When two or more polymers are mixed, the situation may appear when an additional strong intermolecular interaction occurs between chains of these polymers, which is not displayed between macromolecules of each of polymers, taken separately. These may be hydrogen bonds or strong dipole-dipole interactions. Analysis of the influence of these interactions on the glass transition temperature will be shown below.

In a series of works devoted to the analysis of miscibility of polymers and the properties of mixtures obtained, the main attention is paid to these special interactions occurring between macromolecular chains of the mixed polymers. The scheme of this interaction is demonstrated by the following example:

Let us consider in detail examples of such interactions and experimental methods of their determination. Mixtures of styrene copolymer with vinylphenylhexa-fluoromethylcarbynol with the polymers as polycarbonate based on bisphenol A, poly(butyl methacrylate), poly-2,6-dimethyl-1,4-phenylene oxide may represent an example of this significant event [209]. Introduction of hydroxyl groups to the mentioned polymer leads to the formation of hydrogen bonds between the copolymer and polycarbonate, which causes a sharp increase of miscibility. The thermograms obtained by the DSC method for polystyrene mixtures with polycarbonate show clearly two glass transition temperatures indicating immiscibility of these polymers. The situation is changed abruptly when polystyrene introduced to the mixture is substituted by a copolymer of the above given structure: thermograms indicate the single glass transition temperature (which indicates miscibility). Therewith, the glass transition temperature regularly increases with the concentration of polycarbonate. Mixtures of copolymers of the above-mentioned structure...