Development of materials and devices for separation of polyamido[a]mine dendrimers

Graduation date: 2006Over the last decade, the use of highly branched macromolecules, called dendrimers, is emerging. Polyamidoamine (PAMAM) dendrimers, in particular, have attracted high interest due to their unique properties, such as well-defined size, shape, and solubility in water. Our group, as part of an interdisciplinary team, is currently working on developing a nanoextraction technology for high-yield dendrimer syntheses. Impurities may occur during the synthesis of these dendrimers, and therefore, to achieve higher purity products, chromatographic separations of dendrimers are an important part toward this goal. This thesis describes approaches toward this objective, focusing in two areas: at first, development of materials and devices that will enable separations of dendrimers in confines of capillary and chromatographic columns, and second, evaluation of the feasibility of transferring the separation techniques previously developed to the channels of microfluidic devices. The results showed that PAMAM dendrimers of various generations were successfully analyzed using capillary zone electrophoresis (CZE), capillary\ud electrochromatography (CEC), and high-performance liquid chromatography (HPLC). Both CZE and HPLC have allowed for fast generational separations up to the fifth generation. Moreover, CZE can also assess the homogeneity and presence of side products in the synthesized dendrimers. RP-HPLC, on the other hand, allowed for separations of dendrimers with terminal amino and carboxyl groups.\ud PAMAM dendrimers can also be used as template molecules to prepare monolithic capillary columns for liquid chromatography and capillary electrochromatography. This method has provided two advantages: 1) dendrimers can be used as template molecules for controlling pore structures, 2) selective sorbents can be produced with surface sites that are complementary in chemical functionality to the dendrimer template molecule. These highly selective sorbents were able to provide separation of dendrimers from various generations, particularly of high generations, in the CEC mode. As the first step toward the development of a nanoextraction technology for high yield dendrimer syntheses, the feasibility of extending the separation techniques developed on-column into channels of a microfluidic chip was examined. In this study, electrophoresis was employed to separate different generations of dendrimers in glass microfluidic chips using laser-induced fluorescence detection. The use of microfluidic system for dendrimer application offers great potential due to its rapid analysis times, small sample volume requirements, and the ability to integrate several steps of analyses in one chip