TAILIEUCHUNG - Thermodynamics Systems in Equilibrium and Non Equilibrium Part 11

Tham khảo tài liệu 'thermodynamics systems in equilibrium and non equilibrium part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 240 Thermodynamics - Systems in Equilibrium and Non-Equilibrium The value of the cmc is dependent upon a variety of parameters including the nature of the hydrophilic and hydrophobic groups additives present in the solution and external influences such as temperature. The micellization takes place where the energy released as a result of association of hydrophobic part of the monomer is sufficient to overcome the electrostatic repulsion between the ionic head groups and decrease in entropy accompanying the aggregation. The cmc can also be influenced by the addition of a strong electrolyte into the solution. This serves to increase the degree of counterion binding which has the effect of reducing head group repulsion between the ionic head groups and thus decrease the cmc. This effect has been empirically quantified according to Corrin Harkins 1947 log cmc - a log Ct b 16 where a and b are constants for a specific ionic head group ant Ct denotes the total conunterion concentration. Fig. 7. Effect of KCl concentrations on the cmc of IMP solutions. Fig. 8. Effect of temperature on the cmc of IMP solutions. Thermodynamics of Amphiphilic Drug Imipramine Hydrochloride in Presence of Additives 241 The degree of dissociation x of the micelles was determined from the specific conductance vs. concentration of surfactants plot. Actually x is the ratio of the post micellar slope to the premicellar slope of these plots. The counter ion association y of the micelles is equal to 1 -x . The results of cmc and y values obtained for IMP micelles in absence and presence of KCl at different temperatures are given in Table 4. It is found that the cmc of IMP in aqueous solution increased with increase in temperature whereas the cmc of IMP decreased in the presence of additive KCl at all temperatures mentioned above see Table 4 . The increase in cmc and decrease in y values for IMP micelles in aqueous solution suggest that the micelle formation of IMP is hindered with the increase in .

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