Chain stretch and relaxation in transient entangled solutions probed by double-step strain flows

Non-reversing and reversing double-step strain flows on concentrated entangled polystyrene in diethyl phthalate or tricresyl phosphate were employed to characterize transient entanglement properties affecting subsequent chain stretch and relaxation. An extended Doi-Edwards tube theory for double-step strain flows was employed to retrieve the phenomenological stretch relaxation function following a second large probe strain imposed on specially selected time scales that permit a direct assessment of the modified chain stretch with varying transient entanglement structure. Compared with single-step strain result, the maximum mean-square segmental stretch was noted to reduce by as much as 33% and 48% for non-reversing and reversing flows, respectively, with a probe strain gamma(2)=7.