Origins of anomalous micellization in diblock copolymer solutions

Timothy P. Lodge, Joona Bang, Kenneth J. Hanley, James Krocak, Stephanie Dahlquist, Brijesh Sujan, Joseph Ott

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

The phenomenon of "anomalous" micellization is investigated in dilute solutions of two nearly symmetric poly(styrene-b-isoprene) diblock copolymers, via dynamic light scattering. In two polystyrene-selective solvents, diethyl phthalate and dimethyl phthalate, the critical micelle temperatures (cmt) are clearly determined by rather abrupt increases in the hydrodynamic radius and scattered intensity upon cooling; this corresponds to "normal" micellization. In contrast, for the same polymers dissolved in two polyisoprene-selective solvents, tetradecane and squalane, anomalous micellization was consistently observed: the hydrodynamic radius exceeded 1000 Å and the intensity was unusually large, over a modest temperature interval just above the cmt. We propose that anomalous micellization is due to the incipient phase separation of small amounts of polystyrene homopplymer, resulting from incomplete crossover during the sequential anionic polymerization of styrene and isoprene. In one sample, the presence of homopolymer (ca. 1 wt % of copolymer) was confirmed by chromatography, and removal of this impurity eliminated the anomalous micellization. Addition of similar amounts of polyisoprene homopolymer to the same sample induced anomalous micellization in the polystyrene-selective solvents, with the onset of the effect corresponding to the cloud point for the polyisoprene homopolymer. These observations support the proposed hypothesis; the extent to which this hypothesis may extend to previous reports of anomalous micellization is discussed.

Original languageEnglish
Pages (from-to)2103-2109
Number of pages7
JournalLangmuir
Volume19
Issue number6
DOIs
Publication statusPublished - 2003 Mar 18
Externally publishedYes

Fingerprint

Micellization
Polystyrenes
polyisoprenes
Block copolymers
polystyrene
copolymers
Styrene
Micelles
Hydrodynamics
phthalates
Temperature
Polyisoprenes
Homopolymerization
micelles
hydrodynamics
Isoprene
Polymerization
radii
Chromatography
Polymers

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

Cite this

Lodge, T. P., Bang, J., Hanley, K. J., Krocak, J., Dahlquist, S., Sujan, B., & Ott, J. (2003). Origins of anomalous micellization in diblock copolymer solutions. Langmuir, 19(6), 2103-2109. https://doi.org/10.1021/la0268808

Origins of anomalous micellization in diblock copolymer solutions. / Lodge, Timothy P.; Bang, Joona; Hanley, Kenneth J.; Krocak, James; Dahlquist, Stephanie; Sujan, Brijesh; Ott, Joseph.

In: Langmuir, Vol. 19, No. 6, 18.03.2003, p. 2103-2109.

Research output: Contribution to journalArticle

Lodge, TP, Bang, J, Hanley, KJ, Krocak, J, Dahlquist, S, Sujan, B & Ott, J 2003, 'Origins of anomalous micellization in diblock copolymer solutions', Langmuir, vol. 19, no. 6, pp. 2103-2109. https://doi.org/10.1021/la0268808
Lodge TP, Bang J, Hanley KJ, Krocak J, Dahlquist S, Sujan B et al. Origins of anomalous micellization in diblock copolymer solutions. Langmuir. 2003 Mar 18;19(6):2103-2109. https://doi.org/10.1021/la0268808
Lodge, Timothy P. ; Bang, Joona ; Hanley, Kenneth J. ; Krocak, James ; Dahlquist, Stephanie ; Sujan, Brijesh ; Ott, Joseph. / Origins of anomalous micellization in diblock copolymer solutions. In: Langmuir. 2003 ; Vol. 19, No. 6. pp. 2103-2109.
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