We herein report the preparation of thermo- and redox-responsive branched polymers by the condensation reaction of three-armed oligo(ethylene glycol) (trisOEG) and cystamine (CA). The prepared branched polymers exhibited a soluble-insoluble transition at a lower critical solution temperature (LCST) and formed coacervate droplets through a liquid-liquid phase separation process. We then demonstrated control of the LCSTs of the branched polymers by varying the feed ratio of CA and the surrounding salt concentration close to body temperature. In addition, the trisOEG-cys(x) polymer formed coacervate droplets above the LCST, in which hydrophobic molecules were condensed. The redox response of the branched polymers was also investigated. Interestingly, the branched polymers degraded to low-molecular-weight materials (i.e., trisOEG) in the presence of dithiothereitol as a reducing agent through cleavage of the disulfide bond of CA. This facile preparation of branched polymers is expected to be valuable in the context of functional biomedical materials and modifiers for materials surfaces, such as the bases for drug delivery carriers and separation materials. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2623-2629