Block copolyetheresters with poly(trimethylene 2,6-naphthalenedicarboxylate) segments: Effect of composition on thermal properties

Block copolyetheresters with hard segments of poly(trimethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were prepared by melt polycondensation of dimethyl 2,6-naphthalenedicarboxylate, 1,3-propanediol and poly(tetramethylene ether)glycol (PTMEG) of molecular weights of 650, 1000 and 2000. The block copolyetheresters were characterized by FTIR, ¹H NMR, DSC, X-ray diffraction, TSC (thermal stimulated current), DMA and TGA. It was found that the thermal transitions were dependent on the composition. As the charge molar ratio of PTMEG to dimethyl 2,6-naphthalenedicarboxylate, x, increased, the T_m and ΔH_m of the polyester segments decreased, which has been also confirmed by the X-ray diffraction data. The polyether segments of the block copolyetheresters derived from PTMEG2000 could crystallize after cooling, but those of the block copolyetheresters derived from PTMEG1000 and PTMEG650 could not crystallize. The DSC, TSC and DMA results show consistent T_g data of the polyether segments. Based on the shift in T_g of the polyether segments, the amorphous parts of the polyether segments and the amorphous parts of the polyester segments were immiscible for the block copolyetheresters derived from PTMEG2000, but became partially miscible for the block copolyetheresters derived from PTMEG1000 and PTMEG650. The TGA results indicated that composition had little effect on thermal degradation under nitrogen.