Yang Ho Na

TL;DR: A mechanism relating to a heterogeneous structure of the DN gel is convincing for the remarkable large values of G, which increases with decreasing of cross-linking density of the 2nd network.

TL;DR: Observations of the morphological dependency on blend composition indicate that PLA/PCL blends are immiscible but compatible to some extent and that synergism of compatibilizing may be maximized in the compositional blend ratio before apparent phase separation and coarsening.

Abstract: The dynamic aspect of double network (DN) gels showing an extremely high mechanical strength has been investigated by dynamic light scattering (DLS) measurements The DN gels are formed from highly cross-linked poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) as the first network and loosely cross-linked (or non-cross-linked) polyacrylamide (PAAm) as the second network The results of DLS show that the presence of slow mode besides the gel mode (fast mode) enhances the strength of DN gels at the low cross-linking density of the second network The dynamics of the slow mode cannot be explained in terms of reptational motion of the second component in the first network, but it is similar to the translational motion of PAAm polymers in a semidilute solution A strong velocity dependence of the mechanical strength is observed at a shear rate close to the inverse of the relaxation time of the slow mode These results suggest that large “voids” of the first network may exist, and PAAm polymers that exist

TL;DR: It is concluded that the entanglement between the second component PAAm plays an important role of the toughening mechanism of DN gels, which supports the heterogeneous model, which predicts the presence of "voids" of the first network PAMPS with a size much larger than the radius of the second polymer P AAm.