Changes of the Molecular Mobility of Poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone) upon Drawing,Studied by Dielectric Relaxation Spectroscopy

Dielectric relaxation spectroscopy (DRS) of poly(ε-caprolactone) with different draw ratios showed that the mobility of polymer chains in the amorphous part decreases as the draw ratio increases.The activation energy of the α process,which corresponds to the dynamic glass transition,increases upon drawing.The enlarged gap between the activation energies of the αprocess and the β process results in a change of continuity at the crossover between the high temperature a process and the α and β processes.At low drawing ratios the a process connects with the βprocess,while at the highest drawing ratio in our measurements,the a process is continuous with the a process.This is consistent with X-ray diffraction results that indicate that upon drawing the polymer chains in the amorphous part align and densify upon drawing.As the draw ratio increases,the α relaxation broadens and decreases its intensity,indicating an increasing heterogeneity.We observed slope changes in the α traces,when the temperature decreases below that at which τα ≈ 1 s.This may indicate the glass transition from the ‘rubbery’ state to the non-equilibrium glassy state.