Phenylene vinylene based supramolecular materials: Triblock rodcoil molecules and highly branched amphiphiles

This work involved the programming of molecules to spontaneously self organize into supramolecular structures with dimensions in the few to hundred nanometer range. The molecular system investigated is termed a triblock rodcoil system since two of it's blocks are conformationally flexible while the third block is stiff or rod like. The coil segments were found to impart strong steric forces during aggregation which significantly affects the coil segments entropy and thus the free energy of the system. These rodcoil molecules are composed of oligostyrene-b-oligoisoprene diblock coils and rod segments containing biphenyl and phenylene vinylene oligomers. A completely new chemical structure was designed within the triblock rodcoil architecture which contained solely phenylene vinylene rod blocks grafted to ethylene oxide and triphenyl amine diblock coil segments. In these materials, triphenyl amine moietiesare the most sterically demanding residues in the triblock molecules system. These rodcoil molecules showed convincingly that architecture is far more important than any specific chemical sequence in determining nanostructure formation. More recently, a series of novel amphiphiles were designed based on block copolymeric dendrimers and their self assembly in aqueous solution was investigated. The amphiphiles contain lysine derivatives as the hydrophilic segments and phenylene vinylene as the rigid hydrophobe. The larger cross section and planarity of the hydrophobe is a unique design within amphiphilic architectures. These new materials form structures larger than spherical micelles (ca 100 run) in dilute solution as well as smectic and lyotropic liquid crystals in more concentrated solutions. They likely form multilamellar plates or discs in dilute solution and show interesting biological responses by accumulating around the nuclear region of fibroblast cells.