| Abstract
| - Water-soluble, pH-responsive mono- and di-[60]fullerene end-capped poly(acrylic acid)s (PAA−C60 and C60−PAA−C60) were synthesized using the atom transfer radical polymerization technique. Isothermal titration calorimetry,dynamic light scattering, UV−vis spectroscopy, and transmission electron microscopy were employed to study thesupramolecular complexation between fullerene end-capped PAAs and nonionic surfactant, polyethylene glycol (9−10) tert-octylphenyl ether, also known as Triton X100 (TX100) at different pH values. At pH < 4, TX100 boundspecifically to C60 domains driven by hydrophobic and π−π interactions between TX100 and fullerene molecules.The binding was exothermic, and the magnitude of the interaction decreased gradually with increasing pH. The amountof polymer-bound TX100 was proportional to the fullerene content, which was ∼1.3 and ∼2.5 mM for 5 mM(concentration of carboxylic groups) PAA−C60 and C60−PAA−C60, respectively. Morphological transformationsresulting in the formation of polymer/surfactant complex (PSC) precipitates in the course of binding were observedfor both polymers. The PSC of PAA−C60 possessed a dense spherical structure, whereas the PSC of C60−PAA−C60possessed a lamellar stacking structure. The PSC precipitates resolubilized in excess amounts of TX100 to form stableaggregates.
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