Conformational properties and dynamics of molecular bottle-brushes: A cellular-automaton-based simulation

Abstract

Full Paper: Extensive computer simulation was performed using the bond-fluctuation model and cellular-automaton (CA)-based simulation technique to probe the equilibrium structure and dynamical behavior of combbranched polymers in which the flexible side chains of a given length are placed regularly along the backbone and the number of branches increases linearly with total molecular weight. By applying very efficient CA algorithm -the lattice molecular dynamics (LMD) method - we have been able to study the properties of sufficiently large structures (up to 5880 monomeric units). Depending on the length of main and side chains as well as on interbranch spacing, we have calculated mean chain dimensions, local fractal dimensionalities, particle scattering functions, time autocorrelation functions, etc. The following main conclusions may be drawn from the results presented in our study: (i) The critical exponent, governing the mean size of the main chain, remains unchanged from its value known for a 3d self-avoiding walk (SAW). On the other hand, two-dimensional branched macromolecules with one-sided branches are effectively in a collapsed state even under conditions of a good solvent, forming specific helical superstructures. (ii) Comparison of the simulated data with the predictions of the scaling model indicates that the latter is valid in describing the mean dimensions of the backbone as a function of side-chain length and interbranch spacing. (iii) The excluded volume interaction between side chains dramatically slows down the relaxation of the backbone chain.