A new multi-stimuli-responsive homopolymer of poly [N-[2-(diethylamino)ethyl]acrylamide] (PDEAEAM), which combines the thermoresponsive and pH/CO 2 -responsive moieties of the diethylamino and acrylamide groups, was proposed and synthesized by RAFT polymerization. Well-defined PDEAEAM was synthesized by solution RAFT polymerization as indicated by the linear increase in the polymer molecular weight with the monomer conversion and the narrow molecular weight distribution. The appending diethylamino group in the polymer backbone was found to be crucial to determine the thermoresponse of PDEAEAM in water. The parameters including the polymerization degree, the polymer concentration, the deuterated solvent, the terminal attached on the polymer backbone, the additives of salt and urea, and pH and bubbling CO 2 affecting the thermoresponse of PDEAEAM in aqueous solution at the lower critical solution temperature (LCST) were investigated. The temperature-variable 1 H NMR analysis suggests that the dehydration of PDEAEAM at temperature above LCST is ascribed to the weakened hydrogen bonding between the CONHCH 2 and/or (CH 2 N(CH 2 CH 3 ) 2 ) moieties with the solvent of water. The proposed multi-stimuli-responsive homopolymer of PDEAEAM has two advantages of (1) the convenient and controllable RAFT synthesis and (2) the pH/CO 2 tunable LCST at ∼36 °C being very close to body temperature.

The thermo- and pH/CO2-responsive poly[N-[2-(dialkylamino)ethyl]acrylamide]s containing a polyacrylamide backbone but different N-substitutes of dialkylamine were synthesized and their solution properties were comparatively checked.

Well-defined triblock copolymer nanospheres of polystyrene-block-poly­(N-isopropyl­acrylamide)-block-polystyrene (PS-b-PNIPAM-b-PS) containing a hydrophobic core of the polystyrene (PS) block and a looped corona of the thermoresponsive poly­(N-isopropyl­acrylamide) (PNIPAM) block were prepared by the bifunctional macro-RAFT agent mediated dispersion polymerization via polymerization-induced self-assembly. This synthesis affords the fine control on the chemical composition of the PS-b-PNIPAM-b-PS triblock copolymer and on the diameter of the triblock copolymer nanospheres. By precisely investigating the thermoresponse of the PS-b-PNIPAM-b-PS triblock copolymer nanospheres and the poly­(N-isopropyl­acrylamide)-block-polystyrene (PNIPAM-b-PS) diblock copolymer nanospheres under the strictly similar conditions, it is found that the phase transition of the looped PNIPAM chains takes place at a lower temperature and within a narrower temperature range than that of the linear PNIPAM chains. We believe that the present study is helpful to clarify how the topology of the tethered PNIPAM chains affects the phase transition at the lower critical solution temperature (LCST).