Soiree

TYC@UCL - Confined/interfacial fluids in solids/2D materials

Prof Rahul Raveendran Nair, Professor of Materials Physics / Royal Society University Research Fellow, The University of Manchester

Molecules at two-dimensional interfaces and capillaries

Professor Erich A. Müller, Professor in Thermodynamics at Imperial College London and a Fellow of the Royal Society of Chemistry

Multiscale molecular simulations of the formation and structure of polyamide membranes created by interfacial polymerisation

Thursday 23 November 2017
Time: 5pm
Venue: Physics Building, room E7
Contact: Karen Stoneham
Tel: 0207 6797306

Molecules at two-dimensional interfaces and capillaries

Van der Waals assembly of two-dimensional crystals continue attract intense interest due to the prospect of designing novel materials with on-demand properties. One of the unique features of this technology is the possibility of trapping molecules between two-dimensional crystals. The trapped molecules are predicted to experience pressures as high as 1 GPa. In my talk, I will discuss the experimental demonstration of the huge van der Waals pressure inside the nano-enclosures made from 2D crystals. Another feature of van der Waals material assembly is the unique possibility of designing two-dimensional channels for molecular transport. Permeation through nanometre-pore materials has been attracting unwavering interest due to fundamental differences in governing mechanisms at macroscopic and molecular scales, the importance of water permeation in living systems, and relevance for filtration and separation techniques. Graphene-based materials can have well-defined nanometer pores and can exhibit low frictional water flow inside them, making their properties of interest for filtration and separation. In my talk, I will discuss our recent results on molecular and ionic permeation properties of various 2D materials based membranes and its prospect for several applications.

Multiscale molecular simulations of the formation and structure of polyamide membranes created by interfacial polymerisation

Polyamide membranes are the working horse of reverse osmosis processes, allowing the pressure-driven production of desalinized water. In spite of their widespread use, very little is known in terms of the actual structure of the membrane and even less about the transport mechanisms of water through these membranes. This work showcases a multi-scale molecular modelling technique aimed at elucidating some of the important aspects of the formation, structure of the membranes along with the transport of water through it. 

Large scale molecular simulations to model the formation of polyamide membranes have been carried out using a procedure that mimics experimental interfacial polymerization of trimesoyl chloride (TMC) and metaphenylene diamine (MPD) monomers. A coarse-grained representation of the monomers has been developed to facilitate these simulations, which captures essential features of the stereochemistry of the monomers and of amide bonding between them. Atomic models of the membranes are recreated from the final coarse-grained representations.

From our simulations we observe that membranes are formed through the growth and aggregation of oligomer clusters. The membranes are inhomogeneous, displaying opposing gradients of trapped carboxyl and amine side groups, local density variations, and regions where the density of amide bonding is reduced as a result of the aggregation process. We observe the interfacial polymerization reaction is self-limiting and the simulated membranes display a thickness of 5–10 nm. They also display a surface roughness of 1–4 nm. Comparisons are made with recently published experimental results on the structure and chemistry of these membranes and some interesting similarities and differences are found.

 

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    Dr Rahul R. Nair

    Rahul R. Nair is a Professor of Materials Physics at the National Graphene Institute (NGI) and School of Chemical Engineering and Analytical Science at the University of Manchester and holds a prestigious Royal Society Fellowship and ERC grant. The main scope of his research is the novel synthesis and construction of application‐oriented devices based on two‐dimensional (2D) crystals and their modifications. He has published over 45 highly cited peer‐refereed research articles, including four Science, two Nature, one Nature Physics, two Nature Nanotechnology, and seven Nature Communications during the last ten years. His awards include a Leverhulme Early Career Fellowship from the Leverhulme Trust, IUPAP Young Scientist Award (2014) from the International Union of Pure and Applied Physics and the Moseley Medal and Prize (2015) from the Institute of Physics. He has also selected as a Highly Cited Researcher in 2016 by Thomson Reuters.

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    Professor Erich A. Müller

    Erich A. Müller has over 30 years of accumulated experience in the molecular description of complex fluids and interfaces. He is a Professor in Thermodynamics at Imperial College London and a Fellow of the Royal Society of Chemistry with a track record of over 150 papers, over 300 presentations in international conferences, 9 books and chapters. Prof. Müller is a senior researcher in the Molecular Systems Engineering group at the Department of Chemical Engineering at Imperial College, where a combination of theoreticians and modellers work in a productive and collaborative environment focusing on the application of fundamental modelling to engineering scenarios. Some publication highlights include the elucidation by molecular simulation of the adsorption mechanism of water confined in nanopores, the first molecular simulations of Joule-Thomson inversion curves of CO2, along with the development of the SAFT force fields, the most accurate coarse grained models for simulation of complex fluid phase equilibria.

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