## 3 Results and Discussion
### \({}^{1}h\) NMR, FT-IR and UV-Vis Analysis of Polymers  
The \({}^{1}H\) NMR spectra of PTBM-0, PTBM-4, and PBM are shown in Figure 4. The signal peaks at 7.65-7.87 ppm originated from the hydrogen atoms on the phenyl rings in TPS-SS, the single peak at 3.61 ppm was attributed to the hydrogen of \"-O-CH\({}_{3}\)\" units in MMA, the prominent signal peaks at 1.4-1.5 ppm corresponded to the tert-butyl hydrogen in \(t\)BMA, and the peaks at 0.96-0.99 ppm and 0.60-0.64 ppm were associated with the hydrogens of isopropyl and \"Si-CH\({}_{2}\)-\" units in POSS-MA, respectively. The remaining peaks primarily arose from the hydrogens in the main chains of polymers. This analysis data confirmed the successful synthesis of the polymers. The actual proportions of repeat units in the copolymers calculated by \({}^{1}H\) NMR are shown in Table 3.  
\begin{table}
\begin{tabular}{c c c c c} \hline  & **N (\%)** & **C (\%)** & **H (\%)** & **S (\%)** \\ \hline PTBM-4 & 0.23 & 66.22 & 8.667 & 1.749 \\ \hline PTBM-4 without RAFT & & & & \\ terminal group & 0.18 & 64.90 & 8.624 & 1.324 \\ \hline \end{tabular}
\end{table}
Table 2: Elemental analyses of PTBM-4 before and after removal of RAFT terminal group.  
Figure 3: **(A)** GPC curves of PTBM-4 and after removal of RAFT terminal group of PTBM-4. (**B**) Photographs of copolymers with RAFT terminal group, and (**C**) after removal of RAFT terminal group.  
The FT-IR spectra of PTBM-0, PTBM-4, and PBM are shown in Figure 5. The split double peaks near 1380 cm\({}^{-1}\) were attributed to the in-plane bending vibration of tert-butyl methyl (CH\({}_{3}\)) groups. The absorption peak at 1140 cm\({}^{-1}\) was attributed to the stretching vibration of the -C-O-C- groups in the \(t\)BMA and MMA units, and the peak at 1722 cm\({}^{-1}\) was caused by the stretching vibration of the C=O groups. The absorption peaks at 2977 cm\({}^{-1}\), 2930 cm\({}^{-1}\), and 2865 cm\({}^{-1}\) were ascribed to the stretching vibration of C-H in methyl, methylene, and methine groups, respectively. The absorption peak at 1105 cm\({}^{-1}\) corresponds to the stretching vibration of the Si-O-Si groups in the POSS-MA unit. As shown in the enlarged image on the left side in Figure 5, The absorption peaks around 3000-3100 cm\({}^{-1}\) and near 690 cm\({}^{-1}\) were attributed to the stretching vibration and out-of-plane bending vibration of the C-H groups on the phenyl rings of the TPS-SS unit, respectively. The absence of a significant C=C double bond absorption peak in the 1630-1690 cm\({}^{-1}\) range indicates that the polymerization was quite completely, with most of the C=C double bonds being eliminated. Thus, it confirmed the successful synthesis of the copolymers.  
The UV-vis spectra of copolymer solutions and TPS-ST solutions are shown in Figure 6. A comparison between PTBM-0 and PTBM-4 revealed that the addition of POSS units did not change their ultraviolet absorption. PBM, which did not contain the photoacid TPS-SS units, exhibited almost no ultraviolet absorption, while PTBM-0 and PTBM-4, with the  
Figure 4: \({}^{1}\)H NMR spectra of (**A**) PTBM-0, (**B**) PTBM-4, and (**C**) PBM.  
Figure 5: FT-IR curves of PTBM-0, PTBM-4, and PBM.  
addition of TPS-SS units, possessed maximum absorption wavelengths identical to that of TPS-ST. It indicated that the ultraviolet absorption of the polymers was solely provided by the photoacid units, and the other components were entirely transparent in the deep ultraviolet (DUV) range. Therefore, the copolymer PTBM meets the exposure requirements of DUV photoresist.