Mechanistic Aspects of the Cationic Polymerization of Para-Substituted-Alpha- Methylstyrenes." (1982)

University of Massachusetts Amherst ScholarWorks@UMass Amherst Doctoral Dissertations 1896 - February 2014 1-1-1982 Mechanistic aspects of the cationic polymerization of para- substituted-alpha-methylstyrenes. J. Michael Jonte University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/dissertations_1 Recommended Citation Jonte, J. Michael, "Mechanistic aspects of the cationic polymerization of para-substituted-alpha- methylstyrenes." (1982). Doctoral Dissertations 1896 - February 2014. 665. https://scholarworks.umass.edu/dissertations_1/665 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Doctoral Dissertations 1896 - February 2014 by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. MECHANISTIC ASPECTS OF THE CATIONIC POLYMERIZATION OF gara-SUBSTITUTED- alpha- METHYLSTYRENFS A Dissertation Presented By J. MICHAEL JONTE Submitted to the Graduate School of the University of Massachusetts in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY May 1 982 Polymer Science and Engineering J. Michael Jonte 1982 All Rights Reserved MECHANISTIC ASPECTS OF THE CATIONIC POLYMERIZATION OF £ara-SUBSTITUTED-a1pha-METHYLSTYRENES A Dissertation Presented By J. MICHAEL JONTE Approved as to style and content by Robert W. Lenz, Chairman of commfittee Shaw L ing Hsu, hljember Roger S. .Porter, Member William J^. MacKnigh't, Department Head Polymer Science and Engineering ; Fur meine liebe Gabi Danke fur Alles, "Nun aber bleibt Glaube, Hoffnung, Liebe, diese drei aber die Liebe ist die grbsste unter ihnen." [I. Kor. 13,13] i V ACKNOWLEDGEMENTS The author wishes to thank Professor Robert W. Lenz not only for his guidance and direction in matters scientific but also for the introduction to the globe-trotting ways of Polymer Science. Thanks also go to research committee members Professors S.L. Hsu and R.S. Porter. Many people on two continents had a part in the completion of this project. The use of the facilities of the Institut fur Makromolekulare Chemie der Universitat Freiburg, West Germany is gratefully acknowledged. Thanks are due to Dr. Michael Droscher for assistance with the solution crystallization experiments and to his family for providing a "zu Hause" in a far-off land. The assistance of Drs. Lieser and Zugenmeier in obtaining x-ray scattering data is also greatly appreciated. Back in the United States, discussions with Mr. John Minter, Dr. Joseph Weber and Professor R.L. Laurence helped finalize the project. The patience and help of Ron Haberkorn and Dave Ruben of M.I.T. in acquiring NMR spectra are deserving many thanks. The financial support of the National Science Foundation through grant number DMR 30-22273 is gratefully acknowledged. The high field NMR experiments were performed at the NMR Facility for Biomolecular Research located at the F. Bitter National Magnet Laboratory, Massa- chusetts Institute of Technology. V A large thanks goes to Nancy Merritt, the lady with the flying fingers who typed all this, that it might be read. Many thanks also to the author's parents, Eloise and Haworth Jonte, for providing a home atmosphere conducive to learning and the production of a third- generation chemist. The author wishes to thank Ken and Wilma Cashin for the provision of the sylvan setting in which much of this tome was pre- pared, as well as his many other brothers and sisters at College Church for their prayers and support during his tenure in Amherst. Most of all, thanks be to God for His provision, for He alone is worthy to receive glory and honor and power [Revelations 4.11]. vi , ABSTRACT Mechanistic Aspects of the Cationic Polymerization of para- Substituted a^^ha-Methylstyrenes May, 1982 J. Michael Jont^ B.S., South Dakota School of Mines & Technology M.S., University of Massachusetts Ph.D., University of Massachusetts Directed by: Professor Robert W. Lenz Mechanistic studies were carried out on the cationic polymerization reactions of a series of para-substituted alpha-methyl s tyrenes including p-fluoro-, p-chloro-, p-bromo- and p-isopropyl -alpha- methyl styrene, using Friedel -Crafts initiators. Solvent polarity was found to have a large effect on polymer yield, molecular weight and tacticity for the more electron withdrawing p-chloro monomer but not for the p-fluoro monomer. These results were interpreted in terms of free ion and ion pair reaction mechanisms and ca rhenium ion stabilization by the p-fluoro group. Polymers with bimodal molecular weight distributions (MWD's) were fractionated by prepara- tive gel permeation chromatography and analyzed for tacticity by nuclear magnetic resonance spectroscopy. The two modes were postu- lated to have been formed by free ions and by ion pairs. Polymeriza- tion reactions producing polymers with very narrow MWD's were found not to be living polymerization systems on the basis of copolymerization vii . - and polymer conversion studies. Theoretical calculations by Morawetz predicting narrow MWD's in the presence of chain termination were investigated and found not to apply to these systems. The presence of sterically hindered bases such as 2,6-di-tert-butyl-4- methyl pyridine (DBMP) had a profound effect on the polymerization reaction. A reaction mechanism was proposed to account for the observations As a sidelight, studies of some crystalline properties of these polymers showed that crystal 1 inity could be enhanced by annealing or dilute solution crystallization of polymers already showing signs of crystal 1 inity by differential scanning calorimetry. The addition of 15% meta- substituted monomer units was found to completely disrupt crystal 1 inity in p-methyl alpha -methyls tyrene. vi i i TABLE OF CONTENTS DEDICATION .... ' * TV ACKNOWLEDGEMENTS . V ABSTRACT vn LIST OF TABLES LIST OF FIGURES Chapter I. INTRODUCTION ^ Literature Review 3 Terminology 4 Carbenium ions 5 Ion pairs ...... 5 Reaction mechanism . 7 Tacticity ...... 9 References ! ! ! ! 11 II. THE EFFECT OF SOLVENT POLARITY ON THE POLYMERIZATION ... 14 Introduction -14 Tacticity determination by NMR 14 Relating tacticity to ion pairs 15 Solvent polarity and solvation of ion pairs 17 Experimental 18 Purification of solvents 18 Methylene chloride 18 Hexane 18 Purification of monomers 19 Purification of initiators and preparation of initiator solutions 19 Polymerization reactions 19 Polymer characterization 20 Gel permeation chromatography (GPC) 20 Nuclear magnetic resonance spectroscopy (NMR) .... 21 Results and Discussion 21 p-Chloro-a-methyl styrene 21 Tacticity 21 Molecular weight 34 Polymer yield 38 ix Chapter p-Fluoro-a-methylstyrene . ,0 Tacticity Molecular '. weight . Polymer yield ^2„ Summary [ References . , 55 ^^^^^^ ^^^^^^ ^^p^lr^THMc^^^"^^^^^ POLYMERIZATION KtAL I lUNo .... 58 Introduction Theoretical considerations . Experimental ] Gel permeation chromatography (GPC)' . 64 Nuclear magnetic resonance spectroscopy ' (NMR) * 64 Results and Discussion * * * Polymer fractionation ... ca -rj_... ,. , 0*+ Tacticity determination 64 References ] ] 72 IV. STUDIES OF LONG-LIVED POLYMER CHAINS 75 Introduction 75 Experimental 78 Purification of materials 78 Polymerization reactions ........ 78 Molecular weight versus conversion studies ...'.*. 78 Sequential monomer addition studies 78 Polymer characterization . 79 Results and Discussion 79 Studies of molecular weight versus conversion .... 79 Sequential monomer addition studies 81 Summary ] 84 References 87 V. INVESTIGATION OF THEORETICAL DESCRIPTIONS OF POLYMERIZATION REACTIONS PRODUCING POLYMERS OF NARROW MOLECULAR WEIGHT DISTRIBUTION 88 Introduction 88 Experimental 90 Purification of materials 90 Polymerization reactions 90 Polymer characterization 90 Results and Discussion 91 Summary 99 References 100 x Chapter VI. THE EFFECT OF STERICALLY HINDERED BASES ON THE POLYMERIZATION loi Introduction Iq-, Experimental • • • • . ! ! ! 1 ! ! ! 1 ! ] ! ] ] 104 Purification of materials 104 Polymerization reactions ^ 104 Polymer characterization 104 Results and Discussion 105 Polymer yield 105 ratio Mw/Mn Ill Molecular weight 1 1 Ill Summary 112 References ' ' ! ! ! ! 113 VII. STUDIES OF POLYMER CRYSTALLINE PROPERTIES 114 Introduction ]]4 Experimental ! ! ! ! 117 Polymers ] ]7 Dilute solution crystallization studies 117 Apparatus Hy Solvents 118 Drawing of fibers and films 118 Differential scanning calorimetry (DSC) 118 Wide angle x-ray scattering (WAXS) 118 Results and Discussion 119 Wide angle x-ray scattering (WAXS) studies 119 Annealing effects 120 Effect of meta-substi tuent 121 Solution crystallization studies 123 Summary 129 Wide angle x-ray scattering 129 Dilute solution crystallization studies 130 References 131 VIII. SUMMARY 132 Solvent effects 132 Multiple active center polymerization reactions. , . 133 Long-lived polymer chain studies 133 Theoretical descriptions of narrow MWD polymerization processes 134 Effect of sterically hindered bases 134 Polymer crystalline properties 135 APPENDIX 137 xi LIST OF TABLES 2.1. Effect of solvent composition on polymerization of p-chloro-a-methylstyrene. ... 25 2.2. Stereotactic sequence lengths for p-cliloro-a- methyl styrene polymers produced in solvents of different dielectric constant 32 2.3. Effect of solvent composition on polymerization of p-fluoro-a-methyl styrene 42 2.4. Stereotactic sequence lengths for p-fluoro-a- methyl styrene polymers produced in solvents of different

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