Expanding the limits of synthetic macromolecular chemistry through Polyphenylene Dendrimers

Abstract

Polyphenylene dendrimers (PPDs) are a unique class of macromolecules because their backbone is made from twisted benzene repeat units that result in a rigid, shape-persistent architecture as reported by Hammer et al. (Chem Soc Rev 44:4072–4090, 2015) and Hammer and Müllen (Chem Rev 116:2103–210, 2016) These dendrimers can be synthetically tailored at their core, scaffold, and surface to introduce a wide range of chemical functionalities that influence their applications. It is the balance between the macromolecular properties of polyphenylene dendrimers with grandiose synthetic ingenuity that presents a template for the next generation of synthetic dendrimers to achieve complex structures other chemistry fields cannot. This perspective will look at how advances in synthetic chemistry have led to an explosion in the properties of polyphenylene dendrimers from their initial stage, as PPDs that were used as precursors for nanographenes, to next-generation dendrimers for organic electronic devices, sensors for volatile organic compounds (VOCs), nanocarriers for small molecules, and even as complexes with therapeutic drugs and viruses, among others. Ideally, this perspective will illustrate how the evolution of synthetic chemistry has influenced the possible structures and properties of PPDs and how these chemical modifications have opened the door to unprecedented applications.

The Role of Branch Cell Symmetry and Other Critical Nanoscale Design Parameters in the Determination of Dendrimer Encapsulation Properties

“…More recently, it has been reported that CNDP engineering of these shape-persistent PPD structures as a function of size, surface chemistry, architecture, etc. [191] allows these dendrimers to function as encapsulation hosts for a broad range of polar and non-polar guest molecules, as described in Figure 46. More specifically, it was found that when R=H, the PPD hosts were able to encapsulate small non-polar molecules (i.e., benzene, toluene, hexane, etc.).…”

“…A structural comparison of (1) a rigid, shape-persistent (G1); poly(phenylene) dendrimer (PPD) to (2) flexible (G1); poly(propylenimine) (PPI) dendrimers and (3) flexible (G1); poly(amidoamine) (PAMAM) dendrimer[191].…”

Amphiphilic Polyphenylene Dendron Conjugates for Surface Remodeling of Adenovirus 5

“…These dendrimers are internalized into cells while showing low toxicity both in vitro and in vivo and they possess the ability to transport lipophilic drugs within their nonpolar inner cavities . PPDs are unique because of the rigidity of their sterically demanding and space‐filling pentaphenyl‐benzene scaffold, and therefore provide persistent three‐dimensional structures . This class of dendrimer has the advantage that surface patterns can be exactly positioned since no backfolding of single dendritic arms (dendrons) can occur .…”

X‐Ray Crystal Structure of a Second‐Generation Peptide Dendrimer in Complex with Pseudomonas aeruginosa Lectin LecB

“…The invention of dendrimers, or cascade molecules, by Vögtle and Tomalia 40 years ago generated great enthusiasm in the chemistry community as a simple strategy to assemble synthetic macromolecules and polymers resembling the globular shape of proteins . The dendrimer concept, which consists in iteratively assembling dendrons into a regular molecular tree, was realized starting from a variety of building blocks such as benzyl alcohols, glycerols, phosphazenes, poly(amidoamides), polyphenylenes, and amino acids . The approach allowed designing microenvironment effects at the dendrimer core and multivalency effects at the dendrimer periphery, which proved useful in a variety of settings, most notably in catalysis and biomedical applications .…”