## 3 Results  
A schematic diagram, Jablonski diagram [17], (Figure 3) of the photoinitiator's possible action on the polymeric system highlights the excited chemical species' deactivation ways when an intersystem crossing (ISC) process generating triplet excitation state occurs. During the photochemical reaction, such ISC process appears due to the forbidden transition of the excited chemical species directly on a triplet state. BP is excited to singlet state when absorbing a photon, then converts to a triplet state (ISC) and subsequently relaxes from the triplet state through a possible extraction reaction of hydrogen from the hydroxyl group on PDMS (segregation stage on the diagram, in Figure 3). Thus, a radical site could be created on PDMS, generating, in the meantime, the BP ketyl radical [18] and depleting BP. When there are not available H-donors, the triplet state of excited BP could relax to its ground singlet state through a phosphorescence emission (quenching stage, Figure 3), thus regenerating the photo activating BP species [19]. If the BP concentration in the system is high enough, then the depletion effects are not significant, as only the BP molecules reacting with PDMS are consumed. Considering the photochemical reaction's intimate behavior, the UV-curing initiation rate could be fine-tuned through the radiation intensity modification. This is a welcome advantage of photocuring compared to thermal curing. The photoinitiator concentration influences the overall reaction rate, but its level depends on the application specificity, as it depends on the thickness of the generated shapes. For each photocurable system, it should be determined an optimal initiator concentration, because, above this value, the photocuring process does not progress to its completeness. The proposed procedure used a PDMS variety with silanol termination. The groups Si-OH could react with the nanotitania hydroxyl groups present on its surface to generate Si-O-Ti bonds stabilizing the nanocomposite material and assuring a better dispersion of nano-TiO\({}_{2}\) in the polymeric matrix. The nanocomposites obtained were employed to study their processability under UV radiation, in the view of their usage with a stereolithography (SLA) 3D printer. Figure 4 presents the ionic viscosity/log (ionic viscosity) for the studied PDMS mixtures under the mentioned conditions in Section 2.2. Figure 3: Deactivation pathways. The polymeric film's electrochemical parameters (ionic viscosity, impedance, conductivity, permeability, loss factor) evolve abruptly during composite polymeric film-forming (ambient evaporation), after which the values are flattened, which suggests that the film-forming has ended. Through the dielectric analysis, the evolution of the PDMS crosslinking process (curing) was followed up, considering that it starts with the phase transformation, gelation, when the viscous polymeric matrix becomes a gel, and which is marked on the  
Figure 4: Evolution of electrochemical parameters of various PDMS formulations during the film-forming process. (**a**) Ionic viscosity of polydimethylsiloxane cured in opened air (10 mHz); (**b**) Ionic viscosity of polydimethylsiloxane-benzophenone mixture cured in opened air (10 mHz); (**c**) Ionic viscosity of polydimethylsiloxane -benzophenone-titanium dioxide nanoparticles thermally cured (1 Hz); (**d**) Ionic viscosity of polydimethylsiloxane -benzophenone-titanium dioxide nanoparticles UV cured (50 mHz). recorded DEA curves as the \"onset\" value. Practically, the formation of fully reticulated PDMS is considered terminated at the moment when the \"end\" value is reached on the ion viscosity curve. Consequently, from the perspective of PDMS processing, it is essential to identify the debut (gelation--\"onset\" point) and termination (crosslinking--\"end\" point) to follow the curing progression. The \"onset\" (gelation point) and \"end\" (end of curing) values varied significantly between the studied PDMS formulations.