Dendrimers and hyperbranched polymers (HBPs) based on the monomer, 2,2-bis(methylol) propionic acid (bis-MPA) form a multitude of hydrogen bonds (H-bonds) through their hydroxyl and carbonyl functional groups. For perfect dendrimers, the bis-MPA repeat units are incorporated into the perfectly branched structure as fully esterified units and non-esterified moieties with the hydroxyl end-groups being situated only at the exterior surface. In HBPs however, the bis-MPA monomers can additionally be incorporated as partially esterified units, which result in hydroxyl groups being present within the interior of the dendritic structure. Molecular dynamics simulations were performed on the second and fourth generation dendrimers, D20 and D40, as well as on the second generation hyperbranched polymer, H20. The H-bond organization was compared between the dendrimers and hyperbranched polymers in the bulk. The number, type, and distribution of H-bonds, as well as the H-bond related structural order was determined over a wide temperature range and compared between each system. Remarkably, one-dimensional clusters of H-bonded hydroxyl groups, which were reminiscent of those of small molecule H-bond formers such as water and liquid hydrogen fluoride, were found in both the dendrimers and the HBP.  These types of clusters may extend to other dendritic or globular structures, affecting their overall function.

Hydrogen bond organization and related structural order in bis-MPA based dendrimers versus hyperbranched polymers

249th National Meeting (2015)

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