Int J Curr Pharm Res, Vol 7, Issue 1, 62-65Original Article



*Department of Chemistry, Shri Lemdeo Patil Mahavidyalaya, Mandhal (Kuhi): 441210. Nagpur, #Bajaj Super pack (Division of Bajaj Still industries) Hingana, Pvt. Ltd.

Received: 16 Dec 2014, Revised and Accepted: 08 Jan 2015


The density (ρ), viscosity (η) and ultrasonic speeds (U) of copolymer of p-hydroxy benzoic acid and formaldehyde in dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) solutions have been investigated to understand the effect of substituent’s on intermolecular interactions at 283K, 288K, 293K, 298K, and 303K. Various acoustical parameters such as adiabatic compressibility (β), intermolecular free length (Lf), acoustical impedance (Z), internal pressure (π), relaxation time (τ) and relative association (RA) were determined and correlated with concentration (C). A good correlation between a given parameter and concentration is observed at all temperatures and solvent systems studied. The results have been used to discuss the nature and strength of intermolecular interactions in the system.

Keywords: Molecular interaction, Acoustical parameters, Solute-solvent and Solute-Solvent interactions, Internal pressure.


Ultrasonic speeds and related acoustical properties of organic liquids; and non-aqueous electrolytic solutions are extensively useful especially in process industries1. Ultrasonic studies furnish information regarding molecular interactions, nature and strength of interactions. The interactions help in better understanding the nature of solute and solvent i. e. Whether the solute modifies or distorts the structure of the solvent. The measurement of ultrasonic speed enables the thermodynamic parameters which are highly sensitive to molecular interactions in liquid mixtures and pure liquid [2, 3].

Ultrasonic measurement is non-destructive technique to characterize the organic compounds and polymers. Although the relationships between material properties and acoustical parameters have been studied for a long time, ultrasonic devices are not used frequently for material characterization. With the development of high frequency digital and computer techniques it was possible to overcome some of the limitations in applying ultrasonic methods to material characterization and process monitoring. When propagated in polymeric materials acoustic waves are influenced by the polymeric structure as well as by molecular relaxation processes. It is possible to estimate the viscoelastic properties of polymeric materials from the velocity and allied parameters. Also the information about the structure of polymers and molecular interaction occurring in the solution can also be obtained. Literature survey on ultrasonic studies of copolymer of p-hydroxy benzoic acid and formaldehyde revealed that no work has been reported. Thus, in the present paper we have used this technique for the better understanding of the molecular interactions in polymer solutions. The experimental data is used for the evaluation of various thermodynamic and acoustical parameters by which molecular interaction in solutions is interpreted.

Ultrasonic studies in copolymer solution have drawn the attention of several researchers in recent years. Many attempts have been made to study intermolecular interaction between polymer and solvents. The molecular interaction between copolymer of p-hydroxy benzoic acid and formaldehyde in solvents, such as dimethyl formamide (DMF) and dimethyl sulphoxide (DMSO) has been investigated in the present work4. Dimethyl formamide (DMF) is vers a tile solvent, used in the separation of saturated and unsaturated hydrocarbons and serves as a solvent of many polymers and dimethyl sulfoxide (DMSO) is a commercially dipolar aprotic solvent which is also a naturally occurring substance.

In the present paper, we repeat the experimental measurement of the ultrasonic velocity, density and viscosity for copolymer of p-hydroxy benzoic acid and formaldehyde and solvent such as dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) over a wide range of composition at 283K, 288K, 293K, 298K and 303 K. Analysis of the results and their correlation with molecular interaction has also been made using copolymer solution models [5, 6].



The solutes used in the present investigation were synthesized by refluxing 1:2 proportion of p-hydroxy benzoic acid and formaldehyde in 2M hydrochloric acid (as catalyst) for about 4-5 hrs in oil bath at 140oC. The resultant compound was dissolved in concentrated sodium hydroxide and reprecipitated from 50% hydrochloric acid solution. The sample of copolymer of p-hydroxy benzoic acid and formaldehyde was used without purification. Dimethyl formamide (DMF) and dimethylesulfoxide (DMSO) used were of analytical grade. The ultrasonic velocity of the solution of dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) in copolymer of p-hydroxy benzoic acid and formaldehyde of different concentration measured at 283K, 288K, 293K, 298K and 303 K [7, 8].


Density measurements were made by Plunger methods, based on Archimedes principle using bottom loading balance (kRoy, max 100 gm). The accuracy in density measurement was found to be + 0.0001 gm. The viscosity was measurement made by Ostwald’s viscometer with an accuracy 0.001 Ns m-2. Ultrasonic sound velocity measurement were made by variable path single crystal interferometer (Mittal Enterprises, Model F – 81S) at 2 MHz with accuracy of + 0.03%. Electronically digitally operated (Plasto craft Industries) low temperature bath model, LTB – 10 was used to circulate water. The temperature was maintained with an accuracy of 0.1°C.


Measured values of density (ρ), viscosity (η), ultrasonic velocity (U), adiabatic compressibility (β), free length (Lf) at 283K, 288K, 293K, 298K and 303K for copolymer of p-hydroxy benzoic acid and formaldehyde in DMF and DMSO as a solvent9are given table 1 (Fig. 1 and 2) and 2 (Fig. 3 and Fig. 4).

The coefficient of viscosity decreases with temperature as well as concentration up to 1.1% concentration. This may be due to solute – solvent interactions between the molecules. The decrease in viscosity is due to steric effect and may be explained that, as the concentration increases, steric effect or steric crowding is more so that the intermolecular interaction between the copolymer of p-hydroxy benzoic acid and formaldehyde decreases with DMF and DMSO solvent as shown in Table 1 and 2.

With liquids containing molecules held by hydrogen bonds, energy changes markedly with temperature. The viscosity activation energy for these substances consists not only of the fraction i. e. about one-third of the energy of vaporization, which is due to the breaking of what, may be termed “physical” bonds, but also of the energy of these hydrogen bonds which must be broken when the liquid flows. As the temperature is increased the number of hydrogen bonds in the liquid probably diminishes, because of thermal movements of the molecules and the energy of activation will decrease. The larger the number of hydroxy groups in the molecule, the more complexes will be the network of hydrogen bonds and the greater the resistance to flow; the energy required to produce a hole will be large, since work must be done in breaking down part of this system of bonds. In carboxylic acids the hydrogen bonds probably do not extend throughout the whole system, but are probably restricted by the combination of the molecules in pairs; it is significant, therefore that at the same temperature the viscosity of an organic acid is less than that of the corresponding alcohol [10]. The linear increase of density (ρ), viscosity (η), ultrasonic velocity (U) with concentration (C) confirmed increase of cohesive forces because of strong molecular interactions, while decrease of these parameters with temperatures (T) supported decrease of cohesive forces. The increase in temperature has two opposite effects namely structure formation (intermolecular association) and structure destruction. The structure forming tendency is mainly due to solute-solvent interactions, while destruction of structure formed previously is due to thermal fluctuations [11, 12].

In DMSO, due to presence of two oxygen atoms, the copolymer will try to interact via hydrogen bonding. Due to this, there will be more interaction and more compressibility of copolymer of p-hydroxyl benzoic acid and formaldehyde in DMSO as well as DMF and also with temperatures which reflect in increases in adiabatic compressibility with concentration as show in table 1 and 2. In case of DMF, there is presence of unshared electron pair on N-atom, which is accepted by proton. The same trend is observed with intermolecular free length. Increased in intermolecular free length leads to increase adiabatic compressibility, so adiabatic compressibility and free length varies in same manner. And this behavior is observed in both mixtures in Table 1 and 2 [13].

The relative association (RA) is influenced by two factors; the breaking up of the solvent molecules on addition of electrolyte to it and the solvation of ions that is simultaneously present. The former results in the decrease and the later in increase of relative association [14]. In the present case relative association decreases which is due to the breaking up of the solvent molecules on the addition of solute which also indicates prominent polymer-solvent interaction. Copolymer of p-hydroxy benzoic acid and formaldehyde in DMSO shows much variation as compared to the copolymer of p-hydroxy benzoic acid and formaldehyde in DMF solution. So when comparison is made between these two solutions of copolymers the polymer-solvent interaction is much prominent in DMF. This may be due to the fact that hydrogen from competing with lone pair of nitrogen and oxygen of DMF for H- bonding [15].

Table 1: Density, viscosity, ultrasonic velocity, adiabatic compressibility, free length and relative association of p-hydroxy benzoic acid and formaldehyde with DMF solvent

Temp.(oK) DMF
Concentration (%)
0.7 0.9 1.1 1.3 1.5
Kg m-3 283k 0.96341 0.93343 0.96963 0.96802 0.92859
288k 0.96055 0.92877 0.93433 0.93554 0.9362
293k 0.94957 0.96 0.9196 0.95699 0.9237
298k 0.93076 0.91855 0.9005 0.90288 0.8961S
303k 0.92577 0.89681 0.89518 0.90797 0.9065
103Ns m-2 283k 0.99404 0.92809 0.87313 0.94432 0.8623
288k 0.87799 0.82372 0.78637 0.84666 0.80495
293k 0.80459 0.79223 0.74239 0.78974 0.75404
298k 0.72794 0.68646 0.67297 0.69045 0.67856
303k 0.64829 0.62035 0.61158 0.63517 0.63483
U ms-1 283k 1525.61 1530.31 1503.81 1500.7 1512.60
288k 1511.63 1499.72 1489.92 1478.8 1477.90
293k 1487.84 1443.05 1477.76 1487.36 1473.60
298k 1471.04 1433.12 1455.52 1468.32 1472.32
303k 1447.08 1386.61 1443.04 1450.4 1448.16
10[10]Pas-1 283k 4.46E-07 4.57E-07 4.56E-07 4.59E-07 4.71E-07
288k 4.56E-07 4.79E-07 4.82E-07 4.89E-07 4.89E-07
293k 4.76E-07 5E-07 4.98E-07 4.72E-07 4.99E-07
298k 4.96E-07 5.3E-07 5.24E-07 5.14E-07 5.08E-07
303k 5.16E-07 5.8E-07 5.36E-07 5.3E-07 5.26E-07
Lf 10[10]m 283k 40.19289 40.70784 40.64456 40.76237 41.29138
288k 40.62549 41.64252 41.79152 42.07798 42.08718
293k 41.5122 42.56753 42.47096 42.48222 42.49462
298k 42.40842 43.81891 43.5748 43.13797 42.90002
303k 43.22663 44.05123 44.08206 43.83585 43.64988
RA 283k 0.967734 0.967158 0.966411 0.966036 0.965882
288k 0.976534 0.972519 0.980481 0.984201 0.985169
293k 1.003686 1.002534 0.995655 0.986734 0.979551
298k 0.982331 0.980012 0.972436 0.972165 0.976759
303k 0.969456 0.968834 0.967237 0.966591 0.964533

Table 2: Density, viscosity, ultrasonic velocity, adiabatic compressibility, free length and relative association of p-hydroxy benzoic acid and formaldehyde with DMSO solvent

Temp.(oK) DMSO
Concentration (%)
0.7 0.9 1.1 1.3 1.5
Kg m-3 283k 1.11988 1.11222 1.12794 1.13014 1.13014
288k 1.11698 1.11292 1.1228 1.12408 1.12075
293k 1.10475 1.10294 1.10787 1.11073 1.10711
298k 1.03607 1.08458 1.08458 1.70374 1.07889
303k 1. s02686 1.08282 1.11222 1.08474 1.06736
103Ns m-2 283k 2.52108 2.85855 2.61329 1.99264 1.76
288k 2.325 2.31654 2.30663 2.2889 2.32269
293k 1.7 1.9589 2.0869 1.99264 2.18477
298k 1.62962 1.6965 1.81902 1.70374 1.8711
303k 1.53464 1.5258 1.64087 1.50071 1.69543
U ms-1 283k 1527.68 1545.28 1536.32 1530.08 1546.72
288k 1529.12 1531.52 1532.16 1533.44 1533.44
293k 1520.16 1521.60 1530.64 1530.08 1520.81
298k 1501.11 1493.44 1501.60 1502.10 1509.12
303k 1492.08 1488.96 1477.36 1488.96 1481.44
10[10]Pas-1 283k 3.83E-07 3.77E-07 3.76E-07 3.78E-07 3.69E-07
288k 3.83E-07 3.83E-07 3.79E-07 3.78E-07 3.79E-07
293k 3.92E-07 3.92E-07 3.85E-07 3.85E-07 3.91E-07
298k 4.28E-07 4.13E-07 4.09E-07 4.08E-07 4.07E-07
303k 4.37E-07 4.17E-07 4.12E-07 4.16E-07 4.19E-07
Lf 10[10]m 283k 37.22865 36.93116 36.88678 36.75344 36.6030
288k 37.24185 37.25125 37.07151 37.01946 37.7744
293k 37.66814 37.66336 37.35752 37.32305 37.6121
298k 38.88234 38.69697 38.48668 38.44373 38.3957
303k 38.89773 38.84493 38.62903 38.81053 38.9585
RA 283k 0.996527 0.998999 1.001514 1.001898 1.00254
288k 0.992446 0.994534 0.996957 0.997816 1.00301
293k 1.000213 1.000543 1.000744 1.003449 1.00362
298k 1.004533 1.003399 1.001578 1.001021 1.00812
303k 1.043544 1.037466 1.035454 1.030565 1.02441

Fig. 1: Adiabatic compressibility Vs concentration with different temperature in DMF

Fig. 2: Free length Vs concentration with different temperature in DMF

Fig. 3: Adiabatic compressibility Vs concentration with different temperature in DMSO

Fig. 4: Free length Vs concentration with different temperature in DMSO


The authors are very thankful to the Principal, Hislop College, Nagpur, Maharashtra, India and the HOD, Dr. I. N. Nimdeokar P. G. and Research Centre for Chemistry, Hislop College, Nagpur and Maharashtra, India for providing necessary facilities.


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International Journal of Current Pharmaceutical Research
Vol 7, Issue 1, 2015 Page: 62-65

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Authors & Affiliations

S. S. Kharkale
Department of Chemistry, Shri Lemdeo Patil Mahavidyalaya, Mandhal (Kuhi): 441210. Nagpur

S. S. Bhuyar

M. K. Gaidhane


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