Contents 中文摘要..................................I Abstract ................................. III Contents..................................VI List of Schemes ..............................IX List of Tables ............................... X List of Figures ..............................XI 1. Introduction ............................... 1 1-1 Preface……………………………………………………………….. 1 1-2 Research Motivation ........................... 2 2. Literature Review............................ 4 2-1 Introduction of Liquid crystals ..................... 4 2-2 Thermotropic Liquid Crystal ...................... 7 2-2-1 Nematic Liquid Crystal Phase ..................... 7 2-2-2 Smectic Liquid Crystal Phase.................... 8 2-2-3 Cholesteric Liquid Crystal Phase .................. 10 2-3 Characterization Methods of Liquid Crystals............. 13 2-3-1 POM Textures of Liquid Crystals [10] ................ 13 2-3-2 Liquid Crystal Phase Detected by DSC .............. 20 2-3-3 Liquid Crystal Phase Detected by XRD [14] ............ 21 2-4 Lyotropic Liquid Crystals ....................... 22 2-5 Anisotropic Properties of Liquid Crystals[15] ........... 23 2-5-1 Birefeingence of Liquid Crystals[16] ................ 24 2-5-2 Dielectric Properties of Liquid Crystals .............. 25 2-6 Introduction of Structural Colors.................... 27 2-6-1 Structural Colors Based on Photonic Crystals in Nature ...... 27 2-6-1-1 One-Dimensional (1D) Photonic Nanostructures in Nature .... 28 2-6-1-2 Two-Dimensional (2D) Photonic Nanostructures in Nature.... 28 2-6-1-3 Three-Dimensional (3D) Photonic Nanostructures in Nature ... 28 2-6-1-4 Tunable Structural Colors in Nature ................ 29 2-6-2 Structural Colors Based on Cholesteric Liquid Crystals....... 29 2-6-2-1 Cholesteric Liquid Crystal Inks ................. 31 2-6-2-2 Cholesteric Liquid Crystal Polymer Polymers .......... 31 2-7 Introduction of Femtosecond Laser .................. 32 3. Experimental Section .......................... 34 3-1 Materials ............................... 34 3-2 Instrument ............................... 35 3-3 Experimental Part ........................... 36 3-3-1 Synthesis of Bifunctional Monomer [37]............... 36 3-3-2 Fabrication of Liquid Crystal Cells ................. 37 3-3-3 Fabrication of Patterned Optical Object .............. 41 3-3-4 Fabrication of Cholesteric Liquid Crystal Particles ........ 41 4. Results and Discussion ........................ 43 4-1 Characterization of BAHB ....................... 43 4-1-1 Structure Identification of BAHB ................. 43 4-1-2 Thermal Properties of BAHB .................... 45 4-1-3 Optical Properties of BAHB.................... 47 4-2 Characterization of CLC Film .................... 48 4-2-1 Polymerization of CLC Mixtures .................. 48 4-2-2 Thermal Characterization of CLC Films ............... 50 4-2-3 Optical Characterization of CLC Films............... 52 4-2-4 Colorful Patterns Fabricated by Photomasks ............ 56 4-3 Cholesteric Liquid Crystalline Colorants ............... 58 4-3-1 CLC Particles by Suspension Polymerization........... 58 4-3-2 CLC Film Ground Particles..................... 62 4-3-3 Structural Colorants Based on Film Slices.............. 65 5. Conclusions .............................. 70 References ................................ 71 List of Schemes Scheme 3-1 Synthetic route of bifunctional monomer BAHB....... 36 Scheme 3-2 Chemical structures of nematic liquid crystal monomer (RM257), chiral dopant (CB15) and photo initiator (Irg-184) ........ 38 Scheme 3-3 Chemical structures of suspending agent (PVA) and thermal initiator (AIBN) .......................... 42 List of Tables Table 3-1 Components of CLC mixtures. (mg).............. 38 Table 4-1 Physical properties of nematic liquid crystal HSG22200-000. 55 List of Figures Figure 1-1 Various colors of films were produced by quenching CLC films at various temperature. ............................ 3 Figure 2-1 Phase transition of the matter and its molecular arrangement. [3]. 6 Figure 2-2 Various types of liquid crystalline molecules........... 6 Figure 2-3 Schematic representation of the molecular arrangement of nematic liquid crystal phase. ............................. 8 Figure 2-4 (a) smectic A phase, (b) smectic C phase. ............ 9 Figure 2-5 The helical structure of the cholesteric liquid crystal phase and the characteristic of circular dichorism of cholesteric liquid crystals [7]. ... 11 Figure 2-6 Schematic representation of three types of cholesteric liquid crystals under polarized optical microscope. ................ 12 Figure 2-7 Schlieren texture of a nematic phase under planar anchoring conditions, at low magnification [10]. ................... 14 Figure 2-8 Nematic thread-like texture [10]. .................. 14 Figure 2-9 The marble texture is probably the most commonly obtained texture of nematic liquid crystals [10]. .................... 15 Figure 2-10 Typical fan-shaped textures of a SmA phase. The director basically lies in the plane of the substrate and the smectic layers are acrossed the fans [10]............................. 16 Figure 2-11 Transition from a nematic schlieren texture (right) to a SmC schlieren texture (left) [10]. ......................... 17 Figure 2-12 A sample shows the broken fan-shaped texture of SmC on cooling [10]. ................................. 17 Figure 2-13 Oily streaks texture of a cholesteric sample under planar anchoring conditions [12]. ......................... 18 Figure 2-14 Schematic illustration of the cholesteric director configuration in the fingerprint textures observed for homeotropic boundary conditions [10]. ....................................... 19 Figure 2-15 Sample with a diverging cholesteric pitch under homeotropic anchoring conditions, exhibiting so-called cholesteric fingers[10]. ..... 20 Figure 2-16 Schematic illustration of Bragg’s Law [14]............ 21 Figure 2-17 Schematic of 2D X-ray diffraction of dfferent types of liquid crystal phases: (a) isotopic, (b) nematic, (c) smectic A, and (d) smectic C [14]..................................... 22 Figure 2-18 Anisotropic properties of nematic liquid crystals....... 24 Figure 2-19 Schematic illustration of the birefringence of (a) positive uniaxial LCs and (b) negative uniaxial liquid crystals[17]. .............. 25 Figure 2-20 The molecular alignments of liquid crystals with (a) positive . 26 Figure 2-21 Typical photonic nanostructures in natural creatures [20].(A)-(G) exhibit inspiring examples of structural colors in nature. ......... 29 Figure 2-22 Sketch of cholesteric structure, showing the dependence of molecular orientation on position [27]. ................... 30 Figure 2-23 Schematic of lower heat effect in femtosecond laser [36]. ... 33 Figure 2-24 Schematic of nano-slices made by femtosecond laser. .... 33 XIII Figure 3-1 Schematic illustration of the preparation of aligned glass substrate. ....................................... 40 Figure 3-2 Schematic illustration of the preparation of CLC films ..... 40 Figure 4-1 The FT-IR spectrum of bifunctional monomer BAHB. ..... 44 Figure 4-2 The 1H-NMR spectrum of intermediate BHB. ......... 44 Figure 4-3 1H-NMR spectrum of bifunctional monomer BAHB. ..... 45 Figure 4-4 TGA thermogram of BAHB. .................. 46 Figure 4-5 DSC thermogram of BAHB with heating/cooling rate of 1oC/min. ....................................... 46 Figure 4-6 DSC thermogram of BAHB with heating/cooling rate of 1oC/min. ....................................... 47 Figure 4-7 FTIR spectra of (a) P, (b) B and (c) C samples before and after polymerization............................... 49 Figure 4-8 TGA thermograms of (a) P, (b) B and (c) C CLC sample films. 51 Figure 4-9 POM textures of CLC films and appearing color of (a) P, (b) B and (c) C. .................................... 52 Figure 4-10 Real images of (a) purple, (b) blue and (c) cyan CLC films.. 54 Figure 4-11 Reflection spectra of CLC films prepared with LC cells (a) without and (b) with alignment layers. ................... 54 Figure 4-12 Reflection spectrum of the synthesized sample R showing orange-red color............................... 56 Figure 4-13 Fabrication of a colorful pattern through a mask. ........ 57 Figure 4-14 Various colorful patters fabricated via photomasks. ...... 57 XIV Figure 4-15 The SEM image of the synthesized spherical particles.... 59 Figure 4-16 The POM image of the synthesized CLC particles. ....... 59 Figure 4-17 The Schematic illustration of molecular interactions occurred at interface of LC droplets........................... 60 Figure 4-18 The radial conformation and corresponding POM image of 5CB droplets [44]. ................................ 60 Figure 4-19 The reflection spectrum of the synthesized CLC particles. ... 61 Figure 4-20 Real images of the original blue film and the milky white appearance of the ground particles.................... 63 Figure 4-21 The POM image of the ground CLC particles ......... 63 Figure 4-22 The reflection spectrum of the ground particles......... 64 Figure 4-23 The SEM image of ground particles............... 64 Figure 4-24 Appearance of the prepared CLC slices showing various colors. ....................................... 66 Figure 4-25 NCKU pattern fabricated by the developed different color CLC slices fixed by a transparent binder. .................... 67 Figure 4-26 Reflection spectra of binder fixed P and C sample slices showing purple and cyan, respectively. ....................... 67 Figure 4-27 A hummingbird gradient pattern was fabricated by the synthesized CLC slices.......................... 68 Figure 4-28 The schematic reflection of slices free from light scattering . 68 Figure 4-29 The preparation of CLC films with various thickness. .... 69 Figure 4-30 Reflection spectra of CLC films with different film thickness.69