Download or read book Dynamics and Shear Alignment Behavior of a Model Thermotropic Liquid Crystalline Polymer written by Weijun Zhou and published by . This book was released on 2001 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rheology and Processing of Liquid Crystal Polymers written by Domenico Acierno and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid crystal polymers (LCPs) have many strange properties that may be utilized to advantage in the processing of products made from them and their blends with isotropic polymers. This volume (volume 2 in the series Polymer Liquid Crystals) deals with their strange flow behaviour and the models put forward to explain the phenomena that occur in such polymers and their blends. It has been known for some time that small ad ditions of a thermotropic LCP to isotropic polymers not only gives an improvement in the strength and stiffness of the blend but improves the processability of the blend over that of the isotropic polymer. In the case of lyotropic LCPs, it is possible to create a molecular composite in which the reinforcement of an isotropic polymer is achieved at a molecular level by the addition of the LCP in a common solvent. If the phenomena can be fully understood both the reinforcement and an increase in the proces sability of isotropic polymers could be optimized. This book is intended to illustrate the current theories associated with the flow of LCPs and their blends in the hope that such an optimization will be achieved by future research. Chapter 1 introduces the subject of LCPs and describes the ter minology used; Chapter 2 then discusses the more complex phenomena associated with these materials. In Chapter 3, the way in which these phe nomena may be modelled using hamiltonians is fully covered.
Download or read book Investigation of the Effect of Shear Flow on Molecular Orientation in Model Thermotropic Liquid Crystalline Polymers Using in Situ X ray Scattering written by Victor Manuel Ugaz and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Although liquid crystalline polymers (LCPs) offer considerable commercial potential for the production of lightweight materials possessing exceptional mechanical strength, the influence of flow on molecular orientation remains poorly understood in melt processable thermotropic systems. In this thesis, a combination of materials and experimental techniques are employed which allow structural measurements to be obtained under a variety of flow conditions in the melt. In situ x-ray scattering techniques are used as a structural probe to directly measure the influence of flow on molecular orientation, and to identify the presence of other structural arrangements which would otherwise be unobservable. First, we use this structural data to identify a link between the development of a hexagonal microstructure and the onset of region I shear thinning in lyotropic poly(gamma-benzyl-L-glutamate) in m-cresol. Next, two different model thermotropic systems are studied, a polyester and polyether respectively, which incorporate molecular architectures specifically designed to provide a stable nematic phase over a wide temperature range. We present measurements of molecular orientation in steady shear flow, during relaxation after cessation of shear flow, and in the transient periods during shear flow inception and reversal. Under certain combinations of temperature and shear rate, the polyether is found to display a dramatic transition in molecular alignment to a condition where orientation is favored parallel to the vorticity direction, rather than parallel to the flow direction as is typically observed. Both materials exhibit dynamic behavior in the nematic phase consistent with flow alignment, as opposed to director tumbling behavior which is often observed in lyotropic LCPs. This hypothesis is supported by comparison with an adaptation of the Ericksen transversely isotropic fluid model and the Larson-Doi model, both of which account for the polydomain texture characteristic of LCP materials. The Larson-Doi model yields better qualitative predictions of the evolution of orientation and stress during flow reversal, suggesting that distortional elasticity plays a significant role in this type of flow. However, some discrepancies remain between the model predictions and the experimentally observed behavior, suggesting that distortional elasticity may play a different role in the rheology of thermotropic LCPs than in lyotropes.
Download or read book Flow Visualization and Modeling of Liquid Crystalline Polymers written by Mark Naoshi Kawaguchi and published by . This book was released on 1998 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rheological Characterization of a Thermotropic Liquid Crystalline Polymer in the Nematic State written by Susan M. Guskey and published by . This book was released on 1990 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Influence of Phase Behavior and Microstructure on Liquid Crystal Polymer Rheology written by Douglass Steven Kalika and published by . This book was released on 1988 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Liquid Crystal Polymers From Structures to Applications written by A.A. Collyer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 486 pages. Available in PDF, EPUB and Kindle. Book excerpt: The subject of liquid crystals and their use in electronic displays and in non-linear optical systems has become of tremendous importance during the last decade; and the incorporation of liquid crystal units into polymeric materials has led to a group of new materials with diverse properties. Some of these properties have been utilized in new products and some have yet to be used. Much published work has appeared that deals with specific materials or particular applications, and it was felt that a book was needed to examine and explain the underlying principles governing the diverse properties of these liquid crystal polymers, LCPs. The current work describes the diverse nature of LCPs, their synthesis, characterization, properties and finally their applications. It describes the manner in which liquid crystallinity or mesomorphism occurs in small molecules, monomer liquid crystals and polymer liquid crystals. Chapter 1 gives a classification of the various ways in which the meso gens may be connected to the polymer chains. Currently, the bulk of LCP material is based on main chain or longitudinal LCPs for use in engineering applications. The side chain or comb polymers are intended for use in electronics and opto-electronic systems and as surfactants. Many other variants and possibilities exist but their properties have not yet been fully studied or used. In this respect it is hoped that the current work will indicate future possibilities as well as discussing current opinion. v Preface vi Chapters 2 and 3 describe methods of characterizing the mesophases.
Download or read book Shear Rheology and Texture of a Thermotropic Liquid Crystalline Polymer written by Edwin Gyuhue Kim and published by . This book was released on 1996 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of Rheology written by and published by . This book was released on 2003 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow induced Structure in Polymers written by Alan I. Nakatani and published by . This book was released on 1995 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Examines recent advances in understanding the structures of polymer melts, polymer solutions, block copolymers, liquid crystalline polymers, colloid suspensions, and multiphase systems subjected to flow. Reports on advances in instrumental techniques, characterization, theories, and applications. An overview chapter provides a guide and reference source to related reviews and identifies similarities in flow behavior between various materials science disciplines.
Download or read book Computer Simulations of Liquid Crystals and Polymers written by Paolo Pasini and published by Springer Science & Business Media. This book was released on 2005-08-11 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid crystals, polymers and polymer liquid crystals are soft condensed matter systems of major technological and scientific interest. An understanding of the macroscopic properties of these complex systems and of their many and interesting peculiarities at the molecular level can nowadays only be attained using computer simulations and statistical mechanical theories. Both in the Liquid Crystal and Polymer fields a considerable amount of simulation work has been done in the last few years with various classes of models at different special resolutions, ranging from atomistic to molecular and coarse-grained lattice models. Each of the two fields has developed its own set of tools and specialized procedures and the book aims to provide a state of the art review of the computer simulation studies of polymers and liquid crystals. This is of great importance in view of a potential cross-fertilization between these connected areas which is particularly apparent for a number of experimental systems like, e.g. polymer liquid crystals and anisotropic gels where the different fields necessarily merge. An effort has been made to assess the possibilities of a coherent description of the themes that have developed independently, and to compare and extend the theoretical and computational techniques put forward in the different areas.
Download or read book Computer Simulations of Liquid Crystals and Polymers written by Paolo Pasini and published by Springer Science & Business Media. This book was released on 2005 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1995 with total page 742 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Directory of Graduate Research written by and published by . This book was released on 2001 with total page 1846 pages. Available in PDF, EPUB and Kindle. Book excerpt: Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.
Download or read book Progress and Trends in Rheology V written by Igor Emri and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 643 pages. Available in PDF, EPUB and Kindle. Book excerpt: Global sustainable development of the world economy requires better understanding and utilization of natural recourses. In this endeavor rheology has an indispensable role. The Rheology Conferences are therefore always an important event for science and technology. The Fifth European Rheology Conference, held from September 6 to 11 in the Portoro-z, Slovenia, will be the first AlI-European rheology meeting after the formal constitution of the European Society ofRheology. As such it will be a special historical event. At this meeting the European Society of Rheology will introduce the Weissenberg Medal, to be bestowed every four years to an individual for hislhers contribution to the field of Rheology. The recipient ofthe first award will be professor G. Marrucci ofthe Universita degli Studi di Napoli, Italy. Two mini Symposia will be part of the Conference. The first, on Industrial Rheology, will commemorate the late professor G. Astarita. The second will honor the eightieth birthday of professor N.W. Tschoegl. This volume comprises extended abstracts of the 15 plenary and keynote lectures and about 300 oral and poster contributions presented at this conference. AII contributed papers were reviewed by members ofthe European Committee on Rheology, assuring the high standard ofthe Conference. Besides the scientific program, the Organizing Committee has prepared an extensive social program that wilI reveal the culture and the natural beauties of Slovenia.
Download or read book Liquid Crystal Alignment and Relaxation Dynamics at Surface Modified Thin Polymer Films written by Dena Mae Agra-Kooijman and published by . This book was released on 2008 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: The physical and chemical nature of bare surfaces and of thin films of polymers deposited in solid substrates plays a key role in the alignment of liquid crystal (LC). The ability to define the polar and azimuthal direction of the LC director at substrate-LC interface is at the heart of electro-optical applications of liquid crystals. However, the precise mechanism(s) of LC alignment have remained shrouded in mystery. The research conducted under this project was aimed at gaining insight into the relationship between LC alignment and the surface structure/morphology and to understand the dynamics of polymer chains at the polymer-air interface and under confinement to small dimensions. The results presented here show that properties of thin polymer films, such as glass transition temperature, Tg, and chain mobility are significantly different from bulk polymers. However, the understanding of the underlying reasons for these effects is far from complete. The studies of various polymers (weight molecular weight, radius of gyration) in different film geometries (supported on substrate or free standing) using different techniques reveal either an increase or a decrease in Tg and/or chain mobility with decreasing film thickness. Although the shifts of the Tg are a clear indication of the differences between the polymer chain mobility in the bulk and thin films, the measurements of Tg's are only an indirect method to probe their relaxation dynamics. The measurement of optical retardation, a simple optical technique requiring no physical contact with the polymer film, has been employed to directly probe the relaxation dynamics of variously treated thin polymer films routinely used for liquid crystal alignment. Using the relaxation model based on Kohlrausch-Williams-Watts, the Tg's of polystyrene films were determined as a function of the thickness and rubbing strengths (depths). Tg's are significantly reduced by 15-20 K for films of thickness less than 250 ... This correlates very well with previous studies on similar systems but using different methods. In addition, Tg decreases with rubbing depth indicating that polymer molecules close to the film-air interface relax faster than the molecules farther from the interface. The dependence of Tg on the rubbing strength provides clear evidence that polymer chains at the surface relax more readily. The morphology of polymer films was determined using high-resolution x-ray reflectivity, which is a sensitive and direct probe of surface structure at submicron levels. Making use of the inherent anisotropy in the coherence area of the x-ray beam, the morphological anisotropy of the films was quantitatively determined. The films' surfaces were modified by a specific treatment (i.e., rubbing or exposing to linearly polarized UV). Knowledge of the vertical root mean square (rms) roughness parallel and perpendicular to the treatment direction is of great importance in understanding the exact role in liquid crystal alignment of the nature of the surface. Reflectivity scans on the treated surfaces reveal roughness anisotropy, i.e., roughness is significantly different in the two orthogonal directions on the substrate plane. This direction of a more roughness is perpendicular to the azimuthal direction of the liquid crystal alignment. Hence, liquid crystal molecules align in the smoother direction.
Download or read book Viscoelasticity and Dynamics of Alignment in Side group Liquid Crystalline Polymers written by Susan Felicia Rubin and published by . This book was released on 1996 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:
