Functional Polymer Coatings
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Contributors xi
Preface xiii
1 Transparent Organic-Inorganic Nanocomposite Coatings 1
Shuxue Zhou and Limin Wu
1.1 Introduction 1
1.2 Fabrication Strategies 2
1.2.1 Blending Method 2
1.2.2 Sol-Gel Process 10
1.2.3 Intercalation Method 11
1.3 Mechanically Enhanced Nanocomposite Clearcoats 13
1.3.1 Solventborne Polyurethane Nanocomposite Coatings 15
1.3.2 Waterborne Nanocomposite Clearcoats 17
1.3.3 UV?]Curable Nanocomposite Coatings 19
1.3.4 Other Mechanically Strong Nanocomposite Coatings 26
1.4 Optical Nanocomposite Coatings 28
1.4.1 Transparent UV?]Shielding Nanocomposite Coatings 28
1.4.2 High Refractive Index Nanocomposite Coatings 34
1.4.3 Transparent NIR?]Shielding Nanocomposite Coatings 41
1.5 Transparent Barrier Nanocomposite Coatings 45
1.6 Transparent Conducting Nanocomposite Coatings 49
1.7 Other Functional Nanocomposite Coatings 54
1.8 Conclusions and Outlook 57
References 58
2 Superhydrophobic and Superoleophobic Polymeric Surfaces 71
Jie Zhao and W. (Marshall) Ming
2.1 Introduction 71
2.2 Surface Wettability 72
2.3 Various Approaches to Obtain Super?]Repellent Surfaces 74
2.3.1 Template?]Replicating Methods 74
2.3.2 Hierarchically Structured Particles 75
2.3.3 LbL Deposition 78
2.3.4 Plasma Treatment 79
2.3.5 Chemical Vapor Deposition 81
2.3.6 Electrospinning 83
2.3.7 Electrochemical Polymerization 85
2.3.8 Other Methods 86
2.4 Applications of Super?]Repellent Polymeric Surfaces 86
2.4.1 Self?]Cleaning 86
2.4.2 Anti?]bioadhesion 87
2.4.3 Anti?]Icing 89
2.4.4 Oil-Water Separation 89
2.5 Summary and Outlook 90
Acknowledgments 90
References 90
3 Superhydrophilic and Superamphiphilic Coatings 96
Sandro Olveira, Ana Stojanovic, and Stefan Seeger
3.1 Introduction 96
3.2 Basic Concepts of Superhydrophilicity 97
3.3 Naturally Occurring Superhydrophilic and Superamphiphilic Surfaces 100
3.4 Artificial Superhydrophilic Coatings 101
3.4.1 TiO2 Coatings 101
3.4.2 SiO2 Coatings 103
3.5 Methods for Fabricating Superhydrophilic and Superamphiphilic Surfaces 104
3.5.1 Sol-Gel Method 104
3.5.2 Layer?]By?]Layer Assembly 105
3.5.3 Electrochemical Methods 106
3.5.4 Electrospinning 106
3.5.5 Etching 107
3.5.6 Plasma Treatment 107
3.5.7 Hydrothermal Method 108
3.5.8 Dip Coating 109
3.5.9 Phase Separation 109
3.5.10 Templating Method 109
3.6 Applications 110
3.6.1 Self?]Cleaning 110
3.6.2 Antifogging and Antireflective Coatings 111
3.6.3 Antifouling Properties 114
3.6.4 Enhanced Boiling Heat Transfer 115
3.6.5 Efficient Water Evaporation 118
3.6.6 Switchable and Patterned Wettability Coatings 118
3.6.7 Other Applications 119
3.7 Commercial Coatings 120
3.8 Conclusions and Outlook 122
References 123
4 Self?]Healing Polymeric Coatings 133
A.C.C. Esteves and S.J. García
4.1 Introduction 133
4.1.1 Self?]Healing Materials 134
4.1.2 Self?]Healing Polymeric Coatings 137
4.2 Self?]Healing Approaches for Functional Polymeric Coatings 138
4.2.1 Intrinsic Healing 138
4.2.2 Extrinsic Healing 147
4.3 Functionalities Recovery and Possible Applications 149
4.3.1 Surface Properties: Wettability and Anti?](bio)adhesion 149
4.3.2 Barrier and Corrosion Protection 151
4.3.3 Interfacial Bonding between Dissimilar Materials 153
4.4 Concluding Remarks and Challenges 154
Acknowledgments 155
References 155
5 Stimuli-Responsive Polymers as Active Layers for Sensors 163
Sergio Granados?]Focil
5.1 Introduction 163
5.2 Stimuli?]Responsive Soft Materials 164
5.2.1 Thermally Responsive Polymers 165
5.2.2 Field?]Responsive Polymers 166
5.2.3 Biologically Responsive Polymer Systems 168
5.2.4 Multistimuli?]Responsive Materials 172
5.2.5 Stimuli?]Responsive Hydrogels 175
5.3 Sensors from Stimuli?]Responsive Hydrogel Layers 176
5.3.1 pH Sensors 178
5.3.2 Metal Ion Sensors 179
5.3.3 Humidity Sensors 180
5.3.4 DNA Sensors 181
5.3.5 Glucose Sensors 181
5.4 Ionophore?]Based Sensors 182
5.4.1 Ion?]Selective Electrodes 182
5.4.2 Chromoionophores 184
5.4.3 Optodes 185
5.4.4 Dynamic Optodes 185
5.5 Challenges and Opportunities 186
References 187
6 Self?]Stratifying Polymers and Coatings 197
Jamil Baghdachi, H. Perez, and Punthip Talapatcharoenkit
6.1 Introduction 197
6.2 Basic Concepts of Self?]Stratification 200
6.2.1 Evaporation Effect 200
6.2.2 The Surface Tension Gradient 201
6.2.3 The Substrate?]Wetting Force 203
6.2.4 Kinetically Controlled Reactions 205
6.3 Conclusions 214
References 215
7 Surface?]Grafted Polymer Coatings: Preparation, Characterization, and Antifouling Behavior 218
Marc A. Rufin and Melissa A. Grunlan
7.1 Introduction 218
7.2 Surface?]Grafting Methods 219
7.2.1 "Grafting?]From" Method 219
7.2.2 "Grafting?]To" Method 220
7.3 Behavior of Surface?]Grafted Polymers 222
7.3.1 Conformation of Grafted Chains 222
7.3.2 Chain Migration 223
7.4 Characterization Techniques 224
7.4.1 Ellipsometry 224
7.4.2 Contact Angle 224
7.4.3 X?]ray Photoelectron Spectroscopy 225
7.4.4 Scanning Probe Microscopies 226
7.5 Antifouling Coatings 227
7.5.1 Surface?]Grafted PEG 228
7.5.2 Surface?]Grafted Zwitterionic Polymers 229
7.6 Summary 230
References 230
8 Partially Fluorinated Coatings by Surface?]Initiated Ring?]Opening Metathesis Polymerization 239
G. Kane Jennings and Carlos A. Escobar
8.1 Basic Concepts 239
8.2 Surface Chemistry 241
8.3 Kinetics of Film Growth 242
8.4 Surface Energy of pnbfn Films 243
8.5 Micromolding Sip 245
8.6 Conclusions and Outlook 247
Acknowledgments 248
References 248
9 Fabrication and Application of Structural Color Coatings 250
Zhehong Shen, Hao Chen, and Limin Wu
9.1 Introduction 250
9.2 General Methods of Colloidal Assembly 252
9.2.1 Flow?]Induced Deposition 252
9.2.2 Field?]Induced Deposition 257
9.3 Colloidal Assembly of Soft Polymer Spheres 260
9.4 Uses of Structural Colors 265
9.4.1 Photonic Paper 265
9.4.2 Coloring and Protection of Substrates 267
9.4.3 Color Responses 268
9.4.4 Structural Color Coatings with Lotus Effects and Superhydrophilicity 272
9.4.5 Structural Color as Effect Pigments 273
9.5 Conclusions and Outlook 274
References 274
10 Antibacterial Polymers and Coatings 280
Jamil Baghdachi and Qinhua Xu
10.1 Introduction 280
10.2 Basic Concepts 281
10.2.1 Coatings that Resist Adhesion 282
10.2.2 Coatings that Release Toxins 282
10.3 Polymers and Antimicrobial Coating Binders 283
10.3.1 Polymeric Coatings with QA Groups 283
10.3.2 Polymers with Quaternary Phosphonium Groups 284
10.3.3 Norfloxacin?]Containing Polymers 286
10.3.4 Polymeric N?]Halamines 288
10.4 Addition of Inorganic Particles 289
10.4.1 Titanium Dioxide 289
10.4.2 Zinc Oxide 290
10.4.3 Silver Compounds 290
10.5 Conclusions and Outlook 292
References 292
11 Novel Marine Antifouling Coatings: Antifouling Principles and Fabrication Methods 296
Yunjiao Gu and Shuxue Zhou
11.1 Introduction 296
11.2 Marine Biofouling 297
11.3 Enzyme?]Based Coatings 300
11.4 Fouling Release Coatings 302
11.4.1 Principles of FR Coatings 302
11.4.2 Hybrid Silicone?]Based FR Coatings 304
11.4.3 Fluoropolymer?]Based FR Coatings 305
11.5 Nonfouling Coatings 305
11.5.1 Principles of NF Coatings 306
11.5.2 PEG?]Based NF Coatings 307
11.5.3 Poly(Zwitterionic) NF Coatings 311
11.5.4 Other Hydrophilic NF Materials 313
11.6 Bioinspired Micro?]Topographical Surfaces 316
11.6.1 AF Principles of Bioinspired Microtopographical Surfaces 316
11.6.2 Approaches to the Production of AF Coatings with Surface Topographies 320
11.7 Amphiphilic Nanostructured Coatings 322
11.7.1 Principles of Amphiphilic Nanostructured Coatings 323
11.7.2 PEG?]Fluoropolymers Amphiphilic Coatings 325
11.7.3 Other Amphiphilic AF Polymers 329
11.7.4 Characterization Techniques 329
11.8 Summary 331
References 333
Index 338
CHAPTER 1
Transparent Organic-Inorganic Nanocomposite Coatings
Shuxue Zhou and Limin Wu
Department of Materials Science and Advanced Coatings Research Center of Ministry of Education of China, Fudan University, Shanghai, P.R. China
1.1 INTRODUCTION
The combination of organic and inorganic ingredients is the most popular strategy to achieve coatings with optimal properties. The two components with different or even opposing intrinsic properties can be mixed at the microscale, nanoscale, and even molecular level. Composite coatings at the microscale actually are conventional pigmented coatings with an opaque appearance. Molecular hybrids were first reported in the 1980s and are an early form of organically modified ceramics (Ormocers) wherein the organic groups act as an inorganic network modifier or network former [1, 2]. These products were further developed in this century as organic phase-dominated materials with an unmatured inorganic phase especially as crystalline inorganics. Nanoscale hybrid coatings based on an organic matrix are actually organic-inorganic nanocomposite coatings (OINCs). The inorganic domain is a dispersed phase with at least one dimension on the nanometer size regime (1-100 nm). In the past 15 years, OINCs have attracted broad research interest both in academics and in industries. Many papers and patents have been published related to OINCs.
Based on Rayleigh scattering theory, the transmission (T) of light through the heterogeneous coatings like OINCs can be calculated according to the following equation:
(1.1)where L is the thickness of the coatings, rp is the radius of the scattering element (namely, the inorganic phase), ?p is the volume fraction of the inorganic phase, ? is the wavelength of the incident light, and np and nm are the refractive indices of the inorganic phase and the polymer matrix, respectively. It can be clearly seen from Equation (1.1) that the transparency of OINCs depends on the size of the dispersed phase, coating thickness, and the refractive index (RI) difference between the organic matrix and the inorganic phase. The OINCs have a high transparency because the size of the inorganic phase is significantly smaller than the wavelength of light. Normally, 40 nm is an upper limit for nanoparticle diameters to avoid intensity loss of transmitted light due to Rayleigh scattering and thus achieve highly transparent OINCs.
In addition to excellent transparency, OINCs can efficiently combine the advantages of rigidity, functionality (optic, electric, magnetic, etc), durability (to chemicals, heat, light) of the inorganic phase with the softness and processability of the organic phase. They can find wide applications in abrasion- and scratch-resistant coatings, optical coatings, barrier coatings, corrosion-resistant coatings, antibacterial coatings, electrically conductive coatings, self-cleaning coatings (superhydrophilic and superhydrophobic), heat-resistant coatings, flame-retardant coatings, etc. The OINCs are often the best solution especially for those cases that require high coating transparency.
The nanophase of the OINCs can be either simply introduced by blending with ex situ nanostructure materials or in situ by a sol-gel process or intercalation. The blending method is similar to the fabrication process of conventional organic coatings wherein the inorganic nanostructure materials rather than microparticles are used as the filler. As for the sol-gel method, the inorganic nanophase can be created in the formulating step or the drying step in bottom-up strategies. In most cases, the nanophases precursors are first prehydrolyzed and then blended with a binder. Normally, amorphous metal oxides and metal nanophases in OINCs can be fabricated with this method. The intercalation method is particularly suitable for layered inorganic fillers, for example, clay. In this method, the process is quite analogous to the blending method. However, the inorganic nanophase is in situ generated based on a top-down strategy.
In this chapter, the general fabrication principles and performance features of OINCs as well as partially transparent OINCs are presented. Primarily focus is on transparent OINCs with mechanically reinforced, high RI, ultraviolet (UV)-shielding, near-infrared (NIR) light-shielding, barrier, conductive coatings, etc. Because the pigmented OINCs even with the aforementioned performance are opaque, they are beyond the scope of this chapter and not discussed further.
1.2 FABRICATION STRATEGIES
1.2.1 Blending Method
Blending is frequently adopted for inclusion of ex situ nanostructure materials into organic coatings. These nanostructures include nanoparticles, nanofibers, nanorods, nanotubes, nanosheets, etc. Among them, nanoparticles are the most common nanofiller for the fabrication of transparent OINCs. The particles can be nanopowders or colloidal. Figure 1.1 shows the typical morphology of colloidal silica and pyrogenic silica in coatings. Colloidal silica particles are spherical and individually dispersed in the organic matrix, whereas pyrogenic silica particles are irregular aggregates. Table 1.1 summarizes some typical nanostructure materials. All nanostructure materials could be possibly used to produce mechanically reinforced OINCs. Nevertheless, the functionality of nanostructure materials determines the functional performance of the resulting OINCs.
FIG. 1.1 TEM micrographs of nanocoatings filled with 10 wt.% nanoparticles: colloidal nanosilica (left) and pyrogenic nanosilica (right).
Reprinted with permission from Ref. 3. © 2011 Elsevier.
TABLE 1.1 The Physical Properties of Some Typical Nanostructure Materials
Type Density, (g/cm3) Mohn's Hardness Refractive Index Functionality SiO2 2.2 7 1.42-1.46 Mechanical hardness Al2O3 4.0 9 1.7-1.8 Mechanical hardness ZrO2 5.6-6.3 6.5 2.13-2.14 Mechanical hardness, high refractive index TiO2 3.9 6.0-6.5 2.7 UV absorption, photocatalytic activity, anti-bacterial property ZnO 5.6 4.5 2.02 UV absorption, photocatalytic activity, anti-bacterial property ITO 4.3-7.0 - 1.85-1.95 Electric conductivity, near infrared light-shielding ATO - - - Electric conductivity, near infrared light-shielding CaCO3 2.9 3.0 1.6 Mechanical strength Silver 10.5 2.5-4 0.13 Anti-bacterial property, optical Boehmite 3.0-3.1 3.0-3.5 1.64-1.67 Anisotropic mechanics Carbon nanotube ~1.3 25 GPa for single walleda - Electric conductivity, anisotropic mechanics Graphene - - - Electric conductivity, anisotropic mechanics and barrier propertya Indentation hardness.
The nanoparticles in sols are already nanoscale. Thus, they can be directly mixed with other ingredients [4]. However, these metal oxide nanoparticles in commercial sols are generally amphorous, which is useless for the fabrication of functional OINCs. In recent years, colloidal sols using crystalline oxide nanoparticles from nonaqueous synthesis or controlled hydrolysis have been successfully acquired, opening a new route to obtain transparent functional OINCs.
The nanoparticles can be embedded into coatings during formulation. Sometimes, the incorporation of nanoparticles is moved forward to the stage of resin synthesis, that is, the so-called "in situ polymerization" method. This approach enhances the dispersion of nanoparticles and/or the interaction between nanoparticles and the polymer.
1.2.1.1 Deagglomeration of Nanopowder
Nanoparticles in the powder state aggregate due to their large surface areas. The aggregates deteriorate the mechanical properties and transparency of OINCs [5]. Therefore, dispersing nanoparticles in resins or coatings is an extremely important task for the field. Various techniques have been developed for dispersing nanopowders into different liquids, including high shear rate mixing, sonication, milling (or grinding), and microfluidic techniques. Figure 1.2 summarizes the possible routes for preparation of waterborne or solvent-based nanocomposite coatings from nanopowders. Ultrasonic and microfluidic techniques are usually used in the lab but are infeasible for industrial applications. High shear-rate mixing deagglomerates nanopowders somewhat, but not completely. Bead milling is the most efficient current technique.
