Synthesis and characterization of N-halamine based chlorine storage cryogels

Cryogels are formed by crosslinking, polymerizing or physical entanglement or gelling of monomeric or polymeric precursors at low temperatures to form a polymeric chain network heterogeneously distributed throughout the matrix. After dissolving of the frozen solvent, a highly macroporous structure is formed with a high porous interconnection that allows gases, liquid and submicron particles to move freely without too much strain. The most attractive feature of cryogels is that they release the absorbed water very quickly under a force by means of their interconnected macro pores. Therefore, they are widely used in biotechnological and biomedical fields. Because of their antibacterial properties due to their usage areas, cryogels can become more effective materials. For this purpose, N-halamine compounds which are among the most effective bacterial biocides were preferred in this study. Nitrogen-chlorine or nitrogen-bromine bonds and N-halamine compounds in their structures are also referred to as halogen stabilizers. This bond is broken by contact with microorganisms and the oxidative chlorine or bromine atom is transferred to the cell membrane of the microorganism. The oxidation of the proteins in the cell membrane causes inactivation of the microorganisms in a very short time. N-halamines have superior properties such as high stability, low toxicity and rechargeability. In the scope of the study, cryogels with antibacterial potential which can store chlorine were obtained by copolymerization of N-halamine precursors, which are 2-acrylamido-2-methyl-1-propane sulfonic acid sodium salt , acrylamide and N-[3-(Dimethylamino) propyl] methacrylamide monomers, in the presence of N, N'-methylene bis acrylamide as cross-linker. The synthesized cryogels were treated with dilute sodium hypochlorite solution and charged with chlorine. At the same time, chlorination time and pH parameters were optimized for chlorination process. The effect of chlorine loading on water absorption rate, absorption and desorption rate of cryogels were investigated. Functional groups in the obtained cryogel samples were identified by FT-IR. Since the stability of the N-Halamine structure is very sensitive to heat and UV light, the thermal behavior of the biogels by TGA analysis and the changing in chlorine retention ability by exposure to UV light were observed. The mechanical properties of chlorinated and non-chlorinated cryogels in the swollen state were determined by mechanical test device. The change in pore structure in cryogels by SEM imaging technique and the binding state of chlorine atom to the structure were determined by EDS analysis. As a result, cryogels were produced which were able to absorb water rapidly and store chlorine at a fast rate. The developed spherical cryogels have great potential for use in various fields of the biomedical and biotechnological industries.