NEW 3D PRINTABLE POLYMERIC MATERIALS FOR FUSED FILAMENT FABRICATION (FFF) by Gayan Adikari Appuhamillage APPROVED BY SUPERVISORY COMMITTEE: ___________________________________________ Ronald A. Smaldone, Chair ___________________________________________ John P. Ferraris ___________________________________________ Walter E. Voit ___________________________________________ Mihaela C. Stefan Copyright 2018 Gayan Adikari Appuhamillage All Rights Reserved To my family and friends NEW 3D PRINTABLE POLYMERIC MATERIALS FOR FUSED FILAMENT FABRICATION (FFF) by GAYAN ADIKARI APPUHAMILLAGE, BS, MS DISSERTATION Presented to the Faculty of The University of Texas at Dallas in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY IN CHEMISTRY THE UNIVERSITY OF TEXAS AT DALLAS May 2018 ACKNOWLEDGMENTS It was a wonderful experience for me to work in Dr. Smaldone lab for the past five years. I would like to acknowledge my research advisor Dr. Ronald A. Smaldone, for letting me carry out my graduate research work under his supervision. I sincerely appreciate all of his support, guidance, and immense encouragement throughout my graduate studies. I would like to acknowledge the members of my advisory committee- Dr. John P. Ferraris, Dr. Walter E. Voit, and Dr. Mihaela C. Stefan for their valuable suggestions and support. I also appreciate all the valuable help and training given to me by Dr. Christina Thompson for organic synthesis and reaction mechanisms; Dr. Hien Nguyen for nuclear magnetic resonance (NMR) spectroscopy and inductively coupled plasma (ICP) analysis; Dr. Benjamin Batchelor for Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA); Dr. Faisal Mahmood for gel permeation chromatography (GPC); Dr. Layne Winston for the Universal Testing Machine-Instron, and finally, thanks to the clean-room staff. I acknowledge Dr. Walter E. Voit for his productive collaborations and great support, his past graduate students, Dr. Jonathan Reeder, Dr. Gregory Ellson, Dr. Radu Reit, and Dr. Kejia Yang, and his past lab manager, Dr. Benjamin Lund, for helping me in various ways during collaborations. I acknowledge Dr. Jeremiah Gassensmith and his graduate students, Candace Benjamin, Michael Luzuriaga, and Madushani Dharmarwardana, for their valuable collaborations. v I thank the Department of Chemistry and Biochemistry staff for their help- Betty Maldonado, Linda Heard, Kelli Lewis, Lydia Selvidge, Dr. Pathum Panapitiya, Dr. Sumudu Wijenayake and Dr. George McDonald. I thank my past lab members, Dr. Arosha Karunathilake, Joshua Davidson, Xie Yinhuan, Fei Li, and Victoria Cameron, and the current lab members Sampath Alahakoon, Grant Sturgeon, Danielle Berry, Alejandra Silva, and Shashini Diwakara, and also all the undergraduates for all of their valuable help and friendship. I thank my undergraduates, John Reagan and Sina Khorsandi, for their valuable help for research. Also I thank the Sri Lankan Student Association (SLSA) and all of my Sri Lankan friends for their support in various situations. Finally, I would like to thank my loving parents, Thilakarathna Adikari Appuhamillage and Pathmalatha Jayasooriya, my loving uncle, Chandrarathna Adikari Appuhamillage, my in-laws, my loving wife, Sankalya Ambagaspitiye Gedara, and beloved daughter, Oshadhi Imaya Adikari, for their immense love, support, and endless encouragement during this journey. April 2018 vi NEW 3D PRINTABLE POLYMERIC MATERIALS FOR FUSED FILAMENT FABRICATION (FFF) Gayan Adikari Appuhamillage, PhD The University of Texas at Dallas, 2018 ABSTRACT Supervising Professor: Ronald A. Smaldone 3D printing, also known as additive manufacturing, is an advancing technology for fabricating three dimensional objects of simple to complex architectures using computer aided design (CAD) models. Fused Filament Fabrication (FFF) is a relatively cost effective, straightforward 3D printing technique which relies upon utilization of relatively cheap, commercially available thermoplastics like polylactic acid (PLA) and acrylonitrile-butadiene-styrene (ABS) in a coil form to fabricate desired objects in layer-by-layer fashion on a print bed. In spite of the growing popularity of FFF, the technique suffers from poor mechanical strength of 3D printed parts due to weak inter-layer adhesion at interfilamentous junctions. To address these issues related to the materials used for FFF 3D printing, for the first time, we introduce a polymer blending strategy that utilizes Diels-Alder (DA) dynamic covalent chemistry which plays the model role for remending PLA. A partially cross-linked terpolymer having furan-maleimide DA linkages both in the main chain and at cross-linking junctions is used as the mending agent (MA). Results indicate dramatic improvements in both ultimate strength and toughness along the z-print axis for vii remendable PLA than pristine PLA. As a follow-up, we increase the cross-linking density of the MA polymer to yield remendable PLA with isotropic mechanical properties. Finally we are introducing utilization of hydrogels, prepared from a cheap, abundant, biopolymer and 3D printed via direct-write 3D printing technique based on FFF principles, for the removal of toxic heavy metal ions from contaminated water. With promising results in mechanical strength, metal adsorption efficiency, and recyclability, the strategy lays a foundation for future design and development of cheap, safe, and durable 3D printable materials for water purification. Chapter 1 provides a general introduction on 3D printing techniques, issues related to FFF, our approaches to address the issues, and utilizing hydrogel materials in direct-write 3D printing. Chapter 2 describes a design paradigm utilizing reversible Diels-Alder reactions to enhance the mechanical properties of 3D printed materials. Chapter 3 describes 3D printed remendable polylactic acid blends with uniform mechanical strength enabled by a dynamic Diels-Alder reaction. Chapter 4 describes 3D printable hydrogels for toxic heavy metal adsorption from water. viii TABLE OF CONTENTS ACKNOWLEDGMENTS ...............................................................................................................v ABSTRACT .................................................................................................................................. vii LIST OF FIGURES ...................................................................................................................... xii LIST OF TABLES ...................................................................................................................... xvii CHAPTER 1 INTRODUCTION ...................................................................................................1 1.1 Background ....................................................................................................................1 1.2 3D printing technologies ................................................................................................1 1.3 Problems associated with FFF-3D printing ...................................................................8 1.4 Previous research work to improve interlayer adhesion ................................................9 1.5 Challenges encounter using fmDA chemistry in FFF-3D printing ..............................15 1.6 Our approach to enhance the mechanical properties of FFF-3D printed materials .....16 1.7 FDM-based 3D printing of soft materials for environmental remediation ..................16 References ..........................................................................................................................18 CHAPTER 2 DESIGN PARADIGM UTILIZING REVERSIBLE DIELS−ALDER REACTIONS TO ENHANCE THE MECHANICAL PROPERTIES OF 3D PRINTED MATERIALS1 ...............................................................................................................................28 2.1 Abstract ........................................................................................................................29 2.2 Introduction ..................................................................................................................29 2.3 Results ..........................................................................................................................32 2.4 Discussion ....................................................................................................................38 2.5 Conclusion ...................................................................................................................39 2.6 Experimental Section ...................................................................................................40 References ..........................................................................................................................42 CHAPTER 3 3D PRINTED REMENDABLE POLYLACTIC ACID BLENDS WITH UNIFORM MECHANICAL STRENGTH ENABLED BY A DYNAMIC DIELS-ALDER REACTION1 ................................................................................................................................46 3.1 Abstract ........................................................................................................................47 3.2 Introduction ..................................................................................................................47 ix 3.3 Experimental Section ...................................................................................................50 3.3.1 Materials .......................................................................................................50