Synthetic regimes due to packing constraints in dendritic molecules confirmed by labelling experiments

Abstract

Classical theory predicts that branching defects are unavoidable in large dendritic molecules when steric congestion is important. Here we report first experimental evidence of this effect via labelling measurements of an extended homologous series of generations g ¼ 1y6 of dendronized polymers. This system exhibits a single type of defect interrogated specifically by the Sanger reagent thus permitting to identify the predicted upturn in the number of branching defects when g approaches g max and the polymer density approaches close packing. The average number of junctions and defects for each member of the series is recursively obtained from the measured molar concentrations of bound labels and the mass concentrations of the dendritic molecules. The number of defects increases at g ¼ 5 and becomes significant at g ¼ 6 for dendronized polymers where the g max was estimated to occur at 6.1 rg max r 7.1. The combination of labelling measurements with the novel theoretical analysis affords a method for characterizing high g dendritic systems.

Multi-Scale Simulation of Hyperbranched Polymers

“…In that sense, ideal dendrimers (characterized by branching monodispersity) are more easily tractable from a theoretical point of view. Even so, the unavoidable branching defects that arise when the dendrimer nodes form fewer bonds than those attainable according to its functionality (or maximum connectivity) must be quantified in order to have a realistic description of the dendrimer behavior [4,5]. Thus, the irregular branching issue that appears both in real dendrimers due to defects and in truly random hyperbranched polymers (the topic of this work) can be addressed with the aid of computer simulation.…”

Dendronized Polymers with Ureidopyrimidinone Groups: An Efficient Strategy To Tailor Intermolecular Interactions, Rheology, and Fracture

“…the degree of DP structure perfection, was determined by labeling of possibly unreacted peripheral amines with 1-fluoro-2,4-dinitrobenzene (Sanger's reagent) and quantification of the resulting absorbance at 357 nm via UV-Vis spectrophotometry. 32,33 As the characteristic absorbance band of UPy is centered around 282 nm, 34 no interference between UPy and Sanger-labeled sites was assumed. Thus, the calculated degrees of structure perfection exceeded 99% for all g. All details on synthesis and characterization are located in sections S1 and S2 of the Supporting Information.…”

Exploring the Loading Capacity of Generation Six to Eight Dendronized Polymers in Aqueous Solution

“…In this work, we use AFM images of the deprotected, and thus charged, derivatives of PG6 – PG8 , namely PG6 + – PG8 + , to qualitatively address potential aggregation or oligomer formation of high‐ g DPs, which might be formed as a consequence of structural imperfections of polymer backbone and dendrons . Furthermore, we focused on loading studies of PG6 + – PG8 + , performed with continuous wave (CW) EPR spectroscopy on nitroxide spin‐labeled, polarity‐sensitive, fatty acid guest molecules in an aqueous environment.…”