title: Conformational switching of modified guest chains in polymer brushes.
abstract: Using a numerical quasi off-lattice self-consistent field method which describes heterogeneous chains of spherical monomers we study the case of a densely grafted polymer brush with a fraction of free chain ends being replaced by a modified end-group differing in size and solvent selectivity. We can confirm the observation from molecular dynamics simulations that upon changing the solvent conditions, a switching in location of end-groups which are bigger than monomers from a state "exposed" to the solvent (on the top of the brush) to a "hidden" state (inside the brush) takes place. Our numerical method allows a detailed study of the switching effect as a function of the relevant parameters, such as grafting density, chain length, size of end-groups and their volume fraction. We find that the switching effect is enhanced for long chains, low fractions of modified chains, and big end-groups. We consider the case of low fraction of modified chains in more detail using a test chain method. Here, we explore the optimal grafting density as a function of the size of the end-groups, where the switching is most sensitive. These values can be in the experimental range for end-groups which are at least 3-4 times bigger than the monomers. The end-groups can be realized by attaching nano-particles to the last monomer of a brush-chain.
authors.affiliation: Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, 01069 Dresden, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Romeis
authors.forename: J-U
authors.initials: JU
authors.lastname: Sommer
mesh_terms: D008968:Molecular Conformation; D036103:Nanotechnology; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*
chemical_list: D011108:Polymers