Linear dynamics of end-functionalized polymer melts: Linear chains, stars,and blends

We investigated the linear viscoelastic response of model mono-, di-, and t ri-omega -functionalized three-arm star polybutadiene melts with zwitterion ic end groups using dynamic rheological measurements. Depending on the degr ee of functionalization, these polymers self-assembled into distinct supram olecular structures resembling nonspherical starlike objects, transient net works consisting of highly branched structures, and collapsed soft-sphere c onformations, with aggregation numbers affected by the arm molecular weight . The dependence of the relaxation times on the latter indicated activated processes analogous to multiarm star polymers. On the other hand, the dynam ics of omega -functionalized linear chains, forming clusters with tubular o r bcc structures, was characterized by a much smaller energetic barrier. Th e use of different sample preparation protocols as well as binary blends in volving stars demonstrated the stability of the self-organized structures a nd confirmed the assignment of the relaxation processes.