## 3 Results  
### Kinetics of Photocross-Linking  
In this study, the photocross-linking of AESO and the mixtures of AESO and VDM or AESO and VDA was performed without any photoinitiator and solvent. The composition of resins is presented in Table 1. Different ratios of AESO and VDM or VDA were used in the resin series AESO/VDM and AESO/VDA. The resin AESO/VDM1 contains the maximum amount of VDM possible to dissolve in AESO without any solvent at 40 \({}^{\circ}\)C. The same amounts of VDA and VDM were taken in the resin series AESO/VDA and AESO/VDM for comparison. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Resin**} & **Ratio of Functional** & **Ratio of** & **Amount of** \\  & **Groups 1** & **Monomers, mol** & **Monomers, g** \\ \hline AESO & - & 1 & 1.5 \\ AESO/VDM1 & 1.5:1 & 1:1 & 1.5/0.375 \\ AESO/VDM2 & 3:1 & 1:0.5 & 1.5/0.187 \\ AESO/VDM3 & 6:1 & 1:0.25 & 1.5/0.094 \\ AESO/VDA1 & 1.5:1 & 1:1 & 1.5/0.339 \\ AESO/VDA2 & 3:1 & 1:0.5 & 1.5/0.170 \\ AESO/VDA3 & 6:1 & 1:0.25 & 1.5/0.085 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The composition of resins. Figure 1: The explanatory scheme of a sample preparation and Direct Laser Writing (DLW) 3D lithography: (**a**) Kapton tape attached to the glass slide and working as an intermediate, resin’s droplet drop cast on such a substrate; (**b**) another glass slide used as a cover to squeeze the droplet and spread it uniformly through the substrate; (**c**) laser beam focused through the cover glass into the resin and initiating the 3D confined polymerization reaction. The kinetics of photoccross-linking was monitored by real-time photorhoemetry. In the photorhometry test, when the photosensitive resin is being irradiated with UV/VIS light, the values of storage modulus G', loss modulus G'', and complex viscosity \(\eta^{*}\) start to increase. This increment indicates the formation of a three-dimensional polymer network. During the process, the values of G' increase faster and exceed the values of G'' showing the high viscosity Newton liquid transforms into a hard elastic polymer. In this transformation, the point where G' = G'' is commonly used to define the gel point (t\({}_{\text{gel}}\)) [46]. At this point, the loss factor tan\(\delta\), the ratio of the viscous and the elastic portion of the viscoelastic deformation behavior (G''/G') starts to decrease. Then, the values of G' and G'' increase continuously and the tan\(\delta\) value decreases until the final degree of cross-linking is reached [47; 48]. As an example, the dependencies of G', G'', tan\(\delta\) and \(\eta^{*}\) on the irradiation time of the photocross-linking of AESO are presented in Figure 2.  
The values of G', G'', \(\eta^{*}\), and t\({}_{\text{gel}}\) of AESO, the resin series AESO/VDM and AESO/VDA are presented in Table 2. It was determined that the rate of photocross-linking of resins containing AESO and VDM or VDA was lower than that of pure AESO. The addition of VDM or VDA to the resins caused a longer induction period and the higher t\({}_{\text{gel}}\) values. The values of t\({}_{\text{gel}}\) of the resin series AESO/VDA were much higher than those of AESO or the resin series AESO/VDM. Moreover, the G' values of AESO were higher than those of the resin series AESO/VDM and AESO/VDA, indicating the lower rigidity of the latter polymers (Figures 3 and 4).