A Study on Swelling Behavior of Poly(p-chloro styrene) Networks in Some Aromatic Hydrocarbons and Linear Poly(p-chloro styrene) Solutions Onur Celik, Dolunay Sakar, Fatih Cakar, Ozlem Cankurtaran, Ferdane Karaman Department of Chemistry 34220, Yildiz Technical University, Davutpasa Campus, Esenler, Istanbul, Turkey Received 11 July 2006; accepted 22 August 2008 DOI 10.1002/app.29173 Published online 22 October 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Crosslinked networks (NPPCS) and linear polymers (LPPCS) of poly (p-chloro styrene) were synthe- sized by free-radical polymerization of p-chloro styrene. NPPCS networks were swollen in four different molecular weights of LPPCS solutions in toluene at three different concentrations. The equilibrium swelling results were eval- uated by means of Flory-Rehner theory to obtain network– linear polymer interaction parameter, v 0 23 between NPPCS and LPPCS. It was concluded that the parameter v 0 23 decreased with molecular weight but increased with con- centration of LPPCS in outer solution. The solvent inde- pendent interaction parameter between NPPCS and PPCS was estimated as 0.7 by extrapolation of the values of v 0 23 to zero value of the fraction ratio of solvent to linear poly- mer, m 1 /m 3 inside the network. As well as, the binary inter- action parameters, v 12 of NPPCS with benzene, ethyl benzene, n-propyl benzene and isopropyl benzene were obtained by means of Flory-Rehner theory at temperatures between 25 and 55  C. V V C 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1328–1334, 2009 Key words: poly(p-chloro styrene); network; swelling behavior; polymer–solvent interaction parameter; polymer– polymer interaction parameter INTRODUCTION Theoretical analysis of the experimental swelling data of polymer networks assumes that the network immersed in a liquid attains its thermodynamic equilibrium state with the surrounding solution after a finite time like a few weeks. 1–6 The equilibrium volume of the network phase as a function of the solvent composition can be theoretically predicted as the chemical potentials of diffusible components in and outside the network are equal. Investigations on the swelling behavior of a network in the solvents have been reported for the last 60 years. 1–7 Recently, Horta and Pastoriza 8 have reviewed the polymer– solvent interaction parameters reported for cross- linked, star, and linear polymers. It was appeared that the polymer–solvent interaction parameters of the crosslinked networks are higher than those of their uncrosslinked linear polymers. This was because the network acts as a copolymer of the repeating units in the chain and the network junc- tions, as well as it has an extra entropic contribution related to the constraints imposed by the junctions. A polymer network placed in a linear polymer melt barely swells as the entropy of mixing of the polymer is very small, then, it is very difficult to obtain a measurable swelling degree. Polymer net- works swollen in a good solvent deswell when transferred to a solution of a linear polymer in the same solvent because of the osmotic pressure of the polymer solution. Long time ago, it was suggested to use this property to measure linear polymer mo- lecular weight 9 or the interaction parameters of the pairs between solvent, linear polymer, and network. 10 Among the theories, Flory-Rehner is still used suc- cessfully to explain the experimental swelling/desw- elling observations of the networks both in small molecule solvents, in polymer melts and in polymer solutions. In the literature, limited number studies were published concerning the networks in their lin- ear polymer solutions. 9–18 In these studies, it was concluded that the Flory-Rehner theory explain suc- cessfully the experimental swelling/deswelling measurements on gels. Therefore, the Flory-Rehner theory is quite adequate to determine the parameter v 0 23 between a network and a linear polymer. Sakur- ada et al. 10 assumed that the interaction parameter v 0 23 between a network and a linear polymer is inde- pendent on molecular weight and concentration of Journal of Applied Polymer Science, Vol. 111, 1328–1334 (2009) V V C 2008 Wiley Periodicals, Inc. Correspondence to: O. Cankurtaran (kurtaran90@yahoo. com). Contract grant sponsor: Scientific Research Projects Coordination Center of Yildiz Technical University.