Ultrasonic investigation on segmental motion of some polymers in solution

688-694A novel method involving ultrasonic velocity measurement has been adopted to determine temperature of onset of segmental motion in some poly (amide ester)s in solution. Acoustical parameters such as adiabatic compressibility, free length, internal pressure, fractional free volume, coefficient of thermal expansion, coefficient of adiabatic compressibility and exponent of repulsive forces of eight poly(amide ester)s are calculated from the measured ultrasonic velocity and density values at different temperatures in N,N-dimethylacetamide solution. The abrupt change in ultrasonic velocity of polymer solutions at characteristic temperature is primarily due to the molecular interaction between polymeric molecules and to some extent, due to polymer-solvent interaction. Segmental motion starts at this temperature in the polymer solutions and are comparable to the glass transition temperatures determined for the solid samples by differential calorimetric method