Conformation of cyclic and linear polydimethylsiloxane in the melt: a small-angle neutron-scattering study

Gagliardi, Simona; Arrighi, Valeria; Dagger, A C; Semlyen, AJ

doi:10.1007/s003390101110

Cited by 15 publications

(28 citation statements)

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“…Note that in d = 3 this gives ν = 2/5, i.e. a value that closely agrees with the numerical estimates found in simulations [277,278,251] and with recent small-angle neutron scattering experiments carried out on cyclic polydimethylsiloxane (PDMS) [279]. Later numerical investigations with higher values of N and more detailed scaling arguments [280,281] have revealed that actually the value ν = 2 d+2 describes the data in a crossover region of N values separating the short N regime, in which the topological interactions are weak and rings appear to be Gaussian (as their linear counterpart in concentrated solution), and the large N regime in which the rings assume a more globular structure with ν = 1/3.…”

Section: Topological Constraints In Concentrated Solutionssupporting

confidence: 89%

Polymers with spatial or topological constraints: Theoretical and computational results

2011

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In this review we provide an organized summary of the theoretical and computational results which are available for polymers subject to spatial or topological constraints. Because of the interdisciplinary character of the topic, we provide an accessible, non-specialist introduction to the main topological concepts, polymer models, and theoretical/computational methods used to investigate dense and entangled polymer systems. The main body of our review deals with: (i) the effect that spatial confinement has on the equilibrium topological entanglement of one or more polymer chains and (ii) the metric and entropic properties of polymer chains with fixed topological state. These problems have important technological applications and implications for the life-sciences. Both aspects, especially the latter, are amply covered. A number of selected open problems are finally highlighted.

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Section: Topological Constraints In Concentrated Solutionssupporting

confidence: 89%

Polymers with spatial or topological constraints: Theoretical and computational results

2011

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“…1. As found earlier [5][6][7][8][9][10], for all N the conformation is significantly more compact than the Gaussian prediction. For intermediate Q a power law behavior in the form factor following Q −1=ν , with ν ¼ 0.43 AE 0.015, was obtained by fitting a modified Debye function [10].…”

supporting

confidence: 76%

“…From a topological point of view among all polymer architectures, polymer rings are unique since rings are closed structures without ends. In dense melts, this feature significantly influences both ring conformations and dynamics [1][2][3][4][5][6][7][8][9][10][11][12]. Interpenetration of ring polymers is entropically hindered and therefore rings are predicted to prefer the conformations of a crumpled globule [13] or that of a lattice animal [14].…”

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confidence: 99%

Molecular Scale Dynamics of Large Ring Polymers

et al. 2014

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We present neutron scattering data on the structure and dynamics of melts from polyethylene oxide rings with molecular weights up to ten times the entanglement mass of the linear counterpart. The data reveal a very compact conformation displaying a structure approaching a mass fractal, as hypothesized by recent simulation work. The dynamics is characterized by a fast Rouse relaxation of subunits (loops) and a slower dynamics displaying a lattice animal-like loop displacement. The loop size is an intrinsic property of the ring architecture and is independent of molecular weight. This is the first experimental observation of the space-time evolution of segmental motion in ring polymers illustrating the dynamic consequences of their topology that is unique among all polymeric systems of any other known architecture.

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“…Figure displays the values of R G , which were calculated from NMR relaxation data for the first time, in comparison to values reported in different small-angle neutron scattering (SANS) works. ,− …”

Section: Discussionmentioning

confidence: 98%

“…Radius of gyration of PDMS melts determined by FC NMR in comparison to literature values obtained by SANS. ,− A power law with exponent 0.53 is indicated (dashed line). The result of the estimate eq is also included (open triangles).…”

Section: Discussionmentioning

confidence: 99%

Mode Analysis of NMR Relaxation in a Polymer Melt

Hofmann

2018

Macromolecules

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Spin−lattice relaxation rates of unentangled poly-(dimethylsiloxane) (PDMS) melts of different M measured by field-cycling (FC) 1 H NMR are analyzed using a new approach. By fitting the time domain mode distribution of the Rouse model to the experimental data, interpolation of the latter is achieved and a mode separation is performed. The evolution of the Rouse relaxation spectrum with increasing M is studied. From the model parameters, the diffusion coefficient D, the Rouse time τ R , and the statistical length are calculated, all in good agreement with literature values and the Rouse model. The new approach allows for a more accurate calculation of the segmental mean square displacement, removes previous discrepancies between FC and field-gradient NMR and verifies the relevant relaxation theory. Furthermore, for the first time, the analysis provides the radius of gyration R G , the values of which are in agreement with literature values obtained by small-angle neutron scattering. The Mdependence R G ∝ M 0.53±0.04 indicates ideal chain statistics down to M = 860 g/mol.

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Conformation of cyclic and linear polydimethylsiloxane in the melt: a small-angle neutron-scattering study

Cited by 15 publications

References 1 publication

Polymers with spatial or topological constraints: Theoretical and computational results

Polymers with spatial or topological constraints: Theoretical and computational results

Molecular Scale Dynamics of Large Ring Polymers

Mode Analysis of NMR Relaxation in a Polymer Melt

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