Elongational flow studies on the phase separation of hydroxypropylcellulose solution

Abstract

The phase separation of hydroxypropylcellulose (HPC) in a mixed solvent of glycerol and water was investigated by an elongational flow birefringence method. In the one-phase region, the elongational flow birefringence had the characteristics of a typical coil-stretch transition-like pattern with a critical elongational strain rate \documentclass{article}\pagestyle{empty} \begin{document}$\dot \varepsilon_c.$\end{document} \documentclass{article}\pagestyle{empty} \begin{document}$\dot \varepsilon_c.$\end{document} increased monotonously with temperature, but in the vicinity of the phase-separation point, \documentclass{article}\pagestyle{empty} \begin{document}$\dot \varepsilon_c.$\end{document} began to decrease even in the one-phase region. In the two-phase region, the flow-induced birefringence pattern contained both a rigid rod-like response and the coil-stretch transition-like response of a flexible polymer. The appearance of the rod-like birefringence pattern indicates the association of HPC chains to form a precursor of the liquid-crystalline phase formation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2984–2991, 2002