Aging effects on the rheology of lc solutions of hydroxypropylcellulose

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Abstract

We apply the recently developed continuum theory of liquid crystalline polymers1 to interpret the behavior of the shear viscosity 7/(7) and the first normal-stress difference Ni1(γ) measured for liquid crystalline solutions (c=37%, c>c) of HPC (Aldrich, Mw=100,000) in acetic acid (AA) with different ages: 1 day, 1 month and 2 years. n(γ) and N1(γ) were measured over four decades in γ. N1(γ) is observed to change from positive to negative and again to positive, as the shear rate 7 increases. n(γ) shows a small newtonian plateau at low shear rates and a strong shear-thinning at higher values of γ. The rate of decrease of n(γ) in this region is not monotonous, as usual, but shows an “hesitation” similar to one previously observed in a different system2. The aging effect promotes a ”depolymerization3 of HPC. This, in turn, should have a strong influence on the behavior of N1(γ) and n(γ) which is indeed observed4. All these observations can be rationalized within the framework of the theory1.

Original languageEnglish
Pages (from-to)87-93
Number of pages7
JournalMolecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals
Volume261
Issue number1
DOIs
Publication statusPublished - Mar 1995
Event15th International Liquid Crystal Conference - Budapest, Hungary
Duration: 3 Jul 19948 Jul 1994

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