Modeling The Self Assembly Of Ordered Nanoporous Materials

Porous materials are of great importance in many fields due to their wide applications. An ongoing theme in this area is the tailoring of materials for specific applications. With a better understanding of the formation mechanisms, tailoring and controlling the pore structure may be achieved. The objective of this research is acquiring further understanding of the fundamental physics that govern the formation of these materials using molecular simulations. We are aiming to unravel the assembly process of silica porous materials using a semi-rigid silica tetrahedral model. This model together with reaction ensemble Monte Carlo simulations allows us to study the formation of silica nanoparticles, the initial stages of microporous material formation. A two-step formation mechanism was found to be crucial for generating the nanoparticles. A replica-exchange reaction ensemble Monte Carlo sampling together with the silica tetrahedral model is developed and applied to cross the energy barrier between amorphous silica to crystalline silica materials for searching for the ground state structure of this model. The technique involves simulating several system copies with different equilibrium constants controlling silica condensation/hydrolysis reactions, which are essential for building higher-order network structures and eventually crystals, was preformed. Different silica polymorphs including all-silica zeolite frameworks were obtained. This model shows a great potential to study the crystallization of microporous materials. We also study the formation of mesoporous materials using molecular dynamics simulations. We investigate the interplay of silica molecules and surfactants, and different mesophases such as micellar rods, hexagonal, bicontinuous and lamellar phases were obtained. Multiple charges on silicate oligomers were found to play an important role in the formation of hexagonal phases. To study the later stages of MCM-41 formation, a hybrid molecular dynamics and Monte Carlo approach is proposed. The cooperation between the physical interaction and chemical reaction can be taken into account simultaneously. Preliminary study shows that the ratio of silicate to surfactant higher than 4 is essential to the growth of MCM-41. With a further enhancement on the model, this hybrid approach will be a powerful tool to simulate the formation of MCM-41 in a large system and at a long time scale.

Porous materials have long been a research interest due to their practical importance in traditional chemical industries such as catalysis and separation processes. The successful synthesis of porous materials requires further understanding of the fundamental physics that govern the formation of these materials. In this thesis, we apply molecular modeling methods and develop novel models to study the formation mechanism of ordered porous materials. The improved understanding provides an opportunity to rational control pore size, pore shape, surface reactivity and may lead to new design of tailor-made materials. To attain detailed structural evolution of silicate materials, an atomistic model with explicitly representation of silicon and oxygen atoms is developed. Our model is based on rigid tetrahedra (representing SiO4) occupying the sites of a body centered cubic (bcc) lattice. The model serves as the base model to study the formation of silica materials. We first carried out Monte Carlo simulations to describe the polymerization process of silica without template molecules starting from a solution of silicic acid in water at pH 2. We predicted Qn evolutions during silica polymerization and good agreement was found compared with experimental data, where Qn is the fraction of Si atoms with n bridging oxygens. The model captures the basic kinetics of silica polymerization and provides structural evolution information. Next we generalize the application of this atomic lattice model to materials with tetrahedral (T) and bridging (B) atoms and apply parallel tempering Monte Carlo methods to search for ground states. We show that the atomic lattice model can be applied to silica and related materials with a rich variety of structures including known chalcogenides, zeolite analogs, and layered materials. We find that whereas canonical Monte Carlo simulations of the model consistently produce the amorphous solids studied in our previous work, parallel tempering Monte Carlo gives rise to ordered nanoporous solids. The utility of parallel tempering highlights the existence of barriers between amorphous and crystalline phases of our model. The role of template molecules during synthesis of ordered mesoporous materials was investigated. Implemented surfactant lattice model of Larson, together with atomic tetrahedral model for silica, we successfully modeled the formation of surfactant-templated mesoporous silica (MCM-41), with explicit representation of silicic acid condensation and surfactant self-assembly. Lamellar and hexagonal mesophases form spontaneously at different synthesis conditions, consistent with published experimental observations. Under conditions where silica polymerization is negligible, reversible transformation between hexagonal and lamellar phases were observed by changing synthesis temperatures. Upon long-time simulation that allows condensation of silanol groups, the inorganic phases of mesoporous structures were found with thicker walls that are amorphous and lack of crystallinity. Compared with bulk amorphous silica, the wall-domain of mesoporous silicas are less ordered withlarger fractions of three- and four-membered rings and wider ring-size distributions. It is the first molecular simulation study of explicit representations of both silicic acid condensation and surfactant self-assembly.

Porous materials are of scientific and technological importance because of the presence of voids of controllable dimensions at the atomic, molecular, and nanometer scales, enabling them to discriminate and interact with molecules and clusters. Interestingly the big deal about this class of materials is about the “nothingness” within — the pore space. International Union of Pure and Applied Chemistry (IUPAC) classifies porous materials into three categories — micropores of less than 2 nm in diameter, mesopores between 2 and 50 nm, and macropores of greater than 50 nm. In this book, nanoporous materials are defined as those porous materials with pore diameters less than 100 nm.Over the last decade, there has been an ever increasing interest and research effort in the synthesis, characterization, functionalization, molecular modeling and design of nanoporous materials. The main challenges in research include the fundamental understanding of structure-property relations and tailor-design of nanostructures for specific properties and applications. Research efforts in this field have been driven by the rapid growing emerging applications such as biosensor, drug delivery, gas separation, energy storage and fuel cell technology, nanocatalysis and photonics. These applications offer exciting new opportunities for scientists to develop new strategies and techniques for the synthesis and applications of these materials.This book provides a series of systematic reviews of the recent developments in nanoporous materials. It covers the following topics: (1) synthesis, processing, characterization and property evaluation; (2) functionalization by physical and/or chemical treatments; (3) experimental and computational studies on fundamental properties, such as catalytic effects, transport and adsorption, molecular sieving and biosorption; (4) applications, including photonic devices, catalysis, environmental pollution control, biological molecules separation and isolation, sensors, membranes, hydrogen and energy storage, etc./a

Materials Nanoarchitectonics: From Integrated Molecular Systems to Advanced Devices provides the latest information on the design and molecular manipulation of self-organized hierarchically structured systems using tailor-made nanoscale materials as structural and functional units. The book is organized into three main sections that focus on molecular design of building blocks and hybrid materials, formation of nanostructures, and applications and devices. Bringing together emerging materials, synthetic aspects, nanostructure strategies, and applications, the book aims to support further progress, by offering different perspectives and a strong interdisciplinary approach to this rapidly growing area of innovation. This is an extremely valuable resource for researchers, advanced students, and scientists in industry, with an interest in nanoarchitectonics, nanostructures, and nanomaterials, or across the areas of nanotechnology, chemistry, surface science, polymer science, electrical engineering, physics, chemical engineering, and materials science. Offers a nanoarchitectonic perspective on emerging fields, such as metal-organic frameworks, porous polymer materials, or biomimetic nanostructures Discusses different approaches to utilizing "soft chemistry" as a source for hierarchically organized materials Offers an interdisciplinary approach to the design and construction of integrated chemical nano systems Discusses novel approaches towards the creation of complex multiscale architectures

Fabrication and Self-Assembly of Nanobiomaterials presents the most recent findings regarding the fabrication and self-assembly of nanomaterials for different biomedical applications. Respected authors from around the world offer a comprehensive look at how nanobiomaterials are made, enabling knowledge from current research to be used in an applied setting. Recent applications of nanotechnology in the biomedical field have developed in response to an increased demand for innovative approaches to diagnosis, exploratory procedures and therapy. The book provides the reader with a strong grounding in emerging biomedical nanofabrication technologies, covering numerous fabrication routes for specific applications are described in detail and discussing synthesis, characterization and current or potential future use. This book will be of interest to professors, postdoctoral researchers and students engaged in the fields of materials science, biotechnology and applied chemistry. It will also be highly valuable to those working in industry, including pharmaceutics and biotechnology companies, medical researchers, biomedical engineers and advanced clinicians. An up-to-date and highly structured reference source for practitioners, researchers and students working in biomedical, biotechnological and engineering fields A valuable guide to recent scientific progress, covering major and emerging applications of nanomaterials in the biomedical field Proposes novel opportunities and ideas for developing or improving technologies in fabrication and self-assembly

The directed self-assembly (DSA) method of patterning for microelectronics uses polymer phase-separation to generate features of less than 20nm, with the positions of self-assembling materials externally guided into the desired pattern. Directed self-assembly of Block Co-polymers for Nano-manufacturing reviews the design, production, applications and future developments needed to facilitate the widescale adoption of this promising technology. Beginning with a solid overview of the physics and chemistry of block copolymer (BCP) materials, Part 1 covers the synthesis of new materials and new processing methods for DSA. Part 2 then goes on to outline the key modelling and characterization principles of DSA, reviewing templates and patterning using topographical and chemically modified surfaces, line edge roughness and dimensional control, x-ray scattering for characterization, and nanoscale driven assembly. Finally, Part 3 discusses application areas and related issues for DSA in nano-manufacturing, including for basic logic circuit design, the inverse DSA problem, design decomposition and the modelling and analysis of large scale, template self-assembly manufacturing techniques. Authoritative outlining of theoretical principles and modeling techniques to give a thorough introdution to the topic Discusses a broad range of practical applications for directed self-assembly in nano-manufacturing Highlights the importance of this technology to both the present and future of nano-manufacturing by exploring its potential use in a range of fields

Having successfully replaced elements used in traditional, pollution-prone, energy-consuming separation processes, nanoporous materials play an important role in chemical processing. Although their unique structural or surface physicochemical properties can, to an extent, be tailored to meet specific process-related requirements, the task of charac

The first symposium on Access in Nanoporous Materials was held in Lansing, Michigan on June 7-9, 1995. The five years that have passed since that initial meeting have brought remarkable advances in all aspects of this growing family of materials. In particular, impressive progress has been achieved in the area of novel self-assembled mesoporous materials, their synthesis, characterization and applications. The supramolecular self-assembly of various inorganic and organic species into ordered mesostructures became a powerful method for synthesis of mesoporous molecular sieves of tailored framework composition, pore structure, pore size and desired surface functionality for advanced applications in such areas as separation, adsorption, catalysis, environmental cleanup and nanotechnology. In addition to mesostructured metal oxide molecular sieves prepared through supramolecular assembly pathways, clays, carbon molecular sieves, porous polymers, sol-gel and imprinted materials, as well as self-assembled organic and other zeolite-like materials, have captured the attention of materials researchers around the globe. The contents of the current volume present a sampling of more than 150 oral and poster papers delivered at the Symposium on Access in Nanoporous Materials II held in Banff, Alberta on May 25-30, 2000. About 70% of the papers are devoted to the synthesis of siliceous mesoporous molecular sieves, their modification, characterization and applications, which represent the current research trend in nanoporous materials. The remaining contributions provide some indications on the future developments in the area of non-siliceous molecular sieves and related materials. This book reflects the current trends and advances in this area, which will certainly attract the attention of materials chemists in the 21st century.

Nanoporous Materials III contains the invited lectures and peer-reviewed oral and poster contributions to be presented at the 3rd Conference on Nanoporous Materials, which will be hosted in Ottawa, Canada, June 2002. The work covers complementary approaches to and recent advances in the field of nanostructured materials with pore sizes larger than 1nm, such as periodic mesoporous molecular sieves M41S and FSM16 and related materials including clays, carbon molecular sieves, colloidal crystal templated organic and inorganic materials, porous polymers and sol gels. The broad range of topics covered in relation to the synthesis and characterization of ordered mesoporous materials are of great importance for advanced adsorption, catalytic and separation processes as well as the development of nanotechnology. The contents of this title are based on topics to be discussed by invited lecturers, which deal with periodic mesoporous organosilicas, stability and catalytic activity of aluminosilicate mesostructures, electron microscopy studies of ordered materials, imprinted polymers and highly porous metal-organic frameworks. The other contributions deal with tailoring the surface and structural properties of nanoporous materials, giving a detailed characterization as well as demonstrating their usefulness for advanced adsorption and catalytic applications.

The use of spontaneous self-assembly, as a lithographic tool and as an external field-free means to construct well-ordered and intriguing patterns, has received much attention due to its ease of producing complex, large-scale structures with small feature sizes. An extremely simple route to highly-ordered, complex structures is the evaporative self-assembly of nonvolatile solutes (e.g., polymers, nanoparticles, carbon nanotubes, and DNA) from a sessile droplet on a solid substrate. To date, a few studies have elegantly demonstrated that self-organized nanoscale, microscale, and hierarchically structured patterns have been readily obtained from sophisticated control of droplet evaporation. These include convective assembly in evaporating menisci, the alignment of nanomaterials by programmed dip coating and controlled anisotrophic wetting/dewetting processes, facile microstructuring of functional polymers by the “Breath Figure” method, controlled evaporative self-assembly in confined geometries, etc.This book is unique in this regard in providing a wide spectrum of recent experimental and theoretical advances in evaporative self-assembly techniques. The ability to engineer an evaporative self-assembly process that yields a broad range of complex, well-ordered and intriguing structures with small feature sizes composed of polymers of nanocrystals of different size and shapes as well as DNA over large areas offers tremendous potential for applications in electronics, optoelectronics, photonics, sensors, information processing and data storage devices, nanotechnology, high-throughput drug discovery, chemical detection, combinatorical chemistry, and biotechnology.