Rheology of polyethylenes with novel branching topology synthesized by a chain-walking catalyst

Rashmi Patil, Ralph H. Colby, Daniel J. Read, Guanghui Chen, Zhibin Guan

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Ethylene pressure was used to vary the molecular architecture of amorphous polyethylenes synthesized with a palladium-bisimine catalyst. At low ethylene pressure, densely branched polymers are formed, and their melt rheology indicates no entanglement even though the weight-average molar mass is 370 000. Polymers produced at higher ethylene pressures have only slightly higher molar masses but show entanglement effects in their rheology. NMR suggests similar levels of short-chain branching (92-97 branches per 1000 carbons) in all the samples. A simple model of polymerization, based on the proposed "chain-walking" mechanism for this catalyst, is used to generate structures via computer simulation. While some of the experimental data are consistent with the predicted molecular structures, there are discrepancies in (i) the scaling of radius of gyration with molecular weight and (ii) the variation of terminal relaxation time with ethylene pressure, both of which suggest long-chain branching, which is not predicted by the computer simulation.

Original languageEnglish (US)
Pages (from-to)10571-10579
Number of pages9
JournalMacromolecules
Volume38
Issue number25
DOIs
StatePublished - Dec 13 2005

Fingerprint

Polyethylenes
Rheology
Ethylene
Topology
Catalysts
Molar mass
Polymers
Computer simulation
Palladium
Relaxation time
Molecular structure
Carbon
Molecular weight
Polymerization
Nuclear magnetic resonance
ethylene

All Science Journal Classification (ASJC) codes

  • Materials Chemistry

Cite this

Patil, Rashmi ; Colby, Ralph H. ; Read, Daniel J. ; Chen, Guanghui ; Guan, Zhibin. / Rheology of polyethylenes with novel branching topology synthesized by a chain-walking catalyst. In: Macromolecules. 2005 ; Vol. 38, No. 25. pp. 10571-10579.
@article{14315807cfd94631b63f32ca9c543bad,
title = "Rheology of polyethylenes with novel branching topology synthesized by a chain-walking catalyst",
abstract = "Ethylene pressure was used to vary the molecular architecture of amorphous polyethylenes synthesized with a palladium-bisimine catalyst. At low ethylene pressure, densely branched polymers are formed, and their melt rheology indicates no entanglement even though the weight-average molar mass is 370 000. Polymers produced at higher ethylene pressures have only slightly higher molar masses but show entanglement effects in their rheology. NMR suggests similar levels of short-chain branching (92-97 branches per 1000 carbons) in all the samples. A simple model of polymerization, based on the proposed {"}chain-walking{"} mechanism for this catalyst, is used to generate structures via computer simulation. While some of the experimental data are consistent with the predicted molecular structures, there are discrepancies in (i) the scaling of radius of gyration with molecular weight and (ii) the variation of terminal relaxation time with ethylene pressure, both of which suggest long-chain branching, which is not predicted by the computer simulation.",
author = "Rashmi Patil and Colby, {Ralph H.} and Read, {Daniel J.} and Guanghui Chen and Zhibin Guan",
year = "2005",
month = "12",
day = "13",
doi = "10.1021/ma051408p",
language = "English (US)",
volume = "38",
pages = "10571--10579",
journal = "Macromolecules",
issn = "0024-9297",
publisher = "American Chemical Society",
number = "25",

}

Rheology of polyethylenes with novel branching topology synthesized by a chain-walking catalyst. / Patil, Rashmi; Colby, Ralph H.; Read, Daniel J.; Chen, Guanghui; Guan, Zhibin.

In: Macromolecules, Vol. 38, No. 25, 13.12.2005, p. 10571-10579.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Rheology of polyethylenes with novel branching topology synthesized by a chain-walking catalyst

AU - Patil, Rashmi

AU - Colby, Ralph H.

AU - Read, Daniel J.

AU - Chen, Guanghui

AU - Guan, Zhibin

PY - 2005/12/13

Y1 - 2005/12/13

N2 - Ethylene pressure was used to vary the molecular architecture of amorphous polyethylenes synthesized with a palladium-bisimine catalyst. At low ethylene pressure, densely branched polymers are formed, and their melt rheology indicates no entanglement even though the weight-average molar mass is 370 000. Polymers produced at higher ethylene pressures have only slightly higher molar masses but show entanglement effects in their rheology. NMR suggests similar levels of short-chain branching (92-97 branches per 1000 carbons) in all the samples. A simple model of polymerization, based on the proposed "chain-walking" mechanism for this catalyst, is used to generate structures via computer simulation. While some of the experimental data are consistent with the predicted molecular structures, there are discrepancies in (i) the scaling of radius of gyration with molecular weight and (ii) the variation of terminal relaxation time with ethylene pressure, both of which suggest long-chain branching, which is not predicted by the computer simulation.

AB - Ethylene pressure was used to vary the molecular architecture of amorphous polyethylenes synthesized with a palladium-bisimine catalyst. At low ethylene pressure, densely branched polymers are formed, and their melt rheology indicates no entanglement even though the weight-average molar mass is 370 000. Polymers produced at higher ethylene pressures have only slightly higher molar masses but show entanglement effects in their rheology. NMR suggests similar levels of short-chain branching (92-97 branches per 1000 carbons) in all the samples. A simple model of polymerization, based on the proposed "chain-walking" mechanism for this catalyst, is used to generate structures via computer simulation. While some of the experimental data are consistent with the predicted molecular structures, there are discrepancies in (i) the scaling of radius of gyration with molecular weight and (ii) the variation of terminal relaxation time with ethylene pressure, both of which suggest long-chain branching, which is not predicted by the computer simulation.

UR - http://www.scopus.com/inward/record.url?scp=29444435550&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=29444435550&partnerID=8YFLogxK

U2 - 10.1021/ma051408p

DO - 10.1021/ma051408p

M3 - Article

AN - SCOPUS:29444435550

VL - 38

SP - 10571

EP - 10579

JO - Macromolecules

JF - Macromolecules

SN - 0024-9297

IS - 25

ER -