Self-Assembly of Colloidal Quantum Dots on the Scaffold of Triblock Copolymer Micelles

This paper describes the co-self-assembly of a polystyrene-poly(4-vinylpyridine)-poly(ethylene oxide) triblock copolymer with CdSe nanocrystals (quantum dots, QDs) and with a styrene compatible phenylenevinylene conjugated polymer (MEH-PPV) in mixtures of chloroform and 2-propanol. The polymer itself (PS(577)-P4VP(302)-PEO(852), where the subscripts refer to the number average degree of polymerization) forms worm-like micelles when 2-propanol is added to a solution of the polymer in CHCl(3). In the presence of increasing amounts of QDs, the structures become shorter and form only spherical hybrid micelles (with QDs bound to the surface) at 4:1 QD/polymer w/w, accompanied by free QDs. These structures retain their colloidal stability in 2-PrOH, suggesting that even the free QDs bear a surface shell of block copolymer. The presence of MEH-PPV has no affect on this self assembly. One of the most remarkable observations occurred when the samples in 2-PrOH were centrifuged to remove the free QDs accompanying the hybrid micelles. The micelles sedimented, but upon redispersion in 2-PrOH, rearranged to form colloidally stable long branched cylindrical structures including cylindrical networks.