Consideration entanglements, dynamic

The Relation Between Dynamic and Equilibrium Moduli, with Consideration of Entanglements... 

The above consideration suggests that dynamic entanglements per chain are few even in concentrated solutions. Hence, in timescales comparable to the motion of individual chains in such a system may be hardly affected by topological constraint and essentially Rouse-like. Even so, it should differ from the motion of a Rouse chain in dilute solution, because each chain drags another through dynamic entanglements. Thus, Dg for polymer concentrates may be expressed by the Rouse diffusion coefficient Dg — k T/ N if C is corrected for the dragging effect. Skolnick et al. assumed to be proportional... 

For simphcity we consider end-linked polymer networks and we disregard, as is usual with GGS, entanglement effects. A simple model of a three-dimensional structure, which exphcitly takes into accoimt the connectivity between polymer chains, is a regiflar cubic network cross-linked from Rouse chains. Remarkably, it turns out that imder certain conditions the dynamical problem for such a network can be fully solved analytically [25,66,71]. This solution provides insight into the network s dynamics and is, therefore, worth detailed consideration. 

The conformational and dynamic properties of cyclic polymers have been the subject of considerable interest over a number of years [73] [74]. The new synthetic procedure developed for the preparation of per-deuterated cyclic and linear poly(dimethylsiloxane) (PDMS) polymers [12] [13] [14] now offers unique possibilities for neutron scattering studies. For the first time, it has allowed sufficient deuterated materials to be available for fractionation using our preparative GPC instrument. The resulting narrow fractions are ideally suited for both static and dynamic studies of cyclic and linear polymers. This range incorporates the critical molar mass for entanglement in PDMS. 

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