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Color, Structure, and Rheology of a Diblock Bottlebrush Copolymer Solution

Published

Author(s)

Matthew A. Wade, Dylan Walsh, Johnny Ching-Wei Lee, Elizabeth Kelley, Kathleen Weigandt, Damien Guironnet, Simon A. Rogers

Abstract

A structure-property-process relation is established for a diblock bottlebrush copolymer solution, through a combination of rheo-neutron scattering, imaging, and rheological measurements. Polylactic acid-b-polystyrene diblock bottlebrush copolymers were dispersed in toluene with a concentration of 175 mg/ml, making a lamellar phase. All measurements were carried out at 5 °C. The solution color, as observed in reflection, is shown to be a function of the shear rate. Under equilibrium and near-equilibrium conditions, the solution has a green color. At low shear rates the solution remains green, while at intermediate rates it is cyan, and at the highest rates applied the solution is indigo. The lamellar spacing is shown to be a decreasing function of shear rate, partially accounting for the color change. The lamellae are oriented 'face-on' with the wall under quiescence and low shear rates, while a switch to 'edge-on' is observed at the highest shear rates, where the reflected color disappears. The intramolecular distance between bottlebrush polymers does not change with shear rate, although at high shear rates, the bottlebrush polymers are preferentially aligned in the vorticity direction within the lamellae. We therefore form a consistent relation between structure and function, spanning a wide range of length scales and shear rates.
Citation
Soft Matter
Volume
16
Issue
21

Keywords

Rheology, VSANS, Bottlebrush block copolymers

Citation

Wade, M. , Walsh, D. , Lee, J. , Kelley, E. , Weigandt, K. , Guironnet, D. and Rogers, S. (2020), Color, Structure, and Rheology of a Diblock Bottlebrush Copolymer Solution, Soft Matter, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=930153 (Accessed April 21, 2024)
Created June 6, 2020, Updated October 12, 2021