{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,7]],"date-time":"2025-10-07T11:57:29Z","timestamp":1759838249784},"reference-count":19,"publisher":"Wiley","issue":"9","license":[{"start":{"date-parts":[[2003,3,6]],"date-time":"2003-03-06T00:00:00Z","timestamp":1046908800000},"content-version":"vor","delay-in-days":3108,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers for Advanced Techs"],"published-print":{"date-parts":[[1994,9]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>The constitutive equations for liquid crystalline polymers recently proposed by one of us [1] are applied here to interpret the behaviour of the shear viscosity \u03b7\n<jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-1.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content> and the first normal stress difference N<jats:sub>1<\/jats:sub>(<jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-2.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content>) measured for liquid crystalline (LC) solutions of hydroxypropylcellulose in acetic acid. N<jats:sub>1<\/jats:sub>(<jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-3.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content>) is observed to change from positive to negative and again to positive, as the shear rate <jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-4.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content> increases, at lower concentrations, in the LC phase. The <jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-5.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content>\u2010values at which N<jats:sub>1<\/jats:sub> changes sign depend on the molecular mass (degree of polymerization) and on the concentration. \u03b7 <jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-6.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content> shows a small Newtonian plateau at low shear rates and a strong shear\u2010thinning at higher values of <jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-7.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content>. The rate of decrease of \u03b7 <jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-8.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content> in this region shows an \u201chesitation\u201d similar to one previously observed in LC solutions of poly\u2010\u03b3\u2010benzyl\u2010L\u2010glutamate PBLG. All these observations can be rationalized within the frame\u2010work of Martins' theory. The expressions for N<jats:sub>1<\/jats:sub>(<jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-9.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content>) and \u03b7 <jats:styled-content>$ \\dot \\gamma $<jats:inline-graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"graphic\/tex2gif-ueqn-10.gif\" xlink:title=\"equation image\" \/><\/jats:styled-content> derived from this theory fit very well (quantitatively) to the experimental data and some fundamental viscoelastic parameters of the system under study are thereby obtained for the first time.<\/jats:p>","DOI":"10.1002\/pat.1994.220050922","type":"journal-article","created":{"date-parts":[[2003,4,17]],"date-time":"2003-04-17T13:09:22Z","timestamp":1050584962000},"page":"596-599","source":"Crossref","is-referenced-by-count":8,"title":["The first normal stress difference and viscosity in shear of liquid crystalline solutions of hydroxypropylcellulose: new experimental data and theory"],"prefix":"10.1002","volume":"5","author":[{"given":"F.","family":"Fried","sequence":"first","affiliation":[]},{"given":"C. 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