Molecular orientation, "Region I" shear thinning and the cholesteric phase in aqueous hydroxypropylcellulose under shear

Kwan Hongladarom, Wesley Roth Burghardt*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Birefringence and flow visualization are used to study molecular orientation, texture, and the cholesteric nature of a 60 wt% aqueous hydroxypropylcellulose solution at low to moderate shear rates. There is a sharp transition in behavior at a shear rate near 0.5 s-1. Below this rate, the sample shows "Region I" shear thinning, takes on a frosted appearance, has low flow-induced orientation, and exhibits faint optical diffraction characteristic of cholesteric liquid crystals. Upon flow cessation from low rates, a highly organized cholesteric phase showing bright optical diffraction is re-formed in around 5 min. Above the critical shear rate, the sample exhibits much higher orientation and a striped texture which is readily apparent with or without polarized light illumination. Upon flow cessation, molecular orientation decays significantly for up to around 400 s; however, the striped textures established during shear persist. It is suggested that persistence of the cholesteric phase under shear is responsible for the occurrence of Region I shear thinning at low shear rates in this solution.

Original languageEnglish (US)
Pages (from-to)46-53
Number of pages8
JournalRheologica Acta
Volume37
Issue number1
DOIs
StatePublished - Jan 1 1998

Keywords

  • Birefringence
  • Cholesteric phase
  • Flow visualization
  • Hydroxypropylcellulose
  • Liquid crystalline polymer

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

Fingerprint

Dive into the research topics of 'Molecular orientation, "Region I" shear thinning and the cholesteric phase in aqueous hydroxypropylcellulose under shear'. Together they form a unique fingerprint.

Cite this