Reduction of the viscoelastic moduli at large amplitude oscillatory flows ensues essentially for the same reason as discussed above: at large amplitudes, stretching chains along the direction of the flow enhances the desorption of the segments from the particle surface, thereby contributing in dissipation of the applied energy.
Each stretched chain can be pictured as a string of N c Pincus blobs of size R b [18].
The shish kebab structure, composed of stretched chains (shish) and layered crystalline lamellae (kebabs), was found in the sheared layer.
(1) The shish entity consists of stretched chains (or chain segments) that can be in the amorphous, mesomorphic or crystalline state.
It is conceivable that a significant fraction of chain orientation is induced in the vicinity of the nanofillers during stretching, and these stretched chains with reduced mobility significantly enhance the thermal mechanical properties.
Instead, a very broad endothermic curve ranging from 90 °C to 172 °C shows up, suggesting that the stretched chains in a filament with severe dimensional constraint relax slowly toward isotropic state over broad range of temperature.
The initial decrease is thought of in terms of a progressive decrease in the entropy of stretched chains with consecutive extensions where the chains are increasingly less able to contribute to hysteresis until the PS domains become disrupted on a large scale, after which the curves begin to rise.
In this paper we consider a polymer that operates by photoactivated stress relaxation; at the molecular level, photoinitiation of residual initiator molecules generate free radicals that break and then reform in-chain functionalities of stretched chains in an elastomeric network, which results in macroscopic stress relaxation.
Note that a DH value of 94 nm for (M1) 37 - b- M4) 106 is larger than the theoretical sphere with fully stretched chains (Dth=72 nm), suggesting the formation of nonspherical micelles or larger aggregates.
The difference in strain-induced crystallization behavior of amorphous PLA within 70 90 °C can be attributed to the competition between chain orientation caused by stretching and chain relaxation.
