Atomic force microscopy study of hydroxypropylcellulose films prepared from liquid crystalline aqueous solutions

We have shown in this work that a tunable topographical system can be obtained from aqueous hydroxypropylcellulose (HPC) liquid crystalline solutions. The HPC solid films were prepared by casting isotropic and liquid crystalline solutions under shear. Atomic force microscopy (AFM) measurements of their topographical features were performed. The features of the film surface can be affined by controlling the processing conditions. We have demonstrated that the films prepared from liquid crystalline solutions (HPC/water ratio: 50-65% w/w) show two periodic structures, primary and secondary set. The former consists of the bands perpendicular to the shear direction while the latter has the bands slightly tilted from that direction. An out-of-plane angle variation (9°-13°), of the sinusoidal molecular orientation, is also reported. A fractal analysis of these surfaces indicates a scale-invariant nature between 300 nm and 4 μm.