Synthesis and thermal behavior of gem-dinitro valerylated polystyrene

Commercial polystyrene has been chemically modified with 4,4-dinitro valeryl chloride by use of Friedel- Crafts acylation reaction in the presence of anhydrous aluminum chloride in a mixture of 1,2-dichloroethane and nitrobenzene. The modified polystyrene containing -COCH₂CH ₂C(NO₂)₂CH₃ fragments in side phenyl rings, named gem-dinitro valerylated polystyrene (GDN-PS), was characterized by an Ubbelohde's viscometer, FTIR, and 1H NMR spectroscopy. Simultaneous thermogravimetry-differential thermal analysis and differential scanning calorimetry (DSC) have been used to study thermal behavior of the polymer. The results of TG analysis revealed that the main thermal degradation for the GDN-PS occurs during two temperature ranges of 200-300 and 300-430 °C. The DTA curve of GDN-PS is showing a visible exothermic peak at 253.8 °C corresponding to the decomposition of gem-dinitro valeryl groups. The decomposition kinetic of the gem-dinitro groups for GDN-PS with degree of substitution (DS) 11 % was studied by non-isothermal DSC under various heating rates. Kinetic parameters such as activation energy and frequency factor for thermal decomposition of GDN-PS with DS 11 % were evaluated via the ASTM E698 and two isoconversional methods.