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It has been shown that there exist conditions under which thermosensitive copolymers of N-vinylpyrrolidone with methyl acrylate form hydrophobic–hydrophilic associations, which are unstable dynamic meshes, the bonds in which are continuously broken and created again, and the nature of the formation of such meshes depends significantly on the proportion of the hydrophobic component in the copolymer. It is shown that the interaction of the above copolymers with polyacrylic acid results in the formation of not only classical interpolymer complexes, but also hydrophilic interpolymer associates, which also represent unstable networks existing in a dynamic mode. In such meshes, the molecules of the above copolymers serve as a kind of cross-agent connecting the polyacid molecules. There are also conditions under which such meshes acquire a complex structure, since unstable bonds between macromolecular tangles of both the same and different types take part in their formation. It is shown that the transition from the formation of interpolymer complexes to the formation of hydrophilic interpolymer associates can occur, among other things, due to changes in the acidity or concentration of low-molecular salt in solution. [ABSTRACT FROM AUTHOR]

It is shown that the reaction between poly(acrylic acid) and a non-ionic polymer may give two different products. One of them is the well-known interpolymer complex stabilized by hydrogen bonds, and the other belongs to a relatively new class of compounds named hydrophilic interpolymer associates. Networks occurring in the dynamic mode of formation and destruction of hydrogen bond linkages represent the structure of the hydrophilic associates; a single molecule of polyacid may be linked with two or more molecules of non-ionic polymer in such associates. The result of the reaction under consideration strongly depends on the ratio of volumes of swollen coils of ionogenic and electrically neutral macromolecules. Classical interpolymer complexes cannot be formed at a high degree of swelling of polyacid coils, which takes place at high pH values. In contrast, hydrophilic associates are formed under such conditions. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: We designed new terpolymers responsive to pH, temperature, and metal ions. Binding of metal ions amplifies the magnitude of thermal response. Variations in the pH and concentration of metal ions enable tuning the lower critical solution temperature (LCST) and thermosensitivity in a broad range. Upon changes in pH and/or temperature, polymers form associates with narrow size distribution ranging from less than 5nm to more than 250nm in diameter. The multistimuli-responsive properties of newly synthesized polymers are the result of combining hydrophobic, ionogenic, and non-charged hydrophilic moieties within the terpolymer structure. Polymers are produced by a potentially scalable method from inexpensive starting materials, 2-hydroxyethylacrylate (HEA), butylmethacrylate (BMA), and acrylic acid (AA). Polymers and their aggregates are characterized by NMR, dynamic light scattering, and electron microscopy. The ability to control the size of polymer aggregates and the magnitude of response to external stimuli opens exciting opportunities for practical applications. [Copyright &y& Elsevier]