# Tuning of Morphology and Surface Properties of Porous Silicones by Chemical Modification
## 3 Results and Discussion
Thus, the open-cell structure was verified by immersing the samples in an acetone solution of Disperse Red 1 (DR1) for a few minutes. The pieces of porous materials were removed on a filter paper, then gently cut (or crushed). The inner parts of the materials were colored (Figure S5), which is an indication of pore interconnection [33]. When hexene was used as a modifying agent, the formation of a latex was noticed, which can be observed in the final morphology (Figure 4f) showing pores and particles. In the absence of hydrogen evolution, the morphology of the samples obtained by photoaddition was dictated only by the emulsion template and the surface energy of the reaction mixture (Figure 5). UV50 showed fewer and interconnected pores and apparently smooth regions. A combination of particles and holes characterizes sample UVME, due to the water solubility of ME, which probably induced a combination of w/o and o/w emulsion within the reaction mixture, generating the latex. Figure 4: Morphology of the porous silicones in the DH series: (**a**) DH100, (**b**) DH70, (**c**) DH44, (**d**) DH30, (**e**) DHS, and (**f**) DHH. Figure 5: Morphology of samples obtained by photoaddition: (**a**) UV50 and (**b**) UVME. When trying to correlate the wetting behavior with the morphology, it appears that the samples that manifested highly hydrophobic behavior with petal or lotus effects had uniformly small pores and fewer very large pores (tens of micrometers). It is well documented that such effects are generated by combinations of micro- and nanostructures; more precisely, the microstructure pitch and nanostructure density are the key parameters, but the surface energy is an important element as well [25]. It was observed that the sizes of hierarchical micro- and nanostructures are both larger in the petal than in the lotus leaf [21]. Petals from two rose species with microstructures of around 10 \(\upmu\)m could show different effects, depending on fine details [34]: the one with a smaller pitch value (spacing) and a larger P-B height presented a superhydrophobic surface with low adhesion. When similar microstructures and different densities of nanostructures are considered, the lower nanostructure density generates high adhesion (the petal effect) [25]. Compared with the reported examples, in our case, the effect was observed on pores and not on protuberant micro-/nanostructures, not to mention that the surface energy was modified due to changes in the chemical structure of the porous materials. When samples with similar structures (and thus surface energies) were compared at a larger scale (Figure S6), it appeared that in the case of our porous materials, the trend was somehow reversed: DH44, with larger pores, exhibited low adhesion, as compared with sample DH30, with smaller pores, which showed high adhesion. On the other hand, taking into account that the emulsion template dictated the distribution (density) of small (nano-) pores, this should be considered approximately constant in the bulk samples. When micropores are generated as a supplementary element, it results that the share of nanostructures on a microstructure is larger in materials with larger pores. Thus, in fact, when there are larger pores, there should be a higher density of nanopores on a microstructure, giving low adhesion (the case of DH44). This dual-scale porosity tunes the surface properties, similar to the dual-scale roughness [25]. Fine morphological details can be observed in Figure 6 for samples DH44 and UV50. In DH44 (showing the lotus effect), besides large pores, as seen in Figure 4c, a very high density of small (\"nano\") pores of 200-500 nm was observed, with dimensions similar to the droplet sizes measured by DLS for the staring emulsion (Figure S7). These nanopores were distributed inside the larger ones, forming \"windows\" in the open cells. In UV50 (showing the petal effect), hierarchical, dual-scale pores were seen, of a few micrometers and around 500 nm.