Title Page

Abstract

Contents

Chapter 1. Introduction 15

1.1. Stimuli-responsive materials 15

1.2. Homeostasis and temperature control 17

1.3. Smart textiles 18

1.4. Shape memory polymers 23

1.5. Micro/nanoporous structure 25

1.6. Aim of study 25

Chapter 2. Experiments 27

2.1. Materials 27

2.2. Fabrication of porous SMP fibers 27

2.3. Fabrication of porous SMP textiles 27

2.4. Deformation of porous SMP textiles 28

2.5. Characterization 28

Chapter 3. Results and Discussion 29

3.1. Hierarchical micro/nanoporous SMP textile 29

3.2. Modulation of the thermal insulation by stretching and compressing 33

3.3. Modulation of the surface wettability by stretching and compressing 35

3.4. Mechanism of IR- and water-gating properties of the SMP textile 39

3.5. Applications of IR- and water-gating textiles 42

Chapter 4. Conclusion 47

References 48

Figure 1.1. Physical, chemical, and biochemical responsiveness of stimuli-responsive materials. 15

Figure 1.2. (a) Polyampholyte hydrogels with pH modulated shape memory and spontaneous actuation spontaneous twisting of the M₁S₀.₅A₀.₅ hydrogel and recovery to original shape for 10 min (Zhang, Y. et... 16

Figure 1.3. Textiles for outstanding thermal insulation performance (a) Biomimetic porous fibers with different porous structure, mechanical property, and thermal insulation property (Cui, Y. et al. Adv.... 18

Figure 1.4. Janus textile with conical micropores for human body moisture and thermal management (a) Schematics depicting the capillary force with a traditional cotton textile and schematic illustrating... 19

Figure 1.5. Porous membrane with superhydrophilicity-hydrophilicity for unidirectional liquid penetration. (a) A superhydrophilic-hydrophilic self-supported monolayered porous poly(ether sulfone)... 20

Figure 1.6. Water actuation mechanism of knitted woolen fabric. (a) Schematic of water-responsive pore actuation of wool fiber, yarn, and fabric. (b) Reversible changes in area of knitted woolen fabric... 21

Figure 1.7. Graphene-enabled adaptive infrared textiles. (a) Illustration of the textile device with various laminated layers: multilayer graphene, fabric separator, and back electrode layer. The infrared... 22

Figure 1.8. Thermo-responsive shape memory polymer. (a) Schematics showing the mechanism of thermally triggered shape transformation. Shape deformation at a temperature above the melting... 24

Figure 3.1. Design of an IR- and water-gating shape memory polymer (SMP) textile. (a) Scheme of the SMP textile. (b) Schematic illustration of the tunable IR- and water-gating of the SMP textile. 30

Figure 3.2. (a) Scanning electron microscopy (SEM) image of the silver nanowires (AgNWs)-coated porous SMP textile. Inset is the SEM image of AgNWs on the SMP fiber. (b) Cross-sectional SEM... 31

Figure 3.3. Water contact angles of (a) silver nanowire (AgNW) and (b) bare sides. 31

Figure 3.4. Raman mapping images of the cross-section of the shape memory polymer (SMP) fiber. (a) Raman spectrum and (b) optical microscopy image of the cross-section of the SMP fiber. Raman... 32

Figure 3.5. Modulation of the thermal insulation by stretching and compressing. (a-c) (i) SEM images, (ii) photographs, and (iii) IR thermometer images of the SMP textile: (a) after stretching deformation... 33

Figure 3.6. Thermal insulation property of the SMP textile at different deformation ratios under (a) stretching and (b) compressive deformation. (c) Reversible control of thermal insulation by the... 34

Figure 3.7. Modulation of the surface wettability by stretching and compressing. (a) Scheme and optical images of the SMP textiles (i) after stretching deformation, (ii) at the original state, and (iii) after... 35

Figure 3.8. Scanning electron microscopy (SEM) images of SMP textiles after uniaxial stretching deformations of (a) 25%, (b) 50%, (c) 75% and (d) 100%. 36

Figure 3.9. Water contact angle on the AgNW side of the SMP textile after different stretching deformations. 36

Figure 3.10. SEM images of SMP textiles (a) at the original state and after compressive deformation of (b) 61.2 kPa, (c) 122.5 kPa, (d) 183.8 kPa, (e) 245.1 kPa, and (f) 306.4 kPa. 37

Figure 3.11. (a) Change of water contact angle on the bare side with different stretching and compressive deformation. Reversible control of surface wettability after the cyclic (b) stretching (100%) and (c)... 38

Figure 3.12. Scheme of IR- and water-gating mechanism on the stretched (left) and compressed (right) SMP textile. 39

Figure 3.13. Mechanism of IR- and water-gating properties of the SMP textile. (a) Cracked area ratio for the AgNW layer at different stretching deformation ratios. (b) Fiber spacing ratio, AS/AT, at different...[이미지참조] 40

Figure 3.14. Schematic illustration of the SMP textiles and SEM images of the AgNW layer on the SMP fibers which are parallel to the deformation direction (a) at the original state, (b) after 50% and (c) 100%... 41

Figure 3.15. Cross-sectional SEM images of SMP fibers after (a) stretching (fiber parallel to the stretching direction) and (b) compressive deformation. 41

Figure 3.16. Hot environment-induced control of IR- and water-gating properties. (a) Photographs and (b) IR images for the remote recovery of deformed SMP textile using hot air. The textile was place on... 42

Figure 3.17. IR images for the remote recovery test of the SMP textile using (a) hot (~70 ℃) and (b) cold water droplets. 43

Figure 3.18. Applications of IR- and water-gating textiles on human skin. (a) Photographs of human skin without (top) and with the SMP textile (bottom) under the IR irradiation. (b) Time-dependent... 44

Figure 3.19. IR images of human skin after water removal using the SMP textile and cotton. (a) Photograph and (b) IR image of the human skin after attaching the SMP textile and cotton to a water... 45

Figure 3.20. Side-view images of the water transportation test of (a) the SMP textile (bottom: the bare side; top: the AgNW side) and (b) the cotton fabric. The water droplets were placed under the fabrics... 46

 The ability of the human body to regulate its temperature is crucial for adjusting to environmental changes in temperature. Smart textiles which respond to stimuli can effectively shield the human body's temperature from an environment that is always changing. For adaptive modulation of IR and water transmission on human skin, a smart textile based on shape memory polymer (SMP) fibers is proposed. To improve thermal insulation performance, an SMP textile is made with hierarchical micro/nanoporous structures. Also, silver nanowires are coated on one side to produce asymmetric IR reflectance and hydrophilicity. The porous SMP textile exhibits excellent tenability over its asymmetric wettability and thermal insulation through the deformation and recovery of shape and structure in response to stimuli. Due to adaptive IR reflectivity, the surface temperature of SMP textile on a hot plate is successfully managed in the IR images, and the degree of thermal insulation is regulated by 65.7% of the original value. In addition, the shape of the SMP textiles, which can be applied to remove sweat from human skin, can be used to switch on or off the directional transportation of water droplets. This water- and IR-gating smart textile can suggest a feasible approach of protecting the human skin from environmental changes.