The dynamic mechanical properties in shear have been studied for poly(γ‐benzyl‐L‐glutamate), poly(D,L‐propylene oxide), and poly(ethyl vinyl ether) in the 95–100° to 240–340°K. region by use of a torsional pendulum in free decay at frequencies of 0.05–1 cycles/sec. Poly (γ‐benzyl L‐glutamate) exhibits a prominent loss maximum at 288°K. (0.18 cycles/sec.) attributed to reorientational motions principally of the side chains. For poly(D,L‐propylene oxide) two loss peaks are found at ∼120°K. (0.59 cycles/sec.) and 211°K. (0.37 cycle/sec.), being attributed to motion in the amorphous regions of a small (3–4) and large number of segments, respectively. In the case of poly(ethyl vinyl ether) the principal dispersion region is found at ≳230°K., while a secondary loss maximum is located at ∼100°K. This behavior is similar to that reported for polypentene‐1 and polybutene‐1, except that the two motional processes are shifted to lower temperatures.
synopsisDielectric measurements of carefully purified specimens of polystyrene and poly(2,3,4 or 3,4-chlorostyrene) have been obtained at audio frequencies ranging from 0.1 to 20 kHz and a t temperatures between 4 and 300°K. Each of the samples exhibits a dielectric loss maximum in the range 13-50°K. The temperature of the maximum loss decreases with the addition of a substituent which lowers the symmetry of the pendant phenyl group. The results are explained by a model which invokes a coupling mechanism between two distinct modes of side group motions. This same model also explains some results of previously reported measurements of mechanical losses in similar polymers.
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