Effect of substrate anchoring on the mechanical strength of Langmuir-Blodgett bilayers

James Schneider, Yoav Dori, Matthew Tirrell, Ravi Sharma

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Using the surface-force apparatus (SFA), we have made out-of-contact force and in-contact adhesion measurements between composite Langmuir-Blodgett (LB) bilayers. The outer layer is a crystalline monolayer of a novel glycine-containing amphiphile, whose headgroups make a strong, hydrogen-bond-aided adhesion when in normal contact with an identical monolayer. Two different inner layers were studied, with different affinities for the mica substrate. One, a crystalline monolayer of the phospholipid dipalmitoyl phosphatidyl-ethanolamine (DPPE), is held onto mica by comparatively weak interactions. Another monolayer, a covalently polymerized network of octadecyltriethoxysilane (OTE), is covalently anchored to plasma-treated mi ca through the thermal hydrolysis of silanol groups on both substrate and monolayer. We observe that separation of two DPPE/glycine-amphiphile bilayers in hydrogen-bonded contact leads to fracture at the mica/bilayer interface, with a pull-off force of F/R · · 75 mN/m. Bonded OTE/glycine-amphiphile bilayers fracture at the OTE/glycineamphiphile interface, with a pull-off force of F/R · · 142 mN/m. These results demonstrate that the mechanisms of LB film fracture cannot be explained considering only the breaking of hydrophobic contacts between neighboring amphiphile tails.

Original languageEnglish (US)
Pages (from-to)772-777
Number of pages6
JournalThin Solid Films
Volume327-329
Issue number1-2
DOIs
StatePublished - 1998
Externally publishedYes

Keywords

  • Adhesion
  • Langmuir-Blodgett bilayers
  • Surface-force apparatus

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