Nanostructured Crosslinkable Micropatterns by Amphiphilic Dendrimer Stamping

Functional, three-dimensional (3-D) nanostructures and microstructures on surfaces can serve as excellent molecular templates for applications in optoelectronics and biotechnology. Coupling stable, amphiphilic films with hydrophobic biological molecules can yield biomimetic interfaces able to reproduce biological functions in vitro. Recently, thin films of amphiphilic molecules have been used to couple proteins to carbon nanotubes. 3-D patterns of amphiphilic molecules can also be used in photon harvesting, organic and polymeric electroluminescent devices (e.g., light-emitting diodes), organic solid-state lasers, and photonic band gap materials. Microand nanoscale partitioning of regions with different chemical composition, charge, or environmental conditions is a widely used biological motif, as evidenced by the many membraneseparated organelles and membrane-mediated signaling mechanisms found in cells. Dendrimers make up a unique, highly diverse class of polymers that have well-defined macromolecular architectures and are almost perfectly monodisperse. Radially layered poly(amidoamine organosilicon) (PAMAMOS) dendrimers are especially versatile, amphiphilic, and crosslinkable globular-shaped macromolecules. PAMAMOS dendrimers having dimethoxymethylsilyl (DMOMS) endgroups can be denoted as PAMAMOS-DMOMS (p, q), where p and q are integers that define the generation of the polyamidoamine (PAMAM) interior and the number of exterior layers of organosilicon (OS) branch cells, respectively (see Figure 1). PAMAMOS are generally prepared from commercially available PAMAMs with different relative degrees of amino end-group conversion (i.e., OS substitution). In this study, PAMAMOS-DMOMS (2,1) dendrimers were used (see Experimental Part). Microcontact printing (mCP) is a soft lithographic technique used in physics, chemistry, materials science, and biology to transfer patterned thin organic films to surfaces Summary: Microcontact printing was used to deposit stable, nanostructured, amphiphilic and crosslinkable patterns of poly(amidoamine organosilicon) (PAMAMOS)-dimethoxymethylsilyl (DMOMS) dendrimer multilayers onto silicon wafers, glass, and polyelectrolyte multilayers. The effects of dendrimer ink concentration, contact time, and inking method, on the thickness, uniformity, and stability of the resulting patterns were studied using optical microscopy, fluorescence microscopy, atomic force microscopy (AFM), and contactangle analysis. Microarrayed dendrimer film thickness was found to be controllable by conditions used during spin self-assembly.