# Synthesis of Shape-Memory Polyurethanes: Combined Experimental and Simulation Studies
## 3 Results and Discussion
### Results of Monte Carlo Simulations  
#### 3.5.1 Synthesis of Bis(methylcarbonate)decamethylene  
The simulation results obtained within the frame of the DLL model allow not only the prediction of the molar masses of the synthesized products, but also acquaintance with the progress of the reaction regarding the individual components. Figure 11 presents the conversion of the diol component to DMC. As one would expect, all the diol molecules and part of the second starting material reacted, as the latter was added in significant molar excess. Along with the course of the reaction and creation of longer chain structures, the curve slope, i.e., the conversion rate of element (2) in relation to element (1), decreases with the course of the reaction. The curve began to flatten near 0.35 in the case of E_BMC_10, and 0.3 for S_BMC_10, which suggests that, in the final stage of the discussed synthesis, some part of the unreacted DMC was still in the system, which is consistent with the applied synthetic route (Figure S63 in the Supplementary Materials). There is evidence that experimental studies are more accurate because of the sensitivity of the registration process, especially in the final stages of the reaction. Implemented synthesis assumes that, after the discussed step, the DMC excess is removed from the reaction mixture. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{1}{c}{\(\mathbf{R_{r}}\)} & \(\mathbf{R_{f}}\) \\ \cline{2-3}  & **\%** & **\%** \\ \hline E\_PCUU3000\_3.5 & 99.6 \(\pm\) 0.2 & 94.5 \(\pm\) 0.1 \\ E\_PCUU3000\_3 & 99.6 \(\pm\) 0.1 & 95.8 \(\pm\) 0.1 \\ E\_PCUU3000\_2.5 & 99.4 \(\pm\) 0.4 & 98.8 \(\pm\) 0.1 \\ E\_PCUU3000\_2 & 99.0 \(\pm\) 0.6 & 98.2 \(\pm\) 0.5 \\ E\_PCUU3000\_1.5 & nd & nd \\ E\_PCUU5000\_3 & 99.3 \(\pm\) 0.0 * & 99.3 \(\pm\) 0.6 * \\ E\_PCUU5000\_2 & 98.5 \(\pm\) 0.7 * & 98.6 \(\pm\) 0.3 * \\ \hline \hline \end{tabular} nd – no data. R–Shape recovery ratio. R–Shape fifty ratio. *—Measurements conducted with a tensile testing machine.  
\end{table} 
Table 6: Shape-memory properties of PCUU samples. Figure 11: DLL simulation and experimental data of the conversion of 1,10-decanodiol versus the conversion of the DMC. The main focus of the experiments at this stage was to calculate the mass distribution of synthesized BMC. Based on the \({}^{1}\)H NMR results (Figures S1-S3 in the Supplementary Materials), the fraction of dimers and longer homologues obtained in the reaction were determined. The comparison of starting materials and products obtained in the reaction and simulation presented in Table 7 and Figure 12 shows that slightly longer structures are formed in the simulation. Interestingly, the higher excess of DMC in the initial solution was observed, and the higher dimer content in the final product was observed for both the simulations and experiments. Figure 12 presents the molar mass distribution obtained in the experiments and simulations of the synthesis process. In this figure, more extended structures, in the case of experimental studies, have been presented as trimers. It reveals good agreement between both methods; the main characteristics of the curves are similar. Moreover, using the adopted simulation model enables determination of the quantitative shares of the remaining reaction products, which are often too negligible to be detected in less sensitive analytical tests. In the case of S_BMC_18, the longest created structures were octamers, whereas for S_BMC_8 it was decamers. Interestingly, the greater amount of DMC in the reaction mixture led to reduction in longer structures, whereas the dimer mass contribution for S_BMC_18 was 93%, while in the case of S_BMC_8, it decreased to 84%. This is consistent with experimental data, where E_BMC_18 had a 98% dimer mass contribution that decreased to 90% for E_BMC_8 (Figure S1, Supplementary Materials). In Figure 13, the growth of the number average chain length (P\({}_{\text{n}}\)) and weight average (P\({}_{\text{w}}\)) are compared with conversion of elements (1) and (2).