3.5.1. AFM imaging
Fig. 9 illustrates the AFM images of coating films of ALK 1 (0%DPE) and ALK 9 (100% DPE), respectively. The differences in surface smoothness between ALK 1 and ALK 9 can clearly be seen. ALK 1 (0% DPE) has a rough topographywhereas ALK 9 (100% DPE) appears to have comparatively smoother surface. This smoothness may be the reason for higher gloss of films of ALK 9, which is in agreement with glossometer values, mentioned in Table 4. The increase in smoothness is due to better flow and leveling arising out of lower dilution viscosity of the polymers with increased DPE content (Fig. 1) and also the controlled initial drying phenomenon as observed from the DSC study (Fig. 6). Refractive index (RI) of polymers is another
parameter that influences the gloss of coatings [26,27].When measured, ALK 9 showed a higher RI value (1.494) as compared to ALK 1 (1.481). This observation also supports the higher gloss of the ALK 9 film.