Synthesis and characterization of HTPB-GAP cross-linked co-polymers

Abstract

Cross-linked co-polymers containing glycidyl azide polymer (GAP) and hydroxyl-terminated poly(butadiene) (HTPB) segments have been obtained by chemical reactions. The reactions involves two steps. In the first step the GAP macroinitiator (GAPMI) is synthesized by the condensation reaction of GAP-diol with 4,4'-azobis(4-cyanopentanoic acid) (ACPA) in the presence of N-methyl-2-chloropyridinium iodide (MCPI). The GAPMI obtained is used for the cross-linking or grafting reactions with HTPB at an elevated temperature in the second step. The cross-linked co-polymers are isolated from the crude reaction mixture by fractional precipitation technique using chloroform as solvent and methanol as non-solvent. The co-polymers have been well characterized by using IR, 1H-NMR and 13C-NMR spectral analysis, and the molecular weights of the co-polymers have been determined by gel permeation-chromatography (GPC) and vapour pressure osmometry (VPO). The co-polymer exhibited two glass transition temperatures for HTPB-GAP co-polymer, at –74.03°C and –35.84°C. During the thermal analysis, the cross-linked co-polymers exhibited two exothermic peaks and one endothermic peak, indicating the presence of HTPB and GAP polymeric chain segments in the co-polymers. Further, the TGA studies revealed a four step-weight loss, suggesting the decomposition of the co-polymer is similar to that of their homo-polymers.