African Journal of Pure and Applied Chemistry Vol. 2 (4), pp. 041-045, April, 2008 Available online at http://www.academicjournals.org/AJPAC ISSN 1996 - 0840 © 2008 Academic Journals Full Length Research Paper Miscibility studies of PVC/PMMA and PS/PMMA blends by dilute solution viscometry and FTIR Mohammad Saleem Khan 1 *, Raina Aman Qazi 1 and Mian Said Wahid 2 1 Polymer Chemistry Laboratory, National Center of Excellence in Physical Chemistry, University of Peshawar, Peshawar 25120, Pakistan. 2 Government Postgraduate Jehanzeb College, Saidu Sharif, Swat, Pakistan. Accepted 24 April 2008 The effect of polymer-polymer interactions on the miscibility of PVC/PMMA and PS/PMMA blends were studied in a broad composition range using viscosity and FTIR techniques. From the viscometric data, the presence of attractive forces among different polymers was evaluated according to Sun et al. (1990), by the determination of  parameter. Based on sign convention involved in the criterion, PS/PMMA system was found as immiscible while miscibility was observed in PVC/PMMA blend. FTIR analysis also supports the viscometric data. Key words: Viscosity, polymer blends, poly (methyl methacrylate), poly (vinyl chloride), polystyrene, fourier transform infrared spectroscopy. INTRODUCTION Polymer blending provides a powerful route to engi- neering new properties in materials using available poly- mers. From Polymer blending it is possible to produce a range of materials with properties that are superior to that of each individual component polymers (Rhoo et al., 1997; Oh and Kim, 1999; Pielichowski, 1999; Stephen et al., 2000; Tang and Liau, 2000; Pielichowski and Amerton, 2000). The main advantages of the blended systems are simplicity of preparation and ease of control of physical properties by compositional changes, (Acosta and Morales, 1996; Rocco et al., 2001) and also it usually requires little or no extra expenditure compared to new polymer synthesis. However, the miscibility between the constituents of polymer mixture on molecular scale is responsible for material with superior properties (Rajulu et al., 1999). Miscibility may arise from specific interactions, such as dipole-dipole forces (Aubin et al., 1983) and charge trans- fer complexes (Ohno and Kumanotani, 1979) for homo- polymer mixtures or segment-segment repulsion inside the blends. However, due to very small entropy gain in the mixing of long chain polymers and because of the *Corresponding author. E-mail: msalkhan@yahoo.com usually encountered positive heat of mixing, most poly- mer blends form two phases. The majority of known poly- meric mixtures are immiscible; however, several miscible polymer blends have been found in the last three de- cades. There have been numerous techniques of studying the miscibility of the polymeric blend. The most useful techni- ques are viscometry measurements (Sun et al., 1992), thermal analysis (Song and Long, 1991), ultrasonic velo- city (Singh and Paladhi, 1994), refractive index (Rajulu et al., 1999), NMR method (Crispim et al., 2000) and optical spectroscopy (Wu et al., 1999). Dilute solution viscometry (DSV) method provides information about both polymer- polymer interactions and polymer solvent interactions in a solution. The effectiveness of DSV method is based on the assumption that the mutual interactions of macromo- lecules in the solution have a great influence on the viscosity in the ternary systems. It is assumed that poly- mer-polymer interaction usually dominates over polymer- solvent ones (Pingping et al., 1999). Attraction between the two component polymers may cause swelling of ma- cromolecular coils resulting in an increase in viscosity and repulsion may cause shrinkage of the macromo- lecular coils, giving a decrease in viscosity. Various blends have been studied by several authors, Paul and Newman (1978), Schurer et al. (1975), Shen