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Refractive Index Engineering and Optical Properties Enhancement by Polymer Nanocomposites

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Refractive Index Engineering and Optical Properties Enhancement by Polymer Nanocomposites University of Massachusetts Amherst ScholarWorks@UMass Amherst Doctoral Dissertations Dissertations and Theses March 2016 Refractive Index Engineering and Optical Properties Enhancement by Polymer Nanocomposites Cheng Li University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/dissertations_2 Part of the Materials Chemistry Commons, Nanoscience and Nanotechnology Commons, Polymer and Organic Materials Commons, Polymer Chemistry Commons, and the Semiconductor and Optical Materials Commons Recommended Citation Li, Cheng, "Refractive Index Engineering and Optical Properties Enhancement by Polymer Nanocomposites" (2016). Doctoral Dissertations. 587. https://doi.org/10.7275/7668177.0 https://scholarworks.umass.edu/dissertations_2/587 This Open Access Dissertation is brought to you for free and open access by the Dissertations and Theses at ScholarWorks@UMass Amherst. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. REFRACTIVE INDEX ENGINEERING AND OPTICAL PROPERTIES ENHANCEMENT BY POLYMER NANOCOMPOSITES A Dissertation Presented by CHENG LI Submitted to the Graduate School of the University of Massachusetts Amherst in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY February 2016 Polymer Science and Engineering © Copyright by Cheng Li 2016 All Rights Reserved REFRACTIVE INDEX ENGINEERING AND OPTICAL PROPERTIES ENHANCEMENT BY POLYMER NANOCOMPOSITES A Dissertation Presented by CHENG LI Approved as to style and content by: _______________________________________ James J. Watkins, Chair _______________________________________ Kenneth R. Carter, Member _______________________________________ David M. Ford, Member _______________________________________ David A. Hoagland, Department Head Polymer Science and Engineering DEDICATION To my families. ACKNOWLEDGEMENTS First of all, I would like to thank my thesis advisor, Professor James Watkins, for providing me the great opportunity to work in a world-leading group of nanotechnology. Jim introduces to me a totally different research world with my previous research experience. He guides me with patience, and makes me become more comfortable and confident in this field. With high premium on polymer research, Jim also encourages me to open my mind in interdisciplinary research fields. During the five years, Jim has showed me how to achieve successful interdisciplinary collaboration with the internal groups in Umass Amherst, as well as the external partners from all over the world. Through these working experiences, I have learned the ability to collaborate and communicate with other scientists and technicians. Jim is a very generous boss. He provides me great chances to attend conferences and workshops. Jim is a very busy professor, but he is willing to spend time with the group members out of working time, invites us to his house for barbeque and have dinner with us, which I really appreciate. I would like to thank my two excellent committee members, Professor Kenneth Carter and Professor David Ford. I cannot thank them enough for their kind cooperation in my defense time scheduling, as well their precious questions and suggestions for my research and presentations. I also would like to thank my undergraduate advisor Professor Wenbing Hu in Nanjing University. Without his guide, I would never begin to pursue a Ph.D. degree. It is also my pleasure to work with all of the past and present members in Watkins group. Their generous help and inspiring discussion make my research proceed more smoothly. I also would like to thank the students and postdocs who have ever provided v instruments training and helped to solve problems with me. Special thanks are given to Wenxu Zhang, George Chang, Dr. Longyu Li, Dr. Dongpo Song, Dr. Li Yao and Dr. Michael Beaulieu, not only for the discussions in the labs, but also the role model of competent scientists and engineer they have set for me. I would like to thank the NSF’s Center of Hierarchical Manufacturing at UMass Amherst for the financial support through my graduate studies. I would also like to acknowledge the Materials Research Science and Engineering Center (MRSEC) at the UMass Amherst for providing easy access to the various instruments necessary to proceed my research projects. I would like to thank PSE Department staff and technicians. I thank Louis Raboin and Dr. Alex Ribbe for their patient training and help in the SEM and TEM facilities. I also thank Dr. Sekar Thirunavukkarasu for the training in different instruments which most my research depend on, including ellipsometry, nanoindentation, X-ray scattering and AFM. I would like to especially thank Jo-Ann Bourguignon and Lisa Groth for taking care of everything such as events scheduling, chemicals ordering and paperwork, which make my school life much less confusing. I would like to thank all my friends in USA. I am thankful to have them company and have them to grow with me in the last five year in a foreign country. Finally I would like to thank my parents Ming Li and Jiuyun Cheng. I can never thank enough for their support in the five years. They share their experience and wisdom with me without any saving. They are always my backup strength and leading light when I was depressed about life or when I was confused about the future. With them, I feel vi more confident and strong. I also would like to thank my girlfriend Lingyi Li. Her kindness, patience and the smiles in her face are always the best medicine for me. I am so grateful for my parents and Lingyi’s sacrifice in my way to the doctor of philosophy. vii ABSTRACT REFRACTIVE INDEX ENGINEERING AND OPTICAL PROPERTIES ENHANCEMENT BY POLYMER NANOCOMPOSITES FEBRUARY 2016 CHENG LI, B.S., NANJING UNIVERSITY M.A., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor James J. Watkins The major part of this dissertation focuses on the engineering of the refractive index of materials using solution-processable polymer nanocomposites and their applications in building optical components and devices. Three particular polymer nanocomposites have been introduced to achieve materials with tunable refractive indices and enhanced optical properties, which can be used to manipulate the behavior of light or electromagnetic radiation. In the first system, polyhedral oligomeric silsesquioxane (POSS)/polymer nanocomposites are developed. Thin films with tunable, low refractive indicies were fabricated from the composites. The mechanical strength of these films was characterized, and their application in antireflective coatings is discussed. In the second system, a titanium oxide (TiO2)/polymer nanocomposite is developed. For these nanocomposites, a method for fabricating mesoporous TiO2 thin films with tunable refractive indices at room temperature is introduced. The low temperature strategy allows the deposition of mesoporous TiO2 based Bragg mirrors on polymeric substrates. The potential application of the TiO2 Bragg mirror as a gas sensor is discussed. Finally, a viii zirconium oxide (ZrO2)/polymer nanocomposite with a tunable refractive index is developed. The refractive index of the ZrO2 nanocomposites was tuned to match the index of a rare-earth ion doped nanoparticle. Highly transparent composites containing light emitting nanoparticles with minimum Rayleigh scattering can be achieved by blending the two nanoparticle systems in controlled amounts from solution. This is the first exhibition of the successful employment of hybrid polymer composites as a “refractive index matching” matrix, facilitating fabrication of highly transparent nanocomposites. The second part of this dissertation introduces a light-responsive block copolymer composite. Poly [poly(ethylene glycol) monomethyl ether monomethacrylate]-block- poly(ethyl methacrylate) was prepared using reversible addition-fragmentation chain transfer polymerization (RAFT). This block copolymer is an amorphous, phase mixed system at room temperature. The incorporation of organic additives with multiple carboxylic acid groups, such as mellitic acid, induces phase segregation in this system. Furthermore, the use of additives in which the hydrogen bond donating group is protected with an acid labile group in combination with a photo acid generator enables photo-induced ordering of the composite films. Adjacent disordered/ordered patterns can be obtained using this strategy due to the absence of PEO crystals. ix TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ........................................................................................................ v ABSTRACT .......................................................................................................................... viii LIST OF TABLES .................................................................................................................. xiii LIST OF FIGURES ................................................................................................................ xiv CHAPTER 1. INTRODUCTION ............................................................................................................... 1 1.1 Dissertation Overview ....................................................................................... 1 1.2 Polymer Nanocomposites ................................................................................. 6 1.3 Refractive Index ...............................................................................................
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