## 4 Conclusions  
This work presents the way of synthesis and characterization of the porous polymers obtained by suspension polymerization of divinylbenzene. In order to modify porosity of this materials, in the procedure of synthesis, 1 mL of porogenic solvent was replaced with an adequate quantity of phenol, 2,4,6-trichlorophenol or their mixture (1:1 molar ratio). The chemical modification of pDVB was performed using the sulphonation reaction. The successful course of polymerization and modification reactions was confirmed by the elemental and FTIR analyses.  
The DSC analysis proved that all the studied highly cross-linked polymers were thermally stable up to 350 \({}^{\circ}\)C (pDVB) and after sulphonation even to 450 \({}^{\circ}\)C. Moreover, the DSC data indicated that pDVB-SO\({}_{3}\)H polymer has hygroscopic properties.  
The polymers possessed specific surface areas in the range of 440 to 560 m\({}^{2}\)/g and they were mainly mesoporous with bimodal pore size distribution in the range up to 12 nm. Mean pore widths were ca. 3.75 and 4.75-7.15 nm. It is worth noticing that, although the materials with porosity regulated by the addition of phenol, trichlorophenol or their mixture had specific surface areas 2-5% lower and pore volumes 5-18% lower than for pDVB obtained in the presence of toluene, their porous structures were more uniform. It was also proved that the process of chemical modification with sulphuric acid took place in wider mesopores resulting in a decrease of porous structure parameters.  
The studies on phenols sorption with the use of the SPE method showed that the best sorption properties possessed pDVB (unmodified), pDVB-T and pDVB-M. In the case of the two latter polymers positive influence of the compounds modifying porosity was observed by a ca 5% increase in the recoveries in comparison to pDVB. The similar relationship was observed for SPE of ibuprofen. The highest recovery 37.7% was obtained in the case of pDVB-T. Salicylic acid had very low affinity to the surface of the tested polymers. The highest recoveries in SPE experiments were received for pDVB-T and pDVB-SO\({}_{3}\)H: 7.6 and 6.6%, respectively.  
Studies of the sorption properties of the tested polymers towards phenols and ibuprofen revealed that the process of uptake is affected by both porosity and chemical character of the adsorbent, while sorption of strongly acidic molecules like salicylic acid only depends on the sorbent porosity.  
Figure 6: Results of SPE experiments received for the pharmaceuticals.  
The performed studies showed that it is possible to improve the sorption properties of the prepared polymeric materials by changing the chemical composition of the polymerization mixture. Even if the increase is not so significant, the method of the synthesis is really simple and worth considering. The proposed procedure can be optimized to get better results.  
After the sulphonation, the sorption properties of pDVB-SO3H were worse, in comparison, to unmodified pDVB, in the case of adsorbates possessing acidic character. However, due to the presence of a sulphonic group in the structure of adsorbent it can be presumed that sorption of compounds with basic functionalities or those in ionic forms (e.g. paracetamol, tramadol or sodium ibuprofen) could be more effective.  
Conceptualization, M.S.; methodology, M.S.; software, M.S.; investigation, M.S. and J.O.T.; resources, M.G., writing--original draft preparation, M.S.; writing--review and editing M.S and M.G.  
This research received no external funding.  
The authors declare no conflict of interest.