Atomic Force Microscopy (AFM)

The surface morphology of the pure PVA membrane and the PVA-modified nanocomposite membranes were analyzed by Tapping Mode – Atomic Force Microscopy (TM-AFM). Quantitatively, the differences in the morphology can be expressed in terms of various roughness parameters such as the mean roughness Ra, the root mean square (rms) of vertical data Rq, and the maximum height Rmax. Here, the mean roughness is the mean value of surface relative to the center plane, the plane for which the volume enclosed by the image above and below this plane are equal; Rmax the height difference between the highest and lowest points on the surface relative to the mean plane and Rq is the standard deviation of the Z values within the given area. The roughness parameters were calculated for pure PVA and PVA nanocomposite membrane surfaces with critical loading of filler and have been summarized in tabular format.

The TM-AFM images of the Pure PVA membrane is depicted in Fig. 15. The AFM images of PVA membrane shows randomly distributed hard crystalline regions (crystallites) of 100 – 250 nm in dimension on the membrane surface as evident from the observed morphology. The pure PVA membrane surface has a mean roughness of 1.026 nm.

The nanocomposite membrane with critical loading percentage of 3 wt. % BRM content (Fig. 16) shows a homogeneous and non-porous morphology. The mean roughness for the surface topography of the membrane was found to be 6.595nm. This shows that there is a good compatibility between the filler (BRM) and the PVA matrix. While critical loading surface topography of CP4 and PRM4 as shown in Fig. 17 and 18 respectively again showed homogenous and non-porous morphology. The mean roughness of CP4 and PRM4 were observed to be 2.016 nm and 9.22 nm respectively as shown in table 9.