Charla Profesor Andrey Milchev - Buckling or Bending – A Polymer Brush under Pressure

Polymer brushes are of great importance for new technologies and applications in health care, lubrication of surfaces, protective coatings, switchable wetting, etc.  We use Molecular Dynamics simulations to study the behavior of a model polymer brush comprised of semi-stiff linear macromolecules when pressure is applied on the brush surface by a planar piston. We find a two-stage process:  for a small compression the chains were shown to contract by buckling deformation whereas for a larger compression the chains exhibit a collective (almost uniform) bending deformation.
This deformation proceeds as a 2nd-order phase transition. Surprisingly, the pressure, required to keep the stiff brush at a given degree of compression, is significantly smaller than for an otherwise identical brush made of entirely flexible polymer chains!
A simple theoretical consideration suggests a ‘soliton solution’ of the pertinent nonlinear differential equation, which describes the deformation of the stiff brush, in good agreement with results of the computer experiment.

Professor Andrey Milchev
Bulgarian Academy of Sciences, Institute for Physical Chemistry, Sofia, Bulgaria

Sala de conferencias del departamento de Física, Viernes 9 de Junio 15:00 hs