Display omitted •One step synthesis of highly branched polythioureas without catalyst.•Polythioureas with different properties when synthesized using different solvents.•Either a highly selective mercury ion adsorbent or a boiling water resistant adhesive. In this study, tris(2-aminoethyl)amine and carbon disulfide were used as raw materials for the construction of highly branched polythioureas. Firstly, a highly branched polythiourea adsorbent was synthesized through a heating condensation reaction using N, N-dimethylformamide (DMF) as solvent without any catalyst. Interestingly, this study also revealed that a highly branched polythiourea resin was successfully synthesized without any catalyst when water was used as the solvent. Through nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), gel chromatography column (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and other means to characterize the comprehensive properties of the polymer. Then, mercury ions were used as the adsorption model. The effects of adsorbent dosing, adsorption time, and different pH on the adsorption of mercury ions (Hg2+) were investigated by intermittent adsorption experiments. The adsorption kinetics, isotherm model, sensitivity test of mercury extraction, single metal ion test, and the adsorption capacity of the adsorbent for nine metal ions were studied. In addition, bond strength tests were utilized to explore the adhesive properties of the prepared aqueous phase highly branched polythioureas. The results show that in the adsorption performance test, when the dosage of highly branched polythiourea adsorbent is 10 mg, the pH is acidic or neutral, and the adsorption time is 60 min, the adsorption efficiency of P-DMF for Hg2+ is as high as 99.99 %. The adsorption follows the Langmuir isotherm model and fits well with the pseudo-second-order kinetic model. In addition, P-DMF has a certain selectivity for Hg2+, and the adsorption efficiency is positively correlated with the mercury ion concentration. When Hg2+ is 100 mg/L, the adsorption efficiency reaches 99.98 %. In the bond strength test, the dry shear strength of the plywood reached 1.6 MPa, and the strength after soaking in hot water and boiling water for 3 h was 1.5 MPa and 1.4 MPa respectively, exceeding the requirements of GB/T9846-2015 for type II plywood (≥0.7 MPa).