1 Survey of Experimental Results.- 1.1 Preparatory Considerations.- 1.1.1 Introductory Remarks.- 1.1.2 Some Theoretical Basic Concepts.- 1.1.3 Short Review of Mechanical Techniques of Measurements.- 1.1.3.1 Apparatus for the Measurement of Dynamic Shear Moduli.- 1.1.3.2 The Cone-and-Plate Rheometer (Rheogoniometer).- 1.1.3.3 Capillary and Slit Rheometers.- 1.1.3.4 Tensile Rheometers.- 1.1.4 Some Illustrative Results of Mechanical Measurements.- 1.1.4.1 Dynamic Shear Moduli as Functions of the Circular Frequency.- 1.1.4.2 Prescribed Strain Histories.- 1.1.4.3 Prescribed Stress.- 1.1.4.4 Influence of Molecular Parameters.- 1.2 Flow Birefringence Measurements.- 1.2.1 Principles of Measurements.- 1.2.2 A Survey of Flow Birefringence Techniques Suitable for Polymer Melts.- 1.2.2.1 Arrangements for the Measurement of Flow Birefringence in Elongation.- 1.2.2.2 Apparatusses for Birefringence Measurements in the 1, 2-Plane of the Shear Flow.- 1.2.2.3 Apparatusses Derived from Slit and Capillary Rheometers.- 1.2.3 Results of Flow Birefringences Measurements.- 1.2.3.1 The Linear Stress-Optical Rule and its Limits of Validity.- 1.2.3.2 Further Evidence for the Validity of the Linear Stress-Optical Rule.- 1.2.3.3 Zero Shear Properties and Molecular Mass: Evaluation of Cone-and-Plate Measurements.- 1.2.3.4 Evaluation of Slit Rheometer Measurements.- 1.2.3.5 Time-Temperature Superposition and Non-Linear (Equilibrium) Properties.- 1.2.3.6 Further Comments on the Influence of Molecular Mass (Distribution).- 1.2.3.7 Measurement of the Optical Equivalent to the Second Normal Stress Difference.- 1.2.3.8 Transient Flow Birefringence Effects.- References of Chapter 1.- 2 Quasi-Molecular Phenomenological Theories.- 2.1 Rubber Elasticity.- 2.1.1 Results of the Kinetic Theory.- 2.1.1 Behaviour of Real Rubbers.- 2.2 The Linear Stress-Optical Relation.- 2.2.1 Results of the Kinetic Theory of Flexible Cain Molecules.- 2.2.2 Can the Linear Stress-Optical Rule be Understood also without the Assumption of a Temporary Network Structure?.- 2.3 The Most Simple Rubberlike Liquid Model.- 2.3.1 Introduction.- 2.3.2 Formulation of the Theory.- 2.3.2.1 Application to Several Types of Shear Flow.- 2.3.2.2 Application to Elongational Flow.- 2.3.2.3 Problems with Inversion.- 2.3.3 Preliminary Discussion.- 2.3.4 Equivalent Formulations of the Discussed Theory.- 2.3.5 Incorporation of Temperature Changes into the Integral Equation.- 2.3.6 Optical Means to Prove the Validity of the Simple Rubberlike Liquid Theory.- 2.4 More General Discussion of Quasi-Linear Models.- 2.4.1 The Corotational Model.- 2.4.2 Codeformational Models.- 2.4.2.1 Introduction.- 2.4.2.2 Covariant and Contravariant Time Derivatives.- 2.4.2.3 Equations Equivalent to Lodge's Original Formulation.- 2.4.3 The Independent Alignment Model.- 2.4.3.1 Formal Presentation.- 2.4.3.2 Some Physical Considerations.- 2.4.3.3 Evaluation.- 2.4.3.4 Shear Flow.- 2.4.3.5 Elongational Flow.- 2.4.3.6 Damping Functions.- 2.4.3.7 Postscript.- 2.5 Quasi-Linear Models Containing Adjustable Elements.- 2.5.1 Introduction.- 2.5.2 The n-Measure of Strain.- 2.5.3 The Experimental Damping Function.- 2.5.3.1 Introduction.- 2.5.3.2 Experimental Evidence in Shear.- 2.5.3.3 Non-Linear Shear Creep.- 2.5.3.4 How to Find the Damping Function for an Extension Experiment.- 2.5.3.5 Non-Linear Extensional Creep.- 2.5.4 The Irreversibility of the Disentanglement Process.- 2.5.4.1 Introduction.- 2.5.4.2 The Triple Step-Strain Experiment in Shear.- 2.5.4.3 Description of Recovery Experiments.- 2.5.5 A Differential Type Constitutive Equation Containing Time Dependent Structural Parameters.- 2.5.5.1 Introduction.- 2.5.5.2 Formulation of the Theory.- 2.5.5.3 Evaluation for Steady Homogeneous Shear Flow.- 2.5.5.4 Description of Other Deformations with Given Strain History.- 2.5.5.5 Creep and Recovery.- 2.5.5.6 Free Volume as a Structural Parameter.- 2.5.6 The Non-Affine Displacement of Temporary Network Junctions.- 2.5.6.1 Description of the Net