Polymer Saturation Point Research Articles

Experimental research on synergistic drag reduction of cationic surfactant and nonionic polymer

The coupling of surfactant and polymer can weaken their shortcomings, improve drag reduction rate, and enhance the stability of drag reduction. This paper takes the cationic surfactant octadecyl trimethyl ammonium chloride and the nonionic polymer polyethylene oxide as the research objects, and uses the coaxial cylinder system of Anton Paar MCR102 to study the synergistic drag reduction of cationic surfactant and nonionic polymer. The experimental results show that cationic surfactants and nonionic polymers has obvious synergistic drag reduction. Compared with 800 ppm OTAC/NaSal solution or 40 ppm PEO solution, the drag reduction increases by 61.49% and 19.78%, respectively. Moreover, the drag reduction rate of the mixed solution is not monotonically increasing with the surfactant concentration. When the OTAC/NaSal concentration reaches polymer saturation point of 1200 ppm, the drag reduction rate of the mixed solution reaches the maximum value of 14.09% and the drag reduction rate increases by 34.15%; when the concentration of OTAC/NaSal is less than 1200 ppm, the drag reduction rate increases with the increase of the concentration of cationic surfactant; however, when the concentration of OTAC/NaSal is greater than 1200 ppm, the drag reduction rate is basically stable. In addition, the shear resistance of the mixed solution is significantly enhanced.

Effect of gelatin protein on self-association behavior of sodium salt of ibuprofen drug in urea solution

Herein, multi-techniques approaches such as conductometry, tensiometry, fluorometry, and FT-IR were engaged to evaluate the interaction between sodium salt of ibuprofen (IB) and gelatin (GN) at 298.15 K in 250 mmol·kg−1 urea (UR) solution. The current employed drug is used for relief of pain. The employed IB drug interacts through GN protein like the interaction between surfactants and polymers. It is clear that the graph obtained from the conductometric and tensiometry methods shows two clear breaks. Urea acts as water structure breaker and their presence in solution enhance in surface charge of aggregates occurs. The obtained first break spot is labeled critical aggregation concentration (cc) which is quit beneath the usual critical micelle concentration (cmc) besides this the subsequently break spot denotes second one is regarded as polymer saturation point (pp) and this akin to cmc. The interaction between IB and GN in UR solution increases as concentration of protein increases in the solution mixtures as clear from their obtained cc value because the value of cc reduces through enhancing the concentration of GN (%w/v), in spite of this the value of pp value increases with increase in concentration of GN means more drug needed for complete saturation of binding site of protein. In UR solution, the Gibbs free energy of micellization (ΔGmic) for singular IB was achieved negative exploring that micellization process is spontaneous in nature. The other different evaluated thermodynamic parameters such as free energy of aggregation (ΔGagg), free energy of transfer (ΔGt), etc. were found in favor of interaction between IB and GN. Fluorometry technique was utilized to find out the various parameters such as micropolarity, aggregation numbers (Nagg), etc. to verify the interaction amongst studied constituents and with the interaction between them were also assessed by FT-IR study.

Mechanistic study of drag reduction in turbulent pipeline flow over anionic polymer and surfactant mixtures

The mixed aqueous solutions of anionic surfactant sodium dodecyl sulfate with polymer polyacrylamide of various kinds, i.e., cationic, anionic, nonionic, and zwitterion, were firstly tested to study their synergistic effect on drag reduction performance. The optimal combination of sodium dodecyl sulfate with anionic polyacrylamide was confirmed due to their strong hydrophobic interaction and electrostatic repulsion caused by the same charge. The surface tension, conductivity, and viscosity of pure surfactant solution and mixed solutions at different surfactant concentrations with anionic polymer of certain concentration were tested, and their drag reduction behavior in pipe flow was also investigated experimentally. It turns out that drag reduction performance acquired from the combination of anionic surfactant and anionic polyacrylamide is better than either of the single additive, especially under high shear rate. For the mixtures, the degree of drag reduction is strongly dependent on the concentration of SDS and more pronounced in the high Reynolds number range. The best drag reduction performance is obtained for the SDS concentration around the polymer saturation point. Our work should be of value for the drag reduction in the application such as shale gas fracturing and various fluid transports.

Investigation of aggregation behavior of ibuprofen sodium drug under the influence of gelatin protein and salt

The interaction of amphiphilic drug ibuprofen sodium salt (IBS) and gelatin (GT) protein have evaluated in the current system by means of conductometric, tensiometric and fluorometric techniques in aqueous as well as in aqueous electrolytes solutions at 298.15 K. IBS is utilized as an analgesic, an antipyretic and anti-inflammatory drug. Akin to surfactants and polymers interaction drug also interacts through gelatin. For that reason, in the present study, we have evaluated the drug IBS and gelatin (GT) interaction by means of conductimetry, tensiometry as fluorometry in aqueous along with in occurrence of additive (sodium chloride (NaCl)) at 298.15 K. From the graphs of specific conductivity against IBS concentration in case of conductivity and from the plots of surface tension (γ) vs. log IBS concentration, two break point was achieved in the occurrence of GT in absence and the presence of additives. The achieved primary cut-off point is entitled critical aggregation concentration (cc) that obtained lower than the characteristic critical micelle concentration (cmc) and the attained a subsequent cut-off point means the second one is entitled polymer saturation point (pp) i.e. resembling cmc. The interaction amongst IBS and GT occurs as a result of the well formation of the surface active complex by drug and GT as revealed via lessening of γ of gelatin solution through the addition of IBS in all different media. NaCl increases the interaction of IBS-GT mixtures. The achieved cc value of drug and gelatin mixtures reduce via raising the GT concentration (%w/v), while their pp value enhances viewing the clear interaction amid IBS and GT. Free energies of aggregation (ΔGagg) along with micellization (ΔGmic) were also assessed and discussed. Fluorescence spectroscopy was employed to evaluate the aggregation numbers (Nagg) of IBS and IBS-GT mixtures in the absence and occurrence of additive.

Study on the interactions between SDBS/SOE‐60 mixed surfactant and PVP in solution

ABSTRACTThe interactions between the mixed surfactants sodium dodecyl benzenesulfonate (SDBS) and modified oil ethoxylate (SOE‐60) with polyvinylpyrrolidone (PVP) were studied at 25 ± 1 °C using a surface tension meter, Ubbelohde viscometer, and fluorescence spectrophotometer. Interaction mechanisms of SDBS/SOE‐60‐PVP systems were explained by the “necklace and bead” model. The results showed that the interaction could be divided into three parts by two characteristic concentrations: the critical aggregation concentration (cac) and the polymer saturation point (psp). The interaction mechanisms of SDBS/SOE‐60‐PVP systems are consistent with the “necklace and bead” model. The binding mixing surfactant micelles, formed by free SDBS and SOE‐60 molecules, were bound to PVP chains by hydrophobic and ion–dipole interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46717.

Association of imidazolium surfactants with poly(N-isopropylacrylamide)

Most investigations about polymer and surfactant interactions are related to standard surfactants, while the scope of literature using imidazolium surfactants is limited. In this work, conductometric and calorimetric techniques have been combined to determine the interaction of poly(N-isopropylacrylamide) with two surfactants: 1-tetradecyl-3-methylimidazolium chloride and 1-hexadecyl-3-methylimidazolium chloride. The critical aggregation concentration and the polymer saturation point have been determined as a function of the polymer concentration. To explain the conductivity results, a new model has been proposed that considers the possibility of formation of free micelles before the polymer saturation. This model allows estimating the fraction of surfactant molecules aggregated to the polymer and the ionization degree of them, as well as the fraction of surfactant in the form of free micelles. Isothermal titration calorimetry results reveal that the interaction between the polymer and both surfactants is driven by entropic processes and that the aggregation process is non-cooperative at the initial stages.

The property study of sodium dodecyl benzenesulfonate and polyvinylpyrrolidone complexes

In this paper, the physicochemical properties between sodium dodecylbenzenesulfonate (SDBS) and polyvinylpyrrolidone (PVP) in aqueous solutions were studied at 25 °C by Ubbelohde viscometer, conductivity analyzer, and fluorescence spectrophotometer. It was found that viscosity, conductivity, steady-state fluorescence, and Rayleigh scattering curve for SDBS-PVP system could be divided into three regions by two characteristic concentrations: the critical aggregation concentration (cac) and the polymer saturation point (psp). The results revealed that interactions between SDBS and PVP molecules in aqueous solutions could be explained by “necklace and bead” model. Micelle-like surfactant aggregates, formed by SDBS-free molecules, associated with PVP chains mainly by hydrophobic interaction.

Association between the physical stability of flurbiprofen suspension and the interaction of HPMC/SDS

The anionic surfactant sodium dodecylsulfate (SDS) has improved the physical stability of flurbiprofen (FBP) suspension, which was suspended by 0.2% (w/v) hydroxypropylmethyl cellulose (HPMC, K4M). Therefore, the physical stability of FBP suspensions and the interaction of HPMC/SDS were studied, and a certain association between them was revealed. The anti-solvent precipitation method was used to prepare suspensions. The apparent drug concentration from different sites was evaluated to get the dispersion of drug actually. The process of flocculation and deflocculation with the addition of SDS was caught by analyzing the morphology of the suspended particles. The physical stability of the FBP suspensions was characterized mainly by measuring the re-dispersion time, the zeta potential and particle size. Meanwhile, conductivity measurements were carried out to obtain the characteristic concentrations of SDS in HPMC/SDS system. The viscosities, the abilities for improving the solubility and wettability of FBP in the separate and mixed HPMC/SDS solutions were also contrasted respectively. The suspensions prepared with HPMC/SDS possessed better physical stability. The suspensions were uniform when the concentration of SDS was between the critical adsorption concentration (CAC) and the polymer saturation point (PSP). After PSP, the uniformity became worse and worse until the SDS was enough to form a deflocculation state. Besides, the re-dispersion time of FBP suspensions was longest when the concentration of SDS around CAC and shorter by shorter after the critical micelle concentration (CMC). The article provided a new sight on the relation between the interaction of excipient matrix and pharmaceutical preparations.

Capillary electrophoresis investigation on equilibrium between polymer-related and surfactant-related species in aqueous polymer-surfactant solutions

It was inferred from aqueous solution behavior of nonionic polymers and anionic surfactants that the formation of charged polymer-bound surfactant micelle above critical aggregation concentration (cac) and the formation of free surfactant micelle beyond polymer saturation point (psp), but there was still a lack of direct experimental evidence for the considered equilibrium chemical species. Three modes of capillary electrophoresis are applied in this paper to study the complexation between nonionic polymers, polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG), and sodium dodecylbenzenesulfonate (SDBS) by successfully distinguishing the imaginary charged polymer-bound SDBS micelle from nonionic polymer and SDBS molecule. Perhaps even more important, it is the action of SDBS as both a main surfactant and a UV probe that makes the free surfactant micelle emerged in electropherogram beyond psp, and thus makes it possible for the first time to provide the equilibrium relationship of the polymer-related and the surfactant-related species in the concentration regions divided into by cac and psp.

Effect of polymer conformation on polymer-surfactant interaction in salt-free water

The aim of the present paper was to study the interaction between polyvinylpyrrolidone (PVP) and sodium bis(2-ethylhexyl) sulfoccinate (AOT), as an anionic surfactant, over a temperature range of 25–60 °C by viscosity and electrical conductivity measurements. A coil-to-globule transition of PVP in water was observed. The critical micellar concentration (CMC) was determined by conductivity at 25 and 50 °C. The formation of the complex PVP-AOT in water was studied by conductivity and viscometry at 25 and 50 °C, where the polymer chain adopts respectively coil and globule conformations, and the obtained curves show two break points corresponding to the critical aggregation concentration (CAC) and the polymer saturation point (PSP). The viscometric behavior of PVP-AOT system was studied by using three selected AOT concentrations: CAOT,1, CAOT,2, and CAOT,3 with CAOT,1 < CAC < CAOT,2 < PSP < CAOT,3. For CAOT,1, the system behaves as a neutral polymer. A pseudo-polyelectrolyte behavior was observed for the surfactant concentration (CAOT,2). Above the PSP, and for the CAOT,3 concentration, a screening effect appears due to the increase of the free AOT micelles concentrations. In presence of surfactants, the polymer chains swell especially when the PVP is in globular state.

Effect of gelatin on micellization and microstructural behavior of amphiphilic amitriptyline hydrochloride drug solution: A detailed study

Herein we have investigated the dealings between amphiphilic antidepressant drug amitriptyline hydrochloride (AMT) and gelatin interaction using different proposed techniques. AMT is used for the treatment of mental/mood problems such as depression. Gelatin interacts with this drug alike fashions to the interaction of polymers and surfactants i.e., critical aggregation concentration (cac) and polymer saturation point (psp) were together achieved significantly. AMT and gelatin interaction starts due to the highly surface active complex formation as disclosed by decreasing of surface tension of gelatin solution by adding of AMT. It was uncovered from results that cac decreases on increasing the gelatin concentrations, whereas psp increases which is a sign of the attraction between AMT and gelatin. Thermodynamic parameters were also evaluated and discussed in detail. Fluorescence measurements were used to find the values of average aggregation numbers (Nagg) and various other parameters like Stern–Volmer constant (Ksv) and micropolarity. The nuclear magnetic resonance (1H NMR) data suggested that AMT interacts with gelatin by the means of hydrophobic interaction. The 1H NMR experiments explain that the extent of chemical shifts (δ) and line width (lw) increases with the increase in gelatin concentration. Secondary structure of gelatin was also examined via circular dichroism (CD) technique at different concentration of AMT. CD results confirmed that with increasing drug concentration the random coil portion of gelatin enhances. Field emission scanning electron microscope (FESEM) provided clear pictures of (drug+gelatin) interaction.

Effect of salt and urea on complexation behavior of pharmaceutical excipient gelatin with phenothiazine drug promazine hydrochloride

An evaluation of the interactions of cationic phenothiazine drug promazine hydrochloride (PMZ) with gelatin in aqueous solution as well as in the presence of 50mM NaCl and 100mM urea, investigated through different physicochemical measurements is presented in the present study using conductometric method. PMZ is used for the control of mania and schizophrenia. The drug interacts with gelatin similar to the interaction of surfactants and polymers. The plots of specific conductivity versus concentration of the drug were nonlinear with three different linear regions with two clear breaks. The first break point, i.e., critical aggregation concentration (cac), appeared well below the typical critical micelle concentration (cmc). The second break point is considered as polymer saturation point (psp) that is akin to cmc. The cac value decreases on increasing the gelatin concentration, whereas the psp value increases for all fixed concentrations (%w/v) of gelatin which is a clear signal of the interaction of the drug with gelatin. As inorganic salts increase the ionic strength, the solubility of amphiphile (drug) is lowered by ionic screening effects, ensuing in a greater tendency to aggregates at lower concentration. As a result, both the cac and psp/cmc values decrease. By the addition of urea an increase in the surface charge of the micelles was observed followed by halt of the aggregation of the drug hence both the cac and psp/cmc values increase. Free energies of aggregation (ΔGagg), micellization (ΔGmic), polymer saturation (∆Gpsp) and transfer (ΔGt) were also evaluated.

Insight into the Interaction Between Carbopol® 940 and Ionic/Nonionic Surfactant

AbstractMixtures of a cross‐linked polyacrylic acid (Carbopol® 940) and two types of surfactants, namely anionic sodium dodecylsulfate (SDS) and nonionic Tween® 80, were investigated by viscometry, conductometry, tensiometry, spectrophotometry, fluorimetry and scanning electron microscopy (SEM). The addition of nonionic surfactant decreased the reduced viscosity and the transmittance of the Carbopol® polymer aqueous solutions. Furthermore, the interaction between Carbopol® 940 and SDS was characterized by two significant concentration values: the critical aggregation concentration of SDS was particularly independent of Carbopol® polymer concentration while the polymer saturation point of both surfactants increased with the increase in polymer content. The values of critical aggregation concentration and polymer saturation point obtained using various techniques confirmed the occurrence of Carbopol® polymer–surfactant associations. The effect of different SDS and Tween® 80 concentrations on the conformation of Carbopol® 940 in aqueous solution could be explained through hydrophobic association between surfactant micelles and Carbopol® polymer tails and through hydrogen bonding in the case of Tween® 80. Additionally, the surfactant‐induced structural changes were confirmed in Carbopol® 940–SDS and Carbopol® 940–Tween® 80 aqueous solutions by SEM measurements.

Influence of ionic strength on the rheological properties of hydroxypropylmethyl cellulose-sodium dodecylsulfate mixtures

Mixtures of polymers and surfactants are commonly found in a range of products of pharmaceutical, cosmetic, and food industry. Interaction between polymers and surfactants influences different properties of these products, e.g. stability, flow properties, phase behavior, etc. It is known from previous work that an interaction in binary mixtures of hydroxypropylmethyl cellulose (HPMC) and sodium dodecylsulfate (SDS) takes place when SDS concentration (CSDS.) is higher than the critical association concentration (CAC) and lower than the polymer saturation point (PSP). The interaction results in the formation of an HPMC-SDS complex. The objective of this work was to study the effect of the ionic strength on the HPMC-SDS complex formation by rheological investigation. The HPMC/SDS mixtures composed of 0.70 % wt. HPMC, and 0.00 % to 2.50 % wt. SDS were prepared in deionized water, 0.01M and 0.05M NaCl solution. It was found that an increase in the ionic strength influences the HPMC-SDS complex formation by increasing the zero shear viscosity of the mixtures in the interaction region (CAC&lt;CSDS&lt;PSP), while a decrease in the viscosity is observed for CSDS&gt;PSP. The HPMC/SDS mixtures showed a shear thinning or a shear thickening flow properties depending on CSDS. The flow properties were influenced by the ionic strength of the mixtures.

ASSOCIATION OF BRANCHED POLYETHYLENE IMINE WITH SURFACTANTS IN AQUEOUS SOLUTION

Three polymer-surfactant systems comprised of branched polyethylene imine (PEI) with an anionic surfactant (sodium dodecylsulfate; SDS), a cationic surfactant (tetradecyltrimethylammonium bromide; TTAB), and a zwitterionic surfactant (N-tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate; SB3-14) were studied based on the properties of surface tension, pyrene fluorescence emission, dynamic light scattering, pH, and zeta potential measurements. The critical aggregation concentration (cac) and polymer saturation point (psp) were determined for all three systems. The effect of these surfactants on the physico-chemical characteristics (diameter and surface charge) of the complexes formed was determined. Polymer-surfactant interactions occurred in all of the systems studied, with the strongest interactions, electrostatic in nature, occurring in the SDS-PEI system. After the neutralization of the polymer charges with the addition of the surfactant, the hydrophobic effect started to control the interlacing of the polymer chains. For the PEI-TTAB system, a very dense film was formed at surfactant concentrations above 2.0 mmol L-1. In this case, the bromide counter-ion interacted with both the positively-charged PEI and the head of the surfactant, which is responsible for the formation of double layer coordination complexes. For the system composed of PEI and the zwitterionic surfactant, less cooperative associations occurred in comparison with the other systems.

Effect of Head Groups, Temperature, and Polymer Concentration on Surfactant—Polymer Interactions

AbstractThe micellization behaviour of sodium dodecyl sulphate, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetylpyridinium chloride in water and in aqueous solutions of polyethylene oxide (PEO, molecular weight = 100,000) having concentrations (0.005–0.04 %, w/v) has been studied at different temperatures (288.15–318.15 K) using conductivity, surface tension, and viscosity methods. From conductivity measurements various micellar parameters, like critical micellar concentration (CMC), critical aggregation concentration (CAC), polymer saturation point (PSP), degree of ionization (β), and standard free energy of transfer (), have been calculated. CAC values have been found to decrease with polymer concentration and increase with temperature. However, the PSP values increase with both polymer concentration and temperature for all surfactants. Similar parameters have also been calculated from surface tension data (CMCσ, CACσ, PSPσ) along with other parameters such as maximum surface excess concentration at the air/water interface (), minimum area per molecule (Amin), and packing parameter (p). The CMCσ, CACσ, and PSPσ values are smaller than the corresponding CMC, CAC, and PSP values, but both show similar behaviour with temperature and concentration of polymer. Various parameters indicate that the presence of the aromatic ring in the head group of surfactant decreases its interaction with PEO, whereas the increased hydrophobicity in the tail leads to stronger interactions with PEO. Viscosity studies further supplement the conclusions drawn from the above results.

A study of interaction between antidepressant drug nortriptyline hydrochloride with gelatin

The effect of gelatin on the micellization behavior of amphiphilic drug nortriptyline hydrochloride (NOT) in aqueous as well as aqueous urea (250mM) solutions has been studied using conductimetric technique. NOT is indicated for the relief of symptoms of depression. It is a tricyclic antidepressant drug. The drug interacts with gelatin similar to the interaction of surfactants and polymers. The plots of specific conductivity versus concentration of drug were nonlinear with three different linear regions with two clear breaks. The first break point, i.e., critical aggregation concentration (cac), appeared well below the typical critical micelle concentration (cmc). The second break point is considered as polymer saturation point (psp) that is similar to cmc. The cac value decreases on increasing the gelatin concentration, whereas psp value increases for all fixed concentrations (%, w/v) of gelatin which is a clear signal of the interaction of the drug with gelatin. Free energies of aggregation (ΔGagg) and micellization (ΔGmic) were also evaluated. In the presence of urea the increase in the surface charge of the micelles was observed followed by halt of the aggregation. Effect of NOT (drug) on the secondary structure of gelatin in aqueous solutions was also examined using CD measurements. The measurements verified that the random coil content of gelatin increases with increasing the NOT concentration.

Intermolecular Interactions of Polymer/Surfactants Mixture in Aqueous Solution Investigated by Various Techniques

The interaction between diblock copolymer with ionic surfactants in aqueous solution were studied employing surface tensiometery, electrical conductivity, steady-state fluorescence spectroscopy and dynamic laser light scattering at 303 K. Surface tension measurements were used to determine critical micelle concentration (CMC) and, thereby, its free energy of micellization (ΔGm), free energy of adsorption (ΔGads), surface excess concentration (Γ), and minimum area per molecule (A). The negative values of (ΔGm) both in case of SDS and CTAB confirmed the spontaneity of the processes. Conductivity measurements were used to determine critical micelle concentration (CMC), critical aggregation concentration (CAC), polymer saturation point (PSP), degree of ionization (α), and counterion binding (β). Addition of polymers could effectively reduce the CMC value of surfactants and, thus increase the detergency. Dynamic light scattering experiments were performed to check the changes in physiochemical properties of the block copolymer micelles take place due to the interactions of diblock copolymer with ionic surfactants. The ratio of (I1/I3) indicates the polarity of the pyrene micro environment and confirms the detection of micelle as well as polymer-surfactant interactions. Aggregation number (N), number of binding sites (n), and free energy of binding (ΔGb) for pure surfactants as well as for polymer-surfactant mixed micellar systems were determined by fluorescence quenching method.

Thermodynamıc Studıes of Interactıon Between CTAB and Carboxymethylcellulose Usıng Different Techniques

Mixtures of carboxymethyl cellulose (carboxyMC) and cethyltrimethyl ammonium bromide (CTAB) were investigated using surface tension, specific conductivity and density measurements. The parameters of the surfactant to polymer association processes such as the critical aggregation concentration (cac) and the polymer saturation point (psp) were determined from the plots of surface tension, specific conductivity and density versus surfactant concentration. The thermodynamic parameters of polymer-surfactant interaction were calculated at different temperatures. The results showed that the standard Gibbs free energy , the enthalpy and the entropy of the aggregation process were found negative in all cases.

Interaction of gelatin with promethazine hydrochloride: Conductimetry, tensiometry and circular dichroism studies

The interaction of amphiphilic phenothiazine drug promethazine hydrochloride (PMT) with gelatin in aqueous as well as aqueous-electrolyte (50mM NaCl) solutions has been studied by using conductimetry, tensiometry and circular dichroism (CD) techniques. The drug interacts with gelatin similar to the interaction of surfactants and polymers. Hence, we have considered the gelatin–amphiphile interaction approach using conductimetry and tensiometry. The plots of specific conductivity versus concentration of drug were nonlinear with three different linear regions with two clear breaks. The critical aggregation concentration (cac), i.e., first break point, appeared well below the usual critical micelle concentration (cmc). Second break is regarded as polymer saturation point (psp) which is similar to cmc. The interaction starts with the formation of a highly surface-active complex as revealed by the lowering of surface tension on the addition of drug to the macromolecule (gelatin). The results further show that the cac decreases on increasing the gelatin concentration, while psp increases for all concentrations of gelatin which is a clear indication of the interaction between the drug and gelatin. By the use of degree of ionization, free energies of aggregation (ΔGagg) and micellization (ΔGmic) were also evaluated. As inorganic salts increase the ionic strength, the solubility of amphiphile (drug) is lowered by ionic screening effects, resulting in a greater tendency to aggregate at lower concentration. Therefore, both the cac and psp/cmc values decrease. Effect of PMT on the secondary structure of gelatin in aqueous solutions was also investigated using CD measurements. The measurements demonstrated that the random coil content of gelatin increases with increasing the drug concentration.