Ultrasonic studies provide a wealth of information in understanding the molecular behavior and intermolecular interaction of polymer solvent mixtures. Attempts were made to measure ultrasonic velocity, density, and viscosity for the mixture of polyvinylidene fluoride (PVDF) in acetone and dimethylformamide (DMF) of various stoichiometric ratios at 300 K using crystal controlled ultrasonic interferometer (Mittal make), pyknometer (specific gravity bottle), and Ostwald viscometer, respectively. The acoustic parameters adiabatic compressibility (
Ultrasonic studies in polymeric solutions have drawn the attention of many researchers in the recent years [
Polyvinylidene fluoride (PVDF) is a semicrystalline polymer that has a simple chemical structure
In our experimental investigation, we used the ultrasonic technique to find the acoustic parameters such as adiabatic compressibility (
AR grade (99.8% pure) ferroelectric polymer PVDF in powder form is procured from Sigma Aldrich, Bangalore, India. Figure
XRD pattern of virgin PVDF powder confirming the phase formation.
Ultrasonic interferometer, specific gravity bottle, and Ostwald viscometer are used to measure ultrasonic velocity, density, and viscosity, respectively.
Ultrasonic velocity was measured using a single-crystal interferometer (Mittal Enterprises, New Delhi) operating at 1 MHz with an accuracy of ±1.0 m/s. The experimental procedures are standard and described elsewhere [
The acoustic parameters were computed as follows.
The ultrasonic velocity is calculated as
The viscosity of the solution is calculated using
The following equations are used to compute the acoustic parameters: adiabatic compressibility (
Adiabatic compressibility ( Intermolecular free path length ( where Acoustic impedance ( where Relative association (RA) is as follows: where Ultrasonic attenuation ( where
The experimentally obtained values of density, viscosity, and ultrasonic velocity of PVDF with different concentrations of acetone and DMF are reported in Tables
Variation of density, viscosity, and ultrasonic velocity of PVDF with different concentrations of acetone at 300 K.
Concentration |
Density |
Viscosity |
Ultrasonic velocity |
---|---|---|---|
0.00 | 783.00 | 0.3635 | 1165.00 |
0.10 | 783.56 | 0.3665 | 1165.90 |
0.20 | 784.10 | 0.3672 | 1166.50 |
0.30 | 784.68 | 0.3747 | 1168.00 |
0.40 | 787.76 | 0.3836 | 1169.00 |
0.50 | 790.36 | 0.3893 | 1170.80 |
Compounded uncertainty in measurement of density (
Variation of density, viscosity, and ultrasonic velocity of PVDF with different concentrations of dimethylformamide at 300 K.
Concentration |
Density |
Viscosity |
Ultrasonic velocity |
---|---|---|---|
0.00 | 934.20 | 0.7921 | 1454.00 |
0.10 | 934.92 | 0.9084 | 1474.00 |
0.20 | 937.04 | 0.9156 | 1478.00 |
0.30 | 938.16 | 1.0505 | 1482.50 |
0.40 | 939.04 | 1.0818 | 1485.00 |
0.50 | 940.88 | 1.3422 | 1486.60 |
Compounded uncertainty in measurement of density (
The least square equations and regression coefficients for PVDF solution in acetone and DMF.
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Acetone | DMF | |
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In order to understand the effect of concentration and nature of solvent on PVDF polymeric solution, the acoustic parameters such as adiabatic compressibility (
Variation of adiabatic compressibility with concentration of PVDF in acetone and DMF at 300 K.
Variation of intermolecular free path length with concentration of PVDF in acetone and DMF at 300 K.
Variation of acoustic impedance with concentration of PVDF in acetone and DMF at 300 K.
Variation of ultrasonic attenuation with concentration of PVDF in acetone and DMF at 300 K.
Variation of relative association with concentration of PVDF in acetone and DMF at 300 K.
Variation of relaxation time with concentration of PVDF in acetone and DMF at 300 K.
Ultrasonic speed in the solutions depends on intermolecular free path length. When ultrasonic waves are present in the solution, the molecules get perturbed. Due to some elasticity of the medium, perturbed molecules regain their equilibrium positions. When a solute is added to a solvent, its molecules attract certain solvent molecules towards them. The phenomenon is known as compression and also as limiting compressibility. The aggregation of solvent molecules around solute molecules supports powerful solvent-solute interactions. Because of solvent-solute interactions, the structure of the solute is modified to the considerable extent. The adiabatic compressibility and intermolecular free path length decrease from those of pure solution by ~2% and 1% and 5% and 2.5%, respectively, in acetone and DMF. Decrease of
The variation of ultrasonic velocity in a solution depends on the intermolecular free length on mixing. On the basis of a model for sound propagation proposed by Kincaid and Eyring [
The property which can be studied to understand the interaction is relative association (RA). It can be explained by two factors [
The ultrasonic technique is a powerful and effective tool for the investigation of polymer solutions and behavior of polymer chain in an ultrasonic field. The present study describes the acoustic properties that confirm the molecular interaction of PVDF polymer powder with a acetone and DMF. The acoustic parameters like adiabatic compressibility (
The authors declare that they have no competing interests.
The authors express their deep sense of gratitude to Vision Group of Science and Technology for providing the financial support to carry out this research work. The authors are also thankful to Dr. M. Revanasiddappa, PESIT, South Campus, Bangalore, for his valuable suggestions.