Search

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.

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.