Growth of polymer brushes by "grafting from" via ATRP - Monte Carlo simulations

The growth of polymer brushes from flat surfaces via a grafting-from approach by atom transfer radical polymerization (ATRP) was simulated using a Monte Carlo method, the dynamic lattice liquid (DLL) model, under athermal conditions. Sets of probabilities representing reactions participating in ATRP or overall ATRP reaction probability were implemented in the simulation model. The later corresponds to the ATRP system in which statistically less than one monomer is attached to the chain end during its active period. Dense and moderately dense brushes with degrees of polymerization 45-150 were studied assuming various polymerization rates. It was determined that chain length distribution strongly depends on the reaction probability and grafting density (GD). For dense brushes (GD = 0.3-0.6) the dispersity was comparable with the experimental results only for the lowest probabilities used (p - 2 x 10(-5)). For GD - 0.1 and in the presence of free chains 10 or even 100 times higher probabilities gave satisfactory results. If polymerization rate was too high, two groups of chains could be distinguished: slowly growing short chains, the ends of which were close to the flat surface, where monomer concentration was lower and quickly growing long chains with the ends far from the surface, where monomer concentrations were higher. The relationship between experimental parameters of ATRP and parameters used in the simulations are discussed. (C) 2017 Elsevier Ltd. All rights reserved.