The polar side of polyphenylene dendrimers

Abstract

Polyphenylene dendrimers (PPDs) represent a unique class of dendrimers based on their rigid, shape persistent chemical structure. These macromolecules are typically looked at as nonpolar precursors for conjugated systems. Yet over the years there have been synthetic achievements that have produced PPDs with a range of polarities that break the hydrophobic stereotype, and provide dendrimers that can be synthetically tuned to be used in applications such as stable transition metal catalysts, nanocarriers for biological drug delivery, and sensors for volatile organic compounds (VOCs), among many others. This is based on strategies that allow for the modification of PPDs at the core, scaffold, and surface to introduce numerous different groups, such as electrolytes, ions, or other polar species. This review is aimed to demonstrate the versatility of PPDs through their site-specific chemical functionalization to produce robust materials with various polarities.

Spiers Memorial Lecture : Carbon nanostructures by macromolecular design – from branched polyphenylenes to nanographenes and graphene nanoribbons

“…Notably, the concept of repetitive Diels-Alder cycloadditions has also been extended to the synthesis of polyphenylene dendrimers. [141][142][143][144] Therefore, the diene and dienophile functions have been combined with the AB 2 moiety, which serves as a branching unit. The second critical issue in GNR synthesis is cyclodehydrogenation by a Scholl reaction.…”

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

“…Molecular weights as high as 1.9 MDa were confirmed by MALDI-TOF and the shape-persistent PPD structures are compared to flexible PAMAM and PPI dendrimer structures, as illustrated in Figure 45. This work has been reviewed extensively and described elsewhere [189,190]. Seminal synthesis strategies pioneered by the Mullen group (i.e., Max Planck Institute for Polymer Research, Mainz) led to the discovery of a unique class of rigid, aromatic, shape persistent dendritic structures referred to as poly(phenylene) dendrimers (PPDs).…”

Diels–Alder polymerization: a versatile synthetic method toward functional polyphenylenes, ladder polymers and graphene nanoribbons

“…In contrast to the time-consuming step-by-step synthesis of a dendrimer from AB n building blocks 11,14,15 , hyperbranched polymers could be constructed in a one-pot "uncontrolled" polymerization of, in principle the same, but unprotected AB n -type monomers, ideally forming a branch on every repeating unit. Molecularly defined dendrimers as well as dendritic and hyperbranched polymers establish a class of attractive materials in view of their unique properties derived from their branched 3D…”