Piotr Polanowski

Studies of polymer conformation and dynamics in two dimensions using simulations based on the Dynamic Lattice Liquid (DLL) model

The Dynamic Lattice Liquid (DLL) model has been implemented as a simulation algorithm for two-dimensional (2-D) polymeric systems. The model can work with density factor ρ=1 and became a basis for a parallel algorithm, which takes into account coincidences of elementary molecular motion attempts resulting in local cooperative structural transformations. Systematic studies of athermal polymer systems on the two-dimensional triangular lattice are presented for various concentrations of linear polymers with respect to an explicitly considered solvent. Both static and dynamic properties are characterized. The simulation results reflect molecular packing and other properties of monomolecular polymer layers, which can be relevant to these obtained in some thin film formation techniques.

Studies of mobility, interdiffusion, and self-diffusion in two-component mixtures using the dynamic lattice liquid model

The dynamic lattice liquid model was implemented as a simulation algorithm for simple liquids. This model works correctly for the density factor ρ=1 and becomes a base for a parallel algorithm. Such an algorithm takes into account coincidences of elementary molecular motion attempts resulting in local cooperative structural transformations. In this paper general conditions for simulating simple liquids on various lattices are presented. Interdiffusion coefficients were directly monitored as changes of composition profiles with time for both athermal and interacting binary (AB) mixtures. In the athermal case, the coefficients of self-diffusion and interdiffusion are equal. For interacting binary mixtures the interdiffusion exhibits a thermally activated character.

Simulation of polymer–polymer interdiffusion using the dynamic lattice liquid model

In this paper, we present computer simulation results concerning interdiffusion of fully compatible components in symmetric binary (AB) polymer mixtures in solutions. The simulation is performed in two dimensions using the algorithm based on the dynamic lattice liquid model. The solvent molecules are taken into account explicitly. The evolution of the concentration profiles in time at an interface is studied for chain lengths N=2,4,8,16 for three polymer concentrations phi=0.1,0.5,0.9. The tracer diffusion coefficients for polymer chains and for the solvent are obtained by monitoring the mean square displacements of their center of mass. The relationships between coefficients of interdiffusion and self-diffusion are tested.

Phase behavior of block copolymer solutions in thin films studied by Monte Carlo simulations

The phase behavior of an A–B diblock copolymer in a selective solvent of type A in thin films is examined by Monte Carlo simulations, using the coarse-grained lattice model with the Cooperative Motion Algorithm (CMA). This behavior is compared with that of the bulk (3-dimensional) and the 2-dimensional solutions. While we focus the simulations on symmetric 16–16 copolymers with a chain length of N = 32, we also simulate asymmetric 8–24 copolymers and chains with N = 48 and 64. At a relatively low copolymer volume fraction, approximately ϕ ≈ 0.3, the self-assembled micelles lose their long range order, and a solution of disordered micelles is obtained. We simulate the phase behavior of copolymer solutions both for thin films and 2-dimensional systems. Relevant properties, such as squared end-to-end distance, energy, specific heat and structure factor are measured as a function of the reduced temperature, T*. We also characterize the observed micelles by counting the average number of copolymer chains that constitute a single micelle. We observe three phases: layers, hexagonally packed disks and disordered micelles. The phase diagrams from ϕ = 1.0 to 0.1 in the (ϕ, T*) parameter space are shown for both the symmetric and asymmetric copolymer. We find that the phase behavior of the thin film solution is intermediate between that of the 3D and 2D solutions, but it is more similar to 2D because the film thickness is relatively small.

Monte Carlo studies of two-dimensional polymer–solvent systems

AbstractThe static properties of two-dimensional athermal polymer solutions were studied by performing Monte Carlo lattice simulations using the cooperative motion algorithm (CMA) and taking into account the presence of explicit solvent molecules. The simulations were performed for a wide range of polymer chain lengths N (16–1024) and concentrations φ (0.0156–1). The results obtained for short chains (N < 256) were in good agreement with those given by previous simulations. For the longest chains (512 or 1024 beads), some unexpected behavior was observed in the dilute and semidilute regimes. A pronounced change in the concentration dependence of chain size and shape was observed below a certain critical concentration (0.6 for the longest chains under consideration, consisting of 1024 beads). Longer chains became more extended below this concentration. The behavior of the single-chain structure factor confirmed these changes in the fractal dimension of the chain as a function of the concentration. The observed phenomena are related to the excluded volume of solvent molecules, which causes the chain statistics to be modified in the vicinity of other chains; this effect is important in strictly 2D systems. Graphical abstractExtended long chains at moderate density with solvent molecules inside coils.