Title Details

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 xi

1 Soft Materials Driven by Photothermal Effect and Their Applications 1
Hari K. Bisoyi, Augustine M. Urbas, and Quan Li

1.1 Introduction 1

1.2 Liquid Crystals Driven by Photothermal Effect 3

1.3 Polymers Driven by Photothermal Effect 16

1.4 Gels Driven by Photothermal Effect 23

1.5 Summary and Outlook 31

Acknowledgments 32

References 32

2 Photoresponsive Supramolecular Polymers 45
Yuichi Kitamoto, Keisuke Aratsu, and Shiki Yagai

2.1 Introduction 45

2.2 Photoresponsive Supramolecular Polymers by Host–Guest and Coordination Systems 46

2.3 Photoresponsive Supramolecular Polymers by Complementary Hydrogen Bonds 52

2.4 Photoresponsive Supramolecular Polymers by Stacking of Photochromic Molecules 61

2.5 Photoresponsive Supramolecular Polymers with Photocontrollable 1D Topology 76

2.6 Summary and Outlook 83

References 84

3 Light‐Driven Self‐Organized Liquid Crystalline Nanostructures Enabled by Chiral Molecular Switches or Motors: From 1D to 3D Photonic Crystals 91
Ling Wang and Quan Li

3.1 Introduction 91

3.2 Light‐Driven Cholesteric Liquid Crystals 93

3.2.1 Cholesteric LCs with Chiral Azobenzene Photoswitches 93

3.2.2 Cholesteric LCs with Chiral Diarylethene Photoswitches 100

3.2.3 Cholesteric LCs with Chiral Spirooxazine and Overcrowded Alkenes 104

3.3 Light‐Driven Blue Phase Liquid Crystals 106

3.4 Light‐Driven Chiral Liquid Crystal Microdroplets and Microshells 109

3.5 Summary and Perspective 114

Acknowledgments 115

References 116

4 Photochemical Chirality Induction and Inversion in Soft Materials 125
Yuna Kim, Noushaba N. Mafy, and Nobuyuki Tamaoki

4.1 Introduction 125

4.2 Chirality Induction from Achiral Soft Materials by CPL 126

4.2.1 Achiral LMW Liquid Crystals 128

4.2.2 Achiral Polymers 132

4.2.3 Self‐Assembled Supramolecules 137

4.3 Photochemical Chirality Inversion from Chiral Soft Materials 139

4.3.1 Photoresponsive Chiral Dopants for Cholesteric Liquid Crystals 140

4.3.1.1 Azobenzenes 141

4.3.1.2 Diarylethenes 145

4.3.1.3 Overcrowded Alkenes 149

4.3.2 Chiral Polymers 153

4.3.2.1 Azopolymers 156

4.3.2.2 Overcrowded Alkene‐Based Polymers 157

4.4 Summary and Outlook 160

References 161

5 Soft Photoactuators in Microfluidics 167
Lu‐Jian Chen and Quan Li

5.1 Introduction 167

5.2 Photoactive Soft Materials as Generic Microactuators 169

5.2.1 Light‐Driven Microvalves 169

5.2.1.1 Hydrogel Microvalves Actuated by Photothermal Effect 171

5.2.1.2 Hydrogel Microvalves Actuated by Photoisomerization 174

5.2.2 Light‐Driven Micropumps and Micromixers 177

5.2.3 Light‐Driven Emulsification and De‐emulsification 182

5.2.4 New Conceptual Light‐Driven Fluid Motion in Microchannels 184

5.3 Soft Photoactuators as Optical Microcomponents 186

5.3.1 Tunable Microlenses Actuated by Photoactive Hydrogels 187

5.3.2 Microlens Arrays Actuated by Photoactive Emulsions 188

5.4 Summary and Outlook 191

Acknowledgments 192

References 192

6 Liquid Crystal Polymer Networks and Elastomers for Light‐Fueled Robotics 197
Hao Zeng, Markus Lahikainen, Owies M. Wani, Alex Berdin, and Arri Priimagi

6.1 Photoactuation: A New Paradigm for Soft Micro‐robotics 197

6.2 Photoactuation in LCNs 200

6.2.1 Photochemical Actuation 202

6.2.2 Photothermal Actuation 204

6.2.3 Comparison between the Photochemical and Photothermal Effects 205

6.3 Diversity of Shape Changes in LCNs 207

6.3.1 Uniaxial Contraction/Expansion 207

6.3.2 Bending and Coiling 208

6.3.3 From Flat Sheets to Cones 209

6.3.4 Shape Changes via Complex Alignment Patterning 210

6.4 Physics and Dynamics of Small‐Scale Robots 212

6.5 A Historical Overview of Light‐Fueled Micro‐robots 215

6.6 Outlook 219

References 220

7 Light‐Driven Phase Transitions in Liquid Crystals and Their Applications 227
Ammathanadu S. Amrutha, Ammathanadu S. Achalkumar, and Quan Li

7.1 Introduction to Liquid Crystals 227

7.2 Classification of Liquid Crystals 230

7.2.1 Calamitic Liquid Crystals: Phase Types and Structures 230

7.2.1.1 Nematic (N) and Cholesteric (N*) Mesophase 230

7.2.1.2 Smectic (Sm) Mesophase 231

7.2.1.3 Chiral Frustrated Phases 232

7.2.2 Discotic Liquid Crystals: Phase Types and Structures 234

7.2.2.1 Nematic (N) Phase 234

7.2.2.2 Columnar (Col) Mesophases 234

7.3 Light‐Driven Phase Transitions in Liquid Crystals 235

7.3.1 Azobenzenes 235

7.3.1.1 Photoinduced Nematic to Isotropic Phase Transition 236

7.3.1.2 Photoinduced Nematic to Smectic Phase Transition 242

7.3.1.3 Photoinduced Phase Transition in Bent‐Core Systems 244

7.3.1.4 Photoinduced Phase Transitions Involving Smectic and Chiral Phases 247

7.3.1.5 Photoinduced Phase Transitions Involving Columnar Phases 255

7.3.2 Axially Chiral Azo Compounds 256

7.3.3 Azoxybenzenes 258

7.3.4 Spiropyrans and Naphthopyrans 258

7.3.5 Fulgides 261

7.3.6 Ketones 262

7.3.7 Diarylethenes 264

7.3.8 Butadienes 267

7.3.9 Near Infrared Light‐Driven Phase Transition in Hybrid Materials 269

7.4 Applications of Light‐Driven Phase Transitions 272

7.4.1 Holography 272

7.4.2 Optical Storage Device 272

7.4.3 Photocontrol in Liquid Crystal Displays 273

7.4.4 Photocontrol of Mechanical Motion in Liquid Crystal Elastomers 274

7.5 Summary and Perspective 274

References 275

8 Photomechanical Soft Nanocomposites: Synergies between Soft Matrix and Energy Conversion Additives 285
Jing Hu, Shudeng Ma, Haifeng Yu, and Quan Li

8.1 Introduction 285

8.2 Photomechanical Nanocomposites Based on Photothermal Effect 286

8.2.1 Design Strategy 287

8.2.2 Fabrication 289

8.2.2.1 Homogeneous Single‐Layer Films 290

8.2.2.2 Asymmetric Assembled Films 291

8.2.3 Properties of Photothermal Actuators 294

8.2.3.1 Characterization 294

8.2.3.2 Properties 295

8.3 Photomechanical Nanocomposites Based on Photochemical Effect 296

8.3.1 Photodeformable Supramolecular Systems 296

8.3.1.1 Reversible Metal–Ligand Coordination 296

8.3.1.2 Interaction between Cyclodextrin and Azobenzene Derivatives 297

8.3.2 Liquid Crystalline Polymer Nanocomposites 299

8.3.2.1 Aligned Carbon Nanotube 300

8.3.2.2 Polymer‐Dispersed Hybrid Film 301

8.3.2.3 Bilayer Composite Film 303

8.3.3 Incorporation of Upconversion Nanophosphors 303

8.4 Applications 305

8.5 Summary and Perspectives 309

References 309

9 Photoresponsive Polyolefins 319
Shaji Varghese, John R. Severn, and Albertus P. H. J. Schenning

9.1 Introduction 319

9.2 Photoresponsive Polymers 320

9.3 Need for Non‐liquid Crystalline or Commodity Polymeric Materials 322

9.4 Polyolefins 324

9.5 Photoresponsive Polyolefins 325

9.5.1 Bilayer Actuators 326

9.5.2 Single‐Layer Actuators 330

9.6 Photo Patterning 332

9.7 Challenges for Photoresponsive Polyolefins and Future Directions 336

9.8 Conclusions 337

References 337

10 A Photoresponsive Multi‐Bilayered Film for a Tunable Photonic Crystal 341
Sunnam Kim and Seiji Kurihara

10.1 Introduction 341

10.1.1 Photonic Crystals 341

10.1.2 Tunable Photonic Crystals 342

10.2 Photo‐Tunable 1D PCs 344

10.2.1 Photoresponsive Properties of Azobenzene Molecules 344

10.2.1.1 Optical Anisotropy Based on Molecular Orientation 345

10.2.1.2 Refractive Indices Depending on Molecular Orientation States 347

10.2.2 Fabrication of Multi‐Bilayered Films 347

10.2.2.1 Control of Reflection Wavelength 348

10.2.2.2 Control of Reflection Intensity 349

10.2.3 On–Off Switching of Reflection Based on Refractive Index Change 350

10.2.4 Improvement of Response Speed 350

10.2.4.1 Introduction of Biphenyl LC Group 350

10.2.4.2 Introduction of Longer Conjugated LC Groups 352

10.3 Summary and Outlook 357

References 357

11 Photoinduced Liquid Crystal Domain Engineering for Optical Field Control 361
Wei Hu, Peng Chen, and Yan‐Qing Lu

11.1 Introduction 361

11.2 Photoalignment Technology and Photopatterning System 363

11.2.1 Photoalignment Technology 363

11.2.2 Photopatterning System 364

11.3 Binary LC Domains for Binary Optics 365

11.4 Space‐Variant LC Domains for Geometric Phase Modulation 370

11.5 Digitalized LC Domains for Digitalized Geometric Phase 375

11.6 Discussion and Conclusion 379

References 379

12 Azobenzene Polymers as Photoactive Materials for Shape Changes of Micro/Nano‐objects 389
Régis Barillé, Ewelina Ortyl, and Sonia Zielinska

12.1 Why Azobenzene‐Based Photoactive Nano‐objects? 389

12.2 Azopolymer as a Photoactive Material 396

12.3 Fabrication of Photoactive Nano‐objects 398

12.3.1 Fabrication of Photoactive Nanospheres 398

12.3.2 Fabrication of Nanotubes and Nanowires 403

12.3.3 Fabrications of Other Different Nano‐ and Micro‐objects 404

12.4 Results 404

12.5 Summary and Outlook 407

References 407

13 Light‐Controlled Encapsulation and Release Enabled by Photoresponsive Polymer Self‐Assemblies 413
Jesús del Barrio, Milagros Piñol, and Luis Oriol

13.1 Introduction 413

13.2 Photoresponsive Groups 415

13.3 Photoresponsive Polymer Self‐Assemblies for Encapsulation and Release 417

13.3.1 Polymer Self‐Assemblies from Linear Amphiphilic BCs 417

13.3.2 Polymer Self‐Assemblies from Linear‐Dendritic and Branched BCs 423

13.3.3 Polymer Self‐Assemblies from Supramolecular BCs 427

13.3.4 Photoresponsive Polymer Capsules 429

13.3.5 Photoresponsive Microgels and Nanogels 433

13.3.6 Other Miscellaneous Photoresponsive Polymeric Encapsulants 434

13.4 Conclusions 437

References 438

14 Photoresponsive Soft Materials Based on Reversible Proton Transfer 449
Yi Liao and Zhuozhi Wang

14.1 Introduction 449

14.2 Photoactivity and Physicochemical Properties of Metastable‐State Photoacids in Polymer Films 451

14.3 Photochromic Materials Based on Photoinduced Proton Transfer 455

14.4 Photo‐Controlled Fragrant‐Releasing Polymer Based on Acid‐Catalyzed Hydrolysis 459

14.5 Photo‐Controlled Reversible Dissolution/Formation of Polymer Nanoparticles 462

14.6 Conclusion 465

References 466

Index 469