Superparamagnetic Triblock Copolymer/Fe2O3 Hybrid Nanofibers NSERC of Canada is acknowledged for sponsoring this research. Dr. R. Yamdagni and Ms. Q. Wu are thanked for help with the use of their NMR magnet. Dr. Zhao Li is thanked for performing the TGA analysis. G.L. thanks the NSF of China for a distinguished Young Investigator's grant.

Impregnating the cores of triblock-copolymer nanotubes with Fe2O3 renders them superparamagnetic. The resultant polymer/Fe2O3 hybrid nanofibers (see TEM image) have interesting properties in magnetic fields. The nanofibers align themselves in the magnetic-field direction, and mixtures of the nanofibers and nanotubes undergo phase separation.