Structural Oscillations of the Poly(γ-benzyl-L-glutamate) Solution after Reversal of Shear Flow

Abstract

Transient stress of a liquid crystalline solution of poly (γ-benzyl-L-glutamate) after flow reversal was examined to prove shear-induced structural changes in mesoscopic domain level of the system. At first, a theoretical prediction for the transient behavior of flow reversal was discussed using recent polydomain theory of Larson and Doi. After obtaining damped oscillatory stresses for the flow reversal, two experiments such as stress relaxation and stress growth were additionally performed at strains at which stress maxima and minima after the flow reversal appeared. Analysis of characteristic relaxation times for the stress relaxation curves at each extremum can prove the damped oscillatory pattern of domain size after the flow reversal. The orientational change of polydomain field after the reversal also oscillates in the damped manner, which can be demonstrated by the phase shifts deviated from the steady state response.