Unusual thermal behavior of the aromatic polyamide dendrons

Thermal behavior of the second generation aromatic polyamide dendrons was e xamined. The 5-bromo substituted dendron at a focal point (2) which was rep recipitated from methanol had an endothermic peak of 208 degreesC and an ex othermic peak of 254 degreesC in the DSC results. In the observation using a polarization microscope, the dendron 2 seemed to melt and then crystalliz ed by heating. The melt-like state was not observed in the case of the dend ron 2 recrystallized from ethanol. In addition, G2 aromatic polyamide dendr ons having various substituents at a focal point were synthesized. The DSC curve of 4-methyl substituted dendron (5) showed two endothermic peaks of 2 15 degreesC and 237 degreesC, and an exothermic peak of 265 degreesC. The s tate of dendron 5 was consecutively changed to melt-like state having biref ringence, isotropic melt-like state and crystal by heating. Although two en dothermic peaks at 275 degreesC and 327 degreesC were observed in the DSC f or 5-methyl ester substituted dendron (6), the melt-like state and crystall ization were not found.