| Multiscale Modeling and Computation of Liquid Crystal Polymers, Polymer Blends, and Polymer Nanocomposites: Investigation of Rheology and Material Properties |
15 APR 2008 |
11 pages |
| Authors:
Qi Wang; FLORIDA STATE UNIV TALLAHASSEE DEPT OF MATHEMATICS
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 | High-performance polymeric materials such as liquid crystal polymers and polymer nano-particle composites have many military applications. The project aimed to study the mesoscopic structure formation during flow processing and characterization of material properties in solid states. Significant progress has been made to model the materials and to understand their rheological properties in melt or solution processing. Electrical and thermal conduction properties of the nanocomposites are characterized by the low volume ... |
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| Anchoring-Induced Texture & Shear Banding of Nematic Polymers in Shear Cells |
01-Oct-2007 |
28 pages |
| Authors:
Qi Wang; Hong Zhou; M G Forest; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF MATHEMATICS
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| We numerically explore texture (resolved by the second-moment of the orientational distribution) and shear banding of nematic polymers in shear cells, allowing for one-dimensional morphology in the gap between parallel plates. We solve the coupled Navier-Stokes and Doi-Marrucci-Greco orientation tensor model, considering both confined orientation in the plane of shear and full orientation tensor degrees of freedom, and both primary flow and vorticity (in the full tensor model) components. This ... |
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| A Control Strategy for High-Performance Macromolecular Materials |
04 JAN 2007 |
9 pages |
| Authors:
M. G. Forest; NONLINEAR CONTROL STRATEGIES INC TUCSON AZ
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| This contract has led to a design and control capability for high performance, nano-composite materials. Results obtained explicitly link material performance properties to detailed modeling of flow processing. The target materials are nematic polymer nano-composites in which nano-elements are high-aspect-ratio rods or platelets with extreme property contrasts relative to the matrix. Benchmark prototype materials yield striking enhancements in multi-functional properties. A suite of modeling tools for design engineering, which did ... |
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| Nematic Liquids in Weak Capillary Poiseuille Flow: Structure Scaling Laws and Effective Conductivity Implications |
01-Jan-2007 |
19 pages |
| Authors:
Hong Zhou; M G Forest; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF MATHEMATICS
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| We study the scaling properties of heterogeneities in nematic (liquid crystal) polymers that are generated by pressure-driven, capillary Poiseuille flow. These studies complement our earlier drag-driven structure simulations and analyses. We use the mesoscopic Doi-Marrucci-Greco model, which incorporates excluded-volume interactions of the rod-like particle ensemble, distortional elasticity of the dispersion, and hydrodynamic feedback through orientation dependent viscoelastic stresses. The geometry likewise introduces anchoring conditions on the nano-rods which touch the ... |
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| Elongational Perturbations on Nematic Liquid Crystal Polymers Under a Weak Shear |
01-Jan-2007 |
11 pages |
| Authors:
Hong Zhou; Hongyun Wang; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF MATHEMATICS
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| The two-dimensional Smoluchowski equation is employed to study the effect of elongational perturbations on nematic liquid crystal polymers under a weak shear. We use the multiscale asymptotic analysis to show that 1 when the elongational perturbation is small relative to the weak shear, the orientational probability density function pdf tumbles periodically only in an intermediate range of polymer concentration; outside this intermediate range i.e., for very small and very large ... |
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| On the Equilibria of the Extended Nematic Polymers under Elongational Flow |
01-Jan-2007 |
16 pages |
| Authors:
Hong Zhou; Lynda Wilson; Hongyn Wang; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF MATHEMATICS
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| We classify the equilibrium solutions of the Smoluchowski equation for dipolar (extended) rigid nematic polymers under imposed elongational flow. The Smoluchowski equation couples theMaier-Saupe short-range interaction, dipole-dipole interaction, and an external elongational flow. We show that all stable equilibria of rigid, dipolar rod dispersions under imposed uniaxial elongational flow field are axisymmetric. This finding of axisymmetry significantly simplifies any procedure of obtaining experimentally observable equilibria. Copyright 2007 Hong Zhou et ... |
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| Asymptotic Study on the Extendability of Equilibria of Nematic Polymers |
01-Jan-2007 |
16 pages |
| Authors:
Hong Zhou; Hongyun Wang; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| This paper addresses the extendability of equilibrium solutions of pure nematic liquid crystal polymers. More precisely, we apply the asymptotic analysis to show that the Jacobian of the nonlinear system is nonzero for both the prolate branch and the oblate branch when the nematic strength is large enough. This result implies the existence and uniqueness of the equilibrium solutions in the presence of small perturbations. |
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| On the Structure of Holographic Polymer-Dispersed Polyethylene Glycol (Postprint) |
OCT 2006 |
11 pages |
| Authors:
Michael J. Birnkrant; Hilary K. McWilliams; Christopher Y. Li; Lalgudi V. Natarajan; Vincent P. Toodiglia; Richard L. Sutherland; Pamela F. Lloyd; Timothy J. Bunning; DREXEL UNIV PHILADELPHIA PA
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| Holographic polymerization (H-P) has been used to fabricate polymer-dispersed liquid crystals and pattern inert nanoparticles. In this article, one-dimensional grating structures of Norland resin and polyethylene glycol (PEG) were achieved using the H-P technique. Both reflection and transmission grating structures were fabricated. The optical properties of the reflection grating structures (also known as Bragg reflectors, BRs) are thermosensitive, which is attributed to the formation and crystallization of PEG crystals. The ... |
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| Polymer Film with Optically Controlled Form and Actuation (Postprint) |
SEP 2006 |
9 pages |
| Authors:
Timothy Bunning; Nelson Tabiryan; Svetlana Serak; Xiao-Man Dai; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SURVIVABILITY AND SENSOR MATERIALS DIV/HARDENED MATERIALS
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| A low power laser beam is used to induce large and fast variations in the shape of a polymer film due to photoinduced contraction and expansion of the polymer film surface subject to the beam. The direction of the photoinduced bend or twist of the polymer can be reversed by changing the polarization of the beam. Thus the film orientation could be varied within + or - 70 deg. The ... |
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| Polymer Film with Optically Controlled Form and Actuation (Preprint) |
SEP 2006 |
6 pages |
| Authors:
Nelson Tabiryan; Svetlana Serak; Xio-Man Dai; Timothy J. Bunning; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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| Polymer networks containing azobenzene liquid-crystalline (azo LC) moieties are capable of changing their macroscopic shape when influenced by light. Two distinct processes take place in azo LCs due to the photoisomerization of the azobenzene chromophores. Trans-cis isomerization and thus a reduced order parameter is dominant at UV wavelengths whereas trans-cis-trans isomerization processes are dominant at visible wavelengths resulting in orientation of the molecules perpendicular to the beam polarization. |
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| A New Proof on Axisymmetric Equilibria of a Three-Dimensional Smoluchowski Equation |
07-Oct-2005 |
12 pages |
| Authors:
Qi Wang; Hong Zhou; Hongyun Wang; M G Forest; NORTH CAROLINA UNIV AT CHAPEL HILL DEPT OF MATHEMATICS
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| We consider equilibrium solutions of the Smoluchowski equation for rodlike nematic polymers with a Maier-Saupe excluded volume potential. The purpose of this paper is to present a new and simplified proof of classical well-known results: (1) all equilibria are axisymmetric and (2) modulo rotational symmetry, the number and type of axisymmetric equilibria are characterized with respect to the strength of the excluded volume potential. These results confirm the phase diagram ... |
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| Hydrodynamics of Macromolecular and Nano-Composite Materials |
05 AUG 2005 |
8 pages |
| Authors:
Qi Wang; FLORIDA STATE UNIV TALLAHASSEE DEPT OFMATHEMATICS
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| This report summarizes the research work conducted during the period funded by the AFOSR grant. The PI has conducted a series of research projects on (a). development of hydrodynamic theories for inhomogeneous nematic liquid crystal polymers, cholesteric liquid crystals, blends of liquid crystal polymers and flexible polymer solutions or melts, biaxial liquid crystal polymers or suspension flows of biaxial nano-particles; (b). studies of nematodynamics as well as morphology of inhomogeneous ... |
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| Extension-Enhanced Conductivity of Liquid Crystalline Polymer Nano-Composites |
Jan-2005 |
11 pages |
| Authors:
Qi Wang; Xiaoyu Zheng; Hong Zhou; Robert Lipton; M G Forest; ACUREX CORP/AEROTHERM MOUNTAIN VIEW CA
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| Our aim here is to predict elongational flow-induced enhancements in thermal or electrical conductivity of liquid crystal polymer (LCP) nano-composites. To do so, we combine two classical mathematical asymptotic analyses: slender longwave hydro-thermo-dynamics for fibers and exact analysis of pure elongation of LCPs in solvents for bulk phases without boundary effects; and homogenization theory for effective properties of low volume-fraction spheroidal inclusions. Two implications follow: elongational flow dominates fiber free ... |
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| High Performance Electroactive Polymers for Naval Underwater Acoustic Applications |
DEC 2004 |
34 pages |
| Authors:
Qiming Zhang; PENNSYLVANIA STATE UNIV UNIVERSITY PARK MATERIALS RESEARCH LAB
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| Program objective was to develop electroactive polymers with performance superior than current materials for Navy transducers an electromechanical transduction (i.e. smart skins) applications. Three approaches were proposed and 2 of them were investigated (the 3rd approach, which makes use of the polar-vector reorientation of liquid crystal polymers to generate high electromechanical efficiency, was not pursued due to funding limit). First, utilized the large strain associated with the molecular conformation change ... |
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| Vectran Fiber Time Dependant Behavior and Additional Static Loading Properties |
NOV 2004 |
22 pages |
| Authors:
Russell B. Fette; Marjorie F. Sovinski; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GREENBELT MD GODDARD SPACE FLIGHT CENTER
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| Vectran HS appears from literature and testing to date to be an ideal upgrade from Kevlar braided cords for many long-term, static-loading applications, such as tie-downs on solar arrays. Vectran is a liquid crystalline polymer that exhibits excellent tensile properties. The material has been touted as a zero creep product. The testing discussed in this report does not support this statement, though the creep is on the order of four ... |
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| Studies of Polymer-Stabilized Cholesteric Texture Films |
JUL 2000 |
7 pages |
| Authors:
Andy Y. Fuh; Chi-Yen Hung; Chi-Huang Lin; Tsung-Chih Ko; NATIONAL CHENG KUNG UNIV TAINAN (TAIWAN) DEPT OF PHYSICS
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| We report the results obtained from the studies of polymer-stabilized cholesteric texture films. Two sets of samples were fabricated. The first set were fabricated by adding various ferroelectric liquid crystal (SmC*) dopant concentrations in the mixtures. The second were fabricated using a dual-frequency liquid crystal. The experimental results obtained from the first set show that adding a small amount of SmC* could significantly improve the cells' electro-optical (E-O) characteristics. Both ... |
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Reports by Keyword(s)
*LIQUID CRYSTAL POLYMERS
