for his unfailing support and friendship throughout the course of this work. His approach to science and his deep physical intuition will undoubtly influence me throughout all my career. I truly appreciate his concern, understanding, and encouragement, especially during the difficult moments of my stay in Princeton.Many thanks to my second reader, Professor Robert K. Prud'homme, for his genuine interest and useful suggestions, and for the long-term loan of several TSI components. I am indebted to Professor William W. Graessley for his help with the characterization of the polymers, and for giving me the opportunity to perform some important measurements at Exxon. Special mention goes out to Professor William B. Rüssel for his help with important non-technical matters. I would like to acknowledge the entire staff of the department for its support. Special thanks to Peggy Pearce and Betty Bixby for their help with administrative matters, and to Archie Harkness for machining several parts of my apparatus.Outside of the department, I wish to especially thank Professor Alexander J. Smits, in Mechanical and Aerospace Engineering, for his enthusiastic support, and for offering me to use the space and facilities of the Gas Dynamics Laboratory, in Forrestal Campus, in order to perform my experiments. Professor Behrouz Chehroudi, from the University of Illinois at Chicago, helped me a lot with the LDV signal processing, and ν let me use his data acquisition program. Dr. Man Won Kim and Mr. Robert W. Thomas, both from Exxon, have been extremely helpful with the molecular weight and shear viscosity measurements. Professor Antony N. Beris, from the University of Delaware, made helpful suggestions and was always generous with his time. Professor Daniel C. Tsui, in Electrical Engineering, is thanked for the long-term loan of his electromagnet. Several improvements to this thesis are the result of long discussions with my groupmates. Thanks to Martin Wittmann, Dave Davidson, Fred Lim, Frank Torres, Gary Christensen, Mike Koerner, and Rick Mifflin. I would like to especially thank Martin and Dave. The solutions preparation, construction of drag reduction apparatus, and the Exxon experiments, have all been results of a joint effort with Martin, who also answered several questions about UNDC during the after hours. Dave helped me use his nonlinear fitting and IBM plotting routines, and discussed with me numerous topics in non-Newtonian fluid mechanics during coffee breaks. I am particularly grateful to Yiannis Dimitratos for his friendship, for several great weekends together, and for lending me his camera indefinitely. Many thanks to my good friends Dave & Dawn Davidson (for several great evenings, and for convincing me that cows are intelligent), Martin Wittmann (for six years of common experiences in the CAVE), and Stelios Tsinontides (for our numerous discussions, ranging from chemical engineering to presidential politics), and also to Prabhu Nott,