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Randomly hyperbranched polymers containing a core region are a relatively new subclass of materials. In comparison to dendrimeric polymers, there are many similarities, including their proposed applications. Because the core-based hyperbranched polymers can be prepared in a one-pot synthesis, they are an attractive alternative to the dendrimers, which require a laborious multistep process. This research is centered around the comparison of core-based, randomly hyperbranched poly(ethyleneimine) with the dendrimeric poly(propyleneimine) to better understand their host-guest properties. Two sizes of each polymer class were examined, and studies were carried out using the solvatochromic reporter molecule phenol blue. Absorbance and fluorescence measurements (emission and anisotropy) were utilized to determine the location of the fluorophore within the polymer. Results indicate that the phenol blue does associate with both the hyperbranched poly(ethyleneimine) and the dendrmeric poly(propyleneimine), although the association is not the same for the two polymer classes. The loading capacity of both polymer classes was also determined.

[a] Nanometer-scale structures have been formed in a variety of ways including covalent, non-covalent, and metal-directed assembly. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Self-assembling, noncovalent molecular structures have been shown to form a wide range of unique host structures.[17] Previously investigated hexameric C-alkylpyrogallol [4]arene (PgC n ) nanocapsules have an interior volume of % 1250 3 , are seamed together with 72 hydrogen bonds, and are stable in nonpolar and moderately polar solvents. [18][19][20][21][22][23] These hexameric nanocapsules were shown to act as a host to multiple guest molecules, mainly pyrene derivatives. The dimeric nanocapsules that are the focus of this work are seamed together with crystallisation solvent molecules (methanol) and are capable of encapsulating a single acenaphthene molecule.Investigation into the behaviour of these entities in solution has been fairly limited, although our previous reports [24][25][26][27] have provided insight through the use of molecular spectroscopy techniques, particularly steady-state and dynamic fluorescence measurements. This ground-breaking work illustrated the potential of the PgC n nanocapsules for wide-ranging applications including molecular transport, sorting and catalysis. [20,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Previous studies of pyrene butyric acid (PBA) and pyrene butanol (PBOH) encapsulated within the hexameric C-hexylpyrogallol[4]arene (PgC 6 ) nanocapsules remarkably showed that the guest remained entrapped within the hexameric nanocapsules in solution for both systems. [24,25] Single-crystal X-ray crystallographic data revealed that the nanocapsules were mainly doubly occupied by the guest. The fluorophores inside the cavity were separated by sandwiched assembly solvent, acetonitrile. Spectroscopic and crystallographic investigations determined that both guests interacted with the interior walls of the capsule both in solid and solution states.In order to elucidate the role of guest size in encapsulation and stability of the resulting complex, the fluorescence reporter acenaphthene (AN) was investigated. AN differs from previously investigated guest molecules in both its smaller size and lack of a polar functional group within the structure. The PgC 3 OH host forms a dimeric capsule seamed with crystallisation solvent molecules to accommodate a single AN guest molecule. This varies from the hexameric capsules formed when PgC 6 building blocks were utilised to entrap pyrene derivatives. The resulting supramolecular assembly is shown in Figure 1. Alternate positions of the guest within the dimeric nanocapsule have been modelled and additonal images are included in the Supporting Information.Single-crystal X-ray diffraction studies of the pale pink crystals show that the PgC 3 OH self-assembled into a dimeric capsule containing a single AN guest molecule. Each dimeric capsule is seamed together by hydrogen-bonding mediated through four methanol solvent molecules. The interi...

No abstract

Dendritic polymers have a wide range of potential applications; however, the extensive synthesis and limited availability of bulk quantities of dendrimers restrict their use. Core-based hyperbranched polymers (CBHPs) are, therefore, an attractive alternative to dendrimers for many applications. The selectivity of core-based hyperbranched poly(ethyleneimine), as a host for phenol blue and 2-hydroxy Nile red guests, was investigated using absorption and fluorescence spectroscopies. Research results are compared to those for its dendritic counterpart, poly(propyleneimine). Phenol blue is known to associate near the core in both the CBHPs and dendrimers investigated. The interfering agent, 2-hydroxy Nile red, has also been shown to associate with these polymers; however, this interaction occurs in the outermost branches. In this work, it was found that phenol blue was sequestered in both the CBHPs and dendrimers in the presence of interfering agent, and this association appeared to be the same as that of the polymers with phenol blue alone. Although the presence of 2-hydroxy Nile red did affect the association of phenol blue, there was still considerable association even when 2-hydroxy Nile red was in 10-fold excess. The association of phenol blue with both the CBHPs and dendrimers was stable and robust; however, the association of 2-hydroxy Nile red was relatively weak and unstable.