Structure formation of a single polymer chain. I. Growth of trans domains

Abstract

Molecular dynamics simulations are carried out to study structure formation of a single polymer chain with 500 CH2 groups. Our simulations show that the orientationally ordered structure is formed at a low temperature both by gradual stepwise cooling and by quenching from a random configuration at a higher temperature. The growth of the global orientational order proceeds in a gradual manner in the case of gradual stepwise cooling, whereas it proceeds in a stepwise manner in the case of quenching. The latter feature endorses the previously proposed hypothetical grand view of self-organization [e.g., see T. Sato, Phys. Plasmas 3, 2135 (1996)]: when a system is driven far from equilibrium, it will evolve to a more stable state in a stepwise fashion irrespective of its fundamental interaction forces. From the microscopic analysis of the structure formation process, we find the following characteristic features: (i) In the case of gradual stepwise cooling, the global orientational order grows gradually through the incorporation of small trans domains and the surrounding trans segments into the largest trans domain. (ii) In the case of quenching, the growth of the orientational order is either due to the incorporation of small trans domains and the surrounding trans segments into the largest trans domain or to the elongation of the trans segments in the largest trans domain.

Organization of polymer chains onto long, single-wall carbon nano-tubes: Effect of tube diameter and cooling method

“…We initially ran a set of simulations (in the absence of a SWCNT) to validate our simulation technique against the work of Fujiwara and Sato, 33 who studied the change in conformation of a polymer chain with two (different) cooling processes. Figure 2 shows the variation in the radius of gyration with temperature of a single polymer chain of 500 beads, initially at the temperature 800 K using stepwise cooling to 100 K. We ran the simulation for 1000 ps at each temperature step and each step consisted of a decrease in temperature of 50 K. Figure 2 shows the average R g of the polymer chain obtained from our simulations and corresponding value reported in the literature.…”

“…Furthermore, the cooling mode is an important consideration in the processing of polymers. Thus a similar study (to that of Fujiwara and Sato 33 ) is required to understand the organization of semi-flexible polymer chains when absorbing onto a nano-tube. The objectives of the present paper are to find and determine the effects of stepwise cooling and quenching, on the organization of moderately flexible polymer chains on carbon nano-tubes of different diameters.…”

A manifestation of the Ostwald step rule: Molecular-dynamics simulations and free-energy landscape of the primary nucleation and melting of single-molecule polyethylene in dilute solution

“…By the way, similar problems were also noted in other studies on PE single-chain crystals which exhibited global orientational order already at 550 K by using the Dreiding potential. 34 The dynamics is described by the Langevin equation…”

“…The difficult characterization of the primary nucleation regime in dilute solutions motivated several simulations. [21][22][23][32][33][34][35][36][37][38][39] For relatively short chains, the primary nucleation of single-molecule n-alkanes with a number of monomers N = n ഛ 300 were found to end up in the global minimum of the free energy, i.e., in thermodynamic equilibrium, at a quench depth ⌬T ϵ T m − T ϳ 0.2T m , where T m is the melting temperature. 21,22 However, the eventual kinetic arrest of the nucleation in one state during the primary nucleation of longer single molecules cannot be excluded due to the increasing number of entanglements and, consequently, larger energy barriers.…”

Effect of Molecular Rigidity on Micelle Formation in Amphiphilic Solution

“…Such creation of order, or self-organization, is a universal characteristic of nonequilibrium and nonlinear systems interacting with the environment. To explore universal self-organizing properties in nature, we investigate self-organization in other systems such as polymeric systems [1][2][3][4][5][6] and amphiphilic systems [7][8][9].…”