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| Jean Pierre Ibar, New School Polymer Physics (2016) |
My research is dedicated to the understanding of the physics of polymers from a different point of view from the admitted models. See the link at the end of this blog.
In the classical views, the chain is particularized and its interaction with its surrounding is described in terms of a mean field of interactions. The entropy of a single chain is calculated from its intra-molecularly linked covalent bonds and the deformation-to express flow properties, for instance- is due to a modification of the entropy. The presence of the other chains is perceived as a restriction on the entropy, in particular, in de Gennes’s well praised model by the confinement of the motion of the chain within a tube in which the chain can reptate. The sophistication of the “reptation” model comes from the refinement of the definition of the tube itself.
I propose a different model of understanding of the coupling between the bonds of polymer macromolecular chains, creating a novel statistics (the “Grain-Field-Statistics”) that does not singularize individual chains embedded in a sea of mean field interactions. Instead, I consider the global set of chains of conformers with a re-definition of their conformational statistics to account for the coupling of their inter and intra molecular interactions. This new statistics provides a new understanding of entanglements as a two dual-phase system, describes viscoelasticity and flow properties in a quantitative and completely original way and suggests that the entanglement network can become unstable under conditions of non-linear viscoelastic deformation.
In my current research program I suggest that the instability of the network could be used to "disentangle" polymers and, subsequently, "re-entangle" them in a different specific way, creating new exciting materials, such as plastics capable of storing enthalpic energy into the bonds and releasing the energy on demand by mere application of heat, perhaps solar energy (“plastic battery”).
From a practical view point, my current research is on the stability of entanglements of polymer melts and on how to manipulate them to modulate and improve the properties of the molded products. In particular, I studied the correlation between viscosity improvement during processing and entanglement stability and discovered a new property of the liquid state of polymers which is not explained by the current models in polymer physics, yet can be justified by the Crossed-Dual-Phase concept of entanglements: it is called “sustained orientation”. In simple terms, by manipulation of the stability of entanglements, it is possible to create and maintain quasi-stable at high temperature in an amorphous polymeric melt (say 120 oC above Tg) a certain state of orientation that was induced by a mechanical deformation. The manipulation of entanglements is done by Rheo-Fluidification. This discovery is discussed in details in previous blogs and recent publications [1-5].
What the experiments described in Refs 2 and 4 suggest is that the classical concept of Me to describe entanglements is too simplistic and its usefulness is probably limited to the linear range of viscoelasticity. The whole foundation of polymer physics, based on its understanding of entanglements, appears to be shaken by the type of experimental results in Refs 2 and 4.
It is an objective of the New School Polymer Physics research to set new grounds for the understanding of polymer properties using the Grain-Field_Statistics, from the solid state to the liquid state, from flow to molecular motions, for amorphous and crystalline materials. In particular, there is the need to test whether the new statistics can explain “sustained orientation”, and predict the conditions to successfully prepare “plastic battery materials”.
To summarize, the New School Polymer Physics initiative has for prime objective to disseminate broadly the teaching of a different model for the source of molecular motions and flow in polymers that provides a clear, sounded and quantitative explanation of their rheological response including those experiments which the classical approach fails to describe.
This new understanding of polymer interactions and entanglement expresses a paradigm shift in polymer physics; in fact, I have now recorded about 100 hours of video lectures (Video Clip Lectures - VCL series) dedicated to this new polymer physics which I also have the plan to dispense live via online webinars. These lectures also cover thermal analysis data which provide a key insight about the conformational statistics which I use in my new model.
The objective of these lectures is to teach a new generation of students, engineers and researchers this new physics of polymer interactions and entanglement and its practical engineering applications to process melts by entanglement manipulation and drastically reduce their viscosity.
Applications of the “disentanglement technology” are of immediate interest to the plastic industry: decrease energy consumption, increase of permeability in films for the food industry, improved dispersion of nanoparticles in polymer melts, processing under much lower pressure and at lower temperature at identical throughput, increase of productivity and cost reduction for injection molding, extrusion and compounding lines etc. These applications are all covered in the teaching of the melt manipulation technology.
In the link below you will find an INTRODUCTION TO THE DUAL-PHASE MODEL OF POLYMER INTERACTIONS AND TO THE CROSS-DUAL-PHASE MODEL OF ENTANGLEMENTS which I have extracted from the Preamble of a recent paper [6] dedicated to validate the "blinking" and "sweeping" deformation mechanisms of flow and the existence of the elastic dissipative wave in polymer melts.
REFERENCES:
1. J.P Ibar, “ The Great Myths of Polymer Rheology. Part I.
2. J.P. Ibar “ The Great Myths of Polymer Rheology” Part II. Transient and Steady State. The question of the entanglement stability. Journal of Macromolecular Science, Part B, 49, 1148 -1258 (2010). 110 pages.
3. J.P. Ibar, “The Great Myths in Polymer Rheology, Part III: Elasticity of the Network of Entanglements”, J. Macrom. Sci. Part B, Phys. 52:222-308, 2013. 88 pages.
4. J.P.Ibar, “Processing polymer melts under Rheo-Fluidification flow conditions: Part 1. Boosting shear-thinning by adding low frequency non-linear vibration to induce strain softening.”. J. Macromol. Sci. Part B, Phys,, 52:411-445, 2013 (publication on line November 1st 2012. DOI: 10.1080/00222348.2012.711999).
5. J.P. Ibar, “Processing polymer melts under Rheo-Fluidification flow conditions: Part 2. Simple flow Simulation”. J. Macromol. Sci. Part B, Phys., 52:446-465, 2013 (publication on line : November 1st 2012) DOI: 10.1080/00222348.2012.712004) 5b J.P. Ibar, “Mixing Polymers under Rheo-Fluidification Conditions”, Macromolecular Symposia, Special Issue, 11th International European Symposium on Polymer Blends, 2012.
6. J.P. Ibar, Z. Zhang, Z.M. Li, A. Santamaria, “Investigation of the Dynamic Rheological Properties of a Polycarbonate melt presenting solid‐like characteristics and a departure from pure liquid Newtonian behavior at long relaxation times., J. Macromol. Sci. Phys. Volume 54, Issue 6, pp. 649-710 (2015).
