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Phase behavior and miscibility in polymer blends containing styrene and 2,6-dimethyl-1,4-phenylene oxide derivatives

Using the mean-field theory/1/, phase behavior of blends can be described by the pair interactions between all segments in the blends. This theory provided also a general explanation for the effect of chemical composition on miscibility. The basic approximation embodied in the mean-field treatment is of the mean-field nature, ignoring the local concentration fluctuations around individual segments. In this study the miscibility and phase behavior of various polymer systems mainly based on styrene and 2,6-dimethyl-1,4-phenylene oxide derivatives will be considered. A data base has been collected and updated with new experimental results (most of these experimental data have been obtained in our laboratory). For each polymer blend, the computerised data base contains the following informations: component codes or identification numbers, system type code (homopolymer-homopolymer, homopolymer-copolymer or copolymer-copolymer), composition code of the constituents for the copolymers, composition of the blend, number of data points, data type code - such as miscibility/immiscibility behavior of the blend at a given temperature, and finally the data themselves. In addition, the relevant literature references are included. The system used in building up the data base makes provision for an easy update. Applying the mean mean-field theory, the segmental interaction parameters of various polymer blends specified above are revised and the "best fit values" are established. The purpose of this study is to present an evaluation of the mean-field theory for correlating and predicting miscibility of polymer blends. Examples have been chosen to illustrate the influence of the chemical structure of the components of the blends. Three aspects will be considered: the influence of the nature of the substituent on the aromatic ring, the intramolecular repulsion effect and the influence of the position (ortho, para) of the substituent. The predictive qualities of the model are shown and suggestions about group contribution method are made. Calculations based on the revised segmental interaction parameters are in excellent agreement with the experimental data. /Lit. l. G. ten Brinke, F.E. Karasz and W.J. MacKnight, Macromolecules,16(1983)1827-1832./

polymer blends; miscibility; segmental interaction parameters

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