*2.1.1 Cationic charge*

*Colloids - Types, Preparation and Applications*

has also been done by Jianbin Huang on gemini and Bola, and the role of cephalic groups was found to be important as they alter their properties. A. Migahed et al. studied about the ligand length and its effect on the sustained release performance. The analysis showed that the shorter the length of the ligand, the better would be the effect of the sustained release [17]. Huaivu Yang et al. studied the relationship between sustained release and temperature and concluded that sustained release is directly proportional to the temperature [23]. A study done on emulsifier properties of gemini surfactants and applied it to emulsified asphalt and concluded that the minute quantity of gemini surfactant can be used in emulsified asphalt. Zhang Guanghua's et al. confirmed the sustained release effect on tinplate by synthesizing it. Yangiiang et al. studied the anti-corrosion properties of gemini surfactants and found that the surfactant works better during slow compound release [24]. All these studies analyzed the aspects of sustained release, surface properties, and length of the interval. Few of the methods used for synthesis helped in increasing the instability [25]. The gemini surfactants were compared with other single chain molecules, in which the gemini molecule structure was ambiguous. This was further studied to check the uniqueness and sustained release performance of gemini imidazoline surfactant. The comparison has been done between single- chain molecule and gemini imidazoline surfactant to observed the variations more precisely. The outcomes showed the great inhibitve efficiency in HCl solution as compared to single chain molecule. It also showed the better inhibitive effect on copper in HCl solution. The different concentration of gemini surfactant were taken to check the effect of concentration on inhibition property and it results that the inhibitive efficiency was higher when the concentration of HCl solution was less whereas for better inhibitive

effect the concentration of gemini imidazoline surfactant must be more [25].

Gemini imidazoline surfactant can by classified on the basis physicochemical

Gemini imidazolinium belongs to the cationic gemini group but they are also amphoteric in nature. The imidazolinium gemini surfactant are dimeric molecules formed by two head groups associated with the spacer group and two hydrophobic

**66**

**2. Classification**

**Figure 2.**

*Gemini imidazoline surfactant [16].*

characterisitics.

**2.1 On the basis of charge**

tails [26] (**Figure 3**).

The head group in the gemini imidazolinium surfactants contains the positive charge. It possesses long alkyl group, two polar imidazolinium head group and two tails of hydrocarbon in which head groups are linked by a spacer. They are soluble in organic solvents and dispense in water, eg., imidazoline-based dissymmetric bis-quaternary ammonium Gemini surfactant [26–28].

#### *2.1.2 Amphoteric charge*

The head group carries both negative and positive charge groups. They maintained the stability at acidic and basic pH of the solution, soluble in water, e.g. bisalkyl-bisimidazoline surfactant [26, 27, 29].

#### **2.2 On the basis of spacer**

The rigidity, length, polarity of the spacer can vary and leads to the variation in the structure of the gemini imidazoline surfactant as well as the in the surface properties [30, 31] (**Table 1**).

#### **2.3 On the basis of hydrophobic tail**

The variation in the hydrocarbon chain/tail can change the properties of surfactant. The chain can have two identical hydrophobic tails and two non-identical hydrophobic tails [30].


**Table 1.**

*Classification of gemini imidazolinium surfactant on the basis of spacer group.*

## **3. Synthesis**

#### **3.1 Synthesis of Gemini imidazole compound**

Li et al. (1997) synthesized the Gemini imidazoline by a commercial process by taking 46.7 g of triethylene tetramine hydrate (0.25 mol), 146.6 g of oleic acid (0.52 mol) and added them in toludende (100 cm3) (DIAGRAM). With continuous stirring of the solution, it was heated until it reached to the toluene boiling point (120–130 C) almost for 3 hours. After that toluene azeotrope or water was collected from the reaction and temperature has been raised to 160–170 C at 12-16th hour of reaction by simultaneous removal of toluene from the Barrett distilling receiver. Thin layer chromatography was done to check the compounds in the reaction by taking chloroform/methanol (80: 20) as solvent and spot visualized using iodine. The completion of condensation reaction was checked by the TLC plate as the spot disappearance corresponding to the monoamides and diamides resulted in its completion. The reaction further continued till 16 hours for the collection of all byproduct water and yielded 96% of product which further recrystallized for the identification and structure confirmation from chloroform [32].

The two compounds Diethylenetriamine and lauric (molar ratio of 1:1.2) mixed with the xylene, which behaved as a solvent and kept at 140°C. Zinc powder has been added as a catalyzer. The Diethylenetriamine added into the flask at a slow rate and left for the reaction for 2 hours. Later, this flask was connected with the water separator at 200°C for 8 hours. A specific volume of water has been evaporated as per the theoretical calculation after the solvent were removed using the distillation method with the temperature maintained at 140°C to obtained the imidazoline intermediate is oily in nature and yellow in color. The distillation process was performed again to obtain the Single-chain imidazoline quaternary ammonium salt. The temperature was controlled around 80–90°C for 5 hours with the addition of dimethyl- carbonate in it with the same molar quantity as imidazoline intermediate. In this product, some amount of 1,3-dibromopropane has been added as half molar volume compared to intermediate and left for 8 hours for the reactivity, resulted in a sticky liquid of red-brown. Decreased the temperature to 50°C, after that added the less quantity of acetone to it, filtrated out to extract the zinc powder. Solution kept untouched until the crystal appeared, and lifted with sucking filtration and washed with acetone for numerous times. The obtained product was the Gemini imidazolinium surfactant that is solid khaki. (LG is 1,3-di(1-methyl-1-ethylamino-2-n-undecyl-4,5-dihydro-imidazoline) propane Gemini which is the Gemini cationic imidazoline surfactants based on lauric acid and LM is

**69**

**Figure 4.**

*Synthesis of LG [25].*

*Gemini Imidazolinium Surfactants: A Versatile Class of Molecules*

meric surfactants based on lauric acid [25] (**Figure 4**).

1-enthylamino-2-n-undecyl-4,5-dihydro-imidazoline which is the cationic mono-

He further processed the obtained Gemini compounds for the synthesis of Gemini di-quaternary ammonium compound. The 1 mol compound was refluxed with 2 mol of dodecyl chloride in ethanol for 3 days. After that, ethanol was distilled off from the solution. Di- quaternary ammonium chloride has been obtained as resultant which was washed with the diethyl ether. The characterization and structure confirmation was done by FTIR (ATI Mattson series FTIRTM) revealed

A 250-ml four-necked flask was taken in which lauric acid with the twofold amount (in mol) and triethylenetetramine were charged and temperature maintained at 160 C for reaction under atmospheric nitrogen for 1.5 hours. Temperature has been raised to 200 C and heated for 1 hour and again raised to 250 C and heated for 1.5 hours. This process resulted in the formation of a light-yellow solid. This product further washed with ethanol, petroleum ether, and ethyl acetate (1:1:1

The intermediate of imidazoline was taken in a 250 ml four-necked flask and mixed

with the two times the theoretical amount of sodium 2-chloroethanesulfonic acid.

reached to the desired amount to obtain the Gemini compounds [17].

**3.2 Synthesis of Gemini imidazoline amphoteric surfactant**

ratio) and resulted in bisalkyl-bisimidazoline [21] (**Figure 5**).

*3.2.2 Quaternization of the Bisalkyl-bis-imidazoline intermediate*

*3.2.1 Synthesis of Bisalkyl-bis-imidazoline intermediate*

Migahed et al. (2018) synthesized the Gemini imidazole compound by taking the 0.2 mol dicarboxylic acid (aspartic or glutamic) in 100 ml of xylene, which was further mixed with the 0.4 ml of diethylenetriamine followed by refluxed process kept for 3 hours with the addition of catalyst PTSA in 0.1% amount at 140 C. Xylene has been removed from the solution after the required amount of water (0.2 mol) was obtained in the Dean-Stark tube. The resultant product was processed with diethyl ether for required amide compounds. For next 6 hours, the temperature of the reaction has been raised to 200 C. cool down the solution when collected water

*DOI: http://dx.doi.org/10.5772/intechopen.94209*

the functional groups of the compound [17].

#### *Gemini Imidazolinium Surfactants: A Versatile Class of Molecules DOI: http://dx.doi.org/10.5772/intechopen.94209*

*Colloids - Types, Preparation and Applications*

1. Length The surface activity of the surfactant varies with the

2. Rigidity Shows higher surface activity. This can effect the aggregation of surfactant.

3. Polarity Polarity affects the Critical micelle concentration of the surfactant

*Classification of gemini imidazolinium surfactant on the basis of spacer group.*

**S.NO Spacer** 

**properties**

**3.1 Synthesis of Gemini imidazole compound**

identification and structure confirmation from chloroform [32].

Li et al. (1997) synthesized the Gemini imidazoline by a commercial process by taking 46.7 g of triethylene tetramine hydrate (0.25 mol), 146.6 g of oleic acid (0.52 mol) and added them in toludende (100 cm3) (DIAGRAM). With continuous stirring of the solution, it was heated until it reached to the toluene boiling point (120–130 C) almost for 3 hours. After that toluene azeotrope or water was collected from the reaction and temperature has been raised to 160–170 C at 12-16th hour of reaction by simultaneous removal of toluene from the Barrett distilling receiver. Thin layer chromatography was done to check the compounds in the reaction by taking chloroform/methanol (80: 20) as solvent and spot visualized using iodine. The completion of condensation reaction was checked by the TLC plate as the spot disappearance corresponding to the monoamides and diamides resulted in its completion. The reaction further continued till 16 hours for the collection of all byproduct water and yielded 96% of product which further recrystallized for the

**Characteristics Sub-division**

• Shorter spacer chain. • Longer spacer chain.

• Flexible spacer • Non-rigid spacer

• Polar spacer

number of carbon atoms present in the spacer group. Shorter the length of the surfactant better is the surface activity of gemini imidazoline surfactant.

The two compounds Diethylenetriamine and lauric (molar ratio of 1:1.2) mixed with the xylene, which behaved as a solvent and kept at 140°C. Zinc powder has been added as a catalyzer. The Diethylenetriamine added into the flask at a slow rate and left for the reaction for 2 hours. Later, this flask was connected with the water separator at 200°C for 8 hours. A specific volume of water has been evaporated as per the theoretical calculation after the solvent were removed using the distillation method with the temperature maintained at 140°C to obtained the imidazoline intermediate is oily in nature and yellow in color. The distillation process was performed again to obtain the Single-chain imidazoline quaternary ammonium salt. The temperature was controlled around 80–90°C for 5 hours with the addition of dimethyl- carbonate in it with the same molar quantity as imidazoline intermediate. In this product, some amount of 1,3-dibromopropane has been added as half molar volume compared to intermediate and left for 8 hours for the reactivity, resulted in a sticky liquid of red-brown. Decreased the temperature to 50°C, after that added the less quantity of acetone to it, filtrated out to extract the zinc powder. Solution kept untouched until the crystal appeared, and lifted with sucking filtration and washed with acetone for numerous times. The obtained product was the Gemini imidazolinium surfactant that is solid khaki. (LG is 1,3-di(1-methyl-1-ethylamino-2-n-undecyl-4,5-dihydro-imidazoline) propane Gemini which is the Gemini cationic imidazoline surfactants based on lauric acid and LM is

**3. Synthesis**

**Table 1.**

**68**

1-enthylamino-2-n-undecyl-4,5-dihydro-imidazoline which is the cationic monomeric surfactants based on lauric acid [25] (**Figure 4**).

Migahed et al. (2018) synthesized the Gemini imidazole compound by taking the 0.2 mol dicarboxylic acid (aspartic or glutamic) in 100 ml of xylene, which was further mixed with the 0.4 ml of diethylenetriamine followed by refluxed process kept for 3 hours with the addition of catalyst PTSA in 0.1% amount at 140 C. Xylene has been removed from the solution after the required amount of water (0.2 mol) was obtained in the Dean-Stark tube. The resultant product was processed with diethyl ether for required amide compounds. For next 6 hours, the temperature of the reaction has been raised to 200 C. cool down the solution when collected water reached to the desired amount to obtain the Gemini compounds [17].

He further processed the obtained Gemini compounds for the synthesis of Gemini di-quaternary ammonium compound. The 1 mol compound was refluxed with 2 mol of dodecyl chloride in ethanol for 3 days. After that, ethanol was distilled off from the solution. Di- quaternary ammonium chloride has been obtained as resultant which was washed with the diethyl ether. The characterization and structure confirmation was done by FTIR (ATI Mattson series FTIRTM) revealed the functional groups of the compound [17].

### **3.2 Synthesis of Gemini imidazoline amphoteric surfactant**

### *3.2.1 Synthesis of Bisalkyl-bis-imidazoline intermediate*

A 250-ml four-necked flask was taken in which lauric acid with the twofold amount (in mol) and triethylenetetramine were charged and temperature maintained at 160 C for reaction under atmospheric nitrogen for 1.5 hours. Temperature has been raised to 200 C and heated for 1 hour and again raised to 250 C and heated for 1.5 hours. This process resulted in the formation of a light-yellow solid. This product further washed with ethanol, petroleum ether, and ethyl acetate (1:1:1 ratio) and resulted in bisalkyl-bisimidazoline [21] (**Figure 5**).

### *3.2.2 Quaternization of the Bisalkyl-bis-imidazoline intermediate*

The intermediate of imidazoline was taken in a 250 ml four-necked flask and mixed with the two times the theoretical amount of sodium 2-chloroethanesulfonic acid.

**Figure 4.** *Synthesis of LG [25].*

**Figure 5.** *Synthesis of Bisalkyl-bis-imidazoline intermediate [21].*

Isopropyl alcohol or water mixture was added to it with continuation for 8 hours at 80–90 C. simultaneously, the pH of the solution has been around 8–9 by mixing the 10 wt.% NaOH solution. The supernatant liquid of the obtained product was taken in a beaker and mixed with 95% of alcohol for recrystallization. With the use of anhydrous alcohol, unreacted salts were removed from the solution. Thus, it resulted in the final product by removing the amide using chloroform [21] (**Figure 6**).

## **3.3 Synthesis of cationic gemini imidazoline surfactants**
