Preparation and characterization of highly water-soluble pendant fullerenepolymers

Pendant fullerene polymers were prepared by attaching methano[60]fullerene carboxylic acid (MFCA) and methano[60]fullerene phenylpropyl carboxylic aci d (MFPCA) to linear poly(propionyl-ethylenimine-co-ethylenimine) (PPEI-EI) via amide linkages in carbodiimide-catalyzed coupling reactions. The pendan t MFCA-PPEI and MFPCA-PPEI polymers, which were characterized using NMR, ge l permeation chromatography, FT-IR, and other instrumental methods, most li kely have a "charm bracelet" type structure without significant cross-linki ng. MFCA and MFPCA were also coupled with diethylamine in the same carbodii mide-catalyzed reactions, and the methano[60]fullerene amides thus obtained were used as monomeric model compounds for the pendant polymers. UV-vis ab sorption spectra of the polymer-bound fullerenes, though broader, retain th e characteristic features observed in monomeric methano[60]fullerene deriva tives. The pendant MFCA-PPEI and MFPCA-PPEI are highly water-soluble, with the equivalent aqueous solubilities of the polymer-bound fullerene cages si gnificantly higher than that of the parent [60]fullerene in room-temperatur e toluene. Thus, the preparation of pendant fullerene polymers represents a n effective approach for introducing fullerene cages into an aqueous soluti on or hydrophilic environment.