1 JPI: my answer was # 5 I realize that the classical answer would be # 4, but no tubes have ever been seen. Besides, the closest analogy with my Dual-Phase model model of entanglements would be a network of pipelines or river channels constantly in motion. Under stress, the motion of those “phase-lines” changes from a diffusion mode, at very low stresses to an activation-relax cooperative mechanism (“cooperative blinking”) describing shearthinnning followed by the orientation of the phase-lines (entanglement network), followed by the instability of the network and the involvement of enthalpic contributions to the deformation (yielding). 1 The link to the quizz and to the class recording2 are found in the footnote 1 http://www.wiziq.com/online-tests/22446-the-entanglement-quizz. 2 http://www.wiziq.com/online-class/430878-the-need-for-a-new-understanding-of-entanglement-in-polymer-physics http://www.wiziq.com/online-tests/22446-the-entanglement-quizz 2 JPI: the last answer (#4) is the good choice3 JPI: my answer was #1. The reptation protagonists will disagree, but they should read The Great Myths of Rheology part II (downloadable in the MY CONTENT of the WIZIQ courses) and provide another answer that edge fracture for the triggered viscosity time dependence at strain starting around 15%. for PS. 4 JPI: My answer was #1 The tube itself has become another giant “macromolecule”, see de Gennes “scaling concepts in polymer physics”. The fixed obstacles to define the envelope for local motions (Rouse type) are frozen for the time of reptation (td). All these concepts must be easily defined from the inter-intra molecular bonding forces, and, in a sense, it is much easier to define a network of tubes and its diffusive motion (or activated cooperative deformation mechanism) by the Dual-Phase concept. Besides, the dual-phase understanding of entanglement is compatible with the spectroscopic data above and below Tg, and explains all various types of deformation mechanisms as stages of collaborative processes 5 JPI: my answer was #2 Answer #1 would be correct under no stress, for a stable entanglement state which is at equilibrium. Lots of counter-examples can be shown. The stability of the network of entanglement can be modified by thermal-mechanical history. It would be like creating a new set of tubes for the reptation model, with a different topology. In order to link the network pipeline topology with the state of the conformers interactions, one needs to abandon the ad hoc framework of the reptation tubes and adopt the concept of Dual-Phase which allows a living link between the scales , permitting to define time relaxation of the entanglement network in a kinetic fashion. In other words, the re-scaling between the local motions and the motion of the entanglement network is integrated kinetically as well as energetically. The entanglement manipulation consists in unlocking the kinetic dependence to influence the energetic structuring, and vice-versa. 6 JPI: my answer was #1 This is were the reptation model diverges with my understanding of disentanglement/reentangglement It is my opinion that the network of continuous rivers and pipelines described by my phase-lines, a consequence of the Dual-Phase concept, is not a description of the whereabouts of a single chain. The Doi Edwards considers the tube as the space of confinement for a single chain motions. The rms end to end distance of a single chain does not change at all from its value in the Newtonian and the shear-thinning region, according to L. Noirez’s recent SANS data. The statistics should not focus on the single chain, but on the evolution of the mechanism of diffusion of the dual-phases. This may very well make the chain rotate around its gravitational axis as it is been displaced by diffusion. The local interactions are constantly been formed and deformed (say this would be the equilibrium local Rouse description), but the localization of the Dual-Phases is either randomly the same, or it is changing. This is the point of focus, in my opinion. And the definition of the reptation time by 1/wx , without relating it to the stability of the network, makes it as flawed (incomplete) view. 7 JPI: the correct answer was # 1 It is my purpose to teach in this course the bases that will enable the polymer community to modify the state of entanglement of plastic melt in a controllable and designed fashion8 JPI: My answer was #2. I have produced melts with boosted viscosity increase, the reverse of disentangled melts. They are also instable and try to return to a thermodynamically stable state.9 JPI: my answer was #1 (see my previous answer)10 JPI: my answer was #2 11 JPI: my answer was #3 Once the complete answer is known theoretically, we will have established the understanding of a true time dependent renormalization group theory, bridging with Prigogine non-equilibrium concepts of instability. Scaling and universality are defined for steady states, they should be modified to apply to transients, for which universality must incorporate a dissipative component, in my opinion. I once called a very intuitive attempt to do this “ the Interlock Band Model.”, but realized that “IBM” was the focus of attention for doing something else… 12 JPI: my answer was #3. The real time of recovery depends on the state of non-equilibrium achieved for the melt. I have observed for PMMA, 24 hours at T= Tg + 130oC, whereas TAUo at that temperature was less than 1 sec. 13 JPI: my answer was #3 There is perhaps a difference between “re-entanglement” originating from fully unentangled polymers (such as produced by Prof. Rastogi) and the return to equilibrium of melt whose entanglement network has been modified. We suspect that in gap structuring (gradient of entanglement modification) plays a different role than Molecular weight. In conclusion, the answer above is based on the re-entanglement of the Rastogi’s PE sample. 14 JPI: My answer was #2 Previous work by others exclusively focused on branched polyolefins (to increase their TAUo) and believed that linear polymers would not work, but this turned out to be incorrect. It appears that all polymers that have an entanglement network can “disentangle”.15 JPI: my answer was #3 Disentanglement is not local and is not defined by the reptation time. It is a property derived from the relaxation of the network. When the network is not “oriented “, say only shear-thinning is activated, then #1 answer is correct. But when “disentanglement “(distortion of the topology of the dual-phase “phase-wave”) is successfully achieved, the entropic and enthalpic character of the conformer interaction coupling may result in very long time for network thermodynamic recovery.16 JPI: my answer was #1. A disentangled melt has undergone strain softening, which is due to the entalpic contribution to strain production (stress induced conformational changes, from cis-gauche to trans-conformers). Moduli of elasticity are reduced accordingly, normal stresses follow through. .17 JPI: my answer was #1. HOWEVER, I would strongly disagree that this could be derived from the simple concept that this is because Me increases. 18 JPI: my answer was #1. Indeed, see my paper The Great Myths of Rheology, part II which provides many examples of such comparison. In some instances the disentangled melt has the same ETAo (Newtonian value), but a different melt index (pseudoplastiicity) and in other cases the disentangled polymer has a lower Newtonian viscosity as well, we can be observed by measuring the Melt Flow Index (in some instances, we have observed the double for the MFI).19 JPI: my answer was #3. At the beginning of phase-line orientation, the entanglement network may be homogeneously deformed across a gap, especially for thin gauge, but, at higher stresses, the velocity and the gamma dot influence the degree of nonequiliibrium and thus a gradient of entanglement (stratification) is expected.20 JPI: my answer was #3, although I could have also ticked #4, since there is a lot to learn still, and it is somewhat provocative to say that TAUo and Me do not play any role. What I mean to say is that the answer should be better described with a different analytical frame than the linear viscoelastic parameters.21 JPI: my answer was #2. Shear-thinning is not related to disentanglement, but to the increase of the number of activated systems of the network coordinating their response to the strain rate application (interactive coupling of systems). It is translated by an increase of the network diffusion frequency w’.22 JPI: my answer was #2 The ratio between the unentanglement line, proportional to M, and the entanglement line, proportional to M3.423 JPI: my answer is last (#6). This is the heart of my research This will be developed during the other lectures.