Thermo-responsive hydrophilic
polymers, including those showing tuneable lower critical
solution temperature (LCST), represent a continuous subject of exploration for a variety of applications, but particularly in nanomedicine. Since biological pH changes can inform the organism about the presence of disequilibrium or diseases, the development of dual LCST/pH-responsive hydrophilic
polymers with biological potential is an attractive subject in
polymer science. Here, we present a novel
polymer featuring LCST/pH double responsiveness. The monomer ethylthiomorpholine
oxide methacrylate (THOXMA) can be polymerised via the RAFT process to obtain well-defined
polymers. Copolymers with
hydroxyethyl methacrylate (
HEMA) were prepared, which allowed the tuning of the LCST behaviour of the
polymers. Both, the LCST behaviour and pH responsiveness of hydrophilic PTHOXMA were tested by following the evolution of particle size by dynamic light scattering (DLS). In weak and strong alkaline conditions, cloud points ranged between 40-60 °C, while in acidic medium no LCST was found due to the protonation of the
amine of the THOX moieties. Additional cytotoxicity assays confirmed a high biocompatibility of PTHOXMA and
haemolysis and aggregation assays proved that the
thiomorpholine oxide-derived
polymers did not cause aggregation or lysis of red blood cells. These preliminary results bode well for the use of PTHOXMA as
smart material in biological applications.