<p>To strengthen the toughness of thermosetting resins under low temperatures, tetrafunctional epoxy-modified silicone resins (TESR-1/4/9) with different lengths of flexible chains were synthesized and served as tougheners for the epoxy system. The chemical structures of TESR-1/4/9 were determined via Fourier transform infrared spectroscopy as well as nuclear magnetic resonance (¹³C-NMR and ¹H-NMR). At room temperature, with 10&#xa0;wt% of TESR-1, the elongation at break of the epoxy resin (17.67%) was added up to 68.93% in comparison with neat epoxy resin (10.46%). At −70&#xa0;℃, with the content of 5&#xa0;wt% TESR-4, the value of the elongation at break (12.66%) was 37.31% higher than that of the neat epoxy (9.22%). A scanning electron microscope was utilized to observe the fractured surfaces of the resins to investigate the toughening behaviors of the tougheners (TESR-1/4/9). The dynamic mechanical analysis also demonstrated the improvement of the epoxy resins in toughness and good compatibility between TESR-1/4/9 and the epoxy matrix. These research findings can offer a new perspective for the enhancement of epoxy resins in low-temperature toughness.</p> Graphical abstract <p></p>