SYNTHESIS AND CHARACTERIZATION OF COPOLYMERS BASED ON 2,3,4,5,6-PENTAFLUOROSTYRENE A Dissertation Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Marta Paz Pazos December, 2005 SYNTHESIS AND CHARACTERIZATION OF COPOLYMERS BASED ON 2,3,4,5,6-PENTAFLUOROSTYRENE Marta Paz Pazos Dissertation Approved: Accepted: ______________________________ ______________________________ Advisor Department Chair Dr. Coleen Pugh Dr. Mark D. Foster ______________________________ ______________________________ Committee Chair Dean of the College Dr. William J. Brittain Dr. Frank N. Kelley ______________________________ ______________________________ Committee Member Dean of the Graduate School Dr. Stephen Cheng Dr. George R. Newkome ______________________________ Committee Member Dr. Wayne L. Mattice ______________________________ Committee Member Dr. Peter L. Rinaldi i i ABSTRACT 2,3,4,5,6-Pentafluorostyrene (PFS) was polymerized in the presence of a solution of polybutadiene (PB) in tetrahydrofuran using benzoyl peroxide as the radical initiator at 50, 60, 80 ºC. The products were graft copolymers of poly(2,3,4,5,6-pentafluorostyrene) (PPFS) into PB. The copolymerizations follow typical free radical polymerization kinetics and behavior, with the rate of propagation proportional to the monomer concentration and the square root of the initiator concentration. Gel permeation chromatography (GPC) equipped with two detectors (UV and refractive index) has allowed us to determine conversion of the monomer, graft efficiency, graft ratio and graft frequency of the grafted products obtained at different temperatures and initiator concentrations, without the need of purification and/or isolation of the final graft copolymer. Conversion of the monomer and graft ratio increase and grafting frequency decreases with increasing temperature and initiator concentration. The grafting efficiencies and grafting ratios are consistent with a system that terminates mainly by combination and whose graft sites are generated by hydrogen abstraction of allylic radicals by initiator primary radicals. Pure graft copolymers were isolated by extracting unreacted PB into hexanes and PPFS homopolymer generated as a side-product into acetone. The similarity of the glass transition temperatures of the PPFS iii grafts and the corresponding extracted PPFS homopolymers confirms that their lengths are approximately equal. We also attempted to react PFS with PB by an ene reaction, which would result in PB modified with perfluorinated rings connected to the PB backbone through a two carbon spacer. However, we were not able to perform the modification either with PB or with model compounds. One of the reactions tested was PFS with β-pinene, which resulted in the copolymerization of them. The copolymer products are composed of isolated units of β-pinene randomly distributed between blocks of PFS segments, as evidenced from their copolymer reactivity ratios and their glass transitions. PFS was also copolymerized in bulk with styrene (at 70 and 25 ºC), 1-vinyl naphthalene (at 70 and 25 ºC) and 2-vinyl naphthalene (at 70 ºC). In all the systems investigated the copolymer reactivity ratios are indicative of copolymerization with strong tendency to alternation. NMR spectroscopy shows evidence for this alternation by both new resonances and shifting of resonances present in the homopolymers. In addition, their thermal behavior is consistent with that of alternating copolymers. They exhibit only one glass transition, at a temperature greater than the weighted average of the glass transitions of the two homopolymers. The alternation tendency and thermal behavior of the copolymers are attributed to strong interactions developed between perfluorinated aromatic rings and regular aromatic hydrocarbons. iv DEDICATION I would like to dedicate this dissertation to all those people who, some way or another, have helped me supported and believed in me, especially to my husband, Jeffrey Schroeder. Without him, this trip would have been a lot more difficult. v ACKNOWLEDGEMENTS In all the years I spent at the University of Akron (and some of the preceding ones), as a graduate student, there have been many events, stories, circumstances that have surrounded the work in the lab, the reading articles, the classes, the tests, the “cumes”… All of them have contributed a little bit to making this possible. I am now taking the opportunity to thank all those people that have taken part in them, so here is the list of some of them (there is really no room for all of them). I would like to start with my advisor, Dr Coleen Pugh. Someone asked me not that long ago what it was that I had enjoyed the most in grad school. I answered that working for her, and I really meant it. I thank her for her dedication, her willingness to discuss, her ability to get the best out of a student, her constructive criticism, and for how much I have learnt from her. I never thought that a person that has not been in the field for more than 45 years could know so much about polymer science. My mother, Mercedes, who is always there, when I most need a mother, despite of not always being so happy with my decisions. I would also like to thank her for having a contagious strength and perseverance that make you want to get to the end, even if it is just for her. v i Also my sister, Silvia, who has taught me that things with a smile always taste better, and she certainly is the only person guaranteed to get it out of me. Thanks for being so proud of your little sister, for thinking so highly of me. I guess that in this sense I would like to include Carlos, my brother in law. Senen, my father. There are certainly a lot of things I should acknowledge him for, but two of them seem more worthwhile to mention. First, for his love to science in general and polymer physical chemistry in particular, which made him my role model. And also for being the person who encouraged me the most to cross the puddle and pursue my doctorate. Dr. Arturo Lopez-Quintela, my advisor as an undergraduate, who very well understood me when I was going through a rough patch, and had the patience to never give up on me. Thanks also to Manuel Faraco, who got me out of the rough patch and handed me the tools and taught me the mechanisms not to fall in it again. Dr. Javier De Abajo, Dr. Jose de la Campa and Dr. Angel Lozano, my advisors and mentor in my brief stay in the Institute of Polymer Science in Madrid. I owe them my first true polymer synthesis, and small molecules too, experience. I am also extremely grateful to them for being so responsive every time I have contacted them. It is so nice to know that you can count on such great scientists. Angela, Belen, Tatiana, Encarna, Oscar, who no matter what, when or where have always been my friends, and who continuously remind me of the vii reasons why I always considered friendship so important. The incredible Foundation “Pedro Barrie de la Maza”, which does amazing things for the sons and daughters of Galicia, where I was born and grew up. They chose me to be the recipient to one of the graduate scholarships that allowed me to come to the University of Akron, and to the Fulbright Commission, who also took care of my admission and some other important stuff. My good friends in grad school, who made the first years a fun experience and helped me not to feel like at home so far away from mine. To Becky, for being such a great friend, and have treated me as family. I also extend my thanks to her parents, Mr. Mike and Mrs. Marlene Sawayda. Thanks also to Paul, not only for being a great friend but also very helpful with academic stuff. And Goran, for his ability to make anyone laugh, or at least try. There are few people who have also contributed or helped me with some of the work I include in this dissertation. Drs. Rinaldi and Dudipala, from the Chemistry Department at The University of Akron, who helped me with most of the NMR spectroscopy work I include in this dissertation. Dr. Harwood, for always being receptive with my questions and requests anytime I had any. Dr. Brittain, for allowing us to use his lab for the synthesis of a monomer. Brian Mirous, for the measurements of the contact angles, and Dr. Taschner for his help with optical rotation measurements. There are also several members in the Pugh group I am grateful to. Andrea, not only for holding my hand in my first (and sometimes second) steps in viii the lab, but also for being a good friend to always count on, especially when I needed a reminder of why I was here in the first place. Thanks also to Mike (Rubal), for his continuous help in everything I asked him for. I would also like to thank Adam for his patience and receptiveness in my first mentoring experience. He made it a lot more enjoyable than I ever thought it would be. Luca Fontana, Fred Good and Dan Sand, from Ashland Inc. They gave me the first job out of school (which gave more sense to all the effort put into), and were very understanding when I needed to finfish my doctoral degree requirements once I had already started. Mr. Jeffrey and Mrs. Marlene Schroder. They have shown continuous interest, excitement and have been so very proud of their daughter in law. Thanks also for having made me feel all the time like part of the family, like a true daughter. And last, my husband, Jeffrey Schroeder, deliberately for the end; whom I thank for his continuous support, encouragement and understanding.