Adsorption of Linear and Cyclic Multiblock Copolymers from Selective Solvent. A Monte Carlo Study

Abstract

copolymers is especially interesting due to the possibility of self-assembling to various interesting forms. [12-14] Rings were studied in real experiments, [15-22] theoretically [23-30] and by means of computer simulation. [3,31-56] It was shown that the size of single rings (infinitely diluted solution) was smaller by a factor of 1/2 when chains without the excluded volume are compared, when compared to linear precursors of the same length. [1] The scaling behavior of a single ring was the same as of linear polymer, N 1.176. The dynamics of cyclic chains was also found to be similar to that of linear chains: their self-diffusion coefficient scales as D ∼ N −1.59[40,43] but dynamics in dense melts are different for these architectures. [1,10,57,58] The collapse transition of single-ring homopolymers has been the subject of a few theoretical studies [27,28] and computer simulations. [48-50,59] These simulations of rings were mainly focused on the comparison of their structure with linear chains. The size of linear and cyclic chain was found to be identical in a low-temperature collapsed state but has been suggested that the low-temperature structure of rings differs from that of linear chains despite being of similar size and can be called "crumpled globule." [46] The collapse process of rings was found to be a one-step process. There were no rearrangements of rings in the dense collapsed globule as these chains do not have ends that migrate in such conditions. The changes of the solvent quality led to the adjustment of a chain conformation. The temperature of the coil-to-globule transition was found to shift toward lower temperatures when the number of blocks increases but the influence of the macromolecular architecture was found to be relatively small. [59] In addition to the chain sequence and the solvent quality, the changes in the polymer structure can be caused by the presence of a surface. [60-63] The process adsorption of linear and cyclic block copolymer chains is very important from a technological point of view as polymers can significantly modify the properties of the surface. Experiments and simulations showed that the size of long strongly adsorbed rings scales as a 2D random walk, i.e., N 3/4 and it tends to stretch parallel to the surface. [60,63-66] It was shown that the adsorption of cyclic homopolymers is stronger than that of linear ones, i.e., the number of polymer-surface contacts is 15-20% higher for rings. [60,67-71] The critical adsorption temperature where a transition from a 3D to 2D structure was found to be slightly higher A systematic study of the adsorption of linear and cyclic chains on a planar surface is carried out through extensive computer simulations. 3D homopolymer and multiblock copolymer chains are studied. No atomic details are taken into consideration and polymer chains are modeled as sequences of statistical segments on a cubic lattice. Adsorption of macromolecules on a homogenous flat surface is studied at different solvent conditions. Homopolymers are built of solvop...

Modeling the Phase Equilibria of Associating Polymers in Porous Media with Respect to Chromatographic Applications

“…The original CBMC employs the implicit solvent, which means that each unoccupied lattice position implicitly contains a solvent bead. Simultaneously, all interaction parameters with solvent are by definition zero, i.e., , and the nonzero interactions between polymer beads, ( ), indirectly model the solvent quality [ 55 , 56 , 57 , 58 ]. The choice of zero interaction parameters with solvent simplifies the acceptance criterion due to the fact that the transition probability between two states can be expressed as the ratio of the Boltzmann factor and the Rosenbluth weight reflecting the interaction energy [ 54 ].…”