Acoustic Relaxation of Liquid Poly(tetramethylene oxide) with Hydroxyl and AcyL Terminal Groups

摘要

Isotherms of sound absorption and velocity vs. frequency were measured for poly(tetramethylene oxide)-300 ended by CH_3 and OH groups. The measurements were performed 5-2500 MHz and at different tempertures at 313-353 K. The results are presented and analysed using different formats to examine the frequency dependnece of the atenuation alpha(f)/f~2 = f(f) and mu(f) lambda (where alpha(f) is sound attenuation at frequencies f, alpha_exc is excess sound attenuation at frequency f, and lambda is the sound wavelength) as well as frequency dependence of real (M') and imaginary (M") parts of the mechanic modulus. Two dispersion regions are present on all sound absorption isotherms. Arrhenius curves of the relaxation time are fitted and analysed using Vogel-Tamann-Fulcher and Kohlrausch-Williams-Watts functions. Relaxation time in the first dispersion region, as well as relaxation strength, are less affected by the terminal groups of PTMO than in the second dispersion region. Alternation of the different end-capping groups has greater influence on the realaxatioin strength values of the second dispersion region characteristic of the local segmental motions of the polymers.