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Cylindrical Inclusions in a Copolymer Membrane
journal contribution
posted on 2006-12-28, 00:00 authored by Qiyi Zhang, Yuqiang MaThe membrane-mediated interaction between two parallel, cylindrical inclusions is investigated by using the
self-consistent field theory (SCFT). The rodlike inclusions are located within the interior of the bilayer and
are enveloped by two monolayers. They may exhibit one of the two basic types of behaviors involving pinching
two monolayers together and swelling them outward. For different parameters, we calculate the density profile
of the deformation membrane, the associated interaction free energy, as well as the conformational entropy
of polymer chains. The similarity of the two types of interaction potentials is the qualitative characteristics.
An energy barrier separates an attractive from a repulsive region; the repulsive region is preceded by a weak
attraction at a large distance. The difference between them, which is due to the different contact environments
around the rods, lies in the appearance of a small barrier at a short distance in the pinching structure. Particular
emphasis is put on the closely energetic and entropic analyses of the interaction potential. We show that the
chemical potential energy has provided a qualitative trend and roughly dominated the basic shape of the
interaction potential; the amphiphile entropy in the swelling structure and the solvent entropy in the pinching
structure, combined with the corresponding chemical potential energy, are responsible for the repulsive barrier
at an intermediate distance and for the weak attraction at a large distance, respectively. The influence of
inclusion hydrophobicity on the interaction potential is taken into account. In particular, the pinching and
swelling structures can appear and can transform into each other in a system at intermediate hydrophobicity.