Polymer crystallization is notoriously difficult to control. Here, we demonstrate that the orientation of polymer crystals can be fully controlled at the nanoscale by using nanoimprint lithography (NIL) with molds bearing nanotrenches to shape thin films of poly(vinylidene fluoride). This unprecedented control is due to the thermomechanical history experienced by the polymer during embossing, to the shift of the nucleation mechanism from heterogeneous to homogeneous in confined regions of the mold, and to the constraining of the fast growth axis along the direction of the trenches. NIL thus appears as an ideal tool to realize smart polymer surfaces where crystal ordering can be tuned locally.

We report on the exchange between a hydrophilic thiol (11-mercapto-1-undecanol) in a liquid or gas phase and a hydrophobic thiol (dodecanethiol) of similar length self-assembled on a polycrystalline gold surface for a wide range of temperatures and times. The molecular composition of the mixed monolayers is determined by the static water contact angle and X-ray photoelectron spectroscopy measurements. Atomic force microscopy in lateral force mode is used to characterize the molecular domains at the nanometer level. The exchange first occurs rapidly at the gold grain boundaries, with an activation energy of about 66 +/- 4 kJ/mol. Then, boundaries of ordered thiol domains are progressively replaced, and the exchange is slowed because only regions of increasing perfection are left untouched. Higher temperatures lead to faster kinetics of replacement and the removal of larger amounts of the original thiol. No significant difference could be detected between exchange occurring in an ethanol solution or in the gas phase, and the initial rate of exchange was found to be similar for the displacement of dodecanethiol by 11-mercapto-1-undecanol molecules and for the converse displacement.

www.advmat.de 4457 Figure 3. IC-AFM (topography) images of a 16 nm thick PS-PEO film dewetting on striped amino-perfluoro nanopatterns of 400 nm period and 70 nm fluorinated stripe width. a) At room temperature after spin coating. b) After 100 min at 100°C. c) After 160 additional minutes at 130°C. d) After 240 additional minutes at 150°C. e) After quenching at RT; arrows indicate sharper ribbons, probably created at a later stage. f) Magnified image, ×2, after quenching. The insets b-d) show height profiles corresponding to the white lines in the images.

We report on the fabrication of chemically nanopatterned gold surfaces by combining electron-beam lithography with gas and liquid phase thiolization. The line-edge roughness of the patterns is ∼4 nm, corresponding to a limiting feature size in the range of 15 nm. Indications for a lower packing density of the self-assembled monolayers grown in the nanofeatures are given, and evidences for the bleeding of thiols along the grain boundaries of the gold substrate are displayed. A comparison is provided between nanopatterned thiol and silane monolayers on gold and on silicon wafers, respectively. The line-edge roughnesses are shown to be close to each other for these two systems, indicating that the limiting step is currently the lithography step, suggesting possible improvement of the resolution. The advantages and drawbacks of thiol versus silane monolayers are finally discussed with respect to the formation of chemically nanopatterned surfaces. M Supplementary data files are available from stacks.iop.org/Nano/17/1160