A relatively new class of supramolecules�highly entangled, end-functional polymers�are accessible through efficient ROMP+CTA (ring-opening metathesis polymerization with chain transfer agents) synthesis. At high concentration or in the melt, association among the end-groups of entangled chains (>25 Me) frustrates their reptation relaxation. This broadens the time range in which the materials behave in an elastomeric manner. The activation energy of end-association can be tuned using polyvalent hydrogen bonding. Here, we compare polybutadienes that have either two or four carboxylate groups at each end. The activation energy for end-association controls the time scale and temperature dependence of the terminal relaxation. For example, having two carboxylates at each end slows the terminal relaxation of a 50kg/mol PB by three orders of magnitude at ambient temperature�and by more than four orders of magnitude at 5�C. Thus, the terminal relaxation shifts more strongly with temperature than the chain segmental motion, giving an enlightening failure of time-temperature superposition. Two relaxation modes are evident: a �fast mode� assigned to the rearrangement of entangled chains constrained by end association and a �slow mode� assigned to the end group exchange. Adding short polybutadiene as a dilutent helps to expose the underlying dynamics and leads to interesting adhesive materials.

Interplay between end-association and entanglement in hydrogen-bonded telechelic polymers: A sticky situation

248th National Meeting (2014)

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