Wilhelmy plate. Between runs, the trough was cleaned with ethanol and rinsed several times with

Millipore filtered water (resistivity > 18.2 MGZ.cm). The samples were typically prepared by

dissolving approximately 1 mg of polymer in 1 mL of chloroform. Volumes ranging from 10 to

30 puL were spread dropwise on a Millipore filtered water subphase with a gastight Hamilton

syringe. The chloroform was allowed to evaporate for 30 min to ensure no residual solvent

remained. When not in use, the volumetric flasks containing the polymer solutions were wrapped

with Teflon tape followed by Parafilm and stored at 10 OC in order to prevent changes in

concentration due to chloroform evaporation. In all the experiments, subphase temperature and

barrier speed were kept constant at 25 OC and 5 mm/min, respectively, unless otherwise stated.

4.4.2 AFM Imaging

 The LB films were formed by transferring the Langmuir films of the PEO-b-PCL block

copolymers (linear and star-shaped) and the homopolymers onto freshly cleaved mica at the

desired surface pressure which was attained at compression/expansion rates of +/-5 mm/min.

Once the films had equilibrated at a constant surface pressure for 15 min, the mica substrate was

then pulled out of the water subphase at a rate of 1 mm/min. All the transfer ratios were close to

unity unless otherwise stated, which is indicative of successful transfer. The transferred films

were air-dried in a desiccator for 24 h and subsequently scanned in tapping mode with a

Nanoscope III AFM (Digital Instruments, Inc., Santa Barbara, CA) by use of Nanosensors

silicon probes (dimensions: T = 3.8-4.5 pum, W = 26-27 pum, L = 128 pum). All the images were

processed with a second-order flattening routine.