Reptation definition

The justification for the above definition comes from the argument that the disentanglement rate represents a characteristic length for a disentangling chain divided by a characteristic time. We have chosen this length to be the primitive path and the time to be the reptation time. Using the scaling laws developed in the previous section, we can write... 

The findings of Kim et al. and Nemoto et al. on the M dependence of Dg cannot be explained not only by de Gennes original reptation theory but also by its current modifications taking the tube renewal into account. Although it is still too early to conclude that they are definite evidence for the anti-reptation opinion, the following remark may be of some interest. 

Obviously, if found experimentally, the exponent -2 is only a sign of reptation motion but not a sufficient condition for it. Thus, in order to prove that reptation is a really dominant mode of chain motion in polymer concentrates, we have to test it not only with self-diffusion but also with other physical properties which reflect the local motion of polymer chains. One such property is the (coherent) dynamic structure factor 5(fc, r) (see Section 3.2 of Chapter 4 for its definition). In fact, it was predicted theoretically [45-47] that the k dependence of its decay with r in the range of k defined by... 

These g t) data do not favor the reptation model, but are not definitive enough to rule out the possibility of reptation motion. Thus, Kolinski et al. [57] stepped further by calculating the longitudinal and lateral displacements of the primitive path used in the Doi-Edwards theory. Such calculations should give us direct information on local chain motions. 

At present, there appears no definitive evidence against the general validity of the empirical 3.4 power law for rn,. To reconcile this fact with the reptation... 

Figure 19 Different stress definitions used in two tube models pure reptation and reputation + CLF for Z= 16. Two limiting cases are considered ...

Welp et al. (43) continued the ripple experiment, going to 400,000 g/mol polystyrene to obtain a better definition of the ripple. They concluded that the reptation model proposed by de Gennes (44) with parallel development by Doi and Edwards (45) was the best model to describe the dynamics of polymer interdiffusion. There were six dominant ripple characteristics that were examined ... 

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