1. 2nd International Conference on Chemical Engineering and
A study on the molecular interaction of PEG 1000 and its blend in toluene using Ultrasonic technique By
K.Venkatramanan
Paper ID:3997
2nd International Conference on Chemical Engineering and
Advanced Materials
Nov 15th - 26th, 2010

2. Polymer solution
A polymer solution may be defined as "Dispersion of a polymer in a solvent system".
The dispersion may be due to molecular and super molecular arrangement .
The nature of the dispersion can vary with the polymer type, concentration, molecular weight, temperature, solvent system and storage time.
The solvent system may consist of a single solvent, or a mixture of solvents or a complex system incorporating various concentrations and combination of solvents, swelling agents and non solvents.

3. Polymer solution …..
Within a polymer solution, there are a lot of competing forces mainly referred to as polymer-solvent, and polymer-polymer interaction, which tends to increase dispersion.
Molecular dispersion is favoured when strong polymer-solvent interactions are operative.
It has been established that the nature of the solvent mixture from which a dense polymeric membrane is formed has an important influence on the physical, mechanical and permeability properties obtained.

4. The polymer used in the present study is Poly ethylene glycol [PEG] HO-(CH2-CH2-O-)n-H
PEGs are prepared by polymerization of ethylene oxide.
PEG is more water soluble and less oil soluble.
It acts as a dye carrier in paints and inks.
It acts as an anti dusting agent in agricultural formulations.
It also acts as softener and antistatic agent for textiles.
PEG is used in a number of toothpastes as a dispersant

5. Objectives of the study The main objectives of the research work are as follows
Ultrasonic studies:
To determine various ultrasonic parameters like adiabatic compressibility, free volume and internal pressure for PEG of molecular weight 1000 in Toluene at different concentrations and hence to analyse the molecular interaction and solute –solvent interaction taking place in them.

6. Objectives…..
Blends:
To analyse the compatibility nature of the polymer blend PEG 1000 : PPG 1000 in different compositions in Toluene at 303K and to confirm the miscibility nature of the blend using additive law, relative viscosity, ultrasonic velocity and refractometry techniques.

7. Ultrasonic studies
Ultrasonic measurements act as an important tool in the study of liquids.
Ultrasonic and thermodynamic parameters derived from these measurements are extremely useful in the study of molecular interactions.
Propagation of ultrasound in a medium is concentration dependent.
Ultrasonic velocity is measured for PEG 1000 for various concentrations [0.1, 0.25, 0.5, 0.75 and 1%] at 303K in toluene.
The Ultrasonic velocity decreases with increase in concentration for PEG 1000 in toluene and vice versa for Relative viscosity.

8. Variation of Ultrasonic velocity and Viscosity against Concentration for PEG 1000 in Toluene at 303K

9. Adiabatic compressibility
Normally a decrease in adiabatic compressibility indicates closed packing and increased ionic repulsion due to close packing.
In the present study, the adiabatic compressibility value for PEG 1000 is the maximum at high concentration.
This means that the molecules are closely packed at lower concentration.

10. Variation of Adiabatic compressibility against Concentration for PEG 1000 in Toluene at 303K

11. Free Volume
Free volume refers to the void space between the molecules, i.e., the volume present as holes because of irregular packing of the molecules.
It depends on the ultrasonic velocity directly and viscosity inversely.
Free volume reduces when the internal pressure increases.
In this study, free volume for PEG 1000 is the maximum at low concentration in toluene. This may be due to the effect of the solvent.
The free volume shows decreasing trend with increase in concentration.

12. Internal pressure
Internal pressure is a measure of the resultant attractive and repulsive forces between the interacting components in the mixture.
The reduction in the internal pressure at lower concentration may be attributed to breaking of intermolecular forces.
In the present study, the internal pressure increases with increase in the concentration. The polymer at higher concentration is more compact due to the formation of strong intermolecular attraction between solvent and solute molecules. Internal pressure shows a reverse trend to that of free volume as expected.

13. Variation of Free volume and Internal pressure against concentration for PEG 1000 at 303 K in Toluene

14. Polymer Blending
Polymer blending is one of the most commercially significant areas for the development of new polymer materials.
Certain properties of polymers can be enhanced by mixing it with another polymer.
When two or more polymers are intimately mixed in a single continuous solid product, the composition is generally referred to as a polymer blend or polyblend.

15. Polymer Blending
The properties of polymer blends depend on the miscibility of the individual polymers at molecular level.
If a blend is miscible, it can be used to achieve the desired properties by controlling the content of the individual components.
If a blend is immiscible, we can add a third component – the compatibiliser so that the system becomes a polymer alloy which generally possesses superior properties to those of the individual polymers.
Thus, the data on the miscibility of the polymer blends is useful in identifying their possible applications.

16. Techniques used to analyse the compatibility of the blend
Viscosity method
Ultrasonic technique
Refractive index method
Viscosity Method:
Simple.
Relationship between dilute solution properties and bulk structure of polymer blend.

17. Viscosity method- Additive law
Das and Banerjee* have used a few empirical and semi empirical equations for predicting the miscibility of polymer blends based on viscosity viz.,
ADDITIVE RULE,
LOG ADDITIVE RULE AND
FREE VOLUME ADDITIVE RULE.
The additive rule of mixture is given by
b = W 1 * 1 + W 2 * 2
log b = W 1 * log  1 + W 2 * log  2
1 / (log b) = W 1 * (1/ log  1) + W 2 * (1/ log  2)
where
b is the viscosity of the blend ,
 1 ,  2 that of the components and
W 1, W 2 the weight fractions of the components.

18. Positively - Negatively deviating
The viscosity composition behaviour of polymer blends are divided into three categories depending on the deviation from log additive rule.
Positively deviating
Negatively deviating
Positively - Negatively deviating

19. Variation of Viscosity against Blend Composition – [PEG 1000 : PPG 1000] - ADDITIVE RULE

20. This confirms that the blend system taken for study is immiscible.
The experimental values are negatively deviating for all the blend compositions in Toluene and they are closer to log additive values, which refers negative interaction, which in turn causes the macromolecules to shrink.
The negative deviation of the log additive rule in the case of immiscible blends was reported by Venkatramanan et al *.
This confirms that the blend system taken for study is immiscible.
* K. Venkatramanan, V. Arumugam, Viscosity studies on PPG and its blend,
Int.J.Thermophysics 27(1) (2006)

21. If the variation of Ultrasonic Velocity & Refractive index with Concentration is
Linear – Miscible
Non linear – Immiscible
In between – Semi compatible
Rajulu A.V, A review on the importance of ultrasonic technique for the investigation of miscibility of polymer blends, J.Acoust.Soc.India, 23 (1995) 1.

22. Variation of Ultrasonic Velocity and Refractive index against Blend composition PEG 1000 : PPG 1000
The Variation of Ultrasonic velocity and Refractive index with the blend composition is Non Linear which confirms that the blend system is Immiscible.

23. References
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