Photoinitiators

Jean-Pierre Fouassier is Emeritus Professor of the University of Haute Alsace, Mulhouse. His research interests are focused on time resolved laser spectroscopy of photoinitiatiors and the design of efficient systems for applications of photopolymerization reactions in various areas.Jacques Lalevée is Professor at the Ecole Nationale Superieure de Chimie de Mulhouse ENSCMu at the University of Haute Alsace. His research focus is on free radical chemistry and the design of new polymerization initiating systems.

• Volume 1Introduction xvPart I Photopolymerization Reactions and Photoinitiators: Backgrounds 11 Backgrounds in Photopolymerization Reactions: A Short Overview 31.1 Photopolymerization and Photo-cross-linking 31.1.1 Reactions 31.1.2 Photoinitiation Step 41.1.3 Different Kinds of Photopolymerization Reactions 41.1.4 Monomers and Oligomers 41.1.5 Photopolymerizable Formulations 61.1.6 UV Curing 61.1.7 Imaging 61.1.8 Controlled Photopolymerization 71.2 Photopolymerization Reactions 71.2.1 Monomers and Oligomers in Photopolymerization Reactions 71.2.1.1 Monomers/Oligomers in Radical Photopolymerization 81.2.1.2 Monomers/Oligomers in Cationic Photopolymerization 101.2.1.3 Monomers in Thiol–ene Photopolymerization 111.2.1.4 Monomers in Charge Transfer Photopolymerization 121.2.1.5 Monomers in Anionic Photopolymerization 121.2.1.6 Monomers in Photoinduced Copper-Catalyzed Azide–Alkyne Cycloaddition 121.2.1.7 Monomers in Photoactivated Hydrosilylation Reactions 121.2.2 Monitoring the Photopolymerization Reaction 131.2.3 Kinetic Laws in Photopolymerization Reactions 131.2.3.1 Radical Photopolymerization 131.2.3.2 Cationic Photopolymerization 151.2.3.3 Dependence of Photopolymerization Rate 151.2.3.4 Laser-Induced Photopolymerization 161.2.3.5 Kinetics of the Photopolymerization in Bulk 171.2.4 Oxygen Inhibition 181.2.5 Role of Light Stabilizers 181.2.6 Competitive Absorption of Light by a Pigment 201.2.7 Role of Environment in the Polymerization Reaction 211.3 Implementation of Photopolymerization Reactions and Brief Overview of the Applications 221.3.1 Light Sources for Photopolymerization Reactions 221.3.1.1 Electromagnetic Radiation 221.3.1.2 Characteristics of a Light Source 231.3.1.3 Available Light Sources 231.3.2 Brief Overview of the Application Areas 27References 292 Photoinitiating System 352.1 Characteristics of a Photoinitiating System 352.1.1 General Properties 352.1.2 Absorption of Light by a Molecule 352.1.2.1 Absorption Spectrum 352.1.2.2 Molecular Orbitals and Energy Levels 362.1.2.3 Absorption of Light and Optical Transitions 362.1.2.4 Absorption Intensity 372.1.2.5 Reciprocity Law 382.1.2.6 Multiphotonic Absorption 382.1.3 Jablonski’s Diagram 392.1.4 Kinetics of the Excited State Processes 402.1.5 Photoinitiator and Photosensitizer 402.1.6 Absorption of a Photosensitive System 422.1.7 Initiation Step of a Photoinduced Polymerization 422.1.7.1 Production of Initiating Species 432.1.7.2 Competitive Reactions in the Excited States 432.1.7.3 Reactivity in Bulk vs. Solution: Role of Diffusion 432.1.7.4 Cage Effects 442.2 Approach of Photochemical and Chemical Reactivity 452.3 Reactivity of a Photosensitive System 462.4 Efficiency vs. Reactivity 48References 49Part II Photoinitiators: Structures, Excited States, Reactivity, and Efficiency 553 Cleavable Radical Photoinitiators 593.1 Benzoyl Chromophore-Based Photoinitiators 593.1.1 Benzoin Derivatives 613.1.2 Benzoin Ether Derivatives 623.1.2.1 Absorption of Benzoin Ethers 623.1.2.2 Photolysis of Benzoin Ethers 633.1.2.3 Cleavage Process in Benzoin Ethers 643.1.2.4 Initiating Radicals in Benzoin Ethers 643.1.2.5 Substitution Effects in Benzoin Ether Derivatives 643.1.2.6 Effect of Lewis Acids on Benzoin Ethers 653.1.3 Halogenated Ketones 653.1.4 Dialkoxyacetophenones and Diphenylacetophenones 653.1.5 Morpholino and Amino Ketones 663.1.6 Hydroxy Alkyl Acetophenones 673.1.7 Ketone Sulfonic Esters 693.1.8 Thiobenzoate Derivatives 703.1.9 Sulfonyl Ketones 703.1.10 Oxysulfonyl Ketones 713.1.11 Oxime Esters 713.2 Hydroxy Alkyl Heterocyclic Ketones 723.3 Benzophenone and Thioxanthone Moiety-Based Cleavable Systems 723.3.1 Benzophenone Phenyl Sulfides 723.3.2 Ketosulfoxides 723.3.3 Benzophenone Thiobenzoates 733.3.4 Benzophenone Sulfonyl Ketones 733.3.5 Silyl Moiety Containing Cleavable Benzophenone and Thioxanthone Derivatives 733.4 Benzoyl Phosphine Oxide Derivatives: a C—P Bond Breaking 733.5 Trichloromethyl Triazines 763.6 Biradical Generating Ketones 763.7 Diketones 763.8 Silyl Glyoxylates 773.9 Peroxides 773.10 Peresters 783.11 Azides and Aromatic Bis-azides 793.12 Carbon–Germanium Cleavable Bond-Based Derivatives 793.13 Carbon–Tin Cleavable Bond-Based PIs 813.14 Carbon–Silicon Cleavable Bond-Based PIs 813.14.1 Bis Silyl Ketones 813.14.2 Tetraacylsilanes 823.15 Carbon–Nitrogen Cleavable Bond Containing PIs 823.15.1 Azo Derivatives 823.15.2 Phenacyl Pyridinium Derivatives 833.15.3 Phenacyl Ethyl Carbazolium Derivatives 833.15.4 N-substituted Diazabicyclononanes 833.16 Boron–Sulfur Cleavable Bond Containing PIs 843.17 Boron–Nitrogen Cleavable Bond Containing PIs 843.18 Disilane Derivatives 843.19 Diselenide and Diphenylditelluride Derivatives 853.20 Sulfur–Carbon Cleavable Bond-Based Derivatives 853.21 Disulfide Derivatives 863.22 Oxyamines 863.22.1 Alkoxyamines 863.22.2 Silyloxyamines 863.23 Barton’s Ester Derivatives 873.24 Hydroxamic and Thiohydroxamic Acids and Esters 873.25 Ion Pair PIs 873.25.1 Organoborates 883.25.2 Polyoxometalate–onium Salt Ion Pairs 883.25.3 Naphthalimide–Iodonium Salt Ion Pairs 893.26 Organometallic Compounds 903.26.1 Titanocenes 903.26.2 Miscellaneous Organometallic PIs 903.26.2.1 Chromium Complexes 903.26.2.2 Aluminate Complexes 903.26.2.3 Zirconocene Dichloride 913.26.2.4 Zinc Complexes 913.27 Metal Salts and Metallic Salt Complexes 913.28 Miscellaneous Systems 913.28.1 Acetone 913.28.2 Phosphine Oxide Derivatives 923.28.3 Sulfur–Silicon Cleavable Bond-Based Derivatives 923.28.4 Digermane and Distannane Derivatives 923.28.5 Halogenated Ketones 923.28.6 Hydroxy Alkyl-Conjugated Ketones 923.28.7 Dibenzothiophenes 933.28.8 Self-initiating Monomers 933.28.9 Self-assembled PI Monolayers 933.28.10 Silicon–Hydride Terminated Surface 933.28.11 Semiconductor Nanoparticles 933.28.12 Perovskites (Nanocrystals) 94References 954 Two-Component Radical Photoinitiators 1174.1 Ketone/Hydrogen Donor and Ketone/Electron/Proton Donor Couples 1174.1.1 Basic Mechanism 1174.1.2 Hydrogen Donors and Electron/Proton Donors 1194.1.2.1 Amines 1194.1.2.2 Thio Derivatives 1214.1.2.3 Benzoxazines 1214.1.2.4 Aldehydes 1224.1.2.5 Acetals 1224.1.2.6 Hydroperoxides 1224.1.2.7 Silanes 1224.1.2.8 Silylamines 1234.1.2.9 Metal(IV) and Amine Containing Structures 1234.1.2.10 Silyloxyamines 1234.1.2.11 Germanes and Stannanes 1244.1.2.12 Borane Complexes 1244.1.2.13 Phosphorus Containing Compounds 1244.1.2.14 Monomers 1254.1.2.15 Photoinitiator Itself 1254.1.2.16 Alcohols and THF 1254.1.2.17 Polymer Substrates 1254.2 Ketone/Electron Acceptor Systems 1254.2.1 Ketone/Iodonium Salt 1254.2.1.1 Benzophenone (or Thioxanthone)/Iodonium Salt 1254.2.1.2 Silyl Ketone/Iodonium Salt 1264.2.1.3 Silylglyoxylate/Iodonium Salt 1264.2.1.4 Ketone/Novel Iodonium Salts 1264.2.2 Ketone/Triazine 1264.3 Ketone/Diethoxyacetate Salt 1274.4 Well-Known and Novel Type II Ketones 1274.4.1 Benzophenone Derivatives 1274.4.1.1 Benzophenone 1274.4.1.2 Modified Benzophenones 1284.4.2 Thioxanthone Derivatives 1324.4.2.1 Thioxanthone: Absorption and Excited States 1324.4.2.2 Well-Known Thioxanthones as Models 1344.4.2.3 Novel Thioxanthones 1364.4.3 Diketones 1384.4.3.1 Aromatic Diketones 1384.4.3.2 Camphorquinone 1394.4.4 Ketocoumarins 1404.4.5 Coumarins 1404.4.6 Alkyl Phenylglyoxylates 1414.4.7 Silyl Ketones 1414.4.8 Silyl Glyoxylates 1414.4.9 Other Type II Ketone Skeletons 1424.4.9.1 Anthraquinones 1424.4.9.2 Fluorenones 1424.4.9.3 Naphthoquinones 1424.4.9.4 Aliphatic Ketones 1424.4.9.5 Ketoesters 1424.4.9.6 Cleavable Ketones as Type II Photoinitiators 1434.4.9.7 Aldehydes 1434.4.9.8 Acetals 1434.5 Dye-Based Systems 1434.5.1 Usual Dye/Amine Systems 1434.5.1.1 Eosin or Rose Bengal as Models 1434.5.1.2 Dye/Amine Interaction: Some Kinetic Data 1444.5.2 Dye/Additive Systems: Some Examples 1444.5.2.1 Dyes: Overview 1444.5.2.2 Additives 1464.5.2.3 Some Typical Examples of Dye/Additive Systems 1474.5.3 Dye-Linked Additive Ion Pairs 1494.5.4 Dye-Linked Photoinitiator or Co-initiator-Based Systems 1494.5.5 Dye/Onium Salts: A Revival of Interest 1504.5.5.1 Dyes with D–π-A–π-D Arrangements 1504.5.5.2 NIR Polymethine Dyes 1504.5.5.3 Squaraine Dye 1514.5.5.4 Other Examples of Novel Dyes for Novel Applications 1514.6 Organometallic Compound-Based Systems 1654.6.1 Metallocene/Additive 1654.6.2 Metal Carbonyl/Additive 1654.6.3 Metal Complex/Olefin 1684.6.4 Organometallic Complex/Amine 1684.6.5 Copper Complex/Iodonium Salt 1684.6.6 Miscellaneous Organometallic Compound/Additive Couples 1684.6.6.1 Organometallic Compound/Ketone-Based Systems 1684.6.6.2 Ferrocenium Salt/Additive 1694.7 Ketone/Ketone-Based Systems 1694.8 Photoinitiator/Peroxide (or Hydroperoxide)-Based Systems 1704.8.1 Radical Photoinitiator/Peroxide Interactions 1704.8.2 Photobase/Peroxide 1704.9 Type I Photoinitiator/Additive 1714.10 Donor/Acceptor Charge Transfer Systems 1724.10.1 Old Systems 1724.10.2 Amine/Iodonium Salt Systems 172References 1735 Cationic Photoinitiating Systems 1995.1 Diazonium Salts 1995.2 Onium Salts 2005.2.1 Iodonium and Sulfonium Salts 2005.2.1.1 Basic Model Compounds 2005.2.1.2 Photopolymerization Reaction 2015.2.1.3 Absorption Properties 2025.2.1.4 Decomposition Processes of Iodonium Salts 2025.2.1.5 Decomposition Processes of Sulfonium Salts 2055.2.2 Development of N, P, O (and Others) Centered Onium Salts 2065.2.3 Development in the Iodonium and Sulfonium Salt Series 2065.2.3.1 Substitution Effects in Iodonium and Sulfonium Salt Derivatives 2075.2.3.2 Recent Developments in Iodonium and Sulfonium Salt Derivatives 2095.3 Organometallic Derivatives 2125.3.1 Transition Organometallic Complexes 2125.3.2 Inorganic Transition Metal Complexes 2145.3.3 Nontransition Metal Complexes 2145.4 Photosensitized Decomposition of Onium Salts 2145.4.1 Backgrounds 2145.4.1.1 Photosensitization Through Energy Transfer 2145.4.1.2 Photosensitization Through Electron Transfer 2155.4.2 Novel Developments in Electron Transfer Reactions 2195.4.2.1 Photosensitizer-Linked Cationic Monomer 2195.4.2.2 Pyrilium Salt/Hydroperoxide 2195.4.2.3 Novel Series of Photosensitizers 2195.5 Unconventional Cationic Systems 2225.5.1 Upconversion Nanoparticles 2225.5.2 Carbon Nanotubes 222References 2226 Anionic, Photoacid, and Photobase Initiating Systems 2416.1 Anionic Photoinitiators 2416.1.1 Inorganic Complexes 2416.1.2 Organometallic Complexes 2426.1.3 Cyano Derivative/Amine System 2436.1.4 Ketoprofen 2436.1.5 Amines 2436.2 Nonionic Photoacid Generators Systems 2436.2.1 Sulfonates 2446.2.2 N-Arylsulfonimides 2446.2.3 Naphthalimides 2456.2.4 Non-salt Pyrene Derivatives 2456.2.5 α-Disulfones 2456.2.6 Fullerenes 2456.2.7 Terarylene-Based Compounds 2466.3 Photobase Generators Systems 2466.3.1 Oxime Esters 2466.3.2 Carbamates 2466.3.3 N-benzylated Structure-Based Photobases 2466.3.4 Benzoylformamides 2476.3.5 Ammonium Chromophore Containing Borate Salts 2476.3.6 Anionic Chromophore Containing Ammonium Salts 2486.3.7 Super Base Containing PBGs 2486.3.8 Other Miscellaneous Systems 249References 2497 Reactivity of Radicals Toward Various Substrates: Understanding and Discussion 2577.1 Backgrounds 2577.1.1 Direct Detection of Radicals 2577.1.2 Addition of Radicals to Double Bonds 2587.2 Reactivity of Radicals Toward Oxygen, Hydrogen Donors, Monomers, and Additives 2597.2.1 Alkyl and Related Carbon-Centered Radicals 2597.2.2 Aryl Radicals 2617.2.3 Benzoyl Radicals 2627.2.4 Acrylate and Methacrylate Radicals 2637.2.5 Aminoalkyl Radicals 2657.2.5.1 Reactivity 2657.2.5.2 Role of the Class of the Amine 2687.2.5.3 N-Phenyl Glycine Derivatives 2687.2.5.4 Chain Length Effect 2687.2.5.5 Regioselectivity of the Hydrogen Abstraction Reaction 2697.2.5.6 Aminoalkyl Radicals and the Halogen Abstraction Reaction 2707.2.5.7 Reactivity Under Air 2707.2.6 Phosphorus-Centered Radicals 2717.2.7 Thiyl Radicals 2737.2.8 Sulfonyl and Sulfonyloxy Radicals 2767.2.9 Silyl Radicals 2777.2.9.1 Characteristics 2777.2.9.2 Particular Behavior of the Tris(trimethylsilyl)silyl Radical 2797.2.9.3 Reactivity and Photoinitiation Under Air 2807.2.9.4 Silylamines 2817.2.9.5 Other Sources of Silyl Radicals 2827.2.10 Oxyl Radicals 2837.2.11 Peroxyl Radicals 2847.2.11.1 Characteristics 2847.2.11.2 Interaction with H-Donors 2867.2.11.3 Interaction with Monomers 2877.2.11.4 Interaction with Triphenylphosphine 2877.2.11.5 SH2 Substitution 2887.2.11.6 Other Oxyls and Peroxyls 2887.2.12 Aminyl Radicals 2887.2.13 Germyl and Stannyl Radicals 2907.2.13.1 Characteristics 2907.2.13.2 Reactivity 2907.2.13.3 Reactivity Under Air 2907.2.13.4 Reactivity and Structure of (TMS)3Ge• vs. (TMS)3Si• 2917.2.14 Boryl Radicals 2927.2.14.1 Characteristics 2927.2.14.2 Reactivity 2937.2.14.3 Reactivity Under Air 2957.2.14.4 Photoinitiation Under Air 2957.2.15 Lophyl Radicals 2957.2.16 Iminyl Radicals 2967.2.17 Metal-Centered Radicals 2967.2.18 Propagating Radicals 2987.2.19 Radicals in Controlled Photopolymerization Reactions 2997.2.19.1 Photoiniferters and Dithiocarbamyl Radicals 2997.2.19.2 Light-Sensitive Alkoxyamines and Generation of Nitroxides 3007.2.20 Reactivity of Radicals Toward Metal Salts 3027.2.21 Radical/Onium Salt Reactivity in Free Radical Promoted Cationic Photopolymerization (FRPCP) 302References 3058 Role of Experimental Conditions on the Performance of a Radical Photoinitiator 3218.1 Role of Viscosity 3228.2 Role of the Surrounding Atmosphere 3248.3 Role of the Light Source 3258.4 Role of Monomer Matrix: An Example 327References 3289 Reactivity and Efficiency of Radical Photoinitiators 3339.1 Reactivity of Photoinitiators 3349.1.1 Excited State Processes 3349.1.2 Cleavage Processes 3359.1.3 Electron and Hydrogen Transfer Reactions 3369.1.4 Electron Transfer Reactions 3379.1.5 Role of Bond Dissociation Energy 3379.1.5.1 Role of Bond Dissociation Energy in Cleavable Systems 3389.1.5.2 Role of Bond Dissociation Energy in Non-cleavable Systems 3409.1.6 Photoinitiator Quenching by Monomers 3409.1.7 Reactivity of the Initiating Radical: Addition to Double Bonds 3429.1.8 Reactivity of the Initiating Radical: Interaction with Hydrogen Donors 3449.2 Reactivity/Efficiency of Photoinitiators: Examples of Structural Effects 3459.2.1 Reactivity/Efficiency Relationships in Fluid Media 3459.2.1.1 Examples of Oil-Soluble Photoinitiating Systems 3459.2.1.2 Examples of Water-Soluble Photoinitiating Systems 3499.2.2 Reactivity/Efficiency Relationships in Heterogeneous Media 3509.2.3 Reactivity/Efficiency Relationships in Bulk 3529.2.4 Polymerization Efficiency in Bulk: Examples of Some Effects 3549.3 Up-to-date Approach of the Reactivity and the Structure/Property Relationships 359References 362Volume 2Introduction xvPart III High Performance Photoinitiating Systems: Achievements, Trends, Challenges, Opportunities and Applications 37510 Design of Photoinitiators for Enhanced Performance: A Mechanistic Approach 37711 Multicomponent Radical Photoinitiating Systems for Enhanced Reactivity 39912 Photoinitiating Systems for Free Radical Promoted Cationic Polymerization 43513 Photoinitiators for Novel Specific Properties 46314 Industrial Photoinitiators: A Brief Overview 531Part IV Photoinitiators for Specific Reactions and Traditional or Emerging Innovative Applications 53715 Photoinitiators and Light Sources: Novel Developments 53916 Photoinitiators for Controlled/Living Polymerization Reactions 55917 Photoinitiators in Specific Polymerization Processes 59118 Photoinitiators for the Curing of Thick or Filled Samples 64119 Photoinitiators in Various Sectors of Industrial Applications 657Conclusion 699Index 703