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Full-Text Articles in Chemical Engineering
Modeling Chain Packing In Complex Phases Of Self-Assembled Block Copolymers, Anugu Abhiram Reddy
Modeling Chain Packing In Complex Phases Of Self-Assembled Block Copolymers, Anugu Abhiram Reddy
Doctoral Dissertations
Block copolymer (BCP) melts undergo microphase seperation and form ordered soft matter crystals with varying domain shapes and symmetries. We study the con- nection between diblock copolymer molecular designs and thermodynamic selection of ordered crystals by modeling features of variable sub-domain geometry filled with individual blocks within non-canonical sphere-like and network phases that together with layered, cylindrical and canonical spherical phases forms “natural forms” of self- assembled amphiphilic soft matter at large. First, we present a model to revise our understanding of optimal Frank-Kasper sphere-like morphologies by advancing the- ory to account for varying domain volumes. We then develop generic …
Thin-Film Block Copolymers (Bcps) Self-Assembly As Versatile Patterning Scheme For Functional Nanomaterials, Le Zhang
LSU Master's Theses
Nanopattern generation is required for building various structural entities in every production process that involves nanostructures. Advancing nanopatterning technologies play an important role in developing and broadening the current nanopatterning technologies to meet up with the ever-demanding requirements in the realm of smaller feature sizes, smoother line-edge roughness (LER) and facile pattern transfer in pursuit of faster computer processors, better electrocatalysts and more compact and intelligent sensors, etc. Conventionally, patterning needs are heavily relied on photolithography, a technique that dominate chip-making industry for more than 50 years. However conventional photolithography is bounded by inherent resolution limits and difficult to be …
Self-Assembling Networks In Soft Materials, Ishan Prasad
Self-Assembling Networks In Soft Materials, Ishan Prasad
Doctoral Dissertations
This dissertation presents a study on heterogeneous network structure in two distinct classes of soft material systems: disordered assemblies of jammed binary spheres and ordered morphologies of block copolymer melts. The aim is to investigate the combined role of geometry and entropy in structure formation of soft matter assemblies. First, we investigate the influence of particle size asymmetry on structural properties of jammed binary sphere mixtures. We give evidence of two distinct classes of materials separated by a critical size ratio that marks the onset of a sharp transition due to simultaneous jamming of a sub-component of the packing. We …
Cell Adhesion Biophysics On Dynamic Polymer Constructs, Andreas Kourouklis
Cell Adhesion Biophysics On Dynamic Polymer Constructs, Andreas Kourouklis
Doctoral Dissertations
The biophysical characteristics of cell adhesion from single protein to cell length scales have primarily been studied using purely elastic substrates. However, natural extracellular matrix (ECM) is viscoelastic and contains mobile components. In this work, we combined chemistry and cell biology tools to design and characterize laterally mobile viscoelastic polymer films that promote receptor-specific cell adhesion. Moreover, we used amphiphilic block copolymers that are end-labeled with RGD peptide ligands to allow for integrin-mediated cell adhesion. The addition of a trace hydrophobic homopolymer in the supported bilayer block-copolymer films is used to tune the lateral mobility of the films. NIH 3T3 …
Helical Ordering In Chiral Block Copolymers, Wei Zhao
Helical Ordering In Chiral Block Copolymers, Wei Zhao
Open Access Dissertations
The phase behavior of chiral block copolymers (BCPs*), namely, BCPs with at least one of the constituent block is formed by chiral monomers, is studied both experimentally and theoretically. Specifically, the formation of a unique morphology with helical sense, the H* phase, where the chiral block forms nanohelices hexagonally embedded in the matrix of achiral block, is investigated. Such unique morphology was first observed in the cast film of polystyrene-b-poly(L-lactide) (PS-b-PLLA) from a neutral solvent dichloromethane at room temperature with all the nanohelices being left-handed, which would switch to right-handed if the PLLA block changes to …
Symmetry Breaking Of In-Plane Order In Confined Copolymer Mesophases, G. E. Stein, Eric W. Cochran, K. Katsov, G. H. Fredrickson, E. J. Kramer, X. Li, J. Wang
Symmetry Breaking Of In-Plane Order In Confined Copolymer Mesophases, G. E. Stein, Eric W. Cochran, K. Katsov, G. H. Fredrickson, E. J. Kramer, X. Li, J. Wang
Eric W. Cochran
Packing of spherical-domain block copolymer mesophases confined to a thin film is investigated as a function of the number of layers n. We find an abrupt transition from hexagonal to orthorhombic in-plane ordering of domains when n is increased from 4 to 5. As n increases further (up to 23 in this study), the symmetry of the orthorhombic phase asymptotically approaches that of the body-centered cubic (110) plane. These results are interpreted in terms of the energetics of competing packings in the bulk and at the film interfaces. Detailed structural and thermodynamic properties are obtained with self-consistent field theory.
Effect Of Chain Architecture And Surface Energies On The Ordering Behavior Of Lamellar And Cylinder Forming Block Copolymers, V. Khanna, Eric W. Cochran, A. Hexemer, G. E. Stein, G. H. Fredrickson, E. J. Kramer, X. Li, J. Wang, S. F. Hahn
Effect Of Chain Architecture And Surface Energies On The Ordering Behavior Of Lamellar And Cylinder Forming Block Copolymers, V. Khanna, Eric W. Cochran, A. Hexemer, G. E. Stein, G. H. Fredrickson, E. J. Kramer, X. Li, J. Wang, S. F. Hahn
Eric W. Cochran
We investigate the effect of surface energy and chain architecture on the orientation of microdomains in relatively thick films (600-800 nm) of lamellar and cylindrical block copolymers of poly(cyclohexylethylene) (C) and poly(ethylene) (E). The E block has 26 ethyl branches per 1000 backbone carbon atoms. Melt surface energies of the C and E blocks are 22.3 and 20.9 mJ/m 2, respectively. Grazing-incidence small-angle X-ray scattering (GISAXS), scanning force microscopy (SFM), and cross-sectional transmission electron microscopy (TEM) show that cylindrical and lamellar CEC triblock copolymers orient their microdomains normal to the surface throughout the film thickness. However, a lamellar CE diblock …
Stability Of The Gyroid Phase In Diblock Copolymers At Strong Segregation, Eric W. Cochran, Carlos J. Garcia-Cervera, Glenn H. Fredrickson
Stability Of The Gyroid Phase In Diblock Copolymers At Strong Segregation, Eric W. Cochran, Carlos J. Garcia-Cervera, Glenn H. Fredrickson
Eric W. Cochran
The gyroid phase in diblock copolymers at strong segregation was stabilized. The intriguing topology of the network structure has inspired a diverse array of potential applications ranging from high-performance separation membranes to photonic crystals. The pressure field enforces incompressibility, while the exchange field is conjugate to the composition pattern in the melt. The Laplacian operator is treated implicitly with a fourth-order backward differentiation formula (BDF4), whereas the source term is discretized explicitly using fourth-order accurate Adams-Bashford.
Temperature Dependence Of Order, Disorder, And Defects In Laterally Confined Diblock Copolymer Cylinder Monolayers, Matthew R. Hammond, Eric W. Cochran, Glenn H. Fredrickson, Edward J. Kramer
Temperature Dependence Of Order, Disorder, And Defects In Laterally Confined Diblock Copolymer Cylinder Monolayers, Matthew R. Hammond, Eric W. Cochran, Glenn H. Fredrickson, Edward J. Kramer
Eric W. Cochran
Monolayer arrays of polystyrene-poly(2-vinylpyridine) diblock copolymer cylinders with excellent orientational order and a very low density of dislocations are prepared by cooling slowly from above the bulk order - disorder temperature (ODT) ∼212°C within silicon oxide channels one cylinder spacing a in depth and 2 μm in width. The translational order of this array, however, is short range with a correlation length of ∼12a. If such an array is heated to a temperature above the glass transition temperature of the block copolymer (100°C) but well below the ODT, a finite density of thermally generated dislocations is observed, which leads to …
Ordered Network Phases In Linear Poly(Isoprene-B-Styrene-B-Ethylene Oxide) Triblock Copolymers, Thomas H. Epps Iii, Eric W. Cochran, Travis S. Bailey, Ryan S. Waletzko, Cordell M. Hardy, Frank S. Bates
Ordered Network Phases In Linear Poly(Isoprene-B-Styrene-B-Ethylene Oxide) Triblock Copolymers, Thomas H. Epps Iii, Eric W. Cochran, Travis S. Bailey, Ryan S. Waletzko, Cordell M. Hardy, Frank S. Bates
Eric W. Cochran
The equilibrium phase behavior of 43 linear poly(isoprene-b-styrene-b- ethylene oxide) (ISO) triblock copolymer melts, with molecular weights that place these materials near the order-disorder transition, is reported. Ordered phase morphologies were characterized using small-angle X-ray scattering, transmission electron microscopy, dynamic mechanical spectroscopy, and static birefringence measurements. Interpretation of these results was aided by a modeling technique that facilitates resolution of reciprocal and real-space experimental data, leading to definitive three-dimensional morphological structures. Three distinct multiply continuous network morphologies are identified across a range of compositions between 0.1 ≤ f o ≤ 0.3, situated between two-domain and three-domain lamellae, where f o …