Peter Eibeck

Nanostructuring by ultrathin diblock copolymer/titanium composite films

Abstract The usability of ultrathin diblock copolymer films providing a heterogeneous chemical surface in a new nanolithographic technique is described. This technique allows the parallel preparation of periodic point pattern in an inorganic substrate. Diblock copolymers of polystyrene (PS) and poly-2-vinylpyridine (P2VP) are adsorbed from a nonselective solvent like chloroform on an ionic, high surface energy substrate (mica). Under these conditions formation of a regular, chemically heterogeneous nm-sized surface structure is observed consisting of isolated PS clusters which dewet the substrate covered by a 1nm thick film of adsorbed P2VP. Vapour deposition of titanium on the heterogeneous surface occurs preferentially on the less polar polystyrene islands. This way Ti films with regular thickness variations are formed corresponding to the pattern of the laterally segregated PS-b-P2VP film. The films are employed as lithographic masks allowing the transfer of the initial polymer pattern into the inorganic substrate with high aspect ratios.

Ion transport across membranes prepared by gel crystallization

A one-step procedure for the preparation of ion-selective membranes is described. The method employs the thermally induced gel crystallization of ultrahigh molecular weight poly(ethylene) (UHMW-PE) from a dilute xylene solution. After evaporation of the xylene, a microporous UHMW-PE film remains, which can serve as the support for liquid and polymeric ion-selective membranes. The addition of a membrane solvent and suitable receptor molecules to the xylene solution allows a one-step incorporation of these membrane components into the UHMW-PE support. The influence of the preparation conditions of the UHMW-PE support on the rates of the p-tert-butylcalix[4]arene tetraethylester-mediated transport of NaClO 4 was studied. Two concepts to improve the life-time of the membranes are introduced. In a first approach, the addition of photocrosslinkable nitril-substituted siloxane copolymers to the membrane phase has been evaluated. The enhanced viscosity of the membrane phase reduces leaching of carrier and solvent molecules from the membrane into the aqueous phases. In a second approach, the solvent is omitted and the membrane-phase merely consists of a benzo-15-crown-5 or calix[4]arene modified siloxane-copolymer, which is substituted to such a degree that ion transport no longer has to take place via diffusion of host-guest complexes but by jumping of the cations from one fixed carrier to a neighboring carrier

Thermodynamics of a Partially Swollen Polymer Brush

Swelling initially solvent-free monolayers of anchored polymer chains with a gradually increasing amount of solvent significantly influences their thermodynamics, especially the lateral pressure. Upon increasing the amount of solvent, the lateral pressure initially increases inversely proportional to the square of the average volume fraction of the anchored chains but finally levels off to a limiting value independent of the composition. With increasing area per anchored chain the limiting value of the lateral pressure decreases, while the amount of solvent needed to reach the limiting value increases. The observed effects are in good agreement with predictions based on analytical mean field theory.