PI-2 to PI-7 has been prepared in the similar procedure using the chemical compositions as shown in Table 1.
PI-7 was designed to have higher calculated molecular weight (1650 g/mol) than PI-1 (1150 g/mol).
The crystal phase was also observed in PI-3, PI-5, PI-6, and PI-7, and PI-4, similar to PI-2, was amorphous.
Additionally, PI-7 with the higher calculated [M.sub.n] (1650) than PI-1(1150) showed much higher melt viscosity and decreased meltability at temperatures of 270-350[degrees]C, mainly attributed to the increase in polymer chain length.
PI-7 shows the decreased [T.sub.g] value (309[degrees]C) compared with PI-1(317[degrees]C) due to the increase in the calculated [M.sub.n].