Two-fluid model for the interpretation of quartz crystal microbalance response: Tuning properties of polymer brushes with solvent mixtures

Prathima C. Nalam, Leonid Daikhin, Rosa M. Espinosa-Marzal, Jarred Clasohm, Michael Urbakh, Nicholas D. Spencer

Research output: Contribution to journalArticlepeer-review

Abstract

A new approach, involving a two-fluid model, has been developed to interpret the quartz crystal microbalance response of adsorbed viscoelastic polymers. The model utilizes the Navier-Stokes-Brinkmann equation to describe the motion of a porous, semirigid, viscoelastic polymer-brush film with a viscous solvent flowing through it. The two phases, solid (polymer brush) and liquid (solvent mixture), hydrodynamically interact with each other, as represented by means of a Darcy term with a characteristic correlation factor. The two-fluid model is used to estimate structural changes in polymer brushes consisting of the copolymers poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) or poly(l-lysine)-graft-dextran (PLL-g-dextran) adsorbed on an amorphous SiO2-coated quartz surface in aqueous solutions of glycerol, ethylene glycol (EG), and dimethyl sulfoxide (DMSO). Layer thickness, polymer volume fraction, and shear modulus of the polymer films with varying co-solvent concentration are determined with this approach. It was found that preferential hydrogen-bonding interactions of solvent mixtures with the polymers leads to variation in the structural properties of the polymer brushes upon changing the co-solvent composition. Furthermore, the conformation of polymer brushes in solvent mixtures is influenced by the solvent-solvent interactions, which can be explained in terms of the free energy of solvent mixing.

Original languageEnglish (US)
Pages (from-to)4533-4543
Number of pages11
JournalJournal of Physical Chemistry C
Volume117
Issue number9
DOIs
StatePublished - Mar 7 2013
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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