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Hierarchical nanostructures and self -assembly of polymers containing metal complex in the side chain

Khaled A Aamer, University of Massachusetts Amherst


Synthesis of well defined polymers containing metal complexes in the side chain is achieved either by the direct or the indirect approach. The direct approach utilizes NMP and RAFT to copolymerize 2,2':6',2''-terpyridine ligand (terpy) functionalized styrene (Styterpy) monomer in combination with other comonomers. The indirect approach produced polymers using ATRP technique containing either terpy or [Ru(terpy)2]2+ metal complex in the side chain. The indirect approach is considered the best method to obtain terpy or metal complex containing polymers in the side chain. Luminescence block-random copolymers containing [Ir(terpy)2] 3+ in the side chain were studied. Absorbance and emission spectra compared to a model compound shows that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the [Ir(terpy) 2]3+ containing copolymer studied in various solvents showed mono-modal aggregation with decreasing aggregate size as the solvent dielectric increased. The copolymer precursor P(S-b-ACterpy) shows multi-modal aggregation in different solvents with the majority population consistent with single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the metal complex. Homopolymers containing [Ru(terpy)2]+2 in the side chain are prepared in which the complex contained either a long hydrophobic C16-alkyl group or only hydrogen at the 4'-terpy position. The homopolymers containing the C16-alkyl groups showed lyotropic liquid crystalline (LC) behavior in chloroform solutions from room temperature to 60°C and self assembled in the bulk to form hexagonal arrays of cylinders. In addition, this alkyl side chain was observed to crystallize in the solid state. Homopolymers without the C16-alkyl group showed no lyotropic LC nor any crystallization behavior. Diblock and tetra-arm star copolymers containing [Ru(terpy)2] +2 with C16-alkyl group in the side chain were studied in which the diblock show lyotropic LC properties and microphase separate in the bulk into hierarchical cylinder-within-lamella morphology. The star polymer show birefringence and microphase separate in the bulk. Both copolymers have crystalline properties due to the C16-alkylgroup. The material design emphasizes the relationship between the molecular structure and self-organization of these polymers.

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Recommended Citation

Aamer, Khaled A, "Hierarchical nanostructures and self -assembly of polymers containing metal complex in the side chain" (2007). Doctoral Dissertations Available from Proquest. AAI3254907.