Micelles with highly branched nanoporous interior: solution properties and binding capabilities of amphiphilic copolymers with linear dendritic architecture

This article describes the solution behavior of model amphiphilic linear-dendritic ABA block copolymers that self-assemble in aqueous media and form micelles with highly branched nanoporous cores. The materials investigated are constructed of poly(ethylene glycol), PEG, with molecular weight 5,000 or 11,000 as the water-soluble B block and poly(benzyl ether) monodendrons [G] of second and third generation as the hydrophobic A fragments. The process of self-assembly in aqueous media and the character of the micellar core are investigated by fluorescence spectroscopy using pyrene as the molecular probe. The data obtained by different methods indicate that the critical micelle concentrations (cmc) for these systems are between 1.1 × 10^-5 and 2.0 × 10^-5 mol/L for [2]-PEG5000-[G-2] and between 7.08 × 10^-6 and 7.94 × 10^-6 mol/L for [G-3]-PEG11000-[G-3]. It is found that the ratio of the first and third vibronic bands (I₁/I₃) in the fluorescence spectrum of the encapsulated pyrene changes from 1.77 to 1.32 when the concentration of [G-2]-PEG5000-[G-2] increases from 1.1 × 10^-6 mol/L to 1.1 × 10^-4 mol/L. For [G-3]-PEG11000-[G-3] these changes are between 1.77 and 1.17 in the same concentration range. The hybrid copolymers form host-guest complexes with several polyaromatic compounds (phenanthrene, pyrene, perylene and fullerene, C₆₀) that are stable over extended periods of time (more than 12 months).