NUCLEAR-MAGNETIC-RESONANCE APPROACH TO THE CHARACTERIZATION OF THE PHASE-DIAGRAM OF POLYACRYLONITRILE IN TERNARY SOLUTIONS

This work deals with the properties of the temperature concentration p hase diagram of ternary polyacrylonitrile solutions that were mainly o bserved from the transverse magnetic relaxation of protons attached to polymer chains, used to disclose the presence of solid-state domains. The binary solvent was a mixture of dimethylformamide (DMF) and water ; the molar fraction of monomeric units was varied from 0 to 0.5, whil e the relative molar fractions of DMF and water were 1:1 or 2:1. The s olvent quality was found to decrease upon addition of water. A curve ( liquidus) that relates the temperature of formation of solid-state dom ains to the initial polymer concentration in solution was drawn from n uclear magnetic resonance (n.m.r.). The demixing part of the liquidus, determined as a plateau from n.m.r., was identified on observing a cl oud-point curve. The main feature of the phase diagram concerns the sp ecific behaviour of solutions observed whenever the concentration of d isordered segments becomes lower than half the initial polymer concent ration.