Small-angle neutron scattering from star-branched polymers in the molten state

Horton, J.C.; Squires, G. L.; Boothroyd, A. T.; Fetters, L. J.; Rennie, A. R.; Glinka, C. J.; Robinson, R. A.

doi:10.1021/ma00192a029

Cited by 76 publications

(82 citation statements)

References 12 publications

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“…As reported in ref., [16] the molecular model described in Section 2 predicts a value for the characteristic ratio of PE as " X e v equal to C v = 9.03. This value departs from the experimentally known value [29,30] of 6.7 (7.8 according to more recent investigations [31,32] ) by about 30%. Since the anisotropic stress difference Ds is proportional toc xx , which in turn is proportional to the mean-square end-to-end distance of the polymer molecules, our model should over-predict the stress by the same ratio, roughly about 30%.…”

Section: Stress Optical Law Coefficientcontrasting

confidence: 71%

Atomistic Monte Carlo simulation of steady-state uniaxial elongational flow of long-chain polyethylene melts: dependence of the melt degree of orientation on stress, molecular length and elongational strain rate

Mavrantzas

Theodorou²

2000

Macromol. Theory Simul.

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Section: Stress Optical Law Coefficientcontrasting

confidence: 71%

Atomistic Monte Carlo simulation of steady-state uniaxial elongational flow of long-chain polyethylene melts: dependence of the melt degree of orientation on stress, molecular length and elongational strain rate

Mavrantzas

Theodorou²

2000

Macromol. Theory Simul.

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“…Article obtained in molten PE using SANS by Horton et al 65 and Fetters et al 66 (C ∞ = 7.4 ± 0.8) at 413 K. The computed values at 500 K (C n = 8.2 and 7.6 for TraPPe-UA and PYS, respectively) are still slightly larger than the more recent results obtained by Zamponi et al (C n = 7.2 ± 0.2) at 509 K. 44 It is worth mentioning here that the SANS experiments were performed on hydrogenated polybutadiene samples. The polybutadiene parent polymer is obtained by anionic polymerization, and contains a minimum amount of 1.9 vinyl groups per 100 carbon atoms.…”

Section: Macromoleculesmentioning

confidence: 99%

Molecular Dynamics Simulations for the Description of Experimental Molecular Conformation, Melt Dynamics, and Phase Transitions in Polyethylene

2015

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Long molecular dynamics simulations of the melt dynamics, glass transition and nonisothermal crystallization of a C 192 polyethylene model have been carried out. In this model, the molecules are sufficiently long to form entanglements in the melt and folds in the crystalline state. On the other hand, the molecules are short enough to enable the use of atomistic simulations on a large scale of time. Two force fields, widely used for polyethylene, are taken into account comparing the simulation results with a broad set of literature experimental data. Although both force fields are able to capture the general physics of the system, TraPPe-UA is in a better quantitative agreement with the experimental data. According with the simulation results some fundamental aspects of polyethylene physical parameters are discussed such as the characteristic ratio (C n = 8.2 and 7.6 at 500 K, for TraPPe-UA and PYS force fields, respectively), the isothermal compressibility (α = 8.57 × 10 −4 K −1 ), the static structure factor and the melt dynamics regimes corresponding to an entangled polymer. Furthermore, the simulated T g (187.0 K) obtained for linear PE is in a very good agreement with the extrapolated T g values (185−195 K) using the Gordon−Taylor equation. Finally, the simulation of the nonisothermal crystallization process supports the view of a mixed state of adjacent and nonadjacent re-entry model. The simulated two phase model reproduces very well the initial fold length expected for high supercoolings and the segregation of the system in ordered and disordered layers. The paper highlights the importance of combining simulation techniques with experimental data as a powerful means to explain the polymer physics.

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“…The g Θ S ratio for regular stars is reported in figure 4. Here we compare our results, valid for atactic polystyrene (PS) and polyethylene (PE), with the RW prediction and with experimental data from PS [39], PE [40,41] and poly(isoprene) (PIP) [35,42], showing the non-universality of the Θ state [5]. The PE values were tentatively obtained through equations (3.7) and (3.8) by comparison of the radii of gyration measured in solution and in the melt.…”

Section: The Molecular Dimensions At the θ Temperaturementioning

confidence: 88%

Conformations and Dynamics of Stars and Dendrimers: The Gaussian Self-Consistent Approach

Ganazzoli

2002

Condens. Matter Phys.

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Some conformational and dynamical aspects of branched polymer are reviewed. We discuss the theoretical Gaussian Self-Consistent (GSC) approach proposed in our group and used to study the behaviour of regular star polymers and dendrimers in different solvent conditions. Within a single framework, we consider the unperturbed Θ state, as well as the goodsolvent state in comparison with other theoretical or simulation approaches, and with some experimental results. We also briefly report the further results obtained for amphiphilic copolymer stars in selective solvents so as to highlight the potentialities of the method, as well as its strengths and its shortcomings.

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Small-angle neutron scattering from star-branched polymers in the molten state

Cited by 76 publications

References 12 publications

Atomistic Monte Carlo simulation of steady-state uniaxial elongational flow of long-chain polyethylene melts: dependence of the melt degree of orientation on stress, molecular length and elongational strain rate

Atomistic Monte Carlo simulation of steady-state uniaxial elongational flow of long-chain polyethylene melts: dependence of the melt degree of orientation on stress, molecular length and elongational strain rate

Molecular Dynamics Simulations for the Description of Experimental Molecular Conformation, Melt Dynamics, and Phase Transitions in Polyethylene

Conformations and Dynamics of Stars and Dendrimers: The Gaussian Self-Consistent Approach

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