The self-assembly over nano- to submicro-length scales in water of a fluorescent julolidine-labeled amphiphilic random terpolymer

A novel fluorescent-labeled amphiphilic random terpolymer is synthesized by controlled radical polymerization of a fluorescent molecular rotor monomer, 2-cyano-2-[4-vinyl(1,1’-biphenyl)-4’-yl]vinyljulolidine, a hydrophilic monomer, poly(ethylene glycol) methyl ether methacrylate, and a hydrophobic monomer, perfluorohexylethyl acrylate. Combined dynamic light scattering and fluorescence emission spectroscopy measurements are used to investigate its self-assembly in water solution. Self-assembled nanostructures with a hydrodynamic diameter size Dh of 4 ± 1 nm are detected due to the single-chain folding of the terpolymer in unimer micelles. The fluorescence emission intensity of the terpolymer in water solution is found to be one order of magnitude higher than that in organic solvents, as a result of the preferential encapsulation of the julolidine co-units in hydrophobic compartments of the unimer micelles. The temperature dependence of the self-associative behavior of the amphiphilic terpolymer is also investigated and a critical temperature is identified at which a transition between single-chain unimer micelles and multi-chain aggregates (Dh = 400 ± 40 nm) reversibly takes place on heating-cooling cycles.