| Abstract
| - A well-defined, water-soluble, pH and temperature stimuli-responsive [60]fullerene (C60) containing ampholyticblock copolymer of poly((methacrylic acid)-block-(2-(dimethylamino)ethyl methacrylate))-block-C60 (P(MAA-b-DMAEMA)-b-C60) was synthesized by the atom transfer radical polymerization (ATRP) technique. Theself-assembly behavior of the C60 containing polyampholyte in aqueous solution was characterized bypotentiometric and conductometric titration, dynamic light scattering (DLS), and transmission electronmicroscopy. This amphiphilic mono-C60 end-capped block copolymer shows enhanced solubility in aqueousmedium at room and elevated temperatures and at low and high pH but phase separates at intermediate pHbetween 5.4 and 8.8. The self-assembly of the copolymer is different from that of P(MAA-b-DMAEMA).Examination of the association behavior using DLS revealed the coexistence of unimers and aggregates atlow pH at all temperatures studied, with the association being driven by the balance of hydrophobic andelectrostatic interactions. Unimers and aggregates of different microstructures are also observed at high pHand at temperatures below the lower critical solution temperature (LCST) of PDMAEMA. At high pH and attemperatures above the LCST of PDMAEMA, the formation of micelles and aggregates coexisting in solutionis driven by the combination of hydrophobic, electrostatic, and charge-transfer interactions.
|
