Nonthermal Plasmas for Materials Processing: Polymer Surface Modification and Plasma Polymerization

Cover
Half-Title Page
Series Page
Title Page
Copyright Page
Contents
Preface
1 Introduction
	References
2 Basic Principles of the Plasma State of Matter
	2.1 Characteristics and Physical Properties of Plasmas
		2.1.1 Ionization Degree, Energy Content and Classification
		2.1.2 Quasi-Neutrality, Debye Shielding Length, Plasma Frequency
		2.1.3 Ambipolar Diffusion
		2.1.4 High-Frequency Conductivity and Permittivity of Non-Thermal Plasmas
		2.1.5 Charged Particles in External Magnetic Field
		2.1.6 Thermal and Non-Thermal Plasmas
		2.1.7 Plasma Kinetics and Transport Equations
	References
	2.2 Elementary Processes and Collision Cross Section
		2.2.1 Classification of Collision Processes in Non-Thermal Plasmas
		2.2.2 The Collision Cross Section
	References
	2.3 Interaction of Non-Thermal Plasmas with Condensed Matter
		2.3.1 Stationary Plasma Boundary Sheath and Bohm Criterion
		2.3.2 Plasma Boundary Sheath in Front of the Floating Surface
		2.3.3 Generalized Bohm Sheath Criterion
		2.3.4 High-Voltage Plasma Sheath
		2.3.5 Non-Stationary Plasma Sheaths
	References
	2.4 Non-Thermal Plasmas of Electric Gas Discharges
		2.4.1 Overview
		2.4.2 The Electric Breakdown in Gases
		2.4.3 The Glow Discharge
		2.4.4 Glow Discharges at Harmonic Electric Fields, RF and MW Plasmas
		2.4.5 High-Voltage Breakdown at Atmospheric Pressure, Corona and Barrier Discharge
	References
3 Plasma Diagnostics
	3.1 Introduction
	3.2 Overview of Diagnostic Methods Used for the Characterization of Non-Thermal Plasmas
	3.3 Analysis of Charged and Neutral Plasma Particles in Non-Thermal Plasmas
		3.3.1 Electric Probe Measurements
		3.3.2 Special Case for Single Electric Probe Measurements in Radio-Frequency (RF) Plasmas
	3.4 Microwave Interferometry
		3.4.1 Microwave Propagation in Non-Magnetic Plasmas
		3.4.2 Heterodyne Microwave Interferometry at 160 GHz
		3.4.3 Electron Density Analysis in CCP and ICP with Argon and Oxygen as Processing Gas
	3.5 Mass Spectrometry
		3.5.1 Principle of Mass Spectrometry
		3.5.2 Quadrupole Mass Spectrometry
		3.5.3 Analysis of Low-Pressure Plasmas by Quadrupole Mass Spectrometry
	References
	3.6 Plasma and Laser-Induced Optical Emission Spectroscopy
		3.6.1 Spectral Analysis of Plasma Emission (VUV, UV-vis-NIR)
			3.6.1.1 Optical Emission Spectroscopy (OES) of Low-Pressure Plasmas – Examples
			3.6.1.2 Determination of the Rotation Temperature from Atmospheric O₂ A Band, PP and PQ Branch
			3.6.1.3 Determination of Ground State Particle Density from Plasma Emission Spectrum
			3.6.1.4 Abel Inversion
			3.6.1.5 Phase Resolved Optical Emission Spectroscopy (PROES) of RF Plasmas
		3.6.2 Laser-Induced Fluorescence (LIF) Spectroscopy
	3.7 IR Broadband and IR Laser Absorption Spectroscopy
		3.7.1 Fourier Transform Infrared (FTIR) Spectroscopy for Gas Phase Analysis
			3.7.1.1 Principle of FTIR Spectroscopy
			3.7.1.2 FTIR Gas Phase Spectroscopy of RF Plasma with Precursor Ethylenediamine and Argon
		3.7.2 Infrared Tunable Diode Laser Absorption Spectroscopy (IR-TDLAS)
			3.7.2.1 Configuration of the IR-TDLAS Experiment
			3.7.2.2 Principle Procedure for Measuring Single Absorption Lines
			3.7.2.3 IR-TDLAS of Fluorocarbon Radicals and Reaction Products in CF₄ or CF₄+H₂ RF Plasmas
	References
4 Methods of Polymer and Polymer Surface Analysis
	4.1 Introductory Remarks
	4.2 Photoelectron Spectroscopy (XPS) or Electron Spectroscopy for Chemical Analysis (ESCA)
	4.3 Secondary Ion Mass Spectrometry
	4.4 NEXAFS – Use of Synchrotron Radiation
	4.5 Infrared Reflection Absorption Spectroscopy (IRRAS)
	4.6 Size-Exclusion Chromatography (SEC)/Gel Permeation Chromatography (GPC) and Field-Flow-Fractionation (FFF)
	4.7 Matrix-Assisted Laser/Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-ToF-MS)
	4.8 Electrospray Ionization Time-of-Flight Mass Spectrometry (ESI-ToF-MS)
	4.9 Overview of Methods
	References
5 Chemical Interactions Between Polymer and Plasma
	5.1 Introduction
	5.2 General Conflict Between High Plasma Energies and Low Dissociation Energies of Bonds in Polymers
	5.3 Chemical Bonds and Functional Groups in Polymers
	5.4 Response of Different Types of Polymers to Plasma Exposure
	References
6 Polymer Surface Functionalization
	6.1 Important Properties of Polymers
	6.2 Why Pretreatment?
	6.3 Chemical and Structural Problems of Polymers Provoked by Plasma Pretreatment
	6.4 Inevitability of Simultaneous Functionalization and Polymer Degradation
	6.5 Physical and Chemical Attacks of the Plasma to Polyolefin Surfaces
	6.6 Chemical Grafting onto Plasma-Exposed Polymer Surfaces
	6.7 Oxidation of Polymers by Exposure to the Oxygen Low-Pressure Plasma
		6.7.1 Introduction of O-Functional Groups Onto Polymer Surfaces
		6.7.2 Nature of Oxygen-Plasma Introduced Functional Groups
		6.7.3 Identification of O-Functional Groups Bonded Onto the Topmost Polymer Surface Layer
		6.7.4 Fit Strategy of O-Functional Groups as Introduced by D. T. Clark
		6.7.5 Other Surface-Sensitive Analytical Methods
		6.7.6 Derivatization of O-Functional Groups
		6.7.7 Identification of Radicals by Chemical Labeling or ESR Spectroscopy
		6.7.8 Physical Characterization of Oxygen Plasma
		6.7.9 Use of Plasma Afterglow for Polymer Modification
		6.7.10 Surface Oxidation and Etching (see also the special section on etching)
		6.7.11 Changes in Supermolecular Structure in Subsurface Layers Upon Exposure to Oxygen Plasma
		6.7.12 Changes in Polymer Structure Generated by Exposure to the Vacuum UV Radiation of the Oxygen Plasma
		6.7.13 Depth of Modification
		6.7.14 Accelerated Artificial Aging of Polymers by Exposure to Low-Pressure Oxygen Plasma
		6.7.15 Kinetics of Crosslinking
		6.7.16 Time-Dependence of Oxygen Introduction
		6.7.17 Reaction Details of Poly(ethylene terephthalate) Upon Exposure to Oxygen Plasma
		6.7.18 Optimum Time of Exposure to Oxygen Plasma for Formation of O-Functional Groups and Preventive Avoidance of Structural Degradation and Decomposition
		6.7.19 Dependence of Oxygen Introduction on Plasma Parameters
		6.7.20 Behavior of Molecular Orientation and Chain Structure Upon Exposure to Oxygen Plasma
	References
7 Sensitivity of Polymer Units and Functional Groups Towards Exposure to Oxygen Plasma
	7.1 Introductory Remarks
	7.2 Behavior of Polymer Structure Upon Exposure to Oxygen Plasma
	7.3 Etching Behavior of Polymers Upon Exposure to Oxygen Plasma
	7.4 Classification of Polymers with Similar Degradation Behavior on Exposure to Oxygen Plasma
	7.5 Stability of Surface Functionalization and Superposition with Post-Plasma Effects Upon Exposure to Air
	7.6 Surface Oxidation of Polyolefins Using Atmospheric-Pressure Plasmas (DBD, APGD or Corona Discharge, Spark Jet, etc.)
		7.6.1 Dielectric Barrier Discharge
		7.6.2 Plasma-Assisted and Plasma-Less Spraying of Intact High-Molecular-Weight Polymers at Atmospheric Pressure
	7.7 Oxidation of Carbon Nanomaterials
		7.7.1 Graphene
		7.7.2 Oxidation of Carbon Fibers
	7.8 Generation of Monosort O-Functional Groups at Polyolefin Surfaces as Anchor Points for Grafting of Molecules
		7.8.1 OH Groups
		7.8.2 COOH Groups
		7.8.3 CHO Groups
		7.8.4 Super-Acidic Groups via Oxyfluorination
		7.8.5 Functionalization of Fluorine-Containing Polymers with O-Functional Groups
	7.9 Post-Plasma Chemical Grafting of Molecules, Oligomers or Polymers Onto OH-Groups
	7.10 Course of Oxidation from Virgin Polymer to Oxidized Polymer and Finally to CO₂
		7.10.1 Problems of Depth Profiling of Oxidation at Polymer Surface
		7.10.2 Binding Energies of Covalent Bonds in Polyolefins
		7.10.3 Analogy Between Thermal Oxidation and Auto-Oxidation of Paraffins
		7.10.4 Decarboxylation and Emission of CO₂
		7.10.5 Formation of Gaseous Low-Molecular-Weight Etch Products by Oxygen Plasma Treatment
		7.10.6 Introduction of Oxygen-Containing Groups at Surface of Polyolefins as a Forerunner of Gasification/Etching
		7.10.7 Formation and Characterization of Low-Molecular-Weight Oxidized Material (LMWOM)
		7.10.8 LMWOM Formation by Re-Deposition of Etched Fragments
		7.10.9 Depth Profiling of O/C from Surface to Bulk
			7.10.9.1 Angle-Resolved XPS
			7.10.9.2 Dynamic SIMS
			7.10.9.3 Sputtering
			7.10.9.4 Post-Plasma Oxidation
		7.10.10 Tentative Mechanism
	References
8 Ammonia and Bromine Plasmas
	8.1 Generation of Monosort NH₂ Groups
		8.1.1 Brief History of Plasma-Induced Introduction of Primary Amino Groups Into the Surface of Polyolefins
		8.1.2 Ways to Produce Amino Groups at Polymer Surfaces
		8.1.3 Ammonia, Nitrogen-Hydrogen and Hydrazine Plasmas
		8.1.4 Carbon Fibers Exposed to Ammonia Plasma
		8.1.5 Oxygen Post-Plasma Introduction After Ammonia Plasma Exposure
		8.1.6 Invalidity of Le Chatelier’s Principle in Low-Pressure Plasma
		8.1.7 Time Dependence of N and NH₂ Introduction on Exposure of the Ammonia Plasma into Polyolefin Surfaces
		8.1.8 Hydrogenation Effect of NH₃
		8.1.9 Modification of Polyolefin Within a 2µm-Deep Surface Layer
		8.1.10 Bulk Analysis by NMR
		8.1.11 Summary of All Attempts to Increase the Yield in NH₂
		8.1.12 Ammonia Plasma – Undesired Side and Post-Plasma Reactions
		8.1.13 Deposition of Plasma Polymers Carrying Amino Groups as an Alternative to Ammonia Plasma Treatment
		8.1.14 Chemical Labeling and Protection of NH₂ Groups
		8.1.15 Post-Plasma Chemical Grafting Onto NH₂-Groups
		8.1.16 Amino Groups at Polymer Surfaces – A Summary
	8.2 Bromine Plasma
		8.2.1 Chemical Aspects
		8.2.2 Theoretical Considerations of the Plasma Process Using Bromine
		8.2.3 Comparison of Halogen Chemistry
		8.2.4 Behavior of Plasma-Brominated Surface Layers in Solvents
		8.2.5 Plasma Polymerization of Vinyl and Allyl Bromide
		8.2.6 Attempts to Increase Br Concentration in the Plasma Polymer Layers by Admixture of Br₂ to Allyl Bromide or Bromoform
		8.2.7 Dependence of Bromine Introduction Onto Polyolefin Surfaces on Plasma Parameters
		8.2.8 Electron Temperature in the Bromoform Plasma
		8.2.9 Yields in Introduction of Other Halogens
		8.2.10 Plasma Bromination of Other Polymers
		8.2.11 Chemical Post-Plasma Synthesis of New Monosort Functional Groups by Conversion of Plasma-Introduced Bromine Groups
		8.2.12 Grafting of Molecules onto Br Groups by Nucleophilic Substitution
		8.2.13 Grafting Density at Polyolefin Surfaces
		8.2.14 Comparison of Surface Bromination of Polyolefins with Other Processes
		8.2.15 Plasma Bromination of Graphitic and Carbon Surfaces
		8.2.16 Efficiency in Bromination and Grafting of Carbon in Comparison to Polyolefins
		8.2.17 Conclusions to Plasma Bromination
	References
9 Noble Gas Plasmas
	9.1 Characterization of Noble Gas Plasmas
	9.2 Polymer Crosslinking Caused by Noble Gas Plasmas
	9.3 Vacuum-Ultra Violet Radiation Emitted by Noble Gas Plasmas
	References
10 Plasma Polymerization
	10.1 Introduction
	10.2 Milestones in History
	10.3 General Features of Plasma Polymers
	10.4 Mechanisms of Plasma Polymerization
		10.4.1 Absence of Often Proposed Plasma-Induced Radical Chain-Growth Polymerization to Linear Macromolecules?
		10.4.2 Radical Polymerization of Allyl Monomers
		10.4.3 Ion-Molecule Reactions
		10.4.4 Role of Polymerizing Intermediates
		10.4.5 Crosslinking
		10.4.6 Polymerization in Continuous-Wave Plasma
		10.4.7 Pulsed Plasma Polymerization
		10.4.8 Pressure and Plasma-Pulsed Discharge
	10.5 Special Aspects of Plasma Polymerization
		10.5.1 Fragmentation-(poly)Recombination
		10.5.2 Atomic Polymerization
		10.5.3 Rearrangement and Crosslinking of the Already Deposited Plasma Polymer Layer by Plasma Particle Bombardment and Vacuum-UV
		10.5.4 Formation of Unsaturations
		10.5.5 Formation of CH₃ Groups
		10.5.6 H/C Ratio in Plasma Polymers and “Quasi-Hydrogen-Plasma”
		10.5.7 Hydrogen Exchange Between Plasma and Polymer Deposit
		10.5.8 Existence of Crystalline and Supermolecular Structures in Plasma Polymers
		10.5.9 Influence of Monomer or Precursor Type
		10.5.10 Role of Pressure and Flow Rate
		10.5.11 Role of Energy Dose
		10.5.12 Plasma Polymerization of n-Hexane and Other Hydrocarbons
		10.5.13 Dependence of Deposition Rate on Position of Sample in the Plasma Zone
		10.5.14 Retention of Monomer Structure in Plasma Polymer – Changes in Aromaticity and Substitution
		10.5.15 Molecular Weight Distribution
		10.5.16 Energetic Balancing
	10.6 Locus of Plasma Polymerization
		10.6.1 Adsorption or Gas Phase?
		10.6.2 Powder Formation
		10.6.3 Redeposition of Etched Products as Layer
		10.6.4 Special Effects of Irradiation of Growing Polymer Layer by Vacuum-UV Radiation from Plasma
		10.6.5 Formation of a “Polymer Skin”
		10.6.6 Graft Polymerization
	10.7 Plasma Polymers with Monosort Functional Groups
		10.7.1 OH Groups
		10.7.2 COOH Groups
		10.7.3 NH₂ Groups
	10.8 Attempts to Increase the Yield of Functional Group
		10.8.1 Optimization of Plasma Conditions for Generation of NH₂ Groups
		10.8.2 Attempts to Increase the Concentration of NH₂ Groups by Addition of Ammonia to Allylamine Plasma Polymerization
		10.8.3 Alternative Methods
		10.8.4 Plasma-Produced Amino Groups for Promotion of Adhesion
	10.9 Plasma Copolymerization
		10.9.1 General Remarks on the Background of Copolymerization and Its Definition
		10.9.2 Copolymers with Allyl Alcohol
		10.9.3 Copolymers with Acrylic Acid
		10.9.4 Allylamine Copolymers
	10.10 Grafting Onto Plasma Polymers as Special Case of ‘Graft-Copolymerization’
		10.10.1 General Aspects
		10.10.2 Direct Grafting Onto Radical Sites
		10.10.3 Grafting Onto Peroxy Radicals/Hydroperoxides
		10.10.4 Reactions with OH Groups
		10.10.5 Reactions with COOH Groups
		10.10.6 Reactions with NH₂ Groups
		10.10.7 Reactions with Br Groups
		10.10.8 Other Methods
	10.11 Significant Side Reactions
		10.11.1 Details of the IR Bands at 2200 cm-¹
		10.11.2 DSC Results
		10.11.3 Post-Plasma Oxidation
		10.11.4 Attempts to Eliminate Post-Plasma Oxidations
	10.12 Plasma Polymers Deposited by Atmospheric-Pressure Plasmas
	References
11 Technical Applications
	11.1 Introduction
	11.2 Adhesion Promotion
		11.2.1 Polymer Surface Modification
		11.2.2 Combination of Plasma Pretreatment and Wet-Chemical Post-Plasma Treatment
		11.2.3 Deposition of Adhesion-Promoting Polymer Films
			11.2.3.1 Direct Grafting
			11.2.3.2 Grafting via Peroxy Route
			11.2.3.3 Co-Evaporation or Sputtering of Metals During Plasma Polymerization
			11.2.3.4 Plasma Polymer Coating
	11.3 Cleaning
	11.4 Wettability
	11.5 Etching of Polymers
		11.5.1 Preparation and Excavation of Supermolecular Structures of Polymers for Their Characterization by Electron Microscopy
		11.5.2 Ashing
	11.6 Barrier Layers or Barrier Formation
		11.6.1 Organic and Inorganic Barrier Layer for Limiting Diffusion
		11.6.2 Fluorination of Polymers
	11.7 Anti-Fouling Layers
	11.8 Sterilization
	11.9 Water Purification and Desalination
	11.10 Flame Protection
	11.11 Textile Modification
	11.12 Modification of Carbon Fibers and Nanotubes
	11.13 Silent Discharge and Excimer Radiation
	11.14 Conducting Films
	11.15 Scratch-Resistant Coatings
	11.16 Underwater Plasma
	References
Index