III . 2 Preparation of synthetic membranes 72 III . 3 Phase inversion membranes 75 III. 3. 1 Preparation by evaporation 76 III . 3. 2 Precipitation. from the vapour phase 76 III . 3. 3 Precipitation by controlled evaporation 76 Thermal precipitation 76 III . 3. 4 III . 3. 5 Immersion precipitation 77 Preparation techniques for immersion precipitation 77 III . 4 Flat membranes 77 III . 4. 1 78 III . 4. 2 Tubular membranes 81 III . 5 Preparation techniques for composite membranes 82 III. 5. 1 Interfacial polymerisation Dip-coating 83 III . 5. 2 III . 5. 3 Plasma polymerisation 86 III . 5. 4 Modification of homogeneous dense membranes 87 III . 6 Phase separation in polymer systems 89 III . 6. 1 Introduction 89 III . 6. 1. 1 Thermodynamics 89 III . 6. 2 Demixing processes 99 III . 6. 2. 1 Binary mixtures 99 III . 6. 2. 2 Ternary systems 102 III . 6. 3 Crystallisation 104 III . 6. 4 Gelation 106 III . 6. 5 Vitrification 108 III . 6. 6 Thermal precipitation 109 III . 6. 7 Immersion precipitation 110 III . 6. 8 Diffusional aspects 114 III . 6. 9 Mechanism of membrane formation 117 III. 7 Influence of various parameters on membrane morphology 123 III. 7. 1 Choice of solvent-nonsolvent system 123 III . 7. 2 Choice of the polymer 129 III . 7. 3 Polymer concentration 130 III . 7. 4 Composition of the coagulation bath 132 III . 7. 5 Composition of the casting solution 133 III . 7.