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Bridging Dynamics of Telechelic Polymers between Solid Surfaces

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journal contribution
posted on 05.03.2018, 00:00 by Hossein Rezvantalab, Ronald G. Larson
We employ Brownian dynamics simulations combined with forward flux sampling and theoretical first-passage time analyses to describe the rates of transitions between loops and bridges of telechelic polymers between solid surfaces representing e.g. latex colloids in the limit that the telechelic stickers bind strongly enough to the surfaces to make free chains very rare. It is shown that the bridge formation rate can be expressed by combining times for two processes, namely, the escape of one end sticker from the narrow-but-deep association well near the colloidal surface and the longer-range motion of the chain end to the other surface inhibited by stretching free energy. We find that when using multibead chains to represent the telechelic polymers, the longer-range motion requires use of a multidimensional first passage time analysis that we borrow from the work of Likhtman and co-workers, which was originally developed to describe polymer end fluctuations in a one-dimensional reptation tube. From these ingredients, we develop analytical expressions for the loop-to-bridge and bridge-to-loop transition rates as functions of the number of beads per polymer, the ratio of gap to the equilibrium chain length, and the end sticker association energy to the colloids/surfaces. We also suggest that a 20-to-1 mapping of Kuhn steps to springs may allow the analysis to be applied to real chains, rendering the analysis applicable to a broad range of industrial and biological processes.