An interesting category of amphiphilic polymer systems are those that undergo phase transitions in response to environmental stimuli such as temperature and pH. These have been widely investigated for drug delivery, separations, and diagnostics applicatio ns. A key temperature-responsive class is based on alkyl acrylamide polymers, particularly poly(N-iso-propylacrylamide) (pNIPAAm), which at certain conditions may undergo a sharp coil-globule transition and phase separation at its lower critical solution temperature (LCST) in water. The LCST of such thermally sensitive polymers can usually be tuned to a desired temperature range, such as the body temperature.
Even a pNIPAAm polymer with grafted PEO chains (e.g., pNIPAAm-g-PEO) may, at elevated temperatur es, in addition to an intrachain coil-to-globule transition also undergo an interchain association to form a core-shell nanostructure with a hydrophobic pNIPAAm core and a soluble hydrophilic PEO shell. In aqueous solutions of this type of uncharged tempe rature-sensitive polymer, an intricate interplay between intrachain and interchain associations usually occurs at fairly low polymer concentration at elevated temperature. In order to suppress the interchain association, the Polymer Group at UiO has recen tly synthesized a novel charged temperature-responsive copolymer, which undergoes a sharp transition to a more open structure when the temperature is increased. This unique temperature-induced change of the polymer structure has not been reported before, and is at this preliminary stage ascribed to a delicate cooperation between charges and hydrophobic associations. This feature is interesting in connection with drug-release problems.
The aim of this project is to develop an understanding - both mechanis tic and applied - of different thermo-responsive polymers adsorbed to planar and particle substrates. Changes in structural end dynamical properties of the systems under various conditions will be examined.