CHARACTERIZATION OF POLY(AMIDE IMIDE)S IN SOLUTION

Dimethyl acetamide (DMAA) solutions of poly(amide imide)s (PAIs) from dichlorodianhydrides of trimellitimide- and/or pyromellitimide-N-aceti c acids (TMI and PMI), linear aromatic diamines (LADs) and/or cardo 9, 9'-bis-phenylfluorene diamine (CDA) were characterized by measurements of the specific heat capacity in the temperature interval 150-370 K, of heats of dilution in DMAA at room temperature, and of the apparent viscosity in the temperature interval 288-373 K. The main experimental results may be summarized as follows. (i) Cardo PAI(TMI/CDA) and PAI( PMI/CDA) exhibited a higher degree of inter-segmental association in q uiescent solutions compared with PAI(TMI/LAD). (ii) Dilatant flow beha vior attributed to the formation of temporary flow aggregates of shear -oriented chain segments is most pronounced in semi-dilute solutions o f PAI(TMI/DPA). (iii) Discontinuous, jump-like changes of the normaliz ed solvent melting heat, as well as of the activation energy for visco us flow as a function of the PAI concentration in solution, are interp reted as evidence for the onset of the overlap of macromolecular coils at the regime crossover from a dilute solution to a semi-dilute solut ion.