## 3 Results and Discussion
### Material Properties  
The correlation between epoxy conversion and thermophysical properties of the cured matrices is the articulation between molecular structure and the solidification or hardening of reactive epoxy blends subject to polymerization. The thermomechanical spectra of Figure 6a recorded during the first ramp of the DMA analysis show the strong difference between the matrix cured at 10 kGy and at the two higher doses (two times at 25 kGy and four times at 25 kGy). The primary observations are explained by the progress of epoxy polymerization at higher doses or by the resumption of pseudo-living cationic polymerization while the thermal ramp of DMA analysis crosses the glass transition of the analyzed sample. A slight decrease in the temperature of tan \(\delta\) maximum from 190 \({}^{\circ}\)C to 188 \({}^{\circ}\)C between the first and the second run is observed for samples cured at 50 and 100 kGy (Figure 6b). Such a behavior, systematically observed in cured samples, has been discussed already in terms of relaxation of ion pair clusters [28]. There is here an additional observation with the  
Figure 6: Influence of dose and repetition of the DMA run on the thermomechanical properties of a DGEBA resin sample containing 0.5 wt-% of DAIS-B after EB irradiation at 10, 2 \(\times\) 25 and 4 \(\times\) 25 kGy: (a) first DMA run from RT to 230 \({}^{\circ}\)C; (b) second DMA run. very interesting data on the evolution of the width of the loss factor recorded during the first run between the 10 kGy irradiated sample and the one cured at higher doses, an indication of the highly heterogeneous distribution of the cross-link density in the network. Moreover, in the sample cured at the lower dose, the right-hand side of the loss factor peak is shifted towards lower temperature, a feature which does not appear in the networks formed from aromatic diacrylates. This is another supporting argument on the reversible formation of domains with higher rigidity under non-equilibrium conditions, likely through additional interchain bridges involving ionic interactions. At the second run, the relaxation profiles are very similar, and subject to possible small artefacts associated with the clamping of specimens in the measuring cell which might explain the small differences in absolute E\({}^{\prime}\) and E\({}^{\prime\prime}\) moduli. We compared different methods for determining the glass transition Tg of the epoxy networks, either by differential scanning calorimetry (DSC) or by observation of the \(\alpha\) relaxation revealed in the spectra recorded by dynamic mechanical analysis (DMA). In DMA analysis, the thermomechanical relaxation is observed with the onset of the steep decay of the storage modulus E\({}^{\prime}\), the maximum of the loss modulus E\({}^{\prime\prime}\) or on peak of the tan \(\delta\). The plots of Figure 7a were obtained from samples prepared from DGEBA and increasing amounts of TAS-SbF\({}_{6}\). The values determined on the basis of the tan \(\delta\) values are typically 20 \({}^{\circ}\)C higher than those obtained by calorimetry or by the maximum of E\({}^{\prime\prime}\) in DMA spectra, these values being very close for a given material, except for samples of lower conversion and broad distribution of the loss factor, i.e., for highly heterogeneous distribution of cross-link density. This comparison was also applied to composite samples prepared with the same amount of TAS-SbF\({}_{6}\) (0.25 wt-%) and silica powder as an inert filler (60 wt-%) but various contents in benzyl alcohol as a transfer agent. The decrease in Tg shown in Figure 7b confirms the efficiency of benzyl alcohol to decrease the cross-link density within the cured networks. The amount of iodonium salt DAIS-B has a limited effect on the Tg determined as the temperature of the E\({}^{\prime\prime}\) maximum (Figure 8a). One can, however, observe a slight decrease in Tg for the four higher concentrations in initiator and harsher curing conditions after 100 kGy irradiation.