Blends of thermotropic liquid crystalline and thermoplastic polymers: A short review

This chapter contains a short review of the development of computer simulation, and its place in research as a complement to experiment and theory. This is followed by an introduction to intermolecular interactions, and the way that they are modelled on a computer, complete with examples of program code. Force fields are introduced to describe the full range of interactions in atomic and molecular fluids and a number of coarsegrained models for exploring liquid-crystalline and polymer systems are also considered. The consequences of performing bulk simulations using finite-size systems are described, along with the way that these problems can be mitigated by the use of periodic boundary conditions.

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Pollutant Identification by Selected Area Electron Diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052675 ◽

1974 ◽

Vol 32 ◽

pp. 532-533

Author(s):

R. E. Ferrell ◽

G. G. Paulson ◽

C. W. Walker

Keyword(s):

Thermal Treatment ◽

Electron Diffraction ◽

Sample Preparation ◽

Crystal Structures ◽

Water Samples ◽

Environmental Samples ◽

Short Review ◽

Selected Area Electron Diffraction ◽

Multiple Component

Selected area electron diffraction (SAD) has been used successfully to determine crystal structures, identify traces of minerals in rocks, and characterize the phases formed during thermal treatment of micron-sized particles. There is an increased interest in the method because it has the potential capability of identifying micron-sized pollutants in air and water samples. This paper is a short review of the theory behind SAD and a discussion of the sample preparation employed for the analysis of multiple component environmental samples.

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Freeze fracture imaging and computer simulation of liposome structure: Membrane geometry and defects

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076834 ◽

1983 ◽

Vol 41 ◽

pp. 646-647

Author(s):

Joseph A. Zasadzinski

Keyword(s):

Liquid Crystalline ◽

Freeze Fracture ◽

Continuum Theory ◽

Closed Surfaces ◽

Straight Line ◽

Low Weight ◽

Concentric Spheres ◽

Membrane Geometry ◽

Dupin Cyclides ◽

Limiting Case

At low weight fractions, many surfactant and biological amphiphiles form dispersions of lamellar liquid crystalline liposomes in water. Amphiphile molecules tend to align themselves in parallel bilayers which are free to bend. Bilayers must form closed surfaces to separate hydrophobic and hydrophilic domains completely. Continuum theory of liquid crystals requires that the constant spacing of bilayer surfaces be maintained except at singularities of no more than line extent. Maxwell demonstrated that only two types of closed surfaces can satisfy this constraint: concentric spheres and Dupin cyclides. Dupin cyclides (Figure 1) are parallel closed surfaces which have a conjugate ellipse (r1) and hyperbola (r2) as singularities in the bilayer spacing. Any straight line drawn from a point on the ellipse to a point on the hyperbola is normal to every surface it intersects (broken lines in Figure 1). A simple example, and limiting case, is a family of concentric tori (Figure 1b).To distinguish between the allowable arrangements, freeze fracture TEM micrographs of representative biological (L-α phosphotidylcholine: L-α PC) and surfactant (sodium heptylnonyl benzenesulfonate: SHBS)liposomes are compared to mathematically derived sections of Dupin cyclides and concentric spheres.

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Electron microscopy of crystalline structure in thermotropic random copolymers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089585 ◽

1991 ◽

Vol 49 ◽

pp. 1054-1055

Author(s):

Afzana Anwer ◽

S. Eilidh Bedford ◽

Richard J. Spontak ◽

Alan H. Windle

Keyword(s):

Electron Microscopy ◽

Crystalline Structure ◽

Liquid Crystalline ◽

Elevated Temperatures ◽

Random Copolymers ◽

Molecular Characteristics ◽

Scanning Calorimetry ◽

X Ray ◽

Identical Monomer ◽

Periodic Layer

Random copolyesters composed of wholly aromatic monomers such as p-oxybenzoate (B) and 2,6-oxynaphthoate (N) are known to exhibit liquid crystalline characteristics at elevated temperatures and over a broad composition range. Previous studies employing techniques such as X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) have conclusively proven that these thermotropic copolymers can possess a significant crystalline fraction, depending on molecular characteristics and processing history, despite the fact that the copolymer chains possess random intramolecular sequencing. Consequently, the nature of the crystalline structure that develops when these materials are processed in their mesophases and subsequently annealed has recently received considerable attention. A model that has been consistent with all experimental observations involves the Non-Periodic Layer (NPL) crystallite, which occurs when identical monomer sequences enter into register between adjacent chains. The objective of this work is to employ electron microscopy to identify and characterize these crystallites.

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Structure-property relations of liquid crystalline polymers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100127013 ◽

1987 ◽

Vol 45 ◽

pp. 460-463

Author(s):

Linda C. Sawyer

Keyword(s):

Solid State ◽

Liquid Crystalline ◽

Structural Model ◽

Crystalline Polymer ◽

Liquid Crystalline Polymers ◽

Mechanical Anisotropy ◽

Structure Property ◽

Preparation Methods ◽

Crystalline Polymers ◽

Extended Chain

Recent liquid crystalline polymer (LCP) research has sought to define structure-property relationships of these complex new materials. The two major types of LCPs, thermotropic and lyotropic LCPs, both exhibit effects of process history on the microstructure frozen into the solid state. The high mechanical anisotropy of the molecules favors formation of complex structures. Microscopy has been used to develop an understanding of these microstructures and to describe them in a fundamental structural model. Preparation methods used include microtomy, etching, fracture and sonication for study by optical and electron microscopy techniques, which have been described for polymers. The model accounts for the macrostructures and microstructures observed in highly oriented fibers and films.Rod-like liquid crystalline polymers produce oriented materials because they have extended chain structures in the solid state. These polymers have found application as high modulus fibers and films with unique properties due to the formation of ordered solutions (lyotropic) or melts (thermotropic) which transform easily into highly oriented, extended chain structures in the solid state.

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Liquid crystalline ordering of paired helical filaments in neurofibrillary tangles of Alzheimer's disease

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143365 ◽

1986 ◽

Vol 44 ◽

pp. 348-349

Author(s):

D.F. Clapin ◽

V.J.A. Montpetit

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Neurofibrillary Tangles ◽

Liquid Crystalline ◽

Amyloid Fibrils ◽

Geometric Analysis ◽

Paired Helical Filaments ◽

Microscopic Level ◽

Light Microscopic Level ◽

Regular Spacing

Alzheimer's disease is characterized by the accumulation of abnormal filamentous proteins. The most important of these are amyloid fibrils and paired helical filaments (PHF). PHF are located intraneuronally forming bundles called neurofibrillary tangles. The designation of these structures as "tangles" is appropriate at the light microscopic level. However, localized domains within individual tangles appear to demonstrate a regular spacing which may indicate a liquid crystalline phase. The purpose of this paper is to present a statistical geometric analysis of PHF packing.

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