## 3 Results and Discussion
### Analysis of Porous Structure  
The analysis of porosity using low-temperature nitrogen adsorption-desorption measurements showed that the prepared polymers differed significantly in terms of their internal structure. Determined data regarding specific surface areas, total pore volume and mean diameter of pores are collated in Table 4. Citral and limonene-based polymers possessed very well-developed porous structures, while P-DVB was practically nonporous. In the case of oil-based materials, porosities were also developed; however, their values were not as high as those obtained for C-DVB or L-DVB. Very interesting is the graph depicting the adsorption-desorption isotherms (Figure 4). It shows fundamental differences regarding the porous structure of the studied polymers. The isotherms of C-DVB and L-DVB can be classified as Type IV(a) according to the recently updated IUPAC classification [50]. A characteristic feature of this type of isotherm is the final saturation plateau, which in this case is very reduced, and the presence of the hysteresis loop, which proves that capillary condensation took place in the mesopores wider than a certain critical width (ca 4 nm). A small increase of adsorbed amount at p/p\({}^{0}\) close to 1 can be due to the condensation of adsorbates in small macropores or inter-particle voids [50; 51; 52]. The hysteresis loop of C-DVB can be identified as H2(b). Such shape is characteristic of materials with complex porous structures in which network effects are important. Among them, pore-blocking mechanisms [50; 51; 52] and/or percolation effects [53; 54] during desorption from pores of larger neck width size distribution are indicated as the most dominant. Therefore, the following interpretation can be made: in the porous structure of C-DVB dominant pores possess narrow cavity size distributions and wide neck size distributions. The characteristic (asymmetric) shape of the hysteresis loop was probably caused by the percolation effect and suggests an even more complex structure in which the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Polymer** & \begin{tabular}{c} **S\({}_{\text{BET}}\)** \\ **(m\({}^{2}\)/g)** \\ \end{tabular} & \
\begin{tabular}{c} **V\({}_{\text{tot}}\)** \\ **(cm\({}^{3}\)/g)** \\ \end{tabular} &
\begin{tabular}{c} **D\({}_{\text{BH}}\)** \\ **(nm)** \\ \end{tabular} \\ \hline C-DVB & 428 & 0.645 & 5.5 \\ L-DVB & 509 & 0.624 & 4.6 \\ P-DVB & - & - & - \\ Ao-DVB & 64 & 0.421 & 24.7 \\ Lo-DVB & 72 & 0.603 & 26.3 \\ Ro-DVB & 84 & 0.576 & 25.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Porous structure parameters of the prepared polymeric materials. pores are interconnected [53; 54]. Figure 5a presents the pore size distribution (PSD) plots; the curve obtained for C-DVB was bimodal with two unsymmetrical peaks at about 3.75 and 6.36 nm. The latter was wider and larger. Although the curve was bimodal, the PDS remained within a narrow range of values from 2 to 12 nm. Figure 4: The nitrogen adsorption-desorption isotherms of the studied polymers. Figure 5: The pore size distribution plots (**a**) C-DVB and L-DVB, and (**b**) Ao-DVB, Lo-DVB, and Ro-DVB. For L-DVB, the hysteresis loop was more complex and probably should be considered as a combination of types H2(b) and H5 (Figure 4). The distinctive form of Type H5 resulted from the presence of both open and partially blocked mesopores in the polymer network. Another characteristic feature was the steep step down observed in the desorption branch, possibly as a consequence of cavitation [50; 51; 52; 55]. Such an effect usually is located at p/p\({}^{0}\) ca 0.4-0.5 when N\({}_{2}\) at 77 K is used as adsorptive and was also found in the case of L-DVB. Therefore, considering the properties of the porous structure of the L-DVB polymer, it can be concluded that they were similar to C-DVB; the pores form an irregular network of cavities and channels connected to each other, but some were partially blocked. The PSD of L-DVB (Figure 5a) was a little broader than that of C-DVB.