Electrospun Polymer Nanofibers

"Discussing the electrospinning process, the book covers in great depth the current research interest in nanoscience and nanotechnology, especially electrospinning of polymer nanofibers. The main distinction of the proposed book from others devoted to the electrospinning process is in the considiferation of the problem in question from the physical point of view. Focusing on physical aspects, the book contains physical basics regarding the unique features of electrospun polymer nanofibers and the electrospinning resulting in fabrication of these nanofibers."--Provided by publisher Cover 1 Half Title 2 Title 4 Copyright 5 Contents 6 Preface 10 Chapter 1. Introduction 12 Part I The Necessary Basics 16 Chapter 2. Nano-objects 18 2.1 What “Nano-objects” Mean 18 2.2 Physical Properties of Nano-objects Compared to the Bulk 22 2.2.1 Mechanical Properties 23 2.2.2 Thermodynamic Properties 28 2.2.3 Size-Dependent Behavior of Nano-objects 30 Chapter 3. Experimental Examination of Electrospun Polymer Nanofibers 32 3.1 Experimental Examination of Nanofiber Mats 34 3.2 Experimental Examination of Single Nanofiber 37 3.2.1 Atomic Force Microscopy 37 3.2.2 Tensile Test 40 3.2.3 Resonance Method 41 Part II Nanofiber Fabrication 48 Chapter 4. Electrospinning of Polymer Nanofibers 50 4.1 Spinability of Polymer Solution 52 4.2 Hydrodynamics of Electrospinning 57 4.3 Hydrodynamic Instabilities of Spinning Jet 61 4.4 Solvent Evaporation and Polymer Solidification 67 4.5 Post-fabrication Relaxation 75 4.5.1 Experimental Observations 77 4.5.2 Preliminary Estimates 79 4.5.3 Kinetic Equations Describing the System Evolution 81 4.5.4 Pressure and Velocity Distribution 82 4.5.5 Meniscus Moving (Kinetics of Solvent Evaporation 83 4.5.6 Experimental Proof of Post-fabrication Relaxation 85 4.6 Post-processes in Electrospun Tubular Nanofibers 86 4.6.1 Formation of Gas Bubbles 87 4.6.2 Buckling of Tubular Nanofiber 89 Chapter 5. Polymer Dynamics in Semi-dilute Solution During Electrospinning 96 5.1 Theoretical Model Describing Stretching of a Polymer Topological Network 98 5.1.1 Initial State of Entangled Semi-dilute Polymer Solution 98 5.1.2 Axial Stretching of an Entangled Polymer Network during Electrospinning 99 5.1.3 Radial Contraction of an Entangled Polymer Network during Electrospinning 103 5.2 Experimental Observations of Polymer System Evolution under High Stretching 106 5.2.1 Radial Contraction of an Entangled Polymer Network during Electrospinning 106 5.2.2 Stretch-Induced Phase Separation in Polymer Solutions 110 5.3 Disentanglement of Polymer Topological Network in Further Stages of Electrospinning 118 5.3.1 Multiple Necking 119 5.3.2 Short Fiber Fabrication 120 5.3.3 Simulation of Disentanglement Processes with the Help of a Pulley System 122 5.3.4 Spontaneous Symmetry Breaking in a Thermodynamic System of Pulleys 125 5.3.4.1 Mathematical description 126 5.3.4.2 Motion analysis 128 5.3.4.3 The energy balance 132 5.3.4.4 The thermodynamic system 133 5.3.4.5 Numerical simulations 134 Part III Unique Properties of Electrospun Polymer Nanofibers 136 Chapter 6. Size-Dependent Behavior 138 6.1 Size-Dependent Behavior of Electrospun Nanofibers 138 6.1.1 Size-Dependent Behavior in Mechanical Properties 138 6.1.2 Size-Dependent Behavior in Thermodynamic Properties 141 6.2 Do Surface Effects Explain the Unique Elasticity of Polymer Nanofibers 143 6.3 Concept of Near-Surface Layer 149 6.4 Confinement Concept 151 6.4.1 Physical Model of the Phenomenon 153 6.4.2 Theoretical Estimations 154 Chapter 7. Explanations of the Size-Dependent Behavior by a Physicist: Some Possible Reasons and Mechanisms 158 7.1 Confinement Mechanism of Electrospun Polymer Nanofibers Reinforcement 158 7.1.1 Structure of an Amorphous Nanofiber Polymer Matrix 161 7.1.2 Mathematical Model for Polymer Nanofiber Elongation 165 7.1.3 Scaling Properties of the Size-Dependent Elastic Modulus of Electrospun Polymer Nanofibers 170 7.2 Shifting of Melting Point for Semi-Crystalline Polymer Nanofibers 175 7.2.1 Theoretical Background 176 7.2.2 Experimental Results and Discussions 180 7.3 Nonequilibrium State of Polymer Matrix Inside Electrospun Nanofibers 182 7.3.1 Orientation of Polymer Macromolecules as a Result of Electrospinning 182 7.3.2 Stretching of Polymer Matrix of Electrospun Nanofibers 188 7.3.3 Orientation versus Stretching under Confinement 191 Final Remarks 194 Bibliography 196 Index 204 Annotation Discussing the electrospinning process, the book covers in great depth the current research interest in nanoscience and nanotechnology, especially electrospinning of polymer nanofibers. The main distinction of the proposed book from others devoted to the electrospinning process is in the consideration of the problem in question from the physical point of view. Focusing on physical aspects, the book contains physical basics regarding the unique features of electrospun polymer nanofibers and the electrospinning resulting in fabrication of these nanofibers