Preparation And Characterization Of Energetic Metal-porous Polymers

The aim of this paper is to synthesis polymers with different pore structures byusing different size of monomers and in order to broaden their application in energeticmaterials, the polymers were decorated by introducing nitro group into the polymers.The transition metal nitrates were loaded on the nitro-substituted polymers andobtained metal-supported energetic polymers. Herein, synthesises and nitrifications ofpolymers were studied. The metal-supported polymers were prepared andcharacterized. To examine the thermal stability, the thermal decomposition processesof the metal-supported polymers were investigated, which can provide the underlyingdata for the application in the energetic materials fields. The main research contentsand results are summarized as follows:(1)The different porous structures of cross-link polystyrenes with different ratiosof monomers and porogen were obtained by using suspension polymerization method,and the results show that the ratio of styrene and divinylbenzene was equal to1:5,monomer and porogen was1:1, the surface area of the polymer is458m2/g.Nitro-substituted polystyrene was prepared using the mixed acid as nitrationreagents. The effects on nitrification have been discussed, such as nitrification time,the ratio of mixed acid and temperature. By optimizing the reaction conditions, weobtained the nitro-substituted polystyrene with12.5%N content.Different amount of copper nitrates were loaded on the polystyrene and foundthat the more copper nitrate was loaded on, the lower the decomposition temperaturewas. The reason is that the metal nitrates has catalytic function for the decompositionof the energetic polymers. Different kinds of transition metal(Cu、Fe、Co、Ni) nitrateswere loaded on the nitro-polystyrene, found that the peak temperature wereCu(316℃)<Co(343℃)<Ni(353℃)<Fe(357℃). In addition, the peak temperature ofthe copper nitrate loaded nitro-polystyrene was325℃，which is higher than that of tecopper nitrate-loaded nitro-polystyrene. It is obvious that nitro-substituted polymerhave more energetic.(2)Using dichloroethane as solvent, anhydrous ferric chloride as catalyst, fourkinds of biphenyl-dichlorobenzyl homopolymers were synthsised with differentproportions of monomer and catalyst. The best porous structure of the polymer obtained with3068m2/g specific surface area. By introducing the nitro into thebiphenyl-dichlorobenzyl homopolymer, the nitro-substituted polymers with6.9%Ncontent was obtained.Different amount of copper nitrate were loaded on the biphenyl-dichlorobenzylhomopolymers, found that with the increase of the loaded, the decompositiontemperature of the polymer decrease gradually. When the loading amount was100%t,the peak temperature was410℃，which is the same as the80%loading amount.Different kinds of transition metal(Cu、Fe、Co、Ni) nitrates were loaded on the nitro-biphenyl-dichlorobenzyl homopolymers, found that the nitro-polymer loading coppernitrate had the lowest decomposition temperature.(3)Using the same method as above, five benzyl chloride homopolymers wereobtained with different proportions of monomer and catalyst and got the polymerwith1334m2/g specific surface area. Using the same method the nitro groups wereintroduced into the benzyl chloride homopolymer and obtained the nitro-substitutedpolymer with5.2%N content. Different amount of copper nitrate were loaded on thebenzyl chloride homopolymers, found that with the increase of the loaded, thedecomposition peak temperature of the polymer decrease gradually.(4)Using the same method as above, five copolymers were obtained withdifferent proportions of biphenyl-dichlorobenzyl and benzyl chloride. The maximumspecific surface area of the polymers is1810m2/g. Using the same method the nitrogroups were introduced into the copolymers and obtained the nitro-substitutedcopolymer with7.65%N content. Different amount of copper nitrate were loaded onthe copolymers, found that with the increase of the loaded, the decomposition peaktemperature of the polymer decrease gradually, from450℃to415℃, and when theloading amount was100%, the decomposition temperature didn’t change any more.Different kinds of transition metal(Cu、Fe、Co、Ni) nitrates were loaded on thenitro-polystyrene, found the decomposition temperature wereCu(269℃)<Co(342℃)<Ni(356℃).(5)The thermal decomposition processes of four polymers and its correspondingnitro-polymers and copper nitrate loading products were studied. The results showsthat the DSC curve of all the polymers has two exothermic peaks, the first peak temperature was in the360℃-380℃and the second peak temperature was500℃-560℃. It can be concluded that the title polymers have high thermal stability.However, the first step decomposition of the nitro-polymers happened about350℃, the mass loss were between35%and48%, corresponding to the-NO2content.The second step happened in the400-600℃, and there were no residue in the end. Sowe can speculate the first step was the decomposition of nitro, the second step was thedecomposition of the macromolecular chains.The decomposition of the Copper nitrate loaded-nitro-polystyrene happenedbetween200℃-375℃,the peak temperature was306℃,the mass loss was85%.Thepeak temperature of the other Copper nitrate loaded-nitro-polymer were about260℃and400℃. Combined with the infrared spectra of the residue after heattreatment at corresponding temperature,we can speculates that the first step ofdecomposition is the loss of crystallization water of copper nitrate, then copper nitrateand nitro starts to break down, and then the macromolecular chain starts to breakdown.