A novel procedure for the preparation of hydrophobic spherical particles fr
om thermoplastic materials, such as polyethylene (PE) or fossil resin (FR),
is presented. These particles are particularly useful in the determination
of surface forces with the atomic force microscope using the colloidal pro
be technique. The preparation steps include (i) suspending powdered polymer
(PE and FR) in glycerol, (ii) heating the suspension above the melting poi
nt of the polymer. (iii) solidification of dispersed PE/FR droplets at a re
duced temperature, (iv) filtration of the particles, and (v) washing/drying
of the product. Such produced particles of PE and FR had a broad size dist
ribution (2-50 mu m) and a spherical shape. The surfaces of these particles
were relatively smooth, with a small number of asperities, and/or attached
satellite particles or non-spherical debris. Analytical examination of the
polymer surface, before and after treatment with hot glycerol, by SEM, AFM
, contact angle, XPS, and FTIR measurements revealed only slight chemical c
hanges on the surface caused by this treatment, which included a decrease i
n the hydrophobicity of the polymer surface caused by an increased amount o
f oxygen-containing polar groups. These changes were greatly diminished aft
er drying, and the hydrophobicity of the PE and FR surfaces was, at least p
artially. restored.