Interfacial Tension Measurement and Micellization in a Polymer Blend with Copolymer Surfactant: A False Critical Micelle Concentration

Kwanho Chang, Christopher W. Macosko, David C. Morse

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

The interfacial tension between polystyrene (PS) and polybutadiene (PB) homopolymers is measured in the presence of a nearly symmetric poly(styrene-b-butadiene) (SB) copolymer and compared to independent measurements of the critical micelle concentration (CMC) by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS), and to self-consistent field theory (SCFT) predictions. Interfacial tension is measured with a spinning drop tensiometer (SDT) containing a drop of PB in a PS matrix, using samples in which varying concentrations of SB copolymer were initially added to either PS or PB. When SB is premixed with PS, the dependence of the interfacial tension γ upon copolymer concentration c is qualitatively similar to that expected in equilibrium, showing a decrease of γ with increasing c for c less than an apparent CMC and then saturating at higher concentrations. TEM and SAXS studies of a binary mixture of the same copolymer and PS homopolymer show, however, that the true CMC in PS is much lower than the apparent CMC inferred from these SDT experiments. We analyze the role of transport limitations in this experiment and propose that this discrepancy may be a result of a suppressed copolymer chemical potential near the interface due to continual diffusion of copolymer into the PB drop.

Original languageEnglish (US)
Pages (from-to)8154-8168
Number of pages15
JournalMacromolecules
Volume48
Issue number22
DOIs
StatePublished - Nov 16 2015

Fingerprint Dive into the research topics of 'Interfacial Tension Measurement and Micellization in a Polymer Blend with Copolymer Surfactant: A False Critical Micelle Concentration'. Together they form a unique fingerprint.

  • Cite this