Porous thin films containing subnanometer channels oriented normal to the surface exhibit unique transport and separation properties and can serve as selective membranes for separation and protective coatings. While molecularly defined nanoporous inorganic and organic materials abound, generating flexible nanoporous thin films with highly aligned channels over large areas has been elusive. Here, we developed a new approach where the growth of cyclic peptide nanotubes can be directed in a structural framework set by the self-assembly of block copolymers. By conjugating polymers to cyclic peptides, the subunit of an organic nanotube can be selectively solubilized in one copolymer microdomain. The conjugated polymers also mediate the interactions between nanotube and local medium and guide the growth of nanotubes in a confined geometry. This led to subnanometer porous membranes containing high-density arrays of through channels. This new strategy takes full advantage of nanoscopic assembly of BCPs and the reversibility of organic nanotube growth and circumvents impediments associated with aligning and organizing high aspect ratio nano-objects normal to the surface. Furthermore, the hierarchical coassembly strategy described demonstrates the feasibility of synchronizing multiple self-assembly processes to achieve hierarchically structured soft materials with molecular level control.

A facile route to generate cyclic peptide nanotubes with tunable interiors is presented. By incorporating 3-amino-2-methylbenzoic acid in the D,L-alternating primary sequence of a cyclic peptide, a functional group can be presented in the interior of the nanotubes without compromising the formation of high aspect ratio nanotubes. The new design of such a cyclic peptide also enables one to modulate the nanotube growth process to be compatible with the polymer processing window without compromising the formation of high aspect ratio nanotubes, thus opening a viable approach toward molecularly defined porous membranes.

Highly functional and monodisperse macromolecules with tailored architecture constitute the key to designing efficient and smart nanomaterials. Dendrimers offer real potential to achieve this goal, and one of the earlier challenges faced by this novel class of polymers has been addressed by the evolution of synthetic methodologies. This review provides an evaluation of the role played by chemistry in taking these macromolecules of academic relevance to practical industrial and biological applications, in a relatively short period. One can now construct dendrimers in a 'made-to-order' fashion, for numerous applications in a variety of disciplines.

The ability to selectively chemically functionalize silicon nitride (Si3N4) or silicon dioxide (SiO2) surfaces after cleaning would open interesting technological applications. In order to achieve this goal, the chemical composition of surfaces needs to be carefully characterized so that target chemical reactions can proceed on only one surface at a time. While wet-chemically cleaned silicon dioxide surfaces have been shown to be terminated with surficial Si-OH sites, chemical composition of the HF-etched silicon nitride surfaces is more controversial. In this work, we removed the native oxide under various aqueous HF-etching conditions and studied the chemical nature of the resulting Si3N4 surfaces using infrared absorption spectroscopy (IRAS), x-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), and contact angle measurements. We find that HF-etched silicon nitride surfaces are terminated by surficial Si-F and Si-OH bonds, with slightly subsurface Si-OH, Si-O-Si, and Si-NH2 groups. The concentration of surficial Si-F sites is not dependent on HF concentration, but the distribution of oxygen and Si-NH2 displays a weak dependence. The Si-OH groups of the etched nitride surface are shown to react in a similar manner to the Si-OH sites on SiO2, and therefore no selectivity was found. Chemical selectivity was, however, demonstrated by first reacting the -NH2 groups on the etched nitride surface with aldehyde molecules, which do not react with the Si-OH sites on a SiO2 surface, and then using trichloro-organosilanes for selective reaction only on the SiO2 surface (no reactivity on the aldehyde-terminated Si3N4 surface).

Bi-and trifunctional dendrimer and miktoarm nanocarriers, containing a combination of covalently linked model drug (R-lipoic acid), fluorescent dye (BODIPY), and poly(ethylene glycol) (PEG), are synthesized using a core with orthogonal functional groups, on which Huisgen alkyne-azide "click" reactions are performed in sequence. These carriers are internalized into the cells where they reduce H 2 O 2 induced reactive oxygen species formation. In addition, miktoarm nanocarriers conjugated with R-lipoic acid enhance intracellular glutathione (GSH) concentrations.