Effect of Branch Length on 13C NMR Relaxation Properties in Molten Poly[ethylene‐co‐(α‐olefin)] Model Systems

Parkinson, Matthew; Klimke, Katja; Spiess, Hans Wolfgang; Wilhelm, Manfred

doi:10.1002/macp.200700209

Cited by 23 publications

(25 citation statements)

References 21 publications

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“…An early study was reported by Hatfield et al using a 200 MHz spectrometer ( 1 H resonance), [34,35] followed by intensive works of Wilhelm, Kaminsky and their co-workers. [33,36,37] Compared (5 of 20) 1600012 to the solution NMR, which has a sample concentration less than 20 wt%, the melt and solid-state 13 C NMR generate a higher sample filling factor, resulting in a higher sensitivity towards the presence of sparsely branched side chains and end groups in POs. This technique currently allows the characterization of branch lengths up to 16 carbons.…”

Section: Ch(b ) Ch(b )mentioning

confidence: 99%

“…This technique currently allows the characterization of branch lengths up to 16 carbons. [37] In addition, the measurement acquisition times are greatly reduced. LCBD of 7-8 branches per 100 000 CH 2 groups can be determined by melt-state NMR in 13 h, [36] which represents a vast improvement over the multiday acquisitions required for the solution NMR.…”

Section: Ch(b ) Ch(b )mentioning

confidence: 99%

“…The difference between the viscosity PDI and GPC MWD of branched materials corresponds to the degree of LCB. The relationship can be described by Equations (37) and (38) C LCB 10 0, when GPC peak viscosity peak 1;…”

Section: Lcb Index Associated With Activation Energymentioning

confidence: 99%

“…As Equation (37) shows, when the ratio of GPC peak value to the viscosity peak value is less than 1, the materials is linear with LCB = 0. When the ratio is equal to or larger than 1, the LCB degree can be calculated from Equation (38).…”

Section: Lcb Index Associated With Activation Energymentioning

confidence: 99%

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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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Section: Ch(b ) Ch(b )mentioning

confidence: 99%

Section: Ch(b ) Ch(b )mentioning

confidence: 99%

Section: Lcb Index Associated With Activation Energymentioning

confidence: 99%

Section: Lcb Index Associated With Activation Energymentioning

confidence: 99%

See 2 more Smart Citations

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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“…Thus, the values determined for k bb are composite numbers including the k tr,intra contribution. From a pure technical point of view, extremely high resolutions can be obtained, methods based on 13 C NMR spectroscopy can in principle distinguish between long and short chain branching 90 and thus provide access to separate values for k tr,intra and k bb . ).…”

Section: Chain-end Termination Rate Coefficient (Secondary Radicals)mentioning

confidence: 99%

The role of mid‐chain radicals in acrylate free radical polymerization: Branching and scission

Junkers

Barner‐Kowollik

2008

J. Polym. Sci. A Polym. Chem.

213

326

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The past 5 years have seen a significant increase in the understanding of the fate of so‐called mid‐chain radicals (MCR), which are formed during the free radical polymerization of monomers that form highly reactive propagating radicals and contain an easily abstractable hydrogen atom. Among these monomers, acrylates are, beside ethylene, among the most prominent. Typically, a secondary propagating acrylate‐type macroradical (SPR) can easily transfer its radical functionality via a six‐membered transition state to a position within the polymer chain (in a so‐called backbiting reaction), creating a tertiary MCR. Alternatively, the radical function can be transferred intramolecularly to any position within the chain (also forming an MCR) or intermolecularly to another polymer strand. This article aims at providing a comprehensive overview of the up‐to‐date knowledge about the rates at which MCRs are formed, their secondary reactions as well as the consequences of their occurrence under variable reaction conditions. We explore the latest aspects of their detection (via electron spin resonance spectroscopy) as well as the characterization of the polymer structures to which they lead (via high resolution mass spectrometry). The presence of MCRs leads to the formation of branched polymers and the partial formation of polymer networks. They also limit the measurement of kinetic parameters (such as the SPR propagation rate coefficient) with conventional methods. However, their occurrence can also be used as a synthetic handle, for example, the high‐temperature preparation of macromonomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7585–7605, 2008

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Detection of low levels of long‐chain branching in polydisperse polyethylene materials

Karjala

Sammler

Mangnus

et al. 2010

J of Applied Polymer Sci

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ABSTRACT:Creep experiments have been applied to probe the zero-shear viscosity, g 0 , of polyethylene chains directly and precisely in a constant-stress rheometer at 190 C. Such experiments, when combined with precise measurements of the weight-average molecular weight, M w , calibrated relative to linear chains of high-density polyethylene, are shown to provide a very sensitive approach to detect low levels (0.005 branches per 1000 carbons) of long-chain branching (LCB). This detection limit is shown to be insensitive to whether the molecular weight distribution (MWD) breadth, M w /M n , rises from about two to ten.

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Effect of Branch Length on ¹³C NMR Relaxation Properties in Molten Poly[ethylene‐co‐(α‐olefin)] Model Systems

Cited by 23 publications

References 21 publications

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

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

The role of mid‐chain radicals in acrylate free radical polymerization: Branching and scission

Detection of low levels of long‐chain branching in polydisperse polyethylene materials

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