Molecular brushes with poly-2-ethyl-2-oxazoline side chains and aromatic polyester backbone manifesting double stimuli responsiveness

Behavior of grafted copolymers composed of aromatic polyester (PAPE) backbone and poly-2-ethyl-2-oxazoline (PEOZ) side chains differing in grafting density in aqueous solutions was studied when heated at various concentrations and pH using static and dynamic light scattering and turbidimetry. Aggregates and individual macromolecules were registered in solutions at all times. It was shown that the aggregates of the brush with higher PEOZ side chains' grafting density undergo compaction on heating below phase separation, whereas the size of the loose polymer brush aggregates continuously increases with the increase of temperature. Phase separation temperatures of both copolymers decreased with dilution. Strong influence of pH on the thermosensitivity of both samples was shown, the copolymer solubility being decreased with the acidity decrease. The nature of the pH effect is under discussion.

.