Multimode 8

AFM was used to profile the surface topography of spin-cast films containing 10%–40% (w/w) sorbitol within host matrices of PVAc, PVAc (20, 40 DH) after spin-coating and after annealing. Annealing was achieved by heating the films to 70 °C overnight in an oven. 40 × 40 μm, 10 × 10 μm, 5 × 5 μm, and 1 × 1 μm AFM images were acquired using a Bruker^® Multimode 8 with Digital Instruments^® Nanoscope V scanning probe microscope set to operate via the Peakforce QNM in air analysis mode. ARROW-NCR-50 probes with a nominal force constant of 42 N/m were used to collect 512 × 512 pixel images. Images were analysed using Gwyddion software. This programme corrected the natural curvature of height that is caused by rastering of the film sample with respect to the cantilever via a second-order ‘flattening’. Furthermore, the software enabled in depth cross-section and roughness analysis on the scanned images. The root mean square of roughness value R_q represents the standard deviation of the distribution of heights, allowing the surface roughness to be described by a statistical method and is calculated as follows: $R_q=\sqrt{{\displaystyle \sum }_{k=0}^N\frac{1}{N}{\left(z_k-\overline{z}\right)}^2}$

UV-Vis absorption spectra were acquired using a UV-Vis spectrophotometer (CARY-5000, Varian). The thickness values of the cast P3HT films were measured using an ellipsometer (J. A. Woollam Co. Inc.). The film morphologies were characterized by atomic force microscopy (AFM, Multimode 8, Digital Instruments). Grazing incidence X-ray diffraction (GIXD) studies were performed at the 3C, 5A, 9A, and 9C beam lines of the Pohang Accelerator Laboratory, Korea. The electrical performances of the OFETs were characterized using a semiconductor analyzer (Keithley 4200) at room temperature. The field-effect mobility (μ_FET) and threshold voltage (V_T) were estimated in the saturation regime (V_D = −80 V) according to the equation10 :

where I_D is the drain current, C_g is the capacitance of the gate dielectric, and V_G is the gate–source voltage.

Samples (5 µl) of foam were deposited onto a freshly cleaved mica surface (1.5 × 1.5 cm; G250-2 Mica sheets 25 × 25 × 0.15 mm; Agar Scientific Ltd, Essex, UK) and left to dry at room temperature for 1 h before imaging. The images were obtained by scanning the mica surface in air under ambient conditions using a Scanning Probe Microscope (MultiMode^® 8, Digital Instruments, Santa Barbara, CA, USA; Bruker Nanoscope analysis software v. 1.40), operating using the PeakForce QNM mode. The AFM measurements were obtained using ScanAsyst-air probes, for which the spring constant (0.58 N m⁻¹; nominal 0.4 N m⁻¹) and deflection sensitivity had been calibrated, but not the tip radius (the nominal value used was 2 nm).