**4.3 Softening**

*Colloids - Types, Preparation and Applications*

**4. Properties**

**4.1 Surface tension**

unchanged [22].

**4.2 Dispersion**

**Figure 8.**

(JNM ECP 600 MHz spectrometer) [34] (**Figure 7**).

greater the CMC values of surfactant solutions [22].

*Variation in surface tension and CMC values with hydrophobic chain [20].*

alkyl imidazoline and N-dimethyl alkylammonium chloride, N-(3-chloro-2 hydroxypropyl)-N in isopropanol by keeping under the reflux for 10 hours and by putting the excess amount of alkyl imidazoline (10%). The resultant appeared as a waxy compound product. This product was further recrystallized with absolute acetone to obtain the desired compound in the form of a white solid with a melting point of 69–70°C. The characterization of the final product was performed to check the surfactant surfaces using Mass spectra and infrared spectrum, and 1H NMR

Surface tension is the necessary exertion which is obligatory for the enhancement of the surface area of a liquid due to intermolecular force. Surfactant helps in reducing the surface tension of the liquid. An increase in the concentration of surfactants leads to a decrease in surface tension. Gemini imidazoline surfactantcontaining stearic acid solution increased in the concentration from 0.1813 to 0.3626 g/l whereas the surface tension decreased from 42.8 to 28.6 mN/m. Again, the process repeated, the concentration of surfactant increased up to 0.6250 g/l leads to a decrease in the surface tension to 27.6 mN/m and a final increase in the concentration to 1.25 g/l and 2.5 g/l but the surface tension remained

In the same study, the CMC values of 1% aqueous solution of gemini surfactants

were found in the range from 0.0016 to 0.0032 mol/l that depends on the alkyl chain length (**Figure 8**). Greater the chain length of hydrophobic alkyl moiety,

An arrangement in which scattered particles of one substance dispersed to another substance is known as dispersion phenomena. Surfactants help in stabilizing the dispersion phenomena. Cationic gemini imidazoline surfactant showed stable and good dispersion capability. Gemini imidazoline surfactant-containing stearic acid had a cloudiness of about 4.8 ml that decreased with time. After 5 minutes, it was 3.6 ml and decreased to 3.0 ml after 10 minutes [20, 22]. The trend was found same when the gemini surfactants of different length of hydrophobic chain

**72**

Cationic surfactants are used as fabric softening agents. The most common cationic surfactants which are used for softening agents are quaternary ammonium salts, imidazolinium salts, etc. [35]. The softening of surfactants decreases with the decrease in the length of the chain of the alkyl group. When compared with surfactants, it showed that surfactant-containing oleic acid had moderate softening behavior whereas fatty and highest alkyl chain has less softening. Fabrics treated with surfactants found to be soft as compared to untreated fabrics. Therefore, gemini imidazoline surfactants make the fabrics soft.

**Figure 9.** *Dispersibility of gemini surfactants based on different fatty acids.*
