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Synthesis and Self-Assembly of Gradient Copolymers Master of Chemical Engineering Thesis Synthesis and Self-Assembly of Gradient Copolymers Kevin Wylie 260358983 Department of Chemical Engineering McGill University Montréal, Québec, Canada A Thesis submitted to McGill University in partial fulfillment of the requirements of the degree of Master of Engineering March 2016 © Kevin Wylie 2016 ABSTRACT Controlled free radical polymerization allows for the fine control of many key properties of polymers such as the molecular weight, dispersity and composition. Consequently, this permits the attainment of interesting microstructures such as block or tapered/gradient copolymers. In particular, nitroxide-mediated polymerization (NMP) was applied and used for the polymerization of methyl methacrylate (MMA) and styrene (St) block and tapered gradient polymers. With the defined composition and molecular weight, such copolymers are able to self-assemble into sub-50 nm domains. In this thesis, gradient copolymers synthesized in semi- batch mode were produced with varying composition and gradient profiles by alternating the rate of St addition and the length of the reaction. Their self-assembly performance was assessed relative to block copolymers with identical molecular properties and found to have similar feature sizes. However, with increasing gradient length, the self-assembly is negatively affected, producing films with very little order and much higher defect densities than block copolymers or polymers with short gradient lengths. i RÉSUMÉ La polymérisation radicale contrôlée permet le contrôle précis de plusieurs propriétés clés des polymères, tels que la masse moléculaire, dispersité et composition. Par conséquent, ce qui permet la réalisation de microstructures intéressants tels que copolymères bloque ou gradient. En particulier, on a appliqué la polymérisation nitroxide-médié (NMP) pour polymériser le méthacrylate de méthyl (MMA) et le styrène (St) en copolymères bloque et gradient. Avec la composition et masse moléculaire définie, ces polymères peuvent effectuer l’auto-assemblage en domaine moins de 50 nm. Dans cette thèse, des copolymères gradient ont été synthétisé en manière semi-continu avec profils de composition et de gradient variant en alternant le taux d’addition de St et la durée de la réaction. Leur performance d’auto-assemblage a été évaluée par rapport à des copolymères bloque ayant des propriétés moléculaires identiques et ont été trouvés à avoir des tailles de domaines similaire. Cependant, avec l'augmentation de la longueur de gradient, l'auto-assemblage est négativement affecté, la production de films avec très peu d'ordre et beaucoup plus de défauts que des copolymères bloque ou des copolymères avec des longueurs de gradient plus courtes. ii ACKNOWLEDGEMENT I would like to first thank my supervisor Prof. Milan Marić for his support and guidance, without which any of this would be possible. I also want to thank all of the present and former graduate student group members. Special thanks go to Xeniya Savelyeva and Simon Kwan for teaching me polymer synthesis, characterization and general lab practices. I would like to thank the Department of Chemical Engineering of McGill University for providing the office space and research facilities to carry out this work. I would also like to thank the Department of Chemistry, in particular the NMR facility for the use of their analytical equipment. Thank you as well to the McGill Nanotools Microfab (MNM) for the use of their facilities and equipment. In particular, I would like to thank Dr. Sasa Ristic and Dr. Lino Eugene for their clean room training and guidance. Finally, I would like to thank the Department of Chemical Engineering for financial support through the Eugene Ulmer Lamothe scholarship as well as the National Sciences and Engineering Research Council of Canada – Collaborative Research and Development (NSERC- CRD) grant in partnership with NanoQuébec and PCAS. iii CONTRIBUTION OF AUTHORS This thesis is a manuscript-based thesis, which contains one manuscript where I am the first author and have done the majority of the work. The manuscript is titled “Synthesis of Gradient Copolymers Synthesized in Semi-Batch Mode” and is Chapter 3 in this thesis. As a contribution to the manuscript, I performed all of the polymer synthesis, characterization and interpretation of the results. All writing, including tables and figures, were produced by me. Prof. Milan Marić performed the editing and aided with some of the writing. iv TABLE OF CONTENTS Abstract ............................................................................................................................................ i Résumé.............................................................................................................................................ii Acknowledgement .......................................................................................................................... iii Contribution of Authors .................................................................................................................. iv 1. General Introduction................................................................................................................... 3 2. Literature Review ........................................................................................................................ 5 2.1 Controlled Radical Polymerization ........................................................................................ 5 2.2 Copolymer Self-Assembly...................................................................................................... 9 2.3 Electron-Beam Lithography ................................................................................................. 13 2.4 Gradient Copolymers .......................................................................................................... 14 3. Self-Assembly of Gradient Copolymers Synthesized in Semi-Batch Mode .............................. 18 3.1 Abstract ............................................................................................................................... 18 3.2 Introduction ......................................................................................................................... 18 3.3 Experimental Section .......................................................................................................... 21 3.3.1 Materials ....................................................................................................................... 21 3.3.2 Synthesis of Random Terpolymer Brush ...................................................................... 22 3.3.3 Block Copolymer Synthesis ........................................................................................... 23 3.3.4 Synthesis of Blocky Gradient Copolymers .................................................................... 23 1 3.3.5 Synthesis of Smooth Gradient Copolymers .................................................................. 24 3.3.6 Substrate Preparation .................................................................................................. 25 3.3.7 Random Copolymer Grafting ........................................................................................ 25 3.3.8 Copolymer Deposition .................................................................................................. 25 3.3.9 Rapid Thermal Annealing ............................................................................................. 25 3.3.10 Analysis ....................................................................................................................... 26 3.4 Results & Discussion ............................................................................................................ 26 3.4.1 Polymerization Characteristics ..................................................................................... 26 3.4.2 Copolymer Self-Assembly ............................................................................................. 29 3.5 Discussion ............................................................................................................................ 32 3.5.1 Effect of Gradients on Self-Assembly ........................................................................... 32 3.5.2 Effect of Long Injection Time of Gradient Self-Assembly ............................................. 35 3.5.3 Effect of Wetting & Film Thickness on Self-Assembly .................................................. 37 3.6 Conclusion ........................................................................................................................... 38 3.7 Acknowledgements ............................................................................................................. 38 4. Conclusion ................................................................................................................................. 39 5. Future Work .............................................................................................................................. 39 6. References ................................................................................................................................ 40 2 1. GENERAL INTRODUCTION Due to the ever-growing demand for faster and more efficient electronics, manufacturers must continually reduce the feature size in semiconductor devices. Photolithography, the process whereby light is used to chemically change a photoresist in order to etch
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