Hyperbranched Polymers for Coating Applications: A …
After discovery and development of dendrimeric polymers by Newkome, Tomalia, and Vögtle through the 70’s and 80’s, these unique globular molecules began to attract interest for potential use in a variety of applications due to the ease of integration with more mature areas of chemistry. These included nanotechnology, where independent functionalizable macromolecules might act as micro-factories for nanomachines capable of such phenomena as light-harvesting, red-ox catalysis, signal transduction, and electrical conduction. Medicinal chemists also perceived in dendrimers a new customizable vehicle for drug delivery, as well as functional medicinal polymers that could selectively compete for receptor sites for treatment of disease. In this field, dendritic MRI contrast reagents are also being explored because they can potentially provide better images due to their ability to encapsulate more of the MRI-active metals (gadolinium usually). Lastly, dendrimers are seeing use as modifiable additives, to break up clog-causing hydrates in oil pipelines, or as hyperbranched polyesters to improve material properties in synthetic fabrics, or coatings. Dendritic polymers are quickly becoming recognized as potential tools for solving problems and creating new inventions in the material, medicinal, and nanotechnology disciplines.
Hyperbranched Polymers for Coating Applications: A Review ..
In this work, we demonstrate an efficient and high yielding “click” methodology for the synthesis of second generation homo-, block-, and amphiphilic miktoarm block-dendrimers (Scheme 2) in pure form via a convergent strategy10 of coupling dendrons to a base labile core compound using copper wire (Cu (wire)5) in the absence of added N-based ligand. The convergent method has the advantages that the number of reactive groups is low (i.e., low amount of copper is required), and additionally a diverse range of dendrimers can be prepared with mixed chemical compositions (i.e., miktoarm dendrimers of hydrophobic or amphiphilic composition). This methodology has allowed us to synthesize miktoarm dendrimers in much higher yields as compared to those in the presence of CuBr/PMDETA complexes, especially when “clicking” acrylate-type polymers together. This latter result is important for high yield synthesis of amphiphilic miktoarm11 dendrimers. The major advantage of using Cu (wire) is the ease of removal of excess copper from the final product, the reuse of the same Cu (wire) in all subsequent reactions, and in the absence of base (i.e., N-based ligand) the base cleavable ester linkages at the core remain intact.
The dendrimer/dendron product line from FSI offers opportunities for both convergent and divergent syntheses of NTrēon dendrimers, offering comparatively more sites of functionality than currently offered PAMAM dendrimers.