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CPP: Chemische Physik und Polymerphysik

CPP 5: Polyelectrolytes

CPP 5.11: Vortrag

Montag, 27. März 2006, 17:15–17:30, ZEU 160

Melting of Polyelectrolyte Multilayer Capsules Investigated with AFM Force Spectroscopy — •Renate Mueller and Andreas Fery — Max Planck Institute of Colloids and Interfaces, 14424 Potsdam

Microcapsules formed from polymer networks play an important role in both applications like encapsulation (drugs, cosmetics) and in microbiology where these structures are abundant (cell walls, virus capsids). We use Polyelectrolyte multilayer capsules as model systems to study the physico-chemical background of polymeric microcapsule mechanics.

The combination of the colloidal probe AFM technique and an optical microscope allows us to investigate the compliance of individual shells and derive elastic constants of the shell’s wall material [1]. Here we explore how temperature affects the mechanical properties of our system. We find a strong softening for capsules formed from Poly(styrene sulfonate)/Poly(diallydimethylammonium chloride), which we explain as transition from a glassy/rubbery to a viscoelastic state [2]. Shape changes occur in the viscoelastic state like shrinking for spherical shells [3] or more complex phenomena for non-spherical objects; we discuss them as surface tension effects. The shape can be frozen upon returning to T=25 ^∘C, thus the shape can be controlled on the nanoscale. Additional calorimetric experiments on the system will clarify the nature of the softening transition.

[1] F. Dubeuil et al., Eur. Phys. J. E, 2003, 12, 215-221.

[2] R. Mueller et al., Macromolecules, 2005, 38, 9766-9771.

[3] K. Köhler et al., Macromolecules, 2005, 109, 18250-18259.