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Kinetic Study of Coordinative Chain Transfer Polymerization of Ethylene by Neodymium Metallocene Catalysts

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Kinetic Study of Coordinative Chain Transfer Polymerization of Ethylene by Neodymium Metallocene Catalysts Kinetic study of coordinative chain transfer polymerization of ethylene by neodymium metallocene catalysts Rodolfo André da Costa Fialho Ribeiro Thesis to obtain the Master of Science Degree in Chemical Engineering Supervisors Prof.ª Dr.ª Maria do Rosário Gomes Ribeiro Dr. Christophe Boisson Examination Committee Chairperson: Prof. Dr. Carlos Manuel Faria de Barros Henriques Supervisor: Prof.ª Dr.ª Maria do Rosário Gomes Ribeiro Member of the Committee: Prof. Dr. João Carlos Moura Bordado November 2015 This page was intentionally left blank. ii Abstract Ethylene polymerizations at 70-90ºC in toluene were performed using a combination of ∗ Cp2NdCl2Li(OEt2)2 (Cp* = C5Me5) or {Me2SiFlu2Nd(µ-BH4)[(µ-BH4)Li(THF)]}2 (Flu = C13H8) neodymium complexes with n-butyl-n-octyl-magnesium used as both alkylating and chain transfer agent. Kinetic studies were performed for the two catalytic systems by varying the Mg/Nd ratio, which is a critical parameter for polymerization control. Both systems were able to perform a controlled polymerization of ethylene and displayed the same phases on the kinetic profiles, reflecting the Coordinative Chain Transfer Polymerization mechanism. The effect of the polymerization temperature was studied for the determination of the propagation activation energy using the Arrhenius equation. A -1 ∗ value of 17.3 kcal.mol was obtained for the Cp2NdCl2Li(OEt2)2/n-butyl-n-octyl-magnesium system. The {Me2SiFlu2Nd(µ-BH4)[(µ-BH4)Li(THF)]}2/n-butyl-n-octyl-magnesium system did not display a linear Arrhenius plot and consequently the activation energy was not determined for this catalyst. Specific molar masses were targeted in order to evaluate the polymerization control efficiency. The co-solvent effect was also explored via addition of dibutyl ether (Bu2O). Unimodal molar mass distributions were obtained, and polymerization rates were enhanced in the presence of the co-solvent without affecting the polymerization control. Finally, a sampling experiment was performed to observe the pseudo-living behaviour of the Coordinative Chain Transfer Polymerization mechanism. Keywords: Neodymium, polyethylene, metallocene, kinetics, mechanism, coordinative chain transfer polymerization iii This page was intentionally left blank. iv Resumo Polimerizações de etileno a 70-90ºC em tolueno foram realizados usando uma combinação de ∗ complexos de neodímio Cp2NdCl2Li(OEt2)2 (Cp* = C5Me5) ou {Me2SiFlu2Nd(µ-BH4)[(µ-BH4)Li(THF)]}2 (Flu = C13H8) com n-butil-n-octilmagnésio, sendo este usado tanto como agente alquilante e como agente de transferência de cadeia. Estudos cinéticos foram realizados para os dois sistemas catalíticos variando a razão Mg/Nd, que é um parâmetro critíco para o controlo da polimerização. Ambos os sistemas permitiram realizar polimerizações controladas de etileno e mostraram as mesmas fases nos perfis cinéticos, reflectindo o mecanismo de polimerização de coordenação por transferência de cadeia. O efeito da temperatura na polimerização foi estudada de modo a determinar a energia de activação da propagação usando a -1 ∗ equação de Arrhenius. Um valor de 17.3 kcal.mol foi obtido para o sistema Cp2NdCl2Li(OEt2)2/n-butil- n-octilmagnésio. Para o sistema {Me2SiFlu2Nd(µ-BH4)[(µ-BH4)Li(THF)]}2/n-butil-n-octilmagnésio não foi obtido um ajuste linear do gráfico de Arrhenius, pelo que a energia de activação da propagação não foi determinada. Polimerizações tendo como alvo massas molares específicas foram realizadas a fim de avaliar a eficiência do controlo da polimerização. O efeito do co-solvente foi também explorado pela adição de éter dibutílico (Bu2O). Distribuições unimodais de massas molares foram obtidas e a velocidade de polimerização aumentou na presença do co-solvente sem afectar o controlo da polimerização. Por último, foi realizada uma reacção de polimerização com extracção de amostras ao longo do tempo de forma a observar o comportamento pseudo-vivo do mecanismo de polimerização de coordenação por transferência de cadeia. Palavras-Chave: Neodímio, polietileno, metaloceno, cinética, mecanismo, polimerização de coordenação por transferência de cadeia v This page was intentionally left blank. vi Acknowledgments This thesis is the end of a life chapter. It would not be possible without the help, advice and collaboration of some great people, to whom I express a word of gratitude. First of all, I would like to thank my supervisors at the C2P2 laboratory, Dr. Christophe Boisson and Dr. Frank D’Agosto, for their guidance, scientific advice and support during this internship and the final revision of this manuscript. Also, I would like to thank my IST supervisor, Professor Maria Rosário Ribeiro, for the opportunity to do this internship, fruitful discussions and suggestions/remarks given for the revision of this work. I am very grateful to Islem Belaid for her advice, support and patience throughout my entire internship. I also would like to thank Dr. Sébastien Norsic for teaching me all the techniques and polymerization skills which were essential to the completion of this work. A word of appreciation to Manel Taam and Olivier Boyron for all the knowledge and guidance in the SEC analysis. I would like to thank my colleagues from C2P2 for making my stay in Lyon a great experience and also my university colleagues for the friendship during the last five years. A huge thanks to all my closest friends for their friendship and companionship during this last five years, and especially over the course of my life. We shared good and bad moments and I am sure we will be great friends for life. I am deeply grateful to my entire family for their support, especially to my uncle Miguel and to my grandmothers Conceição and Albertina. Last but not least, I would like to dedicate this thesis to my parents, António and Luísa, as a sign of respect and recognition for all their efforts and dedication throughout my entire life. Their love and unconditional support are essential for my happiness and without them I could not achieve my life objectives. A todos, muito obrigado! vii This page was intentionally left blank. viii Table of Contents ABSTRACT ............................................................................................................................................ III RESUMO ................................................................................................................................................. V ACKNOWLEDGMENTS ....................................................................................................................... VII TABLE OF CONTENTS ......................................................................................................................... IX LIST OF FIGURES ................................................................................................................................. XI LIST OF TABLES .................................................................................................................................XIV LIST OF ACRONYMS ..........................................................................................................................XVI LIST OF SYMBOLS ............................................................................................................................XVII 1. INTRODUCTION .............................................................................................................................. 1 1.1. CONTEXT AND OBJECTIVE ............................................................................................................ 1 1.2. THESIS STRUCTURE ..................................................................................................................... 2 2. LITERATURE REVIEW .................................................................................................................... 3 2.1. BRIEF POLYETHYLENE OVERVIEW ................................................................................................ 3 2.2. POLYETHYLENE SYNTHESIS AND NEODYMIUM METALLOCENE CATALYSTS ....................................... 5 2.2.1. Free Radical Polymerization .............................................................................................. 5 2.2.2. Coordination Polymerization .............................................................................................. 6 2.2.2.1. Phillips Catalysts .......................................................................................................................... 8 2.2.2.2. Ziegler-Natta Catalysts ................................................................................................................ 8 2.2.2.3. Late Transition Metals Catalysts .................................................................................................. 8 2.2.2.4. Metallocenes ................................................................................................................................ 8 2.2.3. Conclusion ........................................................................................................................ 11 2.3. COORDINATIVE CHAIN TRANSFER POLYMERIZATION .................................................................... 12 2.3.1. Concept ............................................................................................................................ 12 2.3.2. Specialty Polymers .......................................................................................................... 15 Production of olefin multiblock copolymers via chain shuttling polymerization:
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