Azide Cellulose Molecular Modeling Studies

Azide cellulose is a new energetic binder. Currently, initial progress has been made by traditional experimental methods, but effects of the different groups on performance, compatibility with other components and mechanical properties were not available.Molecular simulation methods show great potential and advantages in the research of energetic materials where the security has been emphasized. In the dissertation, a series of different functional groups and different degree of substitution of azide cellulose were designed by using the software Accelrys Materials Studio. Their structure, mechanical properties, miscibility with plasticzers and binding energy with solid filler were simulated.1. The glass transition temperature Tg, Young's modulus E0 and viscous flow activation energy Eηof nitrocelluloses(NC) and nitrate ester of cellulose glycidyl ether(NGEC) were rapidly estimated by Synthia module of Materials Studio. It is shown that molecular simulation results are practicable in the trend analysis of the system and in agreement with theories and experimental results. In addition, it is found that azidodeoxycellulose nitrate (ACN) and nitrocellulose azidonitrate glycidyl ether(NCAGE) are good energetic binders with better mechanical and processing properties.2. The single chain structure and amorphous structure of azidodeoxycellulose (AC), ACN and NCAGE were simulated by molecular mechanics (MM) method and molecular dynamics (MD) method with COMPASS force field and stable chain structure and amourphous structure were obtained. Infrared vibrational frequencies and X-ray Diffraction (XRD) spectra of stable structure were calculated. The excellent agreement was obtained between the simulated and experimental data for vibrational frequencies and XRD spectra. So applicability of the above method is confirmed.3. The mechanical properties (elastic moduli and glass transition temperature Tg) of azide cellulose were calculated by MD method with COMPASS force field. It is shown that ACN-2 and NCAGE have better mechanical properties than the others, while NCAGE is the best binder, AC is the worst one and ACN is between them, with regard to low-temperature mechanical properties by simulated data of Tg.4. Solubility parameterδof AC, ACN and NCAGE were calculated by MD method, and Flory-Huggins interaction parameterχwere calculated by Monte Carlo (MC) method. The miscibility of azide cellulose with plasticizers could be predicted by integrating the two simulation results. The order of miscibility of AC with plasticizers is Acetone, triethylence glycol dinitrate (TEGDN) > diethylence glycol dinitrate (DEGDN), trimethyolethane trinitrate (TMETN)>1,2,4–butanetriol trinitrate (BTTN) and miscibility of ACN-1, ACN-2 with TEGDN is superior to other nitrate plasticizers, while miscibility of NCAGE with TEGDN,DEGDN and TMETN is superior to BTTN.5. Binding energy of azide cellulose with HMX, RDX were calculated using double layer model. Applicable simulation parameters for HMX and RDX crystal was:COMPASS force field, forcefield assigned charge, atom based summation for vdw and Ewald summation for coulomb. Binding energy of all kinds of azide cellulose with RDX were higher than HMX. The order of binding energy of azide cellulose with HMX at 298K was NCAGE > NC > AC > ACN-1, ACN-2, while the order of binding energy of azide cellulose with RDX at 298K was NCAGE > NC > ACN-2 > AC > ACN-1. It was found that temperature had little effects on binding energy within the range of 233K to 333K. The interaction was mainly characterized by the attraction of nitro-O atoms in HMX, RDX with hydroxyl-H atoms in azide cellulose, and N atoms in HMX, RDX with hydroxyl-O atoms in azide cellulose.