2.4. Curing and thermal performance of HBPSi-R/EP
To investigate the influence of HBPSi-R with varying terminal groups on the curing performance of epoxy resin, the pre-polymer resin compounds were initially characterized using isothermal differential scanning calorimetry (DSC, SeeFigure 2b ). Upon the incorporation of HBPSi-R, the DSC thermograms exhibited a single exothermic peak resembling that of the native EP, indicating excellent compatibility of the three types of HBPSi-R with the epoxy/anhydride matrix. It is noteworthy that the peak temperature slightly decreased from 165°C to 155°C, suggesting that the inclusion of HBPSi-R does not compromise the processability of the epoxy resin. To determine the real chemical bonding of HBPSi-R within epoxy resin, Fourier-transform infrared (FT-IR) spectra of the cured resin samples were performed (Figure 2d ). Obviously, a wider stretching vibration of Si-O at 1080 cm-1 is recognized in spectra of HBPSi-NH2/EP, HBPSi-EP/EP and HBPSi-V/EP, meanwhile, the peak intensity of hydroxyl group is significantly lower than that of the native EP, indicating the consummation of residual hydroxyl groups and confirming the participation of HBPSi-R in the copolymerization and crosslinking with the epoxy network. X-ray diffraction (XRD, Figure S3 ) profiles revealed that the branching structures did not influence the molecular arrangement, thereby maintaining the amorphous crosslinked structure of the epoxy resin.
Thermogravimetric analysis (TGA) was conducted to assess the impact of HBPSi-R on the thermal properties of materials. Given in Figure 2c , overall, the addition of hyperbranched polysiloxanes primarily enhanced the residual char of the materials while exerting minimal influence on the initial decomposition and main decomposition behavior (as indicated by the derivative thermogravimetry, DTG, shown inFigure S7 ). This improvement can be attributed to the introduction of the inert silicon-containing component. Notably, compared to neat EP, HBPSi-EP/EP exhibited the most substantial increase in char residue, rising from 6.0% to 11.7%, whereas the amino and vinyl variants showed a char residue of 9.5%. This can be attributed to the superior uniform dispersion of HBPSi-EP within the resin matrix compared to the other variants. The detailed curing and thermal parameters are supplied in Table S3 .