Charge Domains on Polymer Surfaces

Astrid Drechsler Frank Simon (M) Leibniz Institute of Polymer Research Dresden, Hohe StraBe 6, 01069 Dresden, Germany 

SKZ Suddeutsches Kunststoff-Zentrum, Friedrich-Bergius-Ring 22, 

Keywords Atomic force microscopy Charge dissipation Charge domains Electric charges on polymer surfaces Electric field imaging mode Surface potential imaging mode 

In his phenomenological study [1], Briick ordered a number of polymers in a row describing their affinity to become positively or negatively charged when rubbed with each other. Briick s row and other comparable rows first demonstrated the fundamental relationship between the chemical structure of a polymer and its tribo-electrical charging properties. In a former work [2] we followed that idea and showed that the tribo-electrical charging of two polymer species charged in a fluidized bed clearly depends on the affinity of the polymer surface to take up electron 

All of the measurements described in this paper were carried out with polymers containing a minimum amount of additives, impurities and other accompanying substances (Table 1). 

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The tribo-electric charging of polymers is a collective phenomenon of numerous electron transfer processes in the contact zone of two colliding particles. The SPM technique allows to visualize the charge distribution on polymer surfaces. It was shown that oppositely charge domains can stably exist side by side although considerable filed strengths are present. 

A surface is that part of an object which is in direct contact with its environment and hence, is most affected by it. The surface properties of solid organic polymers have a strong impact on many, if not most, of their apphcations. The properties and structure of these surfaces are, therefore, of utmost importance. The chemical stmcture and thermodynamic state of polymer surfaces are important factors that determine many of their practical characteristics. Examples of properties affected by polymer surface stmcture include adhesion, wettability, friction, coatability, permeability, dyeabil-ity, gloss, corrosion, surface electrostatic charging, cellular recognition, and biocompatibility. Interfacial characteristics of polymer systems control the domain size and the stability of polymer-polymer dispersions, adhesive strength of laminates and composites, cohesive strength of polymer blends, mechanical properties of adhesive joints, etc. 

Fig. 2 Model concept of the contact charging of polymer grains, a Contact between an electron pair donator domain (empty dots) of the particle 1 and an electron pair acceptor domain (grey dots) of the particle 2. Charge transfers (e-) are taking place. After separation the two particles (b), a positively charged ( ) and a negative charged ( ) domain, remain on the particles surface...

Structural descriptors at the secondary level (mesoscale) are topology and domain size of polymeric aggregates (persistence lengths and radius), effective length and density of charged polymer sidechains on the surface, properties of the solution phase (percolation thresholds and critical exponents, water structure, proton distribution, proton mobility and water transport parameters). Moreover, -point correlation fimctions could be defined that statistically describe the structme, containing information about surface areas of interfaces, orientations, sizes, shapes and spatial distributions of the phase domains and their connectivity [65]. These properties could be... 

In this chapter I present the current state of three aspects in physicochemistry of nanoparticles critical for understanding structure and properties of nanocomposites. This also relates to adsorption and chemisorption of macromolecules on nanoparticle surfaces from solutions the generation of interfaces phenomena of surface conductivity and specific interactions that depend on the chain origin and length, its conformation, the composition of copolymers and so on. In polyelectrolytes similarly charged with nanoparticles, hydrophobic polymers are inclined to associate ionic groups and form domains as microphases of ion regions. 

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