The Flow Induced Structure in a Thermotropic Liquid Crystalline Polymer as Studied by SANS

Published

October 16, 2008

Author(s)

M D. Dadmun, S Clingman, Christopher K. Ober, A Nakatani

Abstract

Small angle neutron scattering is utilized to determine the flow induced alignment of a model thermotropic liquid crystalline polymer (LCP) as a function of shear rate and temperature. The results demonstrate that the flow induced structures in thermotropic liquid crystalline polymers have similarities and differences to those in lyotropic liquid crystalline polymer solutions. The shear rate dependence of the alignment shows that the flow induced alignment correlates very well to the viscosity behavior of the LCP in the shear thinning regime while temperature variation results in a change in the extent of alignment within the nematic phase. Relaxation results also demonstrate that the flow induced alignment remains essentially unchanged for up to an hour after the shear field has been removed. Lastly, there exists a regime at low shear rate and low temperature where alignment of the LCP molecule perpendicular to the applied shear flow is stable. These results provide important experimental evidence of the molecular level changes that occur in a thermotropic liquid crystalline polymer during flow which can be utilized to develop theoretical models and more efficiently process thermotropic polymers.

Citation

Journal Of Polymer Science

Pub Type

Journals

Keywords

shear orientation, small angle neutron scattering, thermotropic liquid crystalline polymer, viscosity

Citation

Dadmun, M. , Clingman, S. , Ober, C. and Nakatani, A. (2008), The Flow Induced Structure in a Thermotropic Liquid Crystalline Polymer as Studied by SANS, Journal Of Polymer Science (Accessed March 6, 2025)