Solution behavior of copoly(amide imide)s

Dimethyl acetamide (DMAA) solutions of copoly(amide imide)s (coPAIs) synthe sized from the dichloro-dianhydride of trimellitimide-N-acetic acid and mix tures of diphenylmethane diamine (DPA) with cardo-9,9'-bis-phenylfluorene d iamine (CDA) were characterized by measurements of the specific heat capaci ty in the temperature interval 150-370 K, of heats of dilution in DMAA at r oom temperature, and of the apparent viscosity in the temperature interval 288-373 K. It was established that the degree of inter-segment interactions in quiescent solutions of coPAIs increased, and the contribution of the sh ear-thickening flow mechanism of semi-dilute solutions decreased, the lower the DPA/CDA ratio. The regime cross-over from dilute solution to semi-dilu te solution manifested itself as jump-like changes of the normalized solven t melting heats and of the activation energies for viscous flow, as well as breaks in the heats of dilution vs. concentration plots.