Monte Carlo study of the coil-to-globule transition of a model polymeric system |
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Authors: | Anastassia N Rissanou Spiros H Anastasiadis Ioannis A Bitsanis |
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Institution: | 1. Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, 711 10 Heraklion Crete, Greece
Department of Physics, University of Crete, 710 03 Heraklion Crete, Greece;2. Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, 711 10 Heraklion Crete, Greece |
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Abstract: | Monte Carlo computer simulations of single, flexible, self-avoiding chains on a cubic lattice have been performed upon conditions of increasing segment–segment cohesive energy (deteriorating solvent quality). The simulations spanned a wide range of chain lengths (20–10,000, i.e., up to molecular weights of a few millions) and cohesive energies (0.0–0.45kBT, i.e., from athermal to very poor solvents). The chain length dependence of the chain size in poor solvents was characterized by a wide plateau of almost null growth for intermediate chain lengths. This plateau was linked to the development of the incipient constant density core, while genuine power law dependence (1/3) was not reached even for the longest chains and poorest solvents simulated here. The mere appearance of a core required substantial chain lengths (higher than 1000; molecular weights of a few hundred thousands), while short chains underwent a gradual densification devoid of any qualitative changes in the density distribution. Sufficiently long chains became more but not quite spherical and underwent a reasonably sharp second order phase transition. The findings were generally in agreement with predictions of mean-field theory and with the use of the standard scaling variables, despite slight inconsistencies. Nevertheless, the results stress the fact that short chains never form a constant density core and that core-dominance on the globule's properties (“volume approximation”) is only valid for extraordinarily long chains molecular weight of O(109)], an effect linked to the relatively diffuse nature of the surface layer and originating from chain connectivity in conjunction with spherical geometry. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3651–3666, 2006 |
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Keywords: | coil-to-globule transition computer modeling Monte Carlo simulations statistical thermodynamics |
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