) is valid for monodisperse samples [32,45]. The second virial coefficient (A 2 ) is related to Flory χ parameter by [28] …”

Section: B Hybrid Unified Fit Functionmentioning

confidence: 99%

Quantification of interaction and topological parameters of polyisoprene star polymers under good solvent conditions

et al. 2016

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Mass fractal scaling, reflected in the mass fractal dimension d f , is independently impacted by topology, reflected in the connectivity dimension c, and by tortuosity, reflected in the minimum dimension d min . The mass fractal dimension is related to these other dimensions by d f = cd min . Branched fractal structures have a higher mass fractal dimension compared to linear structures due to a higher c, and extended structures have a lower dimension compared to convoluted self-avoiding and Gaussian walks due to a lower d min . It is found, in this work, that macromolecules in thermodynamic equilibrium display a fixed mass fractal dimension d f under good solvent conditions, regardless of chain topology. These equilibrium structures accommodate changes in chain topology such as branching c by a decrease in chain tortuosity d min . Symmetric star polymers are used to understand the structure of complex macromolecular topologies. A recently published hybrid Unified scattering function accounts for interarm correlations in symmetric star polymers along with polymer-solvent interaction for chains of arbitrary scaling dimension. Dilute solutions of linear, three-arm and six-arm polyisoprene stars are studied under good solvent conditions in deuterated p-xylene. Reduced chain tortuosity can be viewed as steric straightening of the arms. Steric effects for star topologies are quantified, and it is found that steric straightening of arms is more significant for lower-molecular-weight arms. The observation of constant d f is explained through a modification of Flory-Krigbaum theory for branched polymers.

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Branch Content of Metallocene Polyethylene

Cited by 22 publications

References 28 publications

The Role of Solubility in Thermal Field-Flow Fractionation: A Revisited Theoretical Approach for Tuning the Separation of Chain Walking Polymerized Polyethylene

The Role of Solubility in Thermal Field-Flow Fractionation: A Revisited Theoretical Approach for Tuning the Separation of Chain Walking Polymerized Polyethylene

A Comprehensive Review on Controlled Synthesis of Long‐Chain Branched Polyolefins: Part 3, Characterization of Long‐Chain Branched Polymers

Quantification of interaction and topological parameters of polyisoprene star polymers under good solvent conditions

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