A novel thermoresponsive and biodegradable polymer, poly(MDO-co-HEA), was prepared by radical copolymerization of 2-methylene-1,3-dioxepane (MDO) and a hydrophilic vinyl monomer, 2-hydroxyethyl acrylate (HEA), in dimethylsulfoxide (DMSO), varying feed monomer compositions. Poly( MDO-co-HEA) showed lower critical solution temperature (LCST)-type phase separation in aqueous medium, forming coacervate droplets into which low molecular weight hydrophobic molecules could be loaded above the LCST. The LCST could be controlled not only by the chemical compositions of the hydrophobic MDO and hydrophilic HEA in the polymer chains, but also by ion and polymer concentration. Degradation tests in aqueous media indicated that poly(MDO-co-HEA) was converted into hydrophilic oligomers by hydrolysis of the ester groups in the polymer backbone. The facile preparation poly(MDO-co-HEA) are valuable for use in functional biomedical materials, such as base of drug delivery carrier and cell culture scaffold instead of non-degradable stimuli-responsive polymer. (C) 2017 Elsevier Ltd. All rights reserved.