Development of Self-Consistent Field Theory Models for Predicting the Structure and Properties of Inhomogeneous Polymer Systems: Applications to the Description of   Nanocomposite Materials

Ρέβελας,  Κωνσταντίνος; Revelas, Constantinos J.

dc.contributor.author	Ρέβελας, Κωνσταντίνος	el
dc.contributor.author	Revelas, Constantinos J.	en
dc.date.accessioned	2023-06-30T09:37:15Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/57855
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.25552
dc.rights	Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/gr/	*
dc.subject	nanocomposites	en
dc.subject	Grafted	en
dc.subject	Nanoparticles	en
dc.subject	Ffield	en
dc.subject	Self-consistent	en
dc.subject	Ανάπτυξη Προτύπων	el
dc.subject	Θεωρία Αυτο-Συνεπούς Πεδίου	el
dc.subject	Νανοσύνθετα υλικά	el
dc.title	Development of Self-Consistent Field Theory Models for Predicting the Structure and Properties of Inhomogeneous Polymer Systems: Applications to the Description of Nanocomposite Materials	en
dc.title	Ανάπτυξη Προτύπων Βασισμένων στη Θεωρία Αυτο-Συνεπούς Πεδίου για την Πρόρρηση της Δομής και των Ιδιοτήτων μη Ομογενών Συστημάτων Πολυμερών: Εφαρμογή στην Περιγραφή Νανοσύνθετων Υλικών	el
dc.contributor.department	Computational Materials Science and Engineering	el
heal.type	doctoralThesis
heal.classification	Theoretical calculations on nanocomposite materials	en
heal.dateAvailable	2024-01-29T21:00:00Z
heal.language	en
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2023-04-24
heal.abstract	Polymer Self-Consistent Field Theory (SCFT) is an established theoretical tool, broadly used by modelers in academic and industrial environments to obtain quantitative predictions on the equilibrium behavior of inhomogeneous polymer systems such as polymer blends, copolymer melts, gas-polymer and solid/polymer interfaces. This fact has made SCFT one of the most commonly invoked frameworks when someone needs to address polymer systems at length scales inaccessible to particle-based methodologies. Furthermore, the growing interest in the design of nanocomposite materials involving interfaces of polymer melts with inorganic fillers and the need for fast calculations to predict or even manipulate the nanoscale self-assembly properties of composite materials have also been driving forces for the development of rigorous theoretical models to investigate how these materials will respond under various conditions. When conducting SCFT calculations, the primary task is to solve the Edwards diffusion equation. This is a “reaction and diffusion” partial differential equation (PDE) with contour length playing the role of time, whose solution is a restricted partition function, i.e., a quantity proportional to the probability density that a segment which finds itself at a specific contour length from the start of a chain, will occupy a certain position in space. In the context of this PhD, the numerical solution of the PDE is performed via a custom-made in-house code named RuSseL. The one-dimensional version of the code applies a Finite-Differences (FD) scheme, while the three-dimensional version is based on the Finite Element Method (FEM) and can be applied in systems of arbitrary geometry. The first system we addressed was a single polystyrene-grafted silica nanoparticle embedded in polystyrene melt at infinite dilution. The density profiles of matrix and grafted chains, along with additional structural characteristics such as the chain shape, profiles of middle/end segments and adsorbed/free segments were derived for various particle radii, lengths of grafted chains and grafting densities. We have estimated the thickness of the brush across the whole range of parameters and compared our results with experimental findings and scaling laws reported in the literature. The free energy of the system was also derived for the same parameters. Having studied the behavior of the grafted particle inside homopolymer melts, we went a step further and investigated the structural and thermodynamic properties of a system comprising the same particle in contact with vacuum. The difference in the free energy of the two systems (in presence and absence of polymer melt) allowed us to estimate the solvation Gibbs free energy as a function of the grafting density, intensity of solid/polymer interactions, particle size, and lengths of grafted and matrix chains. Next, we implemented our SCFT model in a system of two opposing polystyrene-grafted silica plates to derive the potential of mean force (PMF); i.e., the free energy of the system as a function of the plate-to-plate distance. This system is mathematically equivalent to one containing two grafted particles of extremely large particle radius. The PMF was derived as a function of the length of grafted chains, grafting density and intensity of solid/polymer interactions. In addition, we allowed the two plates to be grafted with different numbers and/or lengths of grafted chains, in order to investigate the impact of grafting asymmetries on the PMF and therefore stability of the nanocomposite system. Such asymmetries are expected to occur when these systems are prepared experimentally. In all cases, we also calculated the PMF between the two brushes in the absence of melt chains by applying a canonical ensemble formulation. All these calculations can be also performed in three-dimensions using the FEM version of RuSseL. This 3D implementation avoids any smearing of the grafting points, normal or parallel to the solid surfaces. We undertook detailed benchmarks on a system of a single nanoparticle immersed in polymer melt and performed a direct comparison between 1D- and 3D-SCFT calculations over a broad range parameters in order to assess the validity of the smearing approximation in terms of both chain structure and system thermodynamics. Moreover, in 3D we are able to impose a variety of irregular grafting distributions on the solid surfaces. We have shown that different grafting distributions result in variations in brush thickness and free energy relative to the case of equidistant grafting, which is the most usual assumption when performing such calculations. Adding the grafting distributions to the degrees of freedom involved in the computational design of polymer-grafted nanoparticle systems takes us closer to experimental practice and to nanocomposites with tailor-made self-assembly properties. In this spirit, we have also determined the PMF between two spherical polystyrene-grafted silica nanoparticles in polystyrene matrix for various grafting distributions. Finally, in order to have the ability to run 3D-SCFT calculations on multi-nanoparticle systems in presence or absence of polymer matrix, we have added in RuSseL the functionality of imposing periodic boundary conditions on the box edges, when the solution of the Edwards diffusion equation takes place. The user can now insert any number of grafted nanoparticles inside the periodic box, arranged in a crystalline or amorphous structure, and run SCFT calculations, as one would do in a particle-based simulation.	en
heal.sponsor	Financial support by the Hellenic Foundation for Research and Innovation (H.F.R.I.), project number 1263, under the “First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant,” is gratefully acknowledged. C.J.R. gratefully acknowledges financial support through a doctoral fellowship from the “Special Account for Research Funding” of the National Technical University of Athens. This work was also supported by computational time granted from the National Infrastructures for Research and Technology S.A. (GRNET S.A.) in the HPC facility ARIS under project ID pa201203 (MuSiPoLI).	en
heal.advisorName	Θεοδώρου Θεόδωρος	el
heal.advisorName	Theodorou, Theodoros	en
heal.committeeMemberName	Theodorou, Theodoros	en
heal.committeeMemberName	Boudouvis, Andreas	en
heal.committeeMemberName	Papagiannakos, Nikolaos	en
heal.committeeMemberName	Schmid, Friederike	en
heal.committeeMemberName	Charitidis, Constantinos	en
heal.committeeMemberName	Mavrantzas, Vlassis	en
heal.committeeMemberName	Kavousanakis, Mihalis	en
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Χημικών Μηχανικών	el
heal.academicPublisherID	ntua
heal.numberOfPages	304 σ.	en
heal.fullTextAvailability	false