Computational Study of Self-assembly in Block Copolymer/superparamagnetic Nanoparticle Composites Under External Magnetic Fields PDF Download
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Author: Vinay Raman Publisher: ISBN: Category : Languages : en Pages : 147
Book Description
This computational and theoretical study investigates the self-assembly of superparamagnetic nanoparticles and block copolymers under external magnetic fields. A variety of morphological transitions are observed based on the field orientation, nanoparticle loading, and selectivity of the nanoparticles for the blocks. For symmetric block copolymers, chaining of superparamagnetic nanoparticles under in-plane magnetic fields is shown to achieve long range orientational order of the block copolymer nanodomains and is found to be dependent on nanoparticle size, volume fraction and magnetization strength. A critical selectivity of the particles for one nanodomain is observed, above which strong alignment results and below which comparatively disordered structures are formed. Higher magnetization strengths are found to reduce equilibrium defect densities in the nematic-isotropic ordering of lamellar thin films, as corroborated by scaling arguments. For asymmetric coil fractions forming hexagonal block copolymer nanostructure, the inplane field induced chaining of the nanoparticles selective for the minority block, leads to the formation of stripe phases oriented parallel to the magnetic field. Furthermore, in-plane field induced chaining of nanoparticles selective for the majority block leads to alignment of hexagonal morphology with 100 direction oriented parallel to the external magnetic field. Out of plane magnetic fields induce repulsive dipolar interactions between the nanoparticles that annihilate the defects in the hexagonal morphology of the block copolymer when the nanoparticle is selective for the minority block. Honeycomb lattices are obtained using nanoparticles selective for majority block under out of plane magnetic fields for certain specific nanoparticle loadings. Commensurability of nanoparticle size and loadings with the block copolymer structure is critical in optimizing the ordering of the final composite. Kinetics of alignment in block copolymer nanocomposites is studied using External Potential Dynamics (EPD) method, wherein an equivalent evolution equation for potential fields is solved instead of conservation equation for the monomer segments. The dynamics study reveals an interesting interplay of nanoparticle mobility, dipolar interaction strength and nanoparticle-polymer interaction strength on the rate of alignment of domains.
Author: Vinay Raman Publisher: ISBN: Category : Languages : en Pages : 147
Book Description
This computational and theoretical study investigates the self-assembly of superparamagnetic nanoparticles and block copolymers under external magnetic fields. A variety of morphological transitions are observed based on the field orientation, nanoparticle loading, and selectivity of the nanoparticles for the blocks. For symmetric block copolymers, chaining of superparamagnetic nanoparticles under in-plane magnetic fields is shown to achieve long range orientational order of the block copolymer nanodomains and is found to be dependent on nanoparticle size, volume fraction and magnetization strength. A critical selectivity of the particles for one nanodomain is observed, above which strong alignment results and below which comparatively disordered structures are formed. Higher magnetization strengths are found to reduce equilibrium defect densities in the nematic-isotropic ordering of lamellar thin films, as corroborated by scaling arguments. For asymmetric coil fractions forming hexagonal block copolymer nanostructure, the inplane field induced chaining of the nanoparticles selective for the minority block, leads to the formation of stripe phases oriented parallel to the magnetic field. Furthermore, in-plane field induced chaining of nanoparticles selective for the majority block leads to alignment of hexagonal morphology with 100 direction oriented parallel to the external magnetic field. Out of plane magnetic fields induce repulsive dipolar interactions between the nanoparticles that annihilate the defects in the hexagonal morphology of the block copolymer when the nanoparticle is selective for the minority block. Honeycomb lattices are obtained using nanoparticles selective for majority block under out of plane magnetic fields for certain specific nanoparticle loadings. Commensurability of nanoparticle size and loadings with the block copolymer structure is critical in optimizing the ordering of the final composite. Kinetics of alignment in block copolymer nanocomposites is studied using External Potential Dynamics (EPD) method, wherein an equivalent evolution equation for potential fields is solved instead of conservation equation for the monomer segments. The dynamics study reveals an interesting interplay of nanoparticle mobility, dipolar interaction strength and nanoparticle-polymer interaction strength on the rate of alignment of domains.
Author: Ryan Michael Schmidt Publisher: ISBN: Category : Block copolymers Languages : en Pages : 153
Book Description
Directed self-assembly of nanomaterials via external fields is an attractive processing tool for industry as it is inherently inexpensive and flexible. The self-assembly of magnetic nanoparticles in particular has gained much recent interest for applications ranging from biomedical imaging and targeted cancer therapy to ferrofluid mechanical damping devices, that rely on the state of aggregation and alignment of the nanoparticles. We utilize an oil-water platform to directly observe directed self-assembly of magnetic nanoparticles that are field ordered into two-dimensional mesostructures through the fossilized liquid assembly method. Our system consisted of polymer-coated iron-oxide nanoparticles which were assembled at the interface between a crosslinkable hydrophobic monomer oil, and water through the use of external magnetic fields, and then cured with UV light. In this study, entire magnetic flux field lines in various geometrical configurations were successfully modeled and mapped out by the magnetic nanoparticles, both in-plane and in perpendicular orientations utilizing FLA. As the microscopic behavior of magnetic nanoparticles is known through this first study, further work can then be conducted through the assembly of block copolymer/magnetic nanoparticle nanocomposites. The morphology of neat self-assembled block copolymers have been extensively studied and it has been proven that the molecular weight, volume fraction of the components, and the degree of segment incompatibility are the three independent parameters used to determine equilibrium morphologies. The assembled orientations of lamellar and cylindrical morphologies in particular develop specific directionalities depending on the natural interactions of the blocks with the substrate and surface. It has been shown that treatments such as UV-Ozone treatment of the substrate, mechanical shear, or electrical fields can force this directionality to be altered, however few methods have been developed to readily alter preferential morphologies through the use of magnetic fields. In order to provide preliminary results toward the validity of a magnetically driven reorientation process, systems of polystyrene-b-poly(methylmethacrylate) with varying molecular weights were loaded with up to 1% polystyrene coated cobalt nanoparticles. This study successfully showed that the particles can be loaded into the block copolymers without disrupting the morphology of the block copolymers, and also provided initial results that this method is plausible.
Author: Ramanathan Nagarajan Publisher: John Wiley & Sons ISBN: 1119001366 Category : Science Languages : en Pages : 364
Book Description
An introduction to the state-of-the-art of the diverse self-assembly systems Self-Assembly: From Surfactants to Nanoparticles provides an effective entry for new researchers into this exciting field while also giving the state of the art assessment of the diverse self-assembling systems for those already engaged in this research. Over the last twenty years, self-assembly has emerged as a distinct science/technology field, going well beyond the classical surfactant and block copolymer molecules, and encompassing much larger and complex molecular, biomolecular and nanoparticle systems. Within its ten chapters, each contributed by pioneers of the respective research topics, the book: Discusses the fundamental physical chemical principles that govern the formation and properties of self-assembled systems Describes important experimental techniques to characterize the properties of self-assembled systems, particularly the nature of molecular organization and structure at the nano, meso or micro scales. Provides the first exhaustive accounting of self-assembly derived from various kinds of biomolecules including peptides, DNA and proteins. Outlines methods of synthesis and functionalization of self-assembled nanoparticles and the further self-assembly of the nanoparticles into one, two or three dimensional materials. Explores numerous potential applications of self-assembled structures including nanomedicine applications of drug delivery, imaging, molecular diagnostics and theranostics, and design of materials to specification such as smart responsive materials and self-healing materials. Highlights the unifying as well as contrasting features of self-assembly, as we move from surfactant molecules to nanoparticles. Written for students and academic and industrial scientists and engineers, by pioneers of the research field, Self-Assembly: From Surfactants to Nanoparticles is a comprehensive resource on diverse self-assembly systems, that is simultaneously introductory as well as the state of the art.
Author: Massimo Lazzari Publisher: Wiley-VCH ISBN: 3527610561 Category : Technology & Engineering Languages : en Pages : 447
Book Description
This first book to take a detailed look at one of the key focal points where nanotechnology and polymers meet provides both an introductory view for beginners as well as in-depth knowledge for specialists in the various research areas involved. It investigates all types of application for block copolymers: as tools for fabricating other nanomaterials, as structural components in hybrid materials and nanocomposites, and as functional materials. The multidisciplinary approach covers all stages from chemical synthesis and characterization, presenting applications from physics and chemistry to biology and medicine, such as micro- and nanolithography, membranes, optical labeling, drug delivery, as well as sensory and analytical uses.
Author: Vibha Kalra Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Advances in materials synthesis and fabrication techniques allow an unprecedented control over the creation of novel building blocks such as polymers and particles. The first principle for effective utilization of these building blocks is to create techniques to control their assembly at length scales ranging from nanoscale to macroscopic scale. Hierarchically structured materials have been fabricated by combining the functionalities of block copolymer nanocomposites with the advantages of nanofibers. First, a novel methodology to synthesize block copolymer nanofibers with ordered self assembly has been developed, followed by a systematic study on how this self assembly is altered due to the cylindrical confinement of nanofibers. Then, this self assembly in nanofibers is used as a template to control the spatial distribution of functional nanoparticles. One of the key findings of this work is that a much larger fraction of nanoparticles can be placed (without agglomeration) within nanofibers compared to films of the same materials. To zero in on the mechanism and to understand the thermodynamic and kinetic processes that drive nanoparticle placement in block copolymers during deformation (an important constituent of electrospinning nanofiber fabrication process), coarse grained molecular dynamics simulations have been conducted. Here, the effect of shear flow on different types of block copolymer/nanoparticle systems has been first studied, followed by a study on effect of elongational flow on various block copolymer nanocomposite systems.
Author: Karim Raafat Gadelrab Publisher: ISBN: Category : Languages : en Pages : 140
Book Description
Spontaneous self-assembly of materials is a phenomenon exhibited by different molecular systems. Among many, Block copolymers (BCPs) proved to be particularly interesting due to their ability to microphase separate into periodic domains. Nonetheless, the rising need for arbitrary, complex, 3D nanoscale morphology shows that what is commonly achievable is quite limited. Expanding the range of BCPs morphologies could be attained through the implementation of a host of strategies that could be used concurrently. Using directed self-assembly (DSA), a sphere forming BCP was assembled in a randomly displaced post template to study system resilience towards defect creation. Template shear-like distortion seemed to govern local defect generation. Defect clusters with symmetries compatible with that of the BCP showed enhanced stability. Using 44 and 32434 Archimedean tiling templates that are incompatible with BCP six-fold symmetry created low symmetry patterns with an emergent behavior dependent on pattern size and shape. A variation of DSA is studied using modulated substrates. Layer-by-layer deposition of cylinder forming BCPs was investigated. Self-consistent field theory (SCFT) and strong segregation theory SST were employed to provide the understanding and the conditions under which particular orientations of consecutive layers were produced. Furthermore, deep functionalized trenches were employed to create vertically standing high-[chi] BCP structures. Changing annealing conditions for a self-assembled lamellar structure evolved the assembled pattern to a tubular morphology that is non-native to diblock copolymers. A rather fundamental but challenging strategy to go beyond the standard motifs common to BCPs is to synthesize multiblock molecules with an expanded design space. Triblock copolymers produced bilayer perforated lamellar morphology. SCFT analysis showed a large window of stability of such structures in thin films. In addition, a model for bottlebrush BCPs (BBCPs) was constructed to investigate the characteristics of BBCPs self-assembly. Pre-stacked diblock sidechains showed improved microphase separation while providing domain spacing relevant to lithography applications. A rich phase diagram was constructed at different block concentrations. The ability to explore new strategies to discover potential equilibrium morphologies in BCPs is supported by strong numerical modeling and simulations efforts. Accelerating SCFT performance would greatly benefit BCP phase discovery. Preliminary work discussed the first attempt to Neural Network (NN) assisted SCFT. The use of NN was able to cut on the required calculations steps to reach equilibrium morphology, demonstrating accelerated calculation, and escaping trapped states, with no effect on final structure.
Author: Hyung Wan Do Publisher: ISBN: Category : Languages : en Pages : 125
Book Description
Unconventional computation is a paradigm of computation that uses novel information tokens from natural systems to perform information processing. Using the complexity of physical systems, unconventional computing systems can efficiently solve problems that are difficult to solve classically. In this thesis, we use block copolymer self-assembly, a well-studied phenomenon in polymer science, to develop a new approach to computing by applying directed self-assembly to implement Ising-model-based computing systems in materials. In the first part of the thesis, we investigate directed self-assembly of block copolymer thin films within templates of different polygonal shapes. We define a two-state system based on the two degenerate alignment orientations of the ladder-shaped block copolymer structures formed inside square confinements, and study properties of the two-state system. In the second part of the thesis, we demonstrate an Ising lattice setup for directed self-assembly of block copolymers defined on two-dimensional arrays of posts. We develop an Ising-model-based simulation method that can perform block copolymer pattern prediction and template design. Finally, we design simple Boolean logic gates as a proof-of-concept demonstration of computation.
Author: Vinay Raman
Author: Vinay Raman
Author: Ryan Michael Schmidt
Author: Ramanathan Nagarajan
Author: Scott Charles Warren
Author: Massimo Lazzari
Author: Xiaowei Teng
Author: Christian Lewin
Author: Vibha Kalra
Author: Karim Raafat Gadelrab
Author: Hyung Wan Do