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Solubility Parameter Study of Polysulfone, Polyvinyl Acetate in Dimethylacetamide Solvent.

Byline: Asim Mushtaq, Hilmi Mukhtar and Azmi Mohd Shariff

Summary: The solubility parameter is calculated to express the magnitude and nature of the interactive forces between the polymers and solvents. It measures the affinity between the components of a mixture. To improve the prediction of the solubility parameter, the group contribution method is used to calculate the overall solubility parameter as suggested by Hildebrand. Hildebrand's method is used to predict the interaction between the polymers and solvent. In this study, calculate the solubility parameters of polysulfone (PSU), polyvinyl acetate (PVAc) polymers and dimethylacetamide (DMAc) solvent by Hildebrand method. The PSU and PVAc solubility were found to be 1.52H and 1.7H, respectively. These solubility values show that both polymers were dissolved readily in the DMAc solvent, resulting in a true solution.

Keywords: Polysulfone, Polyvinyl acetate, Amines, Dimethylacetamide, Hildebrand Method.

Introduction

Polymer for membrane synthesis can be determined by the selection of correct polymers and solvents. Due to the molecular size, structure, and shapes of polymers, its solubility is complex as compared with the solubility of low molecular weight compounds. The purpose of this theoretical study is to find the misibility of different polymeric blends. Blending of glassy and rubbery polymers with different amines for development of Enhanced polymeric blend membranes.

The "like dissolve like" principle is a measure of polymer solubility, for example, polystyrene dissolved in toluene or benzene because they have a similar structure. Polymer solubility occurs in two stages, the first formation of gel secondly gel breaks up, and molecules are dispersed into a true solution. Polymers dissolve if solvent-solvent and polymer-polymer cohesive energy are similar to the solvent-polymer adhesive energy.

Some polymers dissolve in a solvent readily, others requiring prolong period of heating and network polymer do not dissolve. Polymers dissolve in solvents with similar solubility parameter. For a polymer to dissolve in a given solvent.I'1 - I'2 a$? +- 1.8 H (Hildebrand Method); the smaller the difference, the better the solubility I'1 is the solubility of solvent and I'2 is the solubility of the polymer [1, 2]. The solubility parameters of the solvents and polymer are defined in equation 1 and 2, respectively:

(Equations)

Where I' is solubility parameter, I is the density, R is gas constant (1.987cal mol-1 K-1), T is the temperature (K), M is the molecular weight, IH is the molar heat of vaporisation, G is group molar attraction constant derived from experiments, 18.02 MPa1/2 converts into cal1/2 cm-3/2.

It is important to note that solubility parameter does not take into account secondary forces in polymers like dipole-dipole interaction and hydrogen bonding. The molar enthalpy (heat) of vaporisation IHvap, which is characterized by the enthalpy change in the transformation of one mole of fluid to gas at a consistent temperature. The standards are considered, at the normal boiling point Tb, stated to a pressure of 101.325 kPa (760 mmHg), and at 25AdegC. The values were measured by use of the Claperyon equation to the variant of vapour pressure with temperature [3-9].

Experimental

Polysulfone (PSU) UdelA(r) P-1800 is a powdered grade having a glass transition temperature (Tg) of 185AdegC was attained from Solvay Advanced Polymers; L.L.C, U.S. This material deals excellent control of pore size and its distribution, good film-forming properties and high membrane strength. The resulting membranes have incredible hydrolytic stability and are perfect for pH's extending from 2 to 13.

Polyvinyl acetate (PVAc) average Mw ~100,000 by GPC, beads from Sigma-Aldrich, Germany having a glass transition temperature (Tg) of 28AdegC. PSU was selected mainly due to its ease of fabrication, good properties like high strength and good thermal stability associated with low cost and ease of availability. However, PVAc was selected due to its quite flexible strong bonding and non-acidic nature. The chemical structures of PSU and PVAc polymers are shown in Fig. 1 [10].

After reviewing the literature on the solubility of PSU and PVAc polymers, DMAc solvent was selected by its properties. A dimethylacetamide (DMAc) solvent, monoethanolamine (MEA), diethanolamine (DEA) and methyl diethanolamine (MDEA) with a purity of 99.99% was purchased from Merck, Germany. The chemical structures and physical properties of the solvents and amines are shown in Fig. 2 and Table-1 [11, 12].

Results and Discussion

Solubility Parameter Study using Hildebrand Approach

Experimental results, as demonstrated using Hildebrand solubility parameter I', reveal that the polarity has a strong influence on solubility and subsequently the permeability [1]. The solubility parameter of the polymers and solvent was calculated from the group contribution for each molecular structural group by using the Hildebrand method [1, 2].

Solubility parameter values are based on heats of vaporisation. This approach evaluates the strength of the dispersive interactions in a blend of solvent and polymers. A comparison of the solubility parameters of the polymer (I'polymer) and solvent (I'solvent), where I' is a measure of the attractive strength between molecules of the material, allows prediction of miscibility. For a polymer to dissolve in a given solvent, the solubility parameter must satisfy I'1 - I'2 a$? +- 1.8 H. It is noted the smaller the difference, the better the solubility of I'1 (solubility of solvent) and I'2 (the solubility parameter of the polymer) [7, 8].

The calculations regarding the solubility parameter estimation and the group contributions for the structures of each component were well tabulated as shown in Table-2 and 3.

The results in Table-2, found that the PSU and PVAc polymers were completely soluble in DMAc solvent calculated by Hildebrand method. The PSU and PVAc solubility were found to be 1.52H and 1.7H, respectively. These solubility values show that both polymers were dissolved readily in the DMAc solvent, resulting in a true solution. The smaller difference of solubility parameter indicates that PSU and PVAc polymers were soluble in DMAc solvent, indicating that the solvent and polymers have similar internal energies. The numerical value of solubility parameter shows the comparative solvency performance of DMAc solvent in PSU and PVAc polymers.

Table-1: Physical properties of dimethylacetamide solvent and amines.

###Solvent and amines

###Properties

###Dimethyl acetamide###Monoethanolamine###Diethanolamine###Methyl diethanolamine

###Density g.cm -3###0.942###1.012###1.09###1.04

###Molecular mass g.mol-1###87.12###61.08###105.14###119.163

###R is gas constant

###1.987###1.987###1.987###1.987

###(cal.mol-1.K -1)

###Temperature K###298###298###298###298

Table-2: The solubility parameter using Small's Molar Attraction Constant at 25AdegC for polymers functional group component by using Hildebrand method.

###I'2 Solubility parameter I'1 Solubility parameter

###Value###Total

Polymer Funtional groups###Frequency###(cal.cm-3)1/2###(cal.cm-3)1/2###I'1 - I'2 a$? +- 1.8 H

###G(cal.cm3)0.5mol-1###G(cal.cm3)0.5mol-1

###or H###or H

###O (ether)###114.98###2###229.96

###C###98.12###8###784.96

###(aromatic)

###CH###117.15###16###1874.4

###(aromatic)

###6-member ring###-23.44###4###-93.76

PSU###Para substitution###40.33###5###201.65###9.91###11.42###1.52

###CH4###32.03###1###32.03

###CH3###147.3###2###294.6

###O

###S###184.45###1###184.45

###O

###O

###332.58###1###332.58

###CO

###CH3###147.3###1###147.3

PVAc###9.71###11.42###1.7

###CH2###135.5###1###135.5

###CH###93.99###1###93.99

Table-3: Calculation of overall solubility parameter using the molar heat of vaporization at 25AdegC for solvents and amines by using Hildebrand method.

###Solvent and amines

###Properties

###Dimethyl acetamide###Monoethanolamine###Diethanolamine###Methyl diethanolamine

IH molar heat of vaporization cal.mol-1###12,715.1052###10,786.3289###15,583.174###19,079.8279

###I'1 Solubility parameter

###11.44###12.996###12.466###12.70

###(cal.cm-3)1/2or H

###I'1 - I'2 a$? +- 1.8 H###-###-1.55###-1.017###-1.26

It is consequent from the cohesive energy, solvent density, which is resultant from the heat of vaporisation. The solubility of polymer and solvent occurs while their attractive intermolecular forces are analogous, and it is also expected that materials with related cohesive energy density values are miscible. Polymers dissolve if solvent-solvent and polymer-polymer cohesive energy are similar to solvent polymer adhesive energy [1, 2]. The widely recognised particular interactions are hydrogen bonds, however other possible interactions to deliberate are ionic, dipole-dipole, acid-base, cation- p (cations interacting through aromatic rings) and charge transfer complexes [7, 8].

The precise estimates of solubility behaviour will not depend just on deciding the consequence of intermolecular attractions between particles, however in separating between various sorts of polarities also. Polarity, because of unevenness in electron distribution, is depicted by a gathering of properties, such as dipole moment, hydrogen-bonding capacity, charge density and bulk properties like surface tension and dielectric constant [13]. Van der Waals forces are the consequence of intermolecular polarities, due to the structure of a single molecule, may reveal Van der Waals forces that are the improved result of a few various types of polar contributions. Substances will disintegrate in each other if their intermolecular strengths are comparable, as well as uniquely if their composite forces are made up similarly.

Such types of component interactions comprise dispersion forces, induction and orientation effects, and hydrogen bonds [8]. These results are in great concurrence with prior reviews [1, 2, 7, 8].

Conclusion

The solubility parameter of the polymers and solvent was calculated from the group contribution for each molecular structural group by using the Hilde-Brand method. Polymer solubility as calculated by the Hildebrand method found the PSU/PVAc polymer dissolved in a DMAc solvent at a range of I'1-I'2 a$? (+-1.8) H. PSU, PVAc and amine blends of different compositions were all miscible in DMAc solvent. From solubility parameter, the miscibility between the polymers and solvent was confirmed.

Acknowledgement

The authors would like to acknowledge the Universiti Teknologi PETRONAS, Malaysia for supporting this research work and the NED University of Engineering and Technology, Karachi, Pakistan for financial assistance to Asim Mushtaq, studying at this University.

References

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2. A. F. Barton, "Handbook of Poylmer-Liquid Interaction Parameters and Solubility Parameters," CRC Press, pp. 11, 362 (1990).

3. S. P. Verevkin, "Thermochemistry of amines: experimental standard molar enthalpies of formation of some aliphatic and aromatic amines," The Journal of Chemical Thermodynamics 29, 8, 891 (1997).

4. J. L. Abboud and R. Notari, "Critical compilation of scales of solvent parameters. Part I. Pure, non-hydrogen bond donor solvents," Pure and Applied Chemistry, 71, 645 (1999).

5. S. Thomas, Yves Grohens, and Parameswaranpillai Jyotishkumar, eds, Characterization of polymer blends: miscibility, morphology and interfaces, John Wiley and Sons, pp. 18, 111, 626 (2014).

6. B. A. Wolf, "Solubility of polymers," Pure and Applied Chemistry, 57, 323 (1985).

7. H. S. Elbro, Aa Fredenslund, and P. Rasmussen, "A new simple equation for the prediction of solvent activities in polymer solutions," Macromolecules, 23, 4707 (1990).

8. S. M. Walas, "Phase equilibria in chemical engineering," Butterworth-Heinemann, 217, 231 (2013).

9. F. Rodriguez, Claude Cohen, Christopher K. Ober, and Lynden Archer, "Principles of polymer systems," CRC Press, 36 (2014).

10. K. Scott, "Handbook of industrial membranes," Elsevier, pp. 3, 78, 195, 258 (1995).

11. S. Matar, and Lewis F. Hatch, "Chemistry of petrochemical processes," Gulf Professional Publishing, pp. 3-6, 9-10, (2001).

12. N. P. Cheremisinoff, "Industrial Solvents Handbook " vol. Second Edition, pp. 29-32 (2003).

13. H. F. Mark, "Encyclopedia of polymer science and technology, concise," John Wiley and Sons, 151, 1446, 1969, 2363, 3461, 3578, (2013).
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Author:Mushtaq, Asim; Mukhtar, Hilmi; Shariff, Azmi Mohd
Publication:Journal of the Chemical Society of Pakistan
Article Type:Technical report
Date:Feb 28, 2019
Words:2176
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