THE INFLUENCE OF TEMPERATURE ON THE CRITICAL MICELLE CONCENTRATION OF IONIC AND NONIONIC SURFACTANTS

Namen diplomskega dela je določiti kritično micelno koncentracijo (CMC) za kationski surfaktant (trimetil-tetradecilamonijev klorid-TTSCl) in za neionski surfaktant Triton-X-100 pri standardnih pogojih in preučiti vpliv temperature na CMC. Kot topilo smo uporabili Milli-Q vodo. Pri tem smo se osredotočili na dve temperaturni območji. In sicer za kationski surfaktant je bilo območje od 288 K do 313 K, medtem ko za neionskega od 283 K do 313 K. Za vsakega posebej smo uporabili različni metodi: klasično konduktometrično metodo (kationski surfaktant) in metodo površinske napetosti (neionski surfaktant). S pomočjo le-teh smo za kationski surfaktant dobili odvisnost v obliki \u27črke U\u27 ter linearno padajočo odvisnost za neionski surfaktant, tako kot je v skladu z literaturo. Na koncu smo izračunali termodinamske količine: spremembo entalpije micelizacije (ΔH_mic^°), spremembo entropije micelizacije (ΔSmic) in spremembo Gibbsove energije (ΔG_mic^°). Pri tem smo vse tri količine za ionski surfaktant izračunali na dva različna načina in sicer v primeru, kjer se upošteva vpliv temperature na stopnjo disociacije protiiona (β) in kadar se ta vpliv lahko zanemari, če je sprememba β majhna. Za neionski surfaktant smo uporabili enačbe za izračun termodinamskih količin, pri čemu se stopnja disociacije proti-iona ne upošteva, saj neionski surfaktanti ne disociirajo. V obeh primerih smo ugotovili, da je proces micelizacije spontan saj je prosta Gibbsova energija micelizacije (ΔG_mic^°) negativna, medtem ko za ostali termodinamski količini lahko povemo, da sta bistveno drugačni, kar nam nakazujejo rezultati v tabelah.Purpose of this study is to determine the critical micelle concentration (CMC) of cationic surfactant (trimethyl-tetradecylammonium cloride-TTSCl) and the nonionic surfactant Triton X-100 at standard conditions, and to examine the effect of temperature on the CMC. As solvent it was used Milli-Q water. In doing so, we have focused on the two temperature zones. By the cationic surfactant it has been an area of 288 K to 313 K, while for the non-ionic from 283 K to 313 K. For each one, we used two different methods, namely conventional conductivity method (cationic surfactant) and the method of surface tension (nonionic surfactant). With the help of these, we get for the cationic surfactant is a graph of the \u27U-shaped\u27 and linear decreasing graph of nonionic surfactant, as is consistent with the literature. Finally, we calculate the thermodynamic quantities thus: enthalpy of micellization (ΔH_mic^°), the entropy of micellization (ΔS mic^°) and Gibbs free energy (ΔG_mic^°). In doing so, all three quantities of ionic surfactant were calculated in two different ways, namely, in the case where the account of the effect of temperature on dissociation of counter-ions (β), and when this effect can be ignored if it is a small change in β. With the results of the nonionic surfactant we calculated the equation of thermodynamic quantities of where the rates of dissociation of the counter-ions are not taken into account as non-ionic surfactants do not dissociate. In both cases, we found that the micellization process is spontaneous because the Gibbs free energy (ΔG_mic^°) is negative, while for the other thermodynamic quantities we can say that they differ substantially, which we suggest results in the tables