TY - JOUR
T1 - Shear-history dependent 'equilibrium' states of liquid-crystalline hydroxypropylcellulose solutions detected by rheo-nuclear magnetic resonance
AU - Godinho, M. H.
AU - Van Der Klink, J. J.
AU - Martins, A. F.
PY - 2003/8/20
Y1 - 2003/8/20
N2 - The liquid-crystalline polymer system formed by solutions of hydroxypropylcellulose in water has a well known anomaly in the dependence of its mechanical complex modulus on its rheological history. After cessation of an initial rapid shear, the system evolves towards an 'equilibrium' state with a high modulus; after slow shear the 'equilibrium' state has a low modulus. Attempts to distinguish the two states by light scattering, birefringence or x-ray scattering have been unsuccessful. We present the first locally probing experiment, rheo-NMR, that sees a difference between these states. The results show clearly that the low-modulus state is ordered and evolves out of a state that has no macroscopic order (but may be ordered at the mesoscopic level) immediately after cessation of the shear. The high-modulus state is much less ordered, although it evolves from a rather well flow-aligned state immediately after cessation of the shear.
AB - The liquid-crystalline polymer system formed by solutions of hydroxypropylcellulose in water has a well known anomaly in the dependence of its mechanical complex modulus on its rheological history. After cessation of an initial rapid shear, the system evolves towards an 'equilibrium' state with a high modulus; after slow shear the 'equilibrium' state has a low modulus. Attempts to distinguish the two states by light scattering, birefringence or x-ray scattering have been unsuccessful. We present the first locally probing experiment, rheo-NMR, that sees a difference between these states. The results show clearly that the low-modulus state is ordered and evolves out of a state that has no macroscopic order (but may be ordered at the mesoscopic level) immediately after cessation of the shear. The high-modulus state is much less ordered, although it evolves from a rather well flow-aligned state immediately after cessation of the shear.
UR - http://www.scopus.com/inward/record.url?scp=0042789043&partnerID=8YFLogxK
U2 - 10.1088/0953-8984/15/32/307
DO - 10.1088/0953-8984/15/32/307
M3 - Article
AN - SCOPUS:0042789043
VL - 15
SP - 5461
EP - 5468
JO - Journal Of Physics-Condensed Matter
JF - Journal Of Physics-Condensed Matter
SN - 0953-8984
IS - 32
ER -