Liquid Crystalline and Mesomorphic Polymers

ISBN-13: 9781461383352 / Angielski / Miękka / 2011 / 361 str.

Valery P. Shibaev; Lui Lam

Opis

Among the various new directions in modern polymer science, the design and investigation of liquid crystal (LC) polymers have been the ones growing most actively and fruitfully. In spite of that, the possible formation of an anisotropic LC phase was only demonstrated theoretically for the first time in the 1950s by Onsager 1] and Flory 2], and then experimentally verified in the studies with polypeptides solutions. In essence, the studies of these LC lyotropic systems did not deviate from the theme of purely academic interest. It was at the beginning of the 1970s that the experimental "explosion" occurred, when aromatic polyamides were synthesized and their ability to form LC solutions in certain very aggressive solvents was discovered. The search for practical applications of such LC systems was crowned with the successful creation of the new generation of ultrastrong high-modulus ther mostable fibers, such as the Kevlar, due to the high degree of order of the macromolecules in the anisotropic LC state. In fact, these investigations coincided with the swift emergence on the practical "scene" of thermotropic low-molar-mass liquid crystals, with the use of these materials in microelectronics and electro optics (figures and let ters indicators, displays in personal computers, and flat TV, etc.). Polymer scientists also began to develop methods of synthesizing thermotropic LC polymers by incorporating mesogenic fragments in the main (main-chain LC polymers) or side branchings of the macromolecules (side-chain or comb shaped polymers)."

Spis treści

1 Molecular Theory of Cholesteric Polymers.- 1.1 Introduction.- 1.2 Elementary Models for Chiral Molecules.- 1.3 Chiral Anisotropic Interaction Between Macromolecules in the Solvent.- 1.3.1 Model Potentials.- 1.3.2 Solvent Effect on the Chiral Intermolecular Interaction.- 1.4 Statistical Theory of Cholesteric Ordering.- 1.4.1 General Theory.- 1.4.2 Temperature and Solvent Effect on the Cholesteric Pitch in Polypeptide Solutions.- 1.4.3 Cholesteric Ordering in Biopolymer Solutions.- 1.4.4 Influence of Solvent Chirality on the Cholesteric Ordering.- 1.5 Influence of Molecular Flexibility on the Cholesteric Ordering in Polymer Solutions.- References.- 2 Structure of Thermotropic Main-Chain Polymers.- 2.1 Introduction.- 2.1.1 Scope.- 2.1.2 Main-Chain Mesogenic Systems.- 2.2 Molecular Architecture.- 2.2.1 Theoretical Background.- 2.2.2 Architecture of Isolated Polymer Molecules.- 2.2.3 Persistence Length as a Critical Parameter.- 2.2.4 Kuhn Chains.- 2.2.5 Change in Chain Parameters in the Nematic Phase.- 2.2.6 Microstructural Considerations Involving Nematic Polymers.- 2.3 Levels of Order in Mesophases of Main-Chain Liquid Polymers.- 2.3.1 Classification for Polymers.- 2.3.2 Aspects of Chain Structure.- 2.3.3 Basis for Classification.- 2.3.4 Mesophases Formed by Successive Shear Disorder of the Crystal.- 2.3.5 Mesophases Formed by Paracrystalline Disorder in One Lateral Dimension.- 2.3.6 Mesophases Resulting from Paracrystalline Disorder in the Two (Lateral) Dimensions, and Translational Melting in Two Dimensions.- 2.3.7 Audit of Possible Combinations.- 2.3.8 Occurrence of Mesophase Structures.- 2.3.9 Disruption of Order along the Chain Axis.- References.- 3 Molecular Architecture and Structure of Thermotropic Liquid Crystal Polymers with Mesogenic Side Groups.- 3.1 Introduction.- 3.2 Molecular Architecture of Liquid Crystal Polymers.- 3.3 Specific Features of Comb-Shaped Polymers Associated with Their Macromolecular Nature.- 3.4 Mesophase Types of Comb-Shaped Liquid Crystal Polymers. Problems of Classification.- 3.5 Effect of Mesophase Type on the Structure of Polymers Oriented by Uniaxial Drawing.- 3.5.1 Nematic Polymers.- 3.5.2 Smectic Polymers.- 3.6 Placement of the Main-Chain in Smectic and Nematic Phases of Comb-Shaped Liquid Crystal Polymers.- 3.7 Structure of Cholesteric Polymers.- 3.7.1 Structure of Cholesterol-Containing Homopolymers.- 3.7.2 Structure of Cholesterol-Containing Copolymers.- References.- 4 Phase Behavior of High- and Low-Molar-Mass Liquid Crystal Mixtures.- 4.1 Introduction.- 4.2 Binary Mixtures of Low-Molar-Mass Mesogens.- 4.3 Mixtures of a Liquid Crystalline Polymer with a Low-Molar-Mass Liquid Crystal.- 4.3.1 Miscibility Properties.- 4.3.2 Other Nonideal Behaviors.- 4.4 Conclusions.- References.- 5 Polymer-Dispersed Liquid Crystal Films.- 5.1 Introduction.- 5.2 Film Structure and Operation.- 5.3 Film Formation: General Aspects.- 5.3.1 Emulsification—NCAP Films.- 5.3.2 Phase Separation—Polymer-Dispersed Liquid Crystal Films.- 5.4 Polymer-Dispersed Liquid Crystal Formation: Polymer-Induced Phase Separation Systems.- 5.4.1 Formation Model.- 5.4.2 Experimental Studies of Polymer-Dispersed Liquid Crystal Formation.- 5.4.3 Concluding Remarks Regarding Polymer-Dispersed Liquid Crystal Formation.- 5.5 Materials Selection.- 5.5.1 Refractive Indices.- 5.5.2 Solubility of Liquid Crystal in Matrix.- 5.5.3 Operating Temperature Range.- 5.5.4 Environmental Stability.- 5.6 Film Fabrication and Morphology.- 5.6.1 Ultraviolet-Curing Conditions.- 5.6.2 Droplet Size Distribution.- 5.6.3 Color.- 5.7 Electrooptic Properties.- 5.7.1 Refractive Indices and Film Transmittance.- 5.7.2 Transmittance versus Voltage.- 5.7.3 Response Times.- 5.7.4 Spectral Transmittance Characteristics.- 5.8 Light Scattering.- 5.8.1 Theoretical Treatments.- 5.8.2 Angle-Dependent Light Scattering Measurements.- 5.8.3 Transmittance Measurements.- 5.8.4 Droplet Size Effects.- 5.8.5 Concluding Remarks Regarding Light Scattering.- 5.9 Final Comments.- References.- 6 Nuclear Magnetic Resonance Spectroscopy of Thermotropic Liquid Crystalline Polymers.- 6.1 Introduction.- 6.2 Thermotropic Liquid Crystalline Polymers with Mesogenic Groups in the Main Chain.- 6.2.1 1H and 2H Nuclear Magnetic Resonance in Fast Motion Limit.- 6.2.2 Multipulse Dynamic Nuclear Magnetic Resonance.- 6.2.3 Molecular Dynamics.- 6.2.4 Orientational Ordering.- 6.2.5 Biphase Region.- 6.2.6 Macroscopic Ordering.- 6.3 Liquid Crystalline Polymers with Mesogenic Groups in the Side Chains.- 6.3.1 Molecular Dynamics and Ordering in the Glassy State.- 6.3.2 Ordering and Dynamics in Liquid Crystalline Phases above the Glass Transition Temperature.- 6.3.3 Biphase Region.- 6.3.4 Macroscopic Ordering.- References.- 7 Mesophase of Graphitizable Carbons.- 7.1 Introduction.- 7.2 Discotic Nematic Liquid Crystals.- 7.3 Formation of the Mesophase.- 7.4 Structure in the Mesophase.- 7.5 Growth and Coalescence.- 7.6 Formation of Anisotropic Carbons.- 7.7 Factors Influencing the Formation of Anisotropic Carbons.- 7.7.1 Chemical Factors.- 7.7.2 Physical Factors.- 7.8 Graphitization.- 7.9 Industrial Relevance of Mesophase: Discotic, Aromatic, and Nematic Liquid Crystals.- 7.9.1 Delayed Coking.- 7.9.2 Metallurgical Coke.- 7.9.3 Carbon Fibers.- 7.9.4 Graphite Production.- 7.9.5 Carbon Blacks.- References.- 8 Mesophase State of Polyorganophosphazenes.- 8.1 Introduction.- 8.2 Thermodynamics and Structure of Polyorganophosphazenes.- 8.3 Relaxation Transitions of Poly-bis-Trifluoroethoxyphosphazenes.- 8.4 Properties of Diluted Solutions of Poly-bis-Fluoroalkoxyphosphazenes.- 8.5 Rheological Properties of Concentrated Poly-bis-Trifluoroethoxyphosphazene Solutions.- 8.6 Rheological Properties of Poly-bis-Fluoroalkoxyphosphazenes in the Mesophase State.- 8.7 Polymer Blends on a Base of Poly-bis-Trifluoroethoxyphosphazene.- 8.8 Conclusions.- References.- 9 Chiral Nematic Mesophases of Lyotropic and Thermotropic Cellulose Derivatives.- 9.1 Mesophase Formation.- 9.2 Mesophases of Cellulose Derivatives.- 9.3 Chiral Nematic Properties.- 9.3.1 Theories of the Chiral Nematic State.- 9.3.2 Chiral Nematic Properties of Cellulose Derivatives.- 9.3.3 Reversal of Handedness of Chiral Nematic Cellulosics.- 9.4 Circular Dichroism and Induced Circular Dichroism.- 9.5 Chiroptical Properties of Specifically Substituted Cellulose Derivatives.- 9.6 Concluding Remarks.- References.- 10 Bowlics.- 10.1 Introduction.- 10.2 The First Paper.- 10.3 Bowlic Monomers.- 10.3.1 The Molecules.- 10.3.2 Mesophases and Phase Transitions.- 10.3.3 Physical Properties.- 10.3.4 Bowlic Nematics in Electric Fields.- 10.3.5 Bowlic Langmuir Films.- 10.4 Bowlic Polymers.- 10.4.1 The Discrete Model for Dilute Solutions.- 10.4.2 The Worm-Like Model for Bowlic Nematic Polymers.- 10.4.3 Ultrahigh Tc Bowlic Superconductors.- 10.5 Conclusions.- References.