Persistence Length of Short-Chain Branched Polyethylene

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

doi:10.1021/ma801775n

Cited by 80 publications

(108 citation statements)

References 26 publications

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“…The structure also displays topological connectivity that is independent of these thermodynamic and steric constraints. These features can be distinguished by considering the average minimum path of p Kuhn units through the structure [30][31][32]. One possible minimum path is shown in units with dark borders in Fig.…”

Section: Modelmentioning

confidence: 99%

“…Generally, SANS data from a dilute polymer solution displays two structural levels [28,32,35]. In each structural level, a Guinier law I (q) ∼ G exp(−q 2 R 2 g /3) and a power law I (q) ∼ B f q −d f are observed at lower and higher q values, respectively, where G, R g , B f , and d f are the Guinier law prefactor, radius of gyration, power-law prefactor, and fractal dimension (1 d f 3), respectively.…”

Section: B Hybrid Unified Fit Functionmentioning

confidence: 99%

“…K f and K p are ratios of the power-law prefactor to the Guinier prefactor for the fractal and persistent regimes. l p and R g are the persistence length and the radius of gyration of the fractal star polymer, respectively [32]. It is assumed here that the Kuhn length l k = 2l p is the zero-entropy unit [29] for the star.…”

Section: B Hybrid Unified Fit Functionmentioning

confidence: 99%

“…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%

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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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Section: Modelmentioning

confidence: 99%

Section: B Hybrid Unified Fit Functionmentioning

confidence: 99%

Section: B Hybrid Unified Fit Functionmentioning

confidence: 99%

“…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%

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

et al. 2016

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“…[1][2][3][4][5][6][7][8][9] Thus far, however, most research efforts aiming to explore the fundamental role of branches in polymer science have mainly focused on long-chain branched polymers, 2,[10][11][12][13][14][15][16] although it is equally well known that short-chain branching generally significantly affects a wide variety of physical properties such as crystallinity, melting point, modulus, and the hardness of polymeric materials. [16][17][18] From a thermodynamic viewpoint, 19 the standard approach would be to analyze the structure of polymers in solution or melt by accounting simultaneously for the energetics (polymer-polymer and polymer-solvent) and (intramolecular and intermolecular) entropy of the system, and then to determine the properties of the system based on the resulting structural information. This conventional approach, though generally effective for long-chain branched polymers, may cause significant errors in the case of polymeric materials containing chains with branches along the main backbone that are rather short, as this is likely to lead to the presumption of a negligible entropic contribution by such short branches.…”

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confidence: 99%

Communication: Role of short chain branching in polymer structure and dynamics

Kim

Baig

2016

The Journal of Chemical Physics

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A comprehensive understanding of chain-branching effects, essential for establishing general knowledge of the structure-property-phenomenon relationship in polymer science, has not yet been found, due to a critical lack of knowledge on the role of short-chain branches, the effects of which have mostly been neglected in favor of the standard entropic-based concepts of long polymers. Here, we show a significant effect of short-chain branching on the structural and dynamical properties of polymeric materials, and reveal the molecular origins behind the fundamental role of short branches, via atomistic nonequilibrium molecular dynamics and mesoscopic Brownian dynamics by systematically varying the strength of the mobility of short branches. We demonstrate that the fast random Brownian kinetics inherent to short branches plays a key role in governing the overall structure and dynamics of polymers, leading to a compact molecular structure and, under external fields, to a lesser degree of structural deformation of polymer, to a reduced shear-thinning behavior, and to a smaller elastic stress, compared with their linear analogues. Their fast dynamical nature being unaffected by practical flow fields owing to their very short characteristic time scale, short branches would substantially influence (i.e., facilitate) the overall relaxation behavior of polymeric materials under various flowing conditions.

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Neutron Scattering in the Analysis of PolymersUpdate based on the original article by D. G. Bucknall,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.

Roland

2012

Encyclopedia of Analytical Chemistry

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The focus of this article is the application of neutron scattering in polymer science, with various examples given to illustrate the types of problems addressed. Neutron scattering is a powerful analytical tool for investigating polymers. Unique aspects such as the capacity to measure thick samples with an absence heating or radiation-induced damage, selective control of the scattering contrast by isotopic substitution, and the measurement of dynamic properties as a function of length scale are among the many attributes that make neutron methods not just complementary to other analytical techniques, but in many cases the only means to address material issues. The information that can be obtained from neutron scatteringthe size, form, and orientation of molecular chains, Update based on the original article by D. G. Bucknall, Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.the thermodynamics and phase structure of mixtures, interfaces and interfacial phenomena, the dynamics at both the local and global length scales, details of the structure of complex nanocomposites and biological materials, etc.has only been surveyed herein. It is a testament to the utility of neutron scattering that even though the application of neutrons to polymers did not begin in earnest until the 1990s, through the past decade, about 325 peer-reviewed publications per year have appeared on the topic. Whether this figure changes in the future will likely depend on the availability of the specialized, costly facilities required for neutron experiments. Certainly there is no expectation of abatement in the number of important problems in polymer science that can be addressed using neutron methods.

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Persistence Length of Short-Chain Branched Polyethylene

Cited by 80 publications

References 26 publications

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

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

Communication: Role of short chain branching in polymer structure and dynamics

Neutron Scattering in the Analysis of PolymersUpdate based on the original article by D. G. Bucknall,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.

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