Facile access to internally functionalized dendrimers through efficient and orthogonal click reactions.

A simple synthetic strategy has been developed for accessing internally functionalized dendrimers. The key feature of this approach is the use of two orthogonal and efficient reactions--'epoxy-amine' and 'thiol-ene' coupling--for rapid growth of the dendritic scaffold. This sequence of reactions allows for the introduction of reactive hydroxyl groups at each dendritic layer.

Multiple nanoscale templates by orthogonal degradation of a supramolecular block copolymer lithographic system.

An orthogonal approach to the creation of multiple nanoscale templates from a single supramolecular block copolymer system is presented. The enabling feature of this strategy is the design of block copolymers that incorporate independent degradation chemistries which permits each block copolymer to be addressed individually and sequentially. By blending a block copolymer containing H-bond donor groups and a UV-degradable domain with the complementary copolymer containing H-bond acceptor groups and an acid-cleavable segment, diverse and tunable nanoporous thin films with different pore sizes and array patterns can be obtained. This robust strategy demonstrates the potential of combining orthogonal chemistry with the inherent tunability of supramolecular systems.

Site-specific installation and study of electroactive units in every layer of dendrons.

Whereas encapsulation of functional groups at the core of dendrimers is well-understood, very little is known about their intermediate layers or even the periphery. Here we report on a systematic investigation of every layer of dendrimers by incorporating a single ferrocene unit in well-defined locations in dendrons. Site-specific incorporation of the ferrocene unit was achieved by utilizing the dendrimer sequencing methodology. We show here that the redox potential values of ferrocene at intermediate layers were remarkably different from those at the core and the periphery. Although redox potential values were location-dependent, no significant change in the rate of heterogeneous electron transfer (k(0)) was observed with respect to locations. This was attributed to the possibility that free rotation of dendrimer nullifies the distance between the electrode and ferrocene unit. Finally, we also show that no Faradaic current was observed for the amphiphilic assemblies of these dendrons, whereas the same dendron did exhibit significant Faradaic current in nonassembling solvent environments.

FACILE PREPARATION OF NANOPARTICLES BY INTRAMOLECULAR CROSSLINKING OF ISOCYANATE FUNCTIONALIZED COPOLYMERS.

A new synthetic approach to the preparation of intramolecularly collapsed nanoparticles under mild, room temperature conditions has been developed from commercially available vinyl monomers. Reaction of isocyanate functionalized linear copolymers with a diamine in dilute solution leads to the efficient formation of nanoparticles where the diameter of the nanoparticle can be varied by controlling both the molecular weight and mole percentage of isocyanate repeat units. Physical properties for the intramolecularly collapsed nanoparticles were fully consistent with a three-dimensional structure and analysis of the collapse reaction revealed that approximately 75% of the isocyanate groups along the backbone underwent crosslinking with 25% being available for further reaction with mono-functional amines. This stepwise consumption of the isocyanates allows the chemical and physical properties of the nanoparticles to be further tuned and significantly opens up the range of nanoparticles that can be prepared using this mild and highly efficient chemistry.

Probing every layer in dendrons.

Dendrons with a fluorescent probe in a specific location have been synthesized and characterized. Accessibility of guest molecules to each of these layers was then analyzed using an intermolecular photoinduced electron-transfer process. Comparisons of the accessibility among each layer of the dendron and among the generations are provided.

Sequences in dendrons and dendrimers.

Sequential incorporation of a variety of functional groups forms the basis for specificity in biomacromolecules. Introduction of such diversity and sequencing ability in artificial macromolecules is fundamentally interesting. In this paper, three different synthetic approaches have been used to build dendrons and dendrimers in which all the monomer units are different from each other. The synthetic strategies described in this paper involve the use of (i) an ABB(p) monomer, (ii) an ABB' monomer, and (iii) an ABB(m) monomer. The complementarity and the versatility of these synthetic approaches should render them useful for a variety of applications.

Synthesis of dendrimers with multifunctional periphery using an ABB' monomer.

A new methodology using an ABB' monomer for synthesizing dendrons with multiple functionalities in the periphery is described.

Functional group diversity in dendrimers.

[structure: see text] A methodology for synthesizing dendrons with different peripheral functionalities is described. The benzyl ether-based dendrons reported here were synthesized using allyl and methoxymethyl ether-based protection-deprotection strategies.