Swelling of Polymer Films Ex Situ

Swelling of Polymer Films Ex Situ Sample Preparation Spin-coating 

Polymer films, e.g., poly((V-hydroxysuccinimidyl methacrylate) (PNHSMA) [68], are prepared by spin-coating polymer solutions in a suitable solvent (here DMSO with a typical concentration between 10 and 20 mg/ml) onto clean silicon wafers. To remove traces of the solvent, the films are dried in vacuum for several days. Some of the sample is immersed in PBS buffer for swelling time of 100 min, followed by rapid drying of the surface in a gentle stream of nitrogen. For the determination of 

We use a standard tapping/intermittent contact mode set-up, which is set up as described in Sect. 3.2 in Chap. 3. The operation frequency and amplitude are adjusted to v at 0.85 A0 and 150 nm, respectively. Because of the softness and stickiness of the swollen polymer film, this high amplitude is advisable to avoid permanent tip-sample contact/adherence during the scans. Immediately prior to engaging, the phase signal is zeroed. The crude and fine engagement procedures are carried out as described in Chap. 2. After the successful engagement, the operation point must be carefully adjusted. 

The captured AFM height images are subjected to a first-order plane fit (that takes only the film plane into account) followed by a cross-section analysis. As shown in the cross-sectional plots in Fig. 4.37, the polymer film remains homogeneous also after swelling in aqueous buffer (pH = 7.4, ionic strength = 0.15 M). 

4 Polymer Surface and Interface Properties and (Dynamic) Processes 

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