Tacticity Control of Polypropylene Using a C2-Symmetric Family of Catalysts

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Tacticity Control of Polypropylene Using a C2-Symmetric Family of Catalysts TACTICITY CONTROL OF POLYPROPYLENE USING A C2-SYMMETRIC FAMILY OF CATALYSTS A Thesis by NATHAN PRENTICE RIFE Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 2007 Major Subject: Chemistry TACTICITY CONTROL OF POLYPROPYLENE USING A C2-SYMMETRIC FAMILY OF CATALYSTS A Thesis by NATHAN PRENTICE RIFE Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved by: Chair of Committee, Stephen A. Miller Committee Members, David E. Bergbreiter Jaime C. Grunlan Head of Department, David H. Russell December 2007 Major Subject: Chemistry iii ABSTRACT Tacticity Control of Polypropylene Using a C2-Symmetric Family of Catalysts. (December 2007) Nathan Prentice Rife, B.S., McMurry University Chair of Advisory Committee: Dr. Stephen A. Miller A family of C2-symmetric catalysts was designed and synthesized with the intent to polymerize propylene. The catalyst was designed to be C2-symmetric for the specific goal that the catalyst would have two identical sites for the propagation of the polymer and therefore eliminate some of the stereoerrors that occur in the propagation of the polymer chain. This catalyst would also operate under simple enantiomorphic site control and therefore the insertion of the monomer would be governed by the ligand surrounding the active site. The ligands were synthesized with increasing degrees of steric bulk with the intention to determine if a catalyst system could generate elastomeric polypropylene. Enantiomorphic site control polypropylene utilizes statistical methods to determine the Si and Re content of a given polymer chain as a function of the variable . Polypropylene samples generated by the catalyst family were analyzed using high temperature pentad analysis of the methyl region to calculate the value. The goal was to observe to be equal to 0.78 provided that the number molecular weight of the polymer was 100,000. The catalyst systems generated polymers with iv values higher and lower than the desired 0.78, indicating too high or too low enantioselectivity of the catalyst systems respectively at Tp = 0°C. v In Honor and Memory of William “Mr. Bill” P. Holland Jr. vi ACKNOWLEDGMENTS Thanking every single person that has ever helped you through grad school can prove to be an impossible task, as even the smallest gesture can be the difference between a great day or a horrible day. However, there are many key people that persisted in always giving a helpful hand, push, shove or other action to keep me on track through these past three years. I first would like to thank my family, who though all the crazy things that have happened have always been willing to support me and encourage me even in my darkest hours. Their willingness to reschedule their lives to accommodate me has not gone without recognition. My father, who sat and talked through so many things with me about life and my mother who always let me know how much she cared by asking so many questions even when she knew I was tired of answering them. Thank you also to Grandpa, Jordan, Courtney, Craig, Linda and Pam for each of you inspiring me to push forward in your own ways. Lastly, to Pops, you always wanted me to succeed, just as you wanted your own children to. I hope that as you watch from heaven that I grow to become the man you always saw me as. Secondly, I want to thank every one of my coworkers in the Miller Crew. Joe Grill and Jesse Reich were both excellent teachers when I began in the lab. Craig Price, Eric Schwerdtfeger, and Paul Zeits helped so much with making the chemistry happen so effortlessly. Andrea Ilg helped me get set up in the lab, helped with classes, and was always willing to be a listening ear to all aspects of life. Last but not vii least, my undergraduate, Robert Mitchell, without you I probably would not have even made it to this point. I would like to especially thank my advisor, Dr. Stephen A. Miller, who supported me throughout my graduate career, probably in more ways than I realize. I also thank my committee Dr. David Bergbreiter and Dr. Jaime Grunlan for their advice. I would also like to that the many other PhDs that gave insight to my chemistry that were not on my committee including Dr. Christine Thomas, Dr. Jeffery Byers, Dr. Brian Connell and Dr. Marcetta Darensbourg. Lastly I want to thank all of my friends that have been so helpful through all of this process. Unfortunately there is not enough space for me to list everyone but I do want to give special thanks to JennaLynn Styskal, Todd Hudnall, Casey Wade, Mark Young, Tyler Cupit, Michelle Broom, and Ron Henriquez. Every single one of you had a hand in this thesis, whether it was giving me ideas to finish a project, or just knowing when it was time to get me out of the lab so I could reset my brain and try again the next day – Thank you to each of you. viii TABLE OF CONTENTS Page ABSTRACT ...........................................................................................................iii DEDICATION ........................................................................................................ v ACKNOWLEDGMENTS...................................................................................... vi TABLE OF CONTENTS .....................................................................................viii LIST OF FIGURES................................................................................................ix LIST OF TABLES .................................................................................................. x CHAPTER I INTRODUCTION........................................................................... 1 II DESIGN AND SYNTHESIS OF A FAMILY OF C2- SYMMETRIC CATALYSTS......................................................... 6 Introduction ......................................................................... 6 Results and Discussion........................................................ 9 Experimental ..................................................................... 14 III POLYMERIZATION OF PROPYLENE USING THE C2- SYMMETRIC CATALYSTS....................................................... 39 Introduction ....................................................................... 39 Results and Discussion...................................................... 40 Experimental ..................................................................... 45 IV SUMMARY AND CONCLUSIONS............................................ 47 REFERENCES...................................................................................................... 49 APPENDIX A ....................................................................................................... 53 VITA ..................................................................................................................... 66 ix LIST OF FIGURES FIGURE Page 1.1 Typical Ziegler-Natta-type heterogeneous system for the polymerization of propylene ............................................................. 2 1.2 Ewen pre-catalyst for the polymerization of propylene .................... 3 1.3 Brintzinger’s ansa-mateallocene for the polymerization of propylene........................................................................................... 4 1.4 The rotation around the backbone of the ligand causes the formation of the rac and meso diastereomers of the ansa-bis- indene zirconocenes. ......................................................................... 5 2.1 Waymouth’s unbriged catalyst for the polymerization of propylene and Resconi’s C2-symmetric catalyst for the polymerization of propylene........................................................................................... 6 2.2 Typical synthesis of a benzofulvene ................................................. 9 2.3 Typical synthesis of the substituted indene with indenyl lithium ..... 10 2.4 The three possible ligands from left to right: the methylidene bridge, the isopropyl bridge and the dimethylsilane bridge .............. 11 2.5 The undesired meso catalyst and the desired rac catalyst................. 12 3.1 The five catalysts that were used for the polymerization of propylene........................................................................................... 40 3.2 A representative spectrum for a polypropylene sample synthesized by catalyst [1] ................................................................................... 42 x LIST OF TABLES TABLE Page 3.1 The average activity of catalysts 1-5.a .............................................. 41 3.2 Pentad data and epsilon value for polypropylene corresponding to catalyst.a ............................................................................................ 43 1 CHAPTER I INTRODUCTION Polyolefins continue to grow in demand and production every year.1 This commodity was fist discovered in 1898 when Hans von Pechmann heated diazomethane and formed a waxy white solid that he called polymethylene;2 we now refer to the same material as polyethylene due to the use of ethylene as the monomer. The first industrial synthesis of polyethylene was discovered, also by accident, in 1933 by Eric Fawcett and Reginald Gibson at Imperial Chemical Industries.3 The two mixed ethylene and benzaldehyde together and subjected it to ~1400 atmospheres at 175 °C in an effort to observe the effects of high pressure and temperature. They produced a white
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