THE SYNTHESIS AND CHARACTERIZATION OF ENERGETIC MATERIALS FROM SODIUM AZIDE A Thesis Presented to The Academic Faculty By Joshua Aronson In Partial Fulfillment Of the Requirements for the Degree Doctor of Philosophy in the School of Chemistry and Biochemistry Georgia Institute of Technology October 2004 THE SYNTHESIS AND CHARACTERIZATION OF ENERGETIC MATERIALS FROM SODIUM AZIDE Approved by: Charles L. Liotta, Advisor Kent Richman Charles A. Eckert Julia Kubanek David Collard November 17, 2004 ii This thesis is dedicated to M. G. iii ACKNOWLEDGEMENT I would first like to thank Dr. Liotta and Dr. Eckert for their support and encouragement. I will forever envy your enthusiasm and spirit. I would also like to extend my appreciation to everyone at American Pacific. My experiences in Utah and Las Vegas contributed a great deal to my graduate education. In addition, I want to thank the entire Liotta-Eckert research group—especially Kris and Pamela. The two of you made all of this not only bearable, but fun. Finally, I would like to thank my mom and Mary Katherine for their support. I would not have made it without you. iv TABLE OF CONTENTS Acknowledgement iv List of Figures viii List of Tables xii List of Abbreviations xiii Summary xv Chapter I Introduction 1 Chapter II A Novel Approach To The Synthesis Of Tetrazoles 5 Introduction 5 Experimental Methods 10 Materials 10 Apparatus 10 Procedures 11 Results and Discussion 14 Conclusion 37 References 38 Chapter III The Synthesis and Characterization Of Glycidyl 40 Azide Polymer Introduction 40 Experimental Methods 43 Materials 43 Apparatus 43 Procedures 43 Results and Discussion 46 v Conclusion 56 References 57 Chapter IV The Synthesis and Characterization Of Glycidyl 58 Tetrazole Polymers Introduction 58 Experimental Methods 60 Materials 60 Apparatus 60 Procedures 62 Results and Discussion 65 Conclusion 74 References 78 Chapter V The Synthesis and Characterization Of Energetic 80 Foams Introduction 80 Experimental Methods 87 Materials 87 Apparatus 87 Procedures 87 Results and Discussion 89 Conclusion 92 References 96 Chapter VI The Synthesis and Characterization Of Energetic 97 Ionic Liquids Introduction 97 Experimental Methods 104 Materials 104 vi Apparatus 104 Procedures 104 Results and Discussion 106 Conclusion 119 References 122 Chapter VII The Synthesis and Characterization Of Novel 123 Energetic Gels Introduction 123 Experimental Methods 125 Materials 125 Apparatus 125 Procedures 125 Results and Discussion 127 Conclusions 133 References 135 Chapter VIII Recommendations 137 Vita 147 vii LIST OF FIGURES Figure 2-1 Comparison of the carboxylic acid type moiety present 6 in the tetrazole ring. Figure 2-2 The reactive species formed between the teriary amines 16 and sodium azide. Figure 2-3 Reaction scheme using triethylamine hydrochloride and 17 sodium azide in equimolar amounts with benzonitrile as solvent and reactant for the preparation of 5-phenyl-1H-tetrazole. Figure 2-4 Graph of the isolated yields of 5-phenyl-1H-tetrazole 17 versus time for the reaction shown in Figure 5-2 at 50oC. Figure 2-5 The structures of the various amines tested for their 19 effectiveness and solubility in benzonitrile. Figure 2-6 Stepwise reaction scheme showing the formation of tri- 24 ethylammonium 5-phenyltetrazolate and subsequent tetrazole ring protection by reaction with triphenylmethyl chloride. Figure 2-7 Proposed mechanism of the basic tetrazole reaction 27 Figure 2-8 Proposed catalytic cycle for the preparation of 5-pheny 30 -1H-tetrazole using a stoichiometric amount of triethylamine hydrochloride (TEAHC) and a 10 mol% of benzyltriethylammonium chloride (BTEAC). Figure 2-9 Reaction showing the deprotonation of the 5-phenyl-1H- 33 Tetrazole to produce a soluble triethylammonium 5-phenyltetrazolate species. Figure 2-10 Intermolecular hydrogen bonding network of 5-phenyl- 34 1H-tetrazole. Figure 2-11 Reaction scheme for the production of 5-phenyl-1H- 34 tetrazole with 10mol% TEAPT as the proton source. Figure 2-12 Proposed catalytic cycle for the reaction that uses a 10 36 Mol % of the quaternary ammonium salt viii Figure 3-1 The structure of glycidyl azide polymer 41 Figure 3-2 The general process for synthesizing the polyepichloro- 47 Hydrin staring material Figure 3-3 The mechanism for the polymerization of epichlorohydrin 48 using a tin catalyst and trifluoroacetic acid Figure 3-4 The standard process used to generate glycidyl azide 51 polymer from polyepichlorohydrin and sodium azide Figure 3-5 Pictures of common GAP samples 53 Figure 3-6 A depiction of the ionic liquids in which the synthesis of 55 GAP was attempted. Figure 3-7 The procedure used to synthesize GAP in ionic liquids 55 Figure 4-1 The structure of glycidyl azide polymer 59 Figure 4-2 The two isomer of glycidyl tetrazole polymer that are 61 possible Figure 4-3 The scheme using phase transfer catalysis attempted to 66 replace the chlorine of the epichlorohydrin with a nitrile Figure 4-4 The “click” process designed by K. Barry Sharpless for 68 synthesizing tetrazoles Figure 4-5 The physical properties of a wide range of tosyl- 69 Substituted tetrazole Figure 4-6 Differential Scanning Calorimetry Data for the GAP/ 71 Ts-GTP polymers Figure 4-7 Exotherm values (J/g) for GAP/Ts-GTP polymers 72 Figure 4-8 Synthesis of GTP polymers with ethyl and benzyl 73 cyanoformate Figure 4-9 Decarboxylation of GTP polymers with LiOH 73 Figure 4-10 Differential Scanning Calorimetry data for all of 75 the GTP derivatives ix Figure 5-1 A general urethane linkage and the general scheme 81 for the reaction between the hydroxyl-terminated polymer and the diisocyanate Figure 5-2 The mechanism by which water reacts with the 85 diisocyanate to generate the carbon dioxide bubbles in the foam Figure 5-3 The mechanism between the hydroxyl-terminated 86 polymer and the diisocyanate Figure 5-4 Water blown foams created with 5, 10, and 25 mol 90 percent of diisophorone diisocyanate Figure 5-5 The stir blade used in an attempt to mechanically 91 introduce air bubbles into the plastic matrix of the energetic foams Figure 5-6 Comparison of the foams created with mechanical 93 technique and a water blown foam Figure 5-7 Differential scanning calorimetry plots of pure GAP, 94 the energetic foam, and H-GTP Figure 6-1 Two generalized structures for common ionic liquids 98 Figure 6-2 Phase changes of the ionic liquid dictacted by the 100 length of the alkyl chain Figure 6-3 5,5-bi-1H-tetrazole and 5-methyltetrazole 102 Figure 6-4 Class I and Class II tetrazole based ionic liquids 103 Figure 6-5 Acid-base reaction that yields the formation of 107 5-methyl tetrazole salts Figure 6-6 Comparion of specific impulse versus oxidizer/fuel 112 ratio for ionic liquids and other common energetic materials Figure 6-7 Density impulse versus oxidizer/fuel ratio for the 113 tetrazole based ionic liquids and other common energetic materials Figure 6-8 Differential scanning calorimetry plot for butyl- 114 ammonium-5-methyltetrazole and the amyl- x ammonium-5-methyltetrazolide ionic liquids Figure 6-9 Differential scanning calorimetry data for saturated 117 solution of KClO4 in butylammonium-5-methyl- tetrazolide Figure 6-10 Differential scanning calorimetry data for saturated 118 solution of KClO4 in amylammonium 5-methyl- tetrazolide Figure 6-11 Differential scanning calorimetry date for saturated 120 solution of NH4ClO4 in butylammonium 5-methyl- tetrazolide Figure 6-12 Differential scanning calorimetry data for saturated 121 solution of NH4ClO4 in amylammonium 5-methyl- tetrazolide Figure 7-1 General scheme for the preparation of the tetrazole 128 substituted monomer and the polymerization Figure 7-2 General scheme for the preparation of the three- 131 dimensional polymer network Figure 7-3 The three-dimensional polymers 131 Figure 7-4 General scheme for the preparation of the ionic species 132 from the monomer Figure 8-1 Synthetic scheme to prepare long alkyl chain azido- 142 amines Figure 8-2 Synthetic scheme to prepare DMAZ, 5-alkylamino- 143 tetrazole, and 1-alkylaminotetrazole Figure 8-3 Synthesis pathways to prepare novel and enhance 145 energetic polymers xi LIST OF TABLES Table 2-1 The yield of 5-phenyl-1H-tetrazole using each of 20 the amines. Table 2-2 Results from the gaseous HCl recycled experiments 22 Table 2-3 Results from the trityl protection of the 5-phenyl- 26 1H-tetrazole experiments. Table 2-4 Results from the experiments using only a catalytic 29 amount of quaternary ammonium salt. Table 2-5 The results from the temperature, time, and mol% 31 of TEAHC variations. Table 4-1 Exotherm values for each of the glycidyl tetrazole 75 derivatives Table 6-1 Melting points for BHT and 5-MT salts 102 Table 6-2 The six selected and tested amines and their alkyl 105 chain substitution pattern Table 6-3 Amine salts of 5-MT including substitution patterns 109 and physical properties Table 6-4 Amound of NH4ClO4, NaClO4, and NaNO3 needed 114 to reach the saturation of 1g of tetrazole ionic liquids Table 8-1 Energetic azido-amines and tetrazole based amines 140 xii LIST OF ABBREVIATIONS BHT 5,5’-bi-1H-tetrazole BTEACH benzyltriethylammonium chloride DMAZ dimethylethylamino azide DMSO dimethylsulfoxide DSC differential scanning calorimetry ECH epichlorohydrin GAP glycidyl azide polymer GPC gel permeation chromatography GTP glycidyl tetrazole polymer IR infrared spectroscopy Isp specific impulse MMH monomethylhydrazine 5-MT 5-methyltetrazole NaEDTA sodium ethylenediaminetetraacetic acid NMR nuclear magnetic resonance O/F oxidizer/fuel ratio PDI polydispersity index PECH polyepichlorohydrin 5-PT 5-phenyl-1H-tetrazole PTC phase transfer catalysis TBAB tetrabutylammonium bromide xiii TEAHC triethylamine hydrochloride TFA trifluoroacetic acid xiv SUMMARY A tetrazole is a 5-membered ring containing 4 nitrogens and 1 carbon. Due to its energetic potential and structural similarity to carboxylic acids, this ring system has a wide number of applications.