## 5 Experimental Results
### BDS Results  
Each measurement was repeated three times. The obtained values of thermal properties are expressed as the mean value \(\pm\) its standard deviation (SD). To perform a statistical analysis of the results' significance, [PERSON]'s means test (\(p\leq 0.05\)) was used. As a result of the BDS measurements, the signal amplitude and phase characteristics as a function of the EB frequency of modulation were collected (Figure 14). To extract information about the thermal properties (thermal diffusivity, conductivity, and effusivity) of the PBMA layer annealed at different temperatures, the multi-parameter fitting of the theoretical BDS signal dependence (Equation (22)) to the experimental data (Figure 14) was performed. The thermal properties of the aluminum support were taken as the known parameters in the fitting procedure. The obtained results are presented in Table 2.  
Figure 12: Values of the determined thermal conductivities of investigated PBMA–siloxane coatings annealed at different temperatures. The diamonds are experimental data, and the dashed line is a trend line. Figure 13: Values of the determined thermal effusivities of investigated PBMA–siloxane coatings annealed at different temperatures. The triangles are experimental data, and the dashed line is a trend line. With the increase in the annealing temperature values from 25 \({}^{\circ}\)C to 180 \({}^{\circ}\)C, the thermal diffusivity values changed from 2.52\(\cdot\)10\({}^{-3}\) cm\({}^{2}\cdot\)s\({}^{-1}\) to 2.78\(\cdot\)10\({}^{-3}\) cm\({}^{2}\cdot\)s\({}^{-1}\) and from 2.55\(\cdot\)10\({}^{-3}\) cm\({}^{2}\cdot\)s\({}^{-1}\) to 2.73\(\cdot\)10\({}^{-3}\) cm\({}^{2}\cdot\)s\({}^{-1}\) with the use of the PTR and BDS methods, respectively. The thermal conductivity values of the same samples changed from 3.02\(\cdot\)10\({}^{-3}\) W\(\cdot\)cm\({}^{-1}\cdot\)K\({}^{-1}\) to 3.48\(\cdot\)10\({}^{-3}\) W\(\cdot\)cm\({}^{-1}\cdot\)K\({}^{-1}\) and from 2.99\(\cdot\)10\({}^{-3}\) W\(\cdot\)cm\({}^{-1}\cdot\)K\({}^{-1}\) to 3.56\(\cdot\)10\({}^{-3}\) W\(\cdot\)cm\({}^{-1}\cdot\)K\({}^{-1}\) with the use of the PTR and BDS methods, respectively. Finally, the thermal effusivity changed from 6.01\(\cdot\)10\({}^{-2}\) W\({}^{1/2}\cdot\)cm\({}^{-2}\cdot\)K\({}^{-1}\) to 6.61\(\cdot\)10\({}^{-2}\) W\({}^{1/2}\cdot\)cm\({}^{-2}\cdot\)K\({}^{-1}\) and from 5.92\(\cdot\)10\({}^{-2}\) W\({}^{1/2}\cdot\)cm\({}^{-2}\cdot\)K\({}^{-1}\) to 6.81\(\cdot\)10\({}^{-2}\) W\({}^{1/2}\cdot\)cm\({}^{-2}\cdot\)K\({}^{-1}\) with the use of the PTR and BDS methods, respectively. The thermal diffusivity, thermal conductivity, and thermal effusivity increased by 9% with the increase in annealing temperature. It can be concluded from the data presented in Table 2 that the higher the coatings' synthesis temperature, the higher the values of their thermal properties. The reason for this behavior can be explained by the fact that the increase in the curing temperature in the process of sol-gel synthesis causes the breaking of double bonds present in the Si-PBMA material. Because of that, the material becomes more compact without the pores being formed while performing the sol-gel synthesis. In the next step, the results obtained by BDS were compared with those obtained by PTR (Figures 15-17). To compare the results obtained by the PTR and BDS methods and determine whether significant differences exist between the values of the thermal properties found using the two techniques, the related \(p\)-values were calculated at the 95% confidence level [45]. No significant differences were observed in the determined values of either the thermal conductivity or diffusivity since, in all cases, the \(p\)-value was found to be \(>\)0.05, which indicates that the difference between compared properties is not considered to be statistically significant.