Conformational analysis of double-tethered chain molecules at an impenetrable interface: A Monte Carlo study

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Abstract
Due to tremendous interest in surface modification, numerous theoretical and simulation efforts have sought to elucidate the conformational properties of chain molecules grafted, or tethered, at one end to an impenetrable interface. Few studies have, however, addressed the analogous properties of chains in which both ends are anchored to an interface and behave as ‘‘sticky feet’’ in the presence of a good solvent. In this work, on-lattice Monte Carlo simulations have been performed to examine the characteristics of double-tethered chains in the limit of low interfacial coverage. Phantom and self-avoiding chains possessing up to 200 monomers are considered in 2 D random-flight simulations, as are corresponding non- and single-tethered chains to facilitate property comparison. While single-tethered chains adopt a more extended conformation than their nontethered analogs, segmental density distributions reveal that the existence of a second tethered site exerts little influence on monomers near the chain origin, but promotes overall coil localization near the interface. Scaling relationships for chain dimensions such as the root-mean-square (rms) end-to-end distance and coil radius are derived here in terms of both monomer and tether number.