The Formation Of Multidomain Hydrogels Via Thermally Induced Assembly Of Triblock Double Thermoresponsive Nanogels

Polymerization-induced self-assembly(PISA) is a rapidly evolving method for the efficient preparation of well-defined nano-objects. This paper chooses a mixture of water and ethanol as a reaction solvent and using RAFT dispersion polymerization for the synthesis of monodisperse, multi-component dual temperature-sensitive nanogel. The nanogels consist of a thermoresponsive poly(diethylene glycol ethyl acrylate)(PDEGA) outer block with a lower cloud point(9 oC ~15 oC), a hydrophilic poly(N,N-dimethylacrylamide)(PDMA) mid-block, and a N,N?-methylene bisacrylamide(BIS) cross-linked, thermoresponsive poly(N-isopropylacrylamide)(PNIPAM) core block with a higher cloud point(~32 oC). The unique location of these two thermoresponsive blocks of differing transition temperatures in the PDEGA-PDMA-(PNIPAM-co-BIS) nanogels is rationally designed to facilitate room-temperature gelation and is synthetically realized via judicious selection of water-ethanol mixtures under dispersion polymerization conditions. The nanogels were characterized by turbidimetry, dynamic light scattering(DLS), transmission electron microscopy(TEM) and small-angle x-ray scattering(SAXS). Gelation behavior of the nanogels was investigated by inverted vial method as well as dynamic rheology sweeps. In comparison with a triblock terpolymer of similar composition, the triblock terpolymer nanogels exhibit significantly enhanced moduli and narrower gelation window. The gelation ability, sensitivity, and mechanical properties are affected by the block ratios of the nanogels.