Acoustical and Spectroscopical Analysis of Surfactant with Different Alcohols at Various Concentrations and Temperatures

Introduction

The study of ultrasonic has become increasingly fascinating in recent years.  The ultrasonic study of liquids is significant for comprehending molecular interaction type and intensity.  The character of inter- and intra-molecular interactions can be examined in great detail by studying how ultrasonic waves propagate through liquids and liquid mixtures¹.

Understanding the chemical interactions in paired mixes depends on the values of the acoustical parameters. A crucial physical parameter with a physical dependence is ultrasonic velocity^2,3.  Studies on acoustic factors have evolved recently, according to hid^4,5. Acoustic characteristics can be used to explain the solute-solvent interaction since they are sensitive to changes. Additionally, the detection and evaluation of both weak and strong molecule interactions have been effectively accomplished using ultrasonic velocity measurements^6,7.

Surfactants are chemicals that self-assemble molecular clusters in a solution (oil or water phase) known as micelles and adhere to the contact between a solution and another phase.  The surfactants are classified as hydrophilic and hydrophobic depending on how easily they dissolve in water.  Both hydrophilic and hydrophobic surfactants dissolve in lipids and water, respectively.  The use of surfactants in industrial, agricultural, food, cosmetic, and pharmaceutical applications is widespread.  Most of these substances are chemically created and may be poisonous and environmentally harmful^8,9.

The anionic surfactant chosen for the current investigation, sodium dodecyl sulphate, has a negative charge on its head group because of their lower degree of soil adsorption than cationic and non-ionic surfactants¹⁰.

Material and Methods

Materials

An anionic surfactant and alcohols of AnalaR grade were purchased from SD fine chemicals, Mumbai, India.  The experimental solutions were made by dissolving a known weight of anionic surfactant in distilled water and stirring under reflux until clear solutions were achieved. The stock solution was made with double the amount of distilled water.  The ultrasonic velocity measurements in SLS with anise alcohol and cinnamyl alcohol were performed in an ultrasonic interferometer (model F81, Mittal Enterprises, New Delhi, India) at a fixed single frequency of 2 MHz and various temperatures (303, 313, and 323 K).  The temperature was kept constant using circulating water from a thermostatically controlled (0.1K) water bath. The viscosity was measured with an Ostwald’s viscometer and standardized with double distilled water with an accuracy of 0.001%.

Methods

The velocity of SLS in the presence of different alcohols (anise and cinnamyl alcohols) was determined at various temperatures using an ultrasonic interferometer with a fixed frequency of 2 MHz (303, 313, and 323 K).  Densities were determined at a range of temperatures using a specific gravity bottle under standard procedures.  The viscosity was obtained with a 0.001 percent accuracy using an Ostwald viscometer calibrated with double distilled water.  The various velocity and absorption parameters were calculated to explore the molecular interactions between anionic surfactants and aromatic alcohols¹¹. 

Results and discussion

Results

The acoustical parameters such as adiabatic compressibility, free length, internal pressure and Rao’s constant are estimated at all three temperatures from the measured values of ultrasonic velocity, density, and viscosity of the solutions.  That are displayed in Tables 1 and 2.  Tables 3 and 5.2.4 show the fluctuation of the ultrasonic absorption coefficient with concentrations in the solutions and other computed parameters at 303, 313 and 323 K.

Figures 1 to 6 display plots of SLS concentration vs ultrasonic velocity, viscosity and adiabatic compressibility of alcohols at various temperatures.  FTIR analysis of the pure SLS, SLS + anise alcohol and SLS+cinnamyl alcohol spectra was done in a 1:1 ratio.  The recorded FTIR spectra are shown in Figures 7 and 8, respectively. 

Table 1: Ultrasonic Velocity and Related Acoustical Parameters in the Solution of SLS in Anise Alcohol

Temp. K	Conc %	U ms-1	Ρ kgm-3	η x10-3 Nsm-2	β X10 -10 N-1m2	Lf Å	πi X106 Pascal	R X10-3
303	0.0	1412	1127	1.349	4.450	0.421	1.568	2.728
	0.5	1419	1131	1.458	4.391	0.418	2.232	2.079
	1.0	1426	1137	1.574	4.325	0.415	2.640	1.842
	1.5	1436	1144	1.682	4.239	0.411	2.976	1.717
	2.0	1447	1149	1.776	4.157	0.406	3.212	1.642
	2.5	1440	1157	1.897	4.168	0.407	3.461	1.581
313	0.0	1396	1117	1.272	4.594	0.428	1.572	2.742
	0.5	1405	1126	1.338	4.500	0.423	2.214	2.082
	1.0	1417	1131	1.402	4.434	0.419	2.596	1.848
	1.5	1428	1137	1.495	4.313	0.414	2.895	1.724
	2.0	1438	1141	1.607	4.238	0.408	3.151	1.650
	2.5	1432	1146	1.715	4.255	0.412	3.387	1.593
323	0.0	1381	1107	1.218	4.648	0.434	1.587	2.756
	0.5	1392	1113	1.282	4.590	0.430	2.229	2.099
	1.0	1406	1121	1.347	4.506	0.424	2.620	1.859
	1.5	1418	1128	1.402	4.421	0.419	2.888	1.734
	2.0	1429	1133	1.483	4.364	0.410	3.119	1.659
	2.5	1422	1138	1.557	4.303	0.416	3.326	1.60

 

Table 2: Ultrasonic velocity and related acoustical parameters in the solution of SLS in Cinnamyl alcohol

Temp. K	Conc %	U ms-1	Ρ kgm-3	η x10-3 Nsm-2	β X10 -10 N-1m2	Lf Å	πi X106 Pascal	R X10-3
303	0.0	1360	1028	1.245	5.259	0.457	1.444	2.953
	0.5	1372	1131	1.343	4.697	0.432	2.213	2.028
	1.0	1380	1257	1.511	4.177	0.408	2.900	1.618
	1.5	1391	1291	1.621	4.003	0.399	3.296	1.475
	2.0	1385	1346	1.737	3.873	0.393	3.702	1.351
	2.5	1374	1417	1.821	3.738	0.386	4.082	1.247
313	0.0	1348	1007	1.183	5.465	0.464	1.440	3.006
	0.5	1361	1120	1.253	4.802	0.438	2.203	2.043
	1.0	1372	1177	1.321	4.514	0.424	2.686	1.725
	1.5	1384	1234	1.452	4.231	0.410	3.135	1.540
	2.0	1377	1300	1.621	4.057	0.402	3.620	1.396
	2.5	1371	1381	1.834	3.852	0.392	4.164	1.273
323	0.0	1336	999	1.104	5.608	0.473	1.392	3.021
	0.5	1347	1110	1.211	4.965	0.445	2.233	2.054
	1.0	1359	1151	1.300	4.704	0.433	2.722	1.758
	1.5	1371	1201	1.421	4.430	0.419	3.158	1.578
	2.0	1365	1281	1.579	4.190	0.408	3.667	1.413
	2.5	1356	1354	1.713	4.017	0.400	4.121	1.294

 

Table 3: Ultrasonic absorption and related acoustical parameters in the solution of SLS in Anise alcohol

Temp K	Conc %	α/f2 X10-15 Np m-1s2	Vf X10-15 m3mol-1	Cohesive energy X10-8	τ X10-12 sec	za x106 kgm-2 s2	Sn
303	0.0	1.117	1.352	21.194	0.800	1.591	–
	0.5	1.186	1.021	22.794	0.853	1.605	-18.143
	1.0	1.233	0.942	24.885	0.892	1.621	-7.242
	1.5	1.305	0.978	29.095	0.950	1.643	-2.949
	2.0	1.341	1.006	32.318	0.984	1.662	-0.907
	2.5	1.444	1.055	36.500	1.054	1.666	-0.808
313	0.0	1.101	1.217	19.131	0.779	1.559	–
	0.5	1.126	0.844	19.577	0.802	1.582	-25.741
	1.0	1.146	0.805	20.906	0.823	1.603	-10.205
	1.5	1.187	0.812	23.515	0.860	1.623	-4.857
	2.0	1.245	0.858	27.038	0.908	1.640	-2.381
	2.5	1.340	0.899	30.451	0.972	1.641	-2.149
323	0.0	1.098	1.122	17.800	0.770	1.529	–
	0.5	1.123	0.818	18.233	0.792	1.550	-34.958
	1.0	1.137	0.750	19.643	0.810	1.576	-14.034
	1.5	1.146	0.729	21.080	0.824	1.600	-7.154
	2.0	1.179	0.754	23.502	0.854	1.619	-3.908
	2.5	1.251	0.770	25.600	0.902	1.620	-3.467

 

Table 4: Ultrasonic absorption and related acoustical parameters in the solution of SLS in Cinnamyl alcohol.

Temp K	Conc %	α/f2 X10-15 Np m-1s2	Vf X10-15 m3mol-1	Cohesive energy X10-8	τ X10-12 sec	za x106 kgm-2 s2	Sn
303	0	1.266	1.133	16.355	0.873	1.398	–
	0.5	1.209	0.841	18.616	0.841	1.552	-37.970
	1.0	1.203	0.843	24.413	0.841	1.735	-2.273
	1.5	1.227	0.855	28.175	0.865	1.796	2.442
	2.0	1.277	0.882	32.636	0.897	1.864	4.103
	2.5	1.303	0.893	36.978	0.907	1.947	5.173
313	0	1.261	1.036	14.913	0.862	1.357	–
	0.5	1.167	0.749	16.497	0.805	1.524	-46.616
	1.0	1.143	0.683	18.342	0.795	1.615	-13.941
	1.5	1.167	0.719	22.547	0.819	1.708	-2.976
	2.0	1.256	0.788	28.937	0.877	1.790	0.766
	2.5	1.355	0.900	37.549	0.942	1.893	3.466
323	0	1.148	0.842	11.725	0.777	1.335	–
	0.5	1.174	0.701	15.645	0.802	1.495	-56.332
	1.0	1.183	0.657	17.900	0.815	1.564	-20.541
	1.5	1.207	0.686	21.680	0.839	1.647	-7.642
	2.0	1.274	0.748	27.415	0.882	1.749	-1.611
	2.5	1.334	0.799	23.919	0.917	1.836	1.122

Figure 1: Velocity Vs concentration of SLS  in Anise alcohol Click here to View Figure

Figure 2: Viscosity Vs concentration of SLS in Anise alcohol Click here to View Figure

Figure 3: Adiabatic compressibility Vs concentration of SLS in Anise alcohol Click here to View Figure

Figure 4: Ultrasonic velocity Vs concentration of SLS in Cinnamyl alcohol Click here to View Figure

Figure 5: Viscosity Vs concentration of SLS in Cinnamyl alcohol Click here to View Figure

Figure 6: Adiabatic compressibility Vs concentration of SLS in Cinnamyl alcohol Click here to View Figure

Figure 7: FTIR spectra of Sodium Lauryl Sulphate (SLS) +Anisyl alcohol Click here to View Figure

Figure 8: FTIR spectra of Sodium Lauryl Sulphate (SLS) +Cinnamyl alcohol Click here to View Figure

Discussion

Ultrasonic velocity against SLS + (Anise alcohol and Cinnamyl alcohol) initially increased and attained a maximum value at CMC and started decreasing with an increase in concentration for the two systems, as given in Figures 1 and 4.  This may be due to the micelle formation occurring in the system. The percentages of solvated alcohol molecules per repetition unit could be explained in terms of propagated attractions, as Moore and Uddin (1970) noted¹².  

It is observed that both density and viscosity increase with an concentration and decrease with increase of temperature. The plot of viscosity versus concentration at three different temperatures is shown in Figures 2 and 4. Aqueous surfactant is homogeneous solution and become more viscous, as the solute is included.  The first type of mutual interaction, hydrodynamic screening significantly determines the viscous flow characteristics of diluted surfactant solutions.¹¹.

The decrease in compressibility has been seen in surfactant solutions and is explained by a change in the compressibility of the solvent molecules involved in the solutions¹².  The decrease of internal pressure with a concentration of SLS + alcohols confirmed the solute-solvent interactions. The closed packing of molecules within the shield imitates the decrease in intermolecular free length and internal pressure¹³.

From the FTIR studies, the OH stretching bands at around 3445 cm^-1 and the bending vibrations at 1656 cm^-1 in the pure SLS spectrum demonstrate the vibrational frequencies of the functional groups⁷.  But in SLS mixed AA spectrum, these peaks are shifted to 3392 and 1612 cm^‑1 whereas in SLS mixed with CA, the peaks are shifted to 3389 and 1707 cm^‑1.  The symmetric stretching vibrations of CH₃ are detected at 2848 cm^-1 and the CH₃ asymmetric stretching band is found at 2914 cm^-1 in pure SLS.  The Peaks are observed at 2849 and 2918 cm^-1 in SLS+AA, whereas in SLS+CA, it is observed at 2851 and 2916 cm^-1.  These peaks indicate the presence of SLS in the complexes.  Altogether the presence of SLS with the chemical structure (C₁₂H₂₅NaSO₄) in the composites is proved by symmetric stretching at 2843 cm^-1 and asymmetric stretching at 2910 cm ^{-1 14}.  In the investigation, from figure 5.4.2 and 5.4.3, the characteristic peaks observed at 2849 cm^-1 and 2918 cm ^-1 in the SLS+AA system and at 2851 cm^-1 and 2916 cm ^-1 in the SLS+AA system confirms the structure of SLS in alcohol system. 

Conclusion

The cleaning agent, surfactant sodium lauryl sulphate (SLS) is primarily utilized in personal care and cleaning products.  Anisyl Alcohol is a primary alcohol that belongs to the fragrance structural group Aryl Alkyl Alcohols. Cosmetics and personal care products can benefit from anisyl alcohol as a scent component. The present study reveals that the intermolecular interaction of SLS with alcohols (Anise alcohol and Cinnamyl alcohol) and the existence of SLS and alcohol interaction is taking place through hydrogen bonding with an increase of SLS concentration. Different alcohol groups, the potency of interaction are more in SLS + water – Anise alcohol compared to SLS+water- Cinnamyl alcohol system.  Finally, it is concluded that SLS+water- Anise alcohol has been used as the best additive.  This composite has a lower foaming tendency due to lower surface tension, leading to a newer product. Additionally, the solvent used in surfactants is less toxic to human society. In this regard, anisyl alcohol is less harmful and toxic to human society when used as a solvent for SLS.

Conflict of Interest

There are no conflict of interest.

Funding Sources

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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