Interfacial reactivity of block copolymers: Understanding the amphiphile-to-hydrophile transition

Alessandro Napoli, Harry Bermudez, Jeffrey A. Hubbell

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Block copolymers offer an interesting platform to study chemically triggered transitions in self-assembled structures. We have previously reported the oxidative degradation of vesicles made of poly(propylene sulfide)-poly(ethylene glycol) (PPS-PEG) copolymers. Here we propose a mechanism for vesicle degradation deduced from copolymer conformational changes occurring at the air/water interface in a Langmuir trough together with a reactive subphase. The hydrophobic PPS block is converted into hydrophilic poly(propylene sulfoxide) and poly(propylene sulfone) by oxidation upon exposure to 1% aqueous H2O2 subphase. As a result, a dramatic increase in area per molecule at constant surface pressure (II) was observed, followed by an apparent decrease (recorded as decrease in area at constant II) due to copolymer dissolution. For monolayers at the air/water surface, the large interfacial tensions present suppress increases in local curvature for alleviating the increased hydrophilicity of the copolymer chains. By contrast, vesicles can potentially rearrange molecules in their bilayers to accommodate a changing hydrophilic-lipophilic balance (HLB). Similar time scales for monolayer rearrangement and vesicle degradation imply a common copolymer chain solubilization mechanism, which in vesicles lead to an eventual transition to aggregates of higher curvature, such as cylindrical and spherical micelles. Subtle differences in response to the applied surface pressure for the diblock compared to the triblock suggest an effect of the different chain mobility.

Original languageEnglish
Pages (from-to)9149-9153
Number of pages5
JournalLangmuir
Volume21
Issue number20
DOIs
StatePublished - Sep 27 2005
Externally publishedYes

Fingerprint

Amphiphiles
block copolymers
Block copolymers
copolymers
Copolymers
reactivity
polypropylene
Polypropylenes
sulfoxide
degradation
Degradation
Monolayers
curvature
Unilamellar Liposomes
Sulfones
Molecules
sulfones
Water
air
Hydrophilicity

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

Cite this

Interfacial reactivity of block copolymers : Understanding the amphiphile-to-hydrophile transition. / Napoli, Alessandro; Bermudez, Harry; Hubbell, Jeffrey A.

In: Langmuir, Vol. 21, No. 20, 27.09.2005, p. 9149-9153.

Research output: Contribution to journalArticle

Napoli, Alessandro ; Bermudez, Harry ; Hubbell, Jeffrey A. / Interfacial reactivity of block copolymers : Understanding the amphiphile-to-hydrophile transition. In: Langmuir. 2005 ; Vol. 21, No. 20. pp. 9149-9153.
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