438725 Polymerization within Porous Media: Transformative Coatings and Interfaces Lab (TCIL)

Sunday, November 8, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
Siamak Nejati, Department of Chemical and Environmental Engineering, Yale University, New Haven, CT

Polymers are versatile materials with attractive properties ranging from optoelectronic to electrochromic and electrocatalytic. The development of effective approaches for polymer integration into current device architecture is of paramount importance to properly leverage the attractive properties of polymeric materials in diverse contexts. The current emerging energy conversion and storage technologies rely on physical and chemical design of component at nanometer length scale. This translates into a need for the development of an effective method to integrate polymeric materials with accuracy at nanometer length scales. In my research, I rely on Initiated and Oxidative Chemical Vapor Deposition (iCVD/oCVD) as two unique, solvent free methods that enable polymerization and coating in one step. I aim to fundamentally understand polymerization reactions within nanoscale and confined structures, and to study material properties confined within these spaces in a precise and systematic fashion. I envision that the outcome of my research will lead to the discovery and development of new metamaterials and interfaces with attractive properties for applications in clean energy and water resources managements.

During my Ph.D. at the Thin Film and Devices Lab, I contributed to the development of a new branch of oCVD, where the dehydrocoupling reaction of heterocyclic monomer was initiated using readily vaporizable liquid oxidants of weak Lewis acid nature. My experimental observations have led me to conclude that not only can surface conditions significantly change nucleation mechanisms, but that the physical properties of the underlying substrate can define the rate determining process and change the overall polymerization growth rate and final material properties. Additionally I realized that the tight and complex combination of the processes with dynamic time constants spanning a few orders of magnitude, down to the rate of charge transfer at the interface, plays a key role in synthesis and final device properties. Therefore by adjusting the dynamic rate constant and delicately manipulating the interfaces using polymeric materials, I was able to show how one can benefit from the tight integration of the polymeric materials within the nanoscale network of the electrodes typical to many electrochemical devices. The significant improvement in the device performance, the observation of anomalies in charge storage capacity of polymers within nanostructures, and the change in the chemistry of the oxides surface that enables controlling the heterojunction energetic were the significant outcomes of my research. Currently I am doing my postdoctoral training under the supervision of Chinedum Osuji and Menachem Elimelech at Yale University. My research has been focused on transport phenomena within porous media and design and development of processes targeting challenges in the Water-Energy Nexus. I have been actively working on fabrication of ordered and porous polymeric media at micro- and nanoscale range. This exciting experience has broadened my scientific scope and also equipped me with skills for fabricating polymeric based templates.

In my lab, TCIL, I plan to pursue three principal directions and aim at (i) polymer synthesis through vacuum based pathway and within porous matrix (ii) understanding the scale dependence of polymer properties (iii) generating new polymeric interfaces and domains with unprecedented properties.  

Selected publications:

Nejati, S. and K. K. S. Lau “Pore Filling of Nanostructured Electrodes in Dye Sensitized Solar Cells by Initiated Chemical Vapor Deposition”, Nano letters 2011 11 (2), 419–423.

Nejati, S. and K. K. S. Lau “Chemical Vapor Deposition Synthesis of Tunable Unsubstituted Polythiophene”, Langmuir 2011 27(24), 15223-15229.

Nejati, S.; Minford, T.; Smolin, Y. Y. and Lau, K. K. S., “Enhanced Charge Storage of Ultrathin Polythiophene Films within Porous Nanostructures”. ACS Nano 2014 8 (6), 5413–5422.

Nejati, S. and K. K. S. Lau “Integration of polymer electrolytes in dye sensitized solar cells by initiated chemical vapor deposition”, Thin Solid Film 2011 519(14), 4151-4155.

Nejati, S.; Patel, A; Wallowitch G. R. and Lau, K. K. S., Electrical Conductivity and Stability of oCVD Copolymer Thin Films of Thiophene and Pyrrole. Nanoscience and Nanotechnology letters 2015 7 (1) 50-55.

Nejati, S.; Boo, C.; Osuji, C. O. and Elimelech, M. “Engineered Poly(Vinylidene Fluoride) Membrane for Membrane Distillation” Journal of Membrane Science 2015.

Bavarian, M.; Nejati, S.; Lau, K. K.S.; Lee, D; and Soroush M., “Effects of Critical Dye Sensitized Solar Cell Parameters on Cell Performance: a Theoretical Study” Industrial Engineering and chemistry research 2013 53 (13), 5234-5247.

Smolin, Y. Y.; Nejati, S.; Bavarian, M.; Lau, K. K.S.; Lee, D; and Soroush M., “Effects of Polymer Chemistry on Polymer-Electrolyte Dye Sensitized Solar Cell Performance” Journal of Power Sources 2015 274, 156-164

Lin, S.; Nejati, S.; Boo, C.; Hu, Y.; Osuji, C. O. and Elimelech, M. “Omniphobic Membrane for Robust Membrane Distillation” Environmental science and Technology 2014 1 (11), 443-447.

Bose, R.; Nejati, S.; Stufflet, D. and K. K. S. Lau “Grafted Poly(ethylene oxide) (PEO) Anti-fouling Surfaces using Initiated Chemical Vapor Deposition (iCVD)”, Macromolecules 2012 45 (17), 6915–6922.

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