EPR Investigation of the Adsorption of Dendrimers on Porous Surfaces

Guest−host interactions of poly(amidoamine) dendrimers and porous surfaces, such as homoporous silica of different pore sizes, activated alumina (acidic, neutral, basic), and MCM-41 zeolite (Si/Al=30), were investigated by electron paramagnetic resonance (EPR) spectroscopy. Two generations of dendrimers were selected, G2 and G6, representing “early” and “late” generations, which were labeled with a nitroxide radical. It was found that the main parameters regulating the adsorption and interaction of the dendrimers and porous surfaces are (I) the size of the pores of the porous materials (host) relative to the size of the dendrimer (guest), (II) the total surface area of the host that is accessible to the guest dendrimers, and (III) the chemical composition of the host and guest surfaces that come into contact upon adsorption. If the pore size of the host surface is smaller than the guest dendrimer diameter, then adsorption of the dendrimer occurs exclusively on the external host surface. If the pore size o...