A Modular Synthetic Strategy toward Fast-Growing Poly(amide-carbosilane) Dendrimers Based on Click Chemistry and Organic Solvent Nanofiltration

TL;DR

This paper introduces a new modular method to synthesize diverse poly(amide-carbosilane) dendrimers using click chemistry and nanofiltration.

Contribution

A modular synthetic strategy increases dendrimer diversity while maintaining chemical consistency, using click chemistry and OSN.

Findings

14 structural analogs of PAMCAS dendrimers were synthesized across three generations.

Organic solvent nanofiltration (OSN) was successfully used for purification in macromolecular synthesis.

Dendrimers with high valency and controlled interior free volume were achieved using the AB6 module.

Abstract

Dendrimers, constituting a prominent class of monodisperse
and
multivalent macromolecular compounds with outstanding properties,
are characterized by regular and highly branched three-dimensional
architectures and well-defined chemical structures. Within each structural
type, the skeletal diversity is typically limited to the range of
generations. Here, we introduce a novel modular synthetic strategy
enabling an increase in the diversity of the dendrimer interior while
maintaining its chemical nature. Resulting poly­(amide-carbosilane)
(PAMCAS) dendrimers can be fine-tuned within one generation in terms
of size, number, and density of end groups, as well as interior free
volume. Using a tetravalent core and two building blocksdendritic
wedges with branching degrees 3 and 6we demonstrate the potency
of this strategy by producing a family of dendrimers through a controlled
iterative process that combines highly chemoselective amidic coupling
and thiol–ene click reaction (TEC). Within three generations,
we prepared 14 structural analogs of PAMCAS dendrimers, systematically
varying the order of building blocks and thus their structural profile.
The solution properties of the obtained materials were studied by
DLS, A4F, diffusion NMR, and molecular modeling. When using exclusively
the AB6 module, the dendritic growth is accelerated and
allows straightforward access to structures with extremely high valency
in a given generation. As the modular synthetic strategy poses a considerable
purification challenge, we implemented organic solvent nanofiltration
(OSN) as the main separation tool. Herein, we demonstrate proof-of-principle
experiments to evaluate the scope and limits of the use of OSN as
an effective separation method in synthetic macromolecular chemistry.

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