ABSTRACT ZHANG, NANSHAN. Design of Safer Flame Retardant Textiles through Inclusion Complex Formation with Cyclodextrins: A Combined Experimental and Modeling Study. (Under the direction of Dr. Melissa Pasquinelli and Dr. Hinks). Triphenyl phosphate (TPP) is widely used as a phosphorus flame retardant. It is also one component of a commercial flame retardant mixture known as Firemaster 550. TPP is likely to be released into the environment due to its high volatility and has been detected at a concentration as high as 47,000 ng/m3 in air. Recent studies have also indicated that FRs like TPP could contribute to obesity and osteoporosis in humans. Cyclodextrins (CDs) are enzymatic degradation products of starch and consist of several (α-1,4)-linked α-D- glucopyranose units. CDs own a hydrophilic outside and a hydrophobic inner cavity, which enables the formation of non-covalently bonded cyclodextrin inclusion complexes (CD-ICs) with a vast array of molecules. We hypothesize that the formation of inclusion complexes between TPP and cyclodextrins will reduce its exposure yet also retain flame retarding properties of TPP, since the formation of FR-CD-ICs is expected to eliminate unnecessary loss of FRs, especially volatile FR compounds like TPP, and release them only during a fire when they are actually needed. After creating the TPP-β-CD-IC, we applied it to polyethylene terephthalate (PET) films by a hot press technique. Flame tests indicated TPP-β-CD-IC exhibited flame resistant performance matching that of neat TPP, even though much less TPP was contained in its β-CD-IC. Incorporation of FRs and other chemical additives into textile substrates in the form of their crystalline CD-ICs is a promising way to reduce the exposure of hazardous chemicals to humans and to our environment while not impacting their efficacy. Two other parent CDs (α-CD and γ-CD) were applied and their abilities to form ICs with guest TPP were studied. Results from a series of characterization methods, including FTIR, DSC, TGA, XRD and NMR indicated the successful synthesis of TPP-γ-CD-IC via two routes. However, α-CD appears unable to form an IC with TPP, which is likely attributable to a size mismatch between them. A novel analytical chemistry technique -- tandem mass spectrometry (ESI-Q-TOF) was used to study the inclusion complexes of TPP and CDs. Successful formation of TPP-β-/γ-CD-IC was further proved by ESI mass spec in the positive mode. Experimental results demonstrated that 1:1 inclusion complex ions of the guest FR and the host CDs were detected. Experimentally α-CD cannot form an IC with TPP and this was further confirmed by tandem mass spec. Mass spectrometry provides a fast and accurate method to investigate cyclodextrin inclusion complexes and verify the formation of ICs Computational methods were applied to help understand the energetically favorable geometry of TPP and β-/γ-CD in their IC form. Semi-empirical theoretical methods (PM3 and PM6) were used to find the global minima of TPP-CD geometry and density functional theory calculations at a B3LYP/6-31G(d) level were employed for elaborate geometry optimization. Solvent effect was also considered using the polarized continuum model (IEF-PCM). Analysis of the results indicated that after optimization, IC geometries provided by PM6 had stronger interactions and were more energetically favorable than the ones calculated by PM3. DFT calculations are more accurate than PM3/PM6 and enabled more interactions between the host and the guest than two semi-empirical approaches. DFT calculations also proved that initial structures prepared by PM6 were more favorable in H-bonding profiles and key energy parameters. For TPP-β-CD system in vacuum and water, Model A owned a lower total and complexation energy while a stronger interaction between them was present in Model B. In TPP-γ-CD system, Model B was preferred than Model A in both vacuum and water. This was potentially attributed to more H-bonds formed between TPP and γ-CD in Model B and its ability to retain most of the internal linkages among primary hydroxyl groups. © Copyright 2016 by Nanshan Zhang All Rights Reserved Design of Safer Flame Retardant Textiles through Inclusion Complex Formation with Cyclodextrins: A Combined Experimental and Modeling Study by Nanshan Zhang A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Fiber and Polymer Science Raleigh, North Carolina 2015 APPROVED BY: _______________________________ _______________________________ Dr. Melissa Pasquinelli Dr. David Hinks Co-chair of Advisory Committee Co-chair of Advisory Committee _______________________________ _______________________________ Dr. Alan Tonelli Dr. Ahmed El-Shafei _______________________________ Dr. Heather Patisaul ii DEDICATION This work is dedicated to my family and dear friends for their unselfish love and encouragement in all my endeavors. iii BIOGRAPHY Nanshan was born in Zhengzhou, Henan Province of China. He was majored in Textile Testing and Business and received Bachelor’s degree from Donghua University in 2011. Nanshan attended the ‘3+X’ program and joined North Carolina State University in August, 2010 to pursue a Master’s degree in Textile Engineering. He was then enrolled in Fiber and Polymer Science Program in College of Textiles to pursue his PhD degree. iv ACKNOWLEDGMENTS I would like to express my sincere thanks to Dr. Melissa Pasquinelli and Dr. Alan Tonelli for their great guidance and patience throughout my research and dissertation writing. Without their encouragement and confidence in me, this research and dissertation would not have been possible. I greatly appreciate the financial support from Dr. Hinks and for offering his support in green chemistry. I’m also very thankful to Dr. Ahmed El-Shafei and Dr. Heather Patisaul for serving critical roles as my graduate committee. Besides, I would like thank Yufei Chen, Jing Chen, Jialong Shen, Erol Yildirim, Mr. Jeff Krauss, Ms. Judy Elson, Ms. Xiaoyan Sun and Ms. Birgit Andersen for all their kind help during my PhD work. I’m grateful for all the impressive help from my friends, classmates and colleagues who have assisted me in my research work and made my life colorful. Last but not least, I want to give a special thanks to my girlfriend, Sha, the light of my life. You are too good to be true and I will always love you. v TABLE OF CONTENTS LIST OF TABLES ................................................................................................................. ix LIST OF FIGURES .................................................................................................................x CHAPTER 1 BACKGROUND TO THE PROBLEM .........................................................1 CHAPTER 2 MOTIVATION AND OBJECTIVES .............................................................3 2.1. Motivation .................................................................................................................. 3 2.2. Objectives ................................................................................................................... 5 CHAPTER 3 LITERATURE REVIEW ................................................................................6 3.1. Flame Retardants ........................................................................................................ 6 3.1.1. Background ......................................................................................................... 6 3.1.2. The Flammability of Textiles ............................................................................ 11 3.1.3. Impeding the Combustion Cycle ...................................................................... 13 3.1.3.1. The Condensed Phase Mechanism ............................................................ 15 3.1.3.2. The Gas Phase Mechanism ........................................................................ 17 3.1.3.3. Physical Effects ......................................................................................... 20 3.1.4. Classifications of Flame Retardants .................................................................. 22 3.1.4.1. Halogenated Flame Retardants .................................................................. 22 3.1.4.2. Phosphorus Flame Retardants ................................................................... 24 3.1.4.3. Other Flame Retardants ............................................................................. 29 3.1.5. Health and Environmental Concerns of Flame Retardants ............................... 31 3.1.5.1. Polybrominated Diphenyl Ethers ............................................................... 31 3.1.5.2. Fire Safety and Standards .......................................................................... 34 3.1.5.3. Firemaster 550 and Its Components .......................................................... 36 3.2. Cyclodextrins ........................................................................................................... 65 3.2.1. History ............................................................................................................... 65 3.2.2. Physical and Chemical Properties ..................................................................... 66 3.2.3. Crystallography of Cyclodextrins ..................................................................... 68 3.2.3.1. Cage Type Structures ................................................................................