Friction Forces on Oxidized PS

PS films are prepared by spin-coating polystyrene (280 kDa, Sigma Aldrich) from 1% w/v chloroform solutions onto freshly cleaved mica (1 cm2 area) substrates. These films are placed in a standard UV-ozone reactor for 20 and 40 s [9]. Si3N4 cantilevers with integrated tips are precleaned in the UV-ozone chamber and are enriched with surface hydroxyl groups by immersion in 0.5 M NaOH for 20 min, in 0.1 M HC1 for 10 min, and in 0.5 M NaOH for 10 min (in this order). 

Lateral force microscopy (LFM) is performed simultaneously with topographical imaging in contact mode using V-shaped Si3N4 cantilevers with a nominal spring constant of 0.06 N/m. All lateral force data are acquired under Milli-Q water. We use the open cell configuration (see Sect. 3.3 in Chap. 3). To ensure meaningful comparisons of friction data acquired on different films, the same tip must be used for all the films tested. 

Data are captured in trace and retrace at a constant load ( 40 nN) for differently treated films. Secondly, the load is varied by stepwise changing the setpoint (f-d 

4 Polymer Surface and Interface Properties and (Dynamic) Processes 

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