Chapter 5
Calculation of Solubility Parameters by Inverse Gas Chromatography Gareth J. Price
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Downloaded by DICLE UNIV on November 1, 2014 | http://pubs.acs.org Publication Date: April 24, 1989 | doi: 10.1021/bk-1989-0391.ch005
Department of Chemistry, The City University, Northampton Square, London EC1V 0HB, England Inverse Gas Chromatography (IGC) has been used to measure s o l u b i l i t y parameters f o r three polymers at 25°C using the method of G u i l l e t and DiPaola-Baranyi. The l i n e a r relationship noted with other polymers was found and the results add further credance to the method. S o l u b i l i t y parameters have also been calculated for s i x small molecule i n v o l a t i l e compounds of the type use as p l a s t i c i z ers. The o r i g i n a l method did not y i e l d values i n good agreement with l i t e r a t u r e results but estimation of the d i f f e r e n t contributions to the solution interactions allowed c a l c u l a t i o n of more meaningful values. The study of polymer solutions has been an active research f i e l d sifcce the mid 1960s. There are a number of methods available f o r the measurement of thermodynamic parameters such as a c t i v i t y c o e f f i c i e n t s and interaction parameters [1,2]. These techniques, which include membrane osmometry and vapour sorption, involve d i f f i c u l t and time consuming experiments and are usually confined to r e l a t i v e l y d i l u t e solutions although vapor sorption using electronic vacuum microbalances, has been used at high polymer concentrations [3]. Inverse Gas Chromatography (IGC) i s a method that overcomes these l i m i t a t i o n s [4,5] and i s p a r t i c u l a r l y applicable to concentrated solutions, which are of considerable i n d u s t r i a l interest f o r surface coatings, solvent removal etc. Since the early work of Smidsrod and G u i l l e t [6] i n 1969 numerous systems have been studied by t h i s method, and good agreement with the mere t r a d i t i o n a l , s t a t i c equilibrium measurements of acti v i t y c o e f f i c i e n t s , interaction parameters, enthalpies of mixing and solution and contact energy parameters has been demonstrated [7,8]. Another useful facet of the method i s that i t may be extended to the study of mixtures of two or more polymers to obtain information on polymer-polymer interactions [9,10] and also to the study of mixtures of polymers with lower molecular weight compounds such as p l a s t i c i z e r s [11]. P a r a l l e l i n g t h i s experimental work has been considerable a c t i v i t y i n the theoretical treatment of polymer solutions. The o r i g i n a l work of Flory and Huggins i s often used f o r the c a l c u l a t i o n 1Current address: School of Chemistry, University of Bath, Claverton Down, Bath, Avon BA2 7AY, England
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0097-6156/89/0391-0048$06.00/0 1989 American Chemical Society
In Inverse Gas Chromatography; Lloyd, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
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Calculation of Solubility Parameters
of the i n t e r a c t i o n parameter, X, now regarded as a residual free energy function. Other developments i n the interpretation of X have been the Corresponding States theory of Prigogine and Patterson [12, 13], Flory's Equation of State treatment [14], the L a t t i c e F l u i d method of Sanchez and Lacombe [15] and, more recently, the Scaling Concepts of de Gennes [16]. Although these treatments have allowed a more rigorous interpretation of the various parameters, they depend on a number of empirical parameters which cannot be readily predicted; therefore, they are of limited use i n cases where l i t t l e or no experimental data i s a v a i l a b l e . Recourse must often be made to less rigorous, but more e a s i l y applied methods. Amongst the most often used i s that using the Hildebrand s o l u b i l i t y parameter,
