Structure and Excited-State Interactions in Composites of CdSe Nanorods and Interface-Compatible Polythiophene-graft-poly(N,N-dimethylaminoethyl methacrylates)

We report the preparation and characterization of two comblike graft copolymers, polythiophenegraftpolyN,Ndimethylaminoethyl methacrylates PT700gPDMA60and PT220gPDMA16, where the subscripts represent the number average degree of polymerization, and an investigation of their interaction with CdSe nanorods. Each polymer contains a regiorandom polythiophene PT as the backbone, from which polyN,Ndimethylaminoethyl methacrylate PDMA chains are densely grafted. The PDMA arms serve as multidentate ligands for CdSe semiconductor nanocrystals and increase the compatibility between the PT backbone and the nanocrystals. Using electron microscopy, we examined the morphology and the internal structure of the nanorodpolymer composites formed in toluene. The morphology and the internal structure of the composites vary with a change in the nanorodpolymer ratio as well as with the concentration of each component. The results of steadystate fluorescence spectroscopy indicate that the presence of the nanocrystals in toluene leads to photoluminescence PL quenching of the PT backbone in the graft copolymer with relatively short PDMA arms PT220gPDMA16. In contrast, no PL quenching could be detected in composites formed from a similar polymer with longer PDMA arms PT700gPDMA60. A likely explanation of this result is that in composites formed with PT700gPDMA60, the nanocrystals are held too far from the PT backbone for energy transfer or charge transfer to take place.