Controlling the self-assembly and dynamic response of star polymers by selective telechelic functionalization

We report on the structure and dynamics of model mono-, di-, and tri-omega- functionalized three-arm star polybutadiene melts. By using x-ray scatterin g and dynamic rheological measurements, we find that functionalization of t he arm ends can lead to distinctly different supramolecular structures and material behavior. The monofunctionalized samples behave like multiarm noni onic star-like dendrimers, whereas the difunctional stars resemble a transi ent network consisting of highly branched structures with a very broad rela xation spectrum. On the other hand, the trifunctional stars seem to develop an unusually regular structure of dominant intramolecularly aggregated fun ctional groups leading to collapsed star conformations, resembling soft sph eres, and a well-defined terminal relaxation. These results suggest that by tailoring the telechelic functionalization of regular star polymers, a rou te to design and obtain a wealth of controlled supramolecular structures ex hibiting a rich and variable dynamics could open. (C) 1999 American Institu te of Physics. [S0021-9606(99)51528-6].