1. Backbone Relaxation We explore the backbone and arm (or
branch) relaxation for linear comb polymers
by studying the damping function, shown
at the bottom of the slide (left). The data
are compared with predictions from two
well-known theories. The most significant
result is the lack of agreement between the
data for the backbone and the Doi-Edwards
theory. Even after the arms have all relaxed,
we estimate that the backbone has at least
12 entanglements per chain with other back-
bones, and thus dynamic dilution, which has
been used to “explain” this type of disagree-
ment cannot be relevant since it relies on
the system ending up with only a small number
of entanglements after arm relaxation. This
challenges our current understanding of the
rheology for this type of branched polymer