Rheological Evidence of Composition Fluctuations in an Unentangled Diblock Copolymer Melt near the Order-Disorder Transition

Justin G Kennemur; Marc A Hillmyer; Frank S Bates

doi:10.1021/mz4001892

Rheological Evidence of Composition Fluctuations in an Unentangled Diblock Copolymer Melt near the Order-Disorder Transition

ACS Macro Lett. 2013 Jun 18;2(6):496-500. doi: 10.1021/mz4001892. Epub 2013 May 24.

Authors

Justin G Kennemur¹, Marc A Hillmyer², Frank S Bates²

Affiliations

¹ Department of Chemical Engineering and Materials Science and ‡Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States.
² Department of Chemical Engineering and Materials Science and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States.

PMID: 35581805
DOI: 10.1021/mz4001892

Abstract

Rheological and small-angle X-ray scattering (SAXS) measurements were conducted on a symmetric, low molar mass (M_n = 17.6 kg/mol), poly(tert-butylstyrene-block-methyl methacrylate) (PtBS-PMMA) diblock copolymer near the order-disorder transition temperature (T_ODT = 193 ± 1 °C). Evidence of composition fluctuations is apparent in the low frequency elastic (G') and loss (G″) moduli and in the temperature dependence of the peak scattering intensity, I(q*), up to 50 °C above the T_ODT. These findings demonstrate that chain entanglements are not responsible for the well-documented fluctuation mode in the terminal viscoelastic regime of block copolymer melts.