# Doped Epoxy Resins as an Alternative to Luminescent Optical Sensors
## 3 Results and Discussion
### Thermal and Spectroscopic Analysis
The ions recorded in the mass spectra within the proper sample decomposition for the series of samples No.4-6 are identical to those presented for samples No.1-3. The amount of residual mass ranges from 8.2 wt.% to 10.2 wt.%. Samples No.7-15, No.8-15 and No.9-15 show the lowest double-bond conversions among all the analyzed compositions (Table 3). This is most likely due to too-little UV exposure time and too much active solvent addition (50 wt.%). While NVP itself has a positive effect on the final structure of the polymer, longer exposure to UV radiation is necessary in some cases. The best proof of this is the conversion of double bonds at the level of 100% for samples No.8-60. Evidence of an improper polymerization process, or more precisely, its too rapid interruption, is the presence of ions \(m/z\) = 30, 31, 41-44, 56, and 111 at a temperature of about 125 \({}^{\circ}\)C for the mentioned samples. As was the case with the series of samples with the 33 wt.% NVP addition, in this case, for the sample with the 2.7-NAF.EP addition, one maximum is recorded on the DTG curve up to a temperature of 200 \({}^{\circ}\)C (shifted towards higher temperatures when comparing with samples No.7 and No.9). The next maximum is the one related to the proper sample decomposition. Mass spectroscopy confirms the presence of ions \(m/z\) = 14, 15, 17, 18, 26-31,and 40-44 appearing from the temperature of about 130 \({}^{\circ}\)C, but their release from the structure as a result of evaporation/decomposition of the substance is so slow and their intensity so small that only one maximum on the DTG curve is recorded. However, this does not apply to DSC curves, where several endothermic maximums can be observed in the discussed temperature range. The same ions are recorded for the rest of the samples but with the DTG maximum recorded at lower temperatures. Around the second maximum of mass loss for samples No.7 and No.9 the following ions were registered: \(m/z\) = 14, 15, 17-19, 26-30, 40-44, 52-56, 68, 82-85, and 111, which indicate the decomposition of the active solvent. However, no ion confirming the decomposition of the epoxy resin or any of the photosensitive additives was detected. Their presence was recorded only at the temperature of proper decomposition (ions in the mass range that were already presented). The maximum of decomposition does not differ significantly from the values for samples with 33 wt.% NVP content. Residual mass for the discussed samples is within the range of 7-12 wt.%. A total of 1 wt.% mass loss for samples with 25 wt.% NVP content and based on EB600 resin is recorded just after exceeding the temperature of 100 \({}^{\circ}\)C (sample series No.10-12). And, based on spectroscopic spectra, it was determined that it is related to the evaporation of water physically adsorbed on the sample surface. The first maximum on the DTG curve varies between 160 and 190 \({}^{\circ}\)C. Its value shifts towards lower temperatures for samples doped with photosensitive compounds. The endothermic peak is present in the DSC curves, but significantly shifted towards lower temperatures compared to the DTG maximum (around 120-130 \({}^{\circ}\)C). Based on the mass spectra, it was possible to interpret the cause of mass changes in the considered temperature range. There are ions coming from the methylene, methyl and vinyl groups (\(m/z\) = 14, 15, 26-28), and from the decomposition of the lactam ring (\(m/z\) = 40-44, 53-56, 66 (C\({}_{4}\)H\({}_{4}\)N\({}^{+}\)), 67(C\({}_{3}\)HNO\({}^{+}\)), 68, 69(C\({}_{4}\)H\({}_{5}\)O\({}^{+}\))), as well as indicating the presence of benzene ring fragments (\(m/z\) = 39, 50-52, 65, 77-79). This indicates the presence of matrix fragments even before the temperature of 200 \({}^{\circ}\)C. A small addition of active solvent (25 wt.%) does not sufficiently reduce the considerable viscosity of EB600, which means that not only NVP molecules, but also resin, are trapped during polymerization.