Self-assembly behavior of a stimuli-responsive water-soluble [60]fullerene-containing polymer

Anovel pH- and temperature-responsive water-soluble [60]fullerene-containing poly[2-(dimethylamino)ethyl methacrylate] (C-60-b-PDMAEMA) was synthesized by atom transfer radical polymerization. The pH and temperature dependence of the physical properties of the aqueous C-60-b-PDMAEMA solution was studied by potentiometric and conductometric titrations, UV-vis transmittance, and laser light scattering techniques. At low pH and at temperatures ranging from 25 to 55 degreesC, in addition to C-60-b-PDMAEMA unimers, micelle-like aggregates are produced in the aqueous solution containing C-60 hydrophobic cores and protonated PDMAEMA shells. Only unimeric C-60-b-PDMAEMAs are found to exist in solution at high pH and low temperature, where PDMAEMA segments form a charge-transfer complex with C-60 molecules. However, C-60-b-PDMAEMA precipitates from aqueous solution at temperatures exceeing the lower critical solution temperature of PDMAEMA of similar to45 degreesC. The pH and temperature stimuli-responsive properties of the [60]fullerene-containing polymer in aqueous solution are completely reversible.