Photoactive Functional Soft Materials

Quan Li, PhD, is Director of the Organic Synthesis and Advanced Materials Laboratory at Liquid Crystal Institute (LCI), Kent State University, where he is also Adjunct Professor in the Chemical Physics Interdisciplinary Program. He was promoted to the youngest Full Professor of Organic Chemistry and Medicinal Chemistry at the Chinese Academy of Sciences (CAS) in Shanghai, and honored as one of One-Hundred Talent Scientists. He has directed numerous cutting-edge research projects and won the Kent State University Outstanding Research and Scholarship award. He has also been honored as Guest Professor and Chair Professor by several universities.

• Preface xi1 Soft Materials Driven by Photothermal Effect and Their Applications 1Hari K. Bisoyi, Augustine M. Urbas, and Quan Li1.1 Introduction 11.2 Liquid Crystals Driven by Photothermal Effect 31.3 Polymers Driven by Photothermal Effect 161.4 Gels Driven by Photothermal Effect 231.5 Summary and Outlook 31Acknowledgments 32References 322 Photoresponsive Supramolecular Polymers 45Yuichi Kitamoto, Keisuke Aratsu, and Shiki Yagai2.1 Introduction 452.2 Photoresponsive Supramolecular Polymers by Host–Guest and Coordination Systems 462.3 Photoresponsive Supramolecular Polymers by Complementary Hydrogen Bonds 522.4 Photoresponsive Supramolecular Polymers by Stacking of Photochromic Molecules 612.5 Photoresponsive Supramolecular Polymers with Photocontrollable 1D Topology 762.6 Summary and Outlook 83References 843 Light‐Driven Self‐Organized Liquid Crystalline Nanostructures Enabled by Chiral Molecular Switches or Motors: From 1D to 3D Photonic Crystals 91Ling Wang and Quan Li3.1 Introduction 913.2 Light‐Driven Cholesteric Liquid Crystals 933.2.1 Cholesteric LCs with Chiral Azobenzene Photoswitches 933.2.2 Cholesteric LCs with Chiral Diarylethene Photoswitches 1003.2.3 Cholesteric LCs with Chiral Spirooxazine and Overcrowded Alkenes 1043.3 Light‐Driven Blue Phase Liquid Crystals 1063.4 Light‐Driven Chiral Liquid Crystal Microdroplets and Microshells 1093.5 Summary and Perspective 114Acknowledgments 115References 1164 Photochemical Chirality Induction and Inversion in Soft Materials 125Yuna Kim, Noushaba N. Mafy, and Nobuyuki Tamaoki4.1 Introduction 1254.2 Chirality Induction from Achiral Soft Materials by CPL 1264.2.1 Achiral LMW Liquid Crystals 1284.2.2 Achiral Polymers 1324.2.3 Self‐Assembled Supramolecules 1374.3 Photochemical Chirality Inversion from Chiral Soft Materials 1394.3.1 Photoresponsive Chiral Dopants for Cholesteric Liquid Crystals 1404.3.1.1 Azobenzenes 1414.3.1.2 Diarylethenes 1454.3.1.3 Overcrowded Alkenes 1494.3.2 Chiral Polymers 1534.3.2.1 Azopolymers 1564.3.2.2 Overcrowded Alkene‐Based Polymers 1574.4 Summary and Outlook 160References 1615 Soft Photoactuators in Microfluidics 167Lu‐Jian Chen and Quan Li5.1 Introduction 1675.2 Photoactive Soft Materials as Generic Microactuators 1695.2.1 Light‐Driven Microvalves 1695.2.1.1 Hydrogel Microvalves Actuated by Photothermal Effect 1715.2.1.2 Hydrogel Microvalves Actuated by Photoisomerization 1745.2.2 Light‐Driven Micropumps and Micromixers 1775.2.3 Light‐Driven Emulsification and De‐emulsification 1825.2.4 New Conceptual Light‐Driven Fluid Motion in Microchannels 1845.3 Soft Photoactuators as Optical Microcomponents 1865.3.1 Tunable Microlenses Actuated by Photoactive Hydrogels 1875.3.2 Microlens Arrays Actuated by Photoactive Emulsions 1885.4 Summary and Outlook 191Acknowledgments 192References 1926 Liquid Crystal Polymer Networks and Elastomers for Light‐Fueled Robotics 197Hao Zeng, Markus Lahikainen, Owies M. Wani, Alex Berdin, and Arri Priimagi6.1 Photoactuation: A New Paradigm for Soft Micro‐robotics 1976.2 Photoactuation in LCNs 2006.2.1 Photochemical Actuation 2026.2.2 Photothermal Actuation 2046.2.3 Comparison between the Photochemical and Photothermal Effects 2056.3 Diversity of Shape Changes in LCNs 2076.3.1 Uniaxial Contraction/Expansion 2076.3.2 Bending and Coiling 2086.3.3 From Flat Sheets to Cones 2096.3.4 Shape Changes via Complex Alignment Patterning 2106.4 Physics and Dynamics of Small‐Scale Robots 2126.5 A Historical Overview of Light‐Fueled Micro‐robots 2156.6 Outlook 219References 2207 Light‐Driven Phase Transitions in Liquid Crystals and Their Applications 227Ammathanadu S. Amrutha, Ammathanadu S. Achalkumar, and Quan Li7.1 Introduction to Liquid Crystals 2277.2 Classification of Liquid Crystals 2307.2.1 Calamitic Liquid Crystals: Phase Types and Structures 2307.2.1.1 Nematic (N) and Cholesteric (N*) Mesophase 2307.2.1.2 Smectic (Sm) Mesophase 2317.2.1.3 Chiral Frustrated Phases 2327.2.2 Discotic Liquid Crystals: Phase Types and Structures 2347.2.2.1 Nematic (N) Phase 2347.2.2.2 Columnar (Col) Mesophases 2347.3 Light‐Driven Phase Transitions in Liquid Crystals 2357.3.1 Azobenzenes 2357.3.1.1 Photoinduced Nematic to Isotropic Phase Transition 2367.3.1.2 Photoinduced Nematic to Smectic Phase Transition 2427.3.1.3 Photoinduced Phase Transition in Bent‐Core Systems 2447.3.1.4 Photoinduced Phase Transitions Involving Smectic and Chiral Phases 2477.3.1.5 Photoinduced Phase Transitions Involving Columnar Phases 2557.3.2 Axially Chiral Azo Compounds 2567.3.3 Azoxybenzenes 2587.3.4 Spiropyrans and Naphthopyrans 2587.3.5 Fulgides 2617.3.6 Ketones 2627.3.7 Diarylethenes 2647.3.8 Butadienes 2677.3.9 Near Infrared Light‐Driven Phase Transition in Hybrid Materials 2697.4 Applications of Light‐Driven Phase Transitions 2727.4.1 Holography 2727.4.2 Optical Storage Device 2727.4.3 Photocontrol in Liquid Crystal Displays 2737.4.4 Photocontrol of Mechanical Motion in Liquid Crystal Elastomers 2747.5 Summary and Perspective 274References 2758 Photomechanical Soft Nanocomposites: Synergies between Soft Matrix and Energy Conversion Additives 285Jing Hu, Shudeng Ma, Haifeng Yu, and Quan Li8.1 Introduction 2858.2 Photomechanical Nanocomposites Based on Photothermal Effect 2868.2.1 Design Strategy 2878.2.2 Fabrication 2898.2.2.1 Homogeneous Single‐Layer Films 2908.2.2.2 Asymmetric Assembled Films 2918.2.3 Properties of Photothermal Actuators 2948.2.3.1 Characterization 2948.2.3.2 Properties 2958.3 Photomechanical Nanocomposites Based on Photochemical Effect 2968.3.1 Photodeformable Supramolecular Systems 2968.3.1.1 Reversible Metal–Ligand Coordination 2968.3.1.2 Interaction between Cyclodextrin and Azobenzene Derivatives 2978.3.2 Liquid Crystalline Polymer Nanocomposites 2998.3.2.1 Aligned Carbon Nanotube 3008.3.2.2 Polymer‐Dispersed Hybrid Film 3018.3.2.3 Bilayer Composite Film 3038.3.3 Incorporation of Upconversion Nanophosphors 3038.4 Applications 3058.5 Summary and Perspectives 309References 3099 Photoresponsive Polyolefins 319Shaji Varghese, John R. Severn, and Albertus P. H. J. Schenning9.1 Introduction 3199.2 Photoresponsive Polymers 3209.3 Need for Non‐liquid Crystalline or Commodity Polymeric Materials 3229.4 Polyolefins 3249.5 Photoresponsive Polyolefins 3259.5.1 Bilayer Actuators 3269.5.2 Single‐Layer Actuators 3309.6 Photo Patterning 3329.7 Challenges for Photoresponsive Polyolefins and Future Directions 3369.8 Conclusions 337References 33710 A Photoresponsive Multi‐Bilayered Film for a Tunable Photonic Crystal 341Sunnam Kim and Seiji Kurihara10.1 Introduction 34110.1.1 Photonic Crystals 34110.1.2 Tunable Photonic Crystals 34210.2 Photo‐Tunable 1D PCs 34410.2.1 Photoresponsive Properties of Azobenzene Molecules 34410.2.1.1 Optical Anisotropy Based on Molecular Orientation 34510.2.1.2 Refractive Indices Depending on Molecular Orientation States 34710.2.2 Fabrication of Multi‐Bilayered Films 34710.2.2.1 Control of Reflection Wavelength 34810.2.2.2 Control of Reflection Intensity 34910.2.3 On–Off Switching of Reflection Based on Refractive Index Change 35010.2.4 Improvement of Response Speed 35010.2.4.1 Introduction of Biphenyl LC Group 35010.2.4.2 Introduction of Longer Conjugated LC Groups 35210.3 Summary and Outlook 357References 35711 Photoinduced Liquid Crystal Domain Engineering for Optical Field Control 361Wei Hu, Peng Chen, and Yan‐Qing Lu11.1 Introduction 36111.2 Photoalignment Technology and Photopatterning System 36311.2.1 Photoalignment Technology 36311.2.2 Photopatterning System 36411.3 Binary LC Domains for Binary Optics 36511.4 Space‐Variant LC Domains for Geometric Phase Modulation 37011.5 Digitalized LC Domains for Digitalized Geometric Phase 37511.6 Discussion and Conclusion 379References 37912 Azobenzene Polymers as Photoactive Materials for Shape Changes of Micro/Nano‐objects 389Régis Barillé, Ewelina Ortyl, and Sonia Zielinska12.1 Why Azobenzene‐Based Photoactive Nano‐objects? 38912.2 Azopolymer as a Photoactive Material 39612.3 Fabrication of Photoactive Nano‐objects 39812.3.1 Fabrication of Photoactive Nanospheres 39812.3.2 Fabrication of Nanotubes and Nanowires 40312.3.3 Fabrications of Other Different Nano‐ and Micro‐objects 40412.4 Results 40412.5 Summary and Outlook 407References 40713 Light‐Controlled Encapsulation and Release Enabled by Photoresponsive Polymer Self‐Assemblies 413Jesús del Barrio, Milagros Piñol, and Luis Oriol13.1 Introduction 41313.2 Photoresponsive Groups 41513.3 Photoresponsive Polymer Self‐Assemblies for Encapsulation and Release 41713.3.1 Polymer Self‐Assemblies from Linear Amphiphilic BCs 41713.3.2 Polymer Self‐Assemblies from Linear‐Dendritic and Branched BCs 42313.3.3 Polymer Self‐Assemblies from Supramolecular BCs 42713.3.4 Photoresponsive Polymer Capsules 42913.3.5 Photoresponsive Microgels and Nanogels 43313.3.6 Other Miscellaneous Photoresponsive Polymeric Encapsulants 43413.4 Conclusions 437References 43814 Photoresponsive Soft Materials Based on Reversible Proton Transfer 449Yi Liao and Zhuozhi Wang14.1 Introduction 44914.2 Photoactivity and Physicochemical Properties of Metastable‐State Photoacids in Polymer Films 45114.3 Photochromic Materials Based on Photoinduced Proton Transfer 45514.4 Photo‐Controlled Fragrant‐Releasing Polymer Based on Acid‐Catalyzed Hydrolysis 45914.5 Photo‐Controlled Reversible Dissolution/Formation of Polymer Nanoparticles 46214.6 Conclusion 465References 466Index 469