## 2 Results and Discussion
### Polymerization of Acrylonitrile and Styrene Initiated with PLA-PU Containing TPE Groups
First, different structural polymers were analyzed by SEC chromatography using unsuitable standards (polystyrene). Another possible reason for the observed decrease in the molecular weight is the sensitivity of polylactide to high temperature, and its possible degradation in the presence of small traces of catalyst and free -OH groups [28; 29; 30]. An additional experiment was performed where polyurethane prepared from PLA alone and HDI was heated for 24 h in DMF. It appeared that the molecular weight of PU dropped from 36,000 to 7000 as determined by SEC. In the \({}^{1}\)H NMR spectrum, new signals appeared corresponding to newly formed -OH groups (<CHOH and -OH). The results are presented in the SI (Figure S5). It is not excluded that DMF also contributed somehow to the PLA decomposition, because when the same PU prepared from PLA did was heated in anisole, decomposition products were not detected in the \({}^{1}\)H NMR spectrum (although the Mn determined by SEC also decreased). It should also be considered that a molecular weight decrease is a result of the incomplete recombination of growing -VM\(\bullet\) radicals. If some growing radicals terminate by recombination and others by disproportionation, the products would be a mixture of multiblock copolymers of different lengths, which could explain the relatively broad dispersity observed by SEC. Because PLA-PU used as an infer contains many TPE units, if the contribution of termination mechanism other than the recombination is not insignificant, the molecular weight of the final product may indeed be lower than that of the initial molecular weight of the PLA-PU. Because the results obtained from the SEC analysis could not be treated as fully reliable, we searched for another method by which we could confirm the formation of copolymers. Such a possibility is offered by the application of diffusion-ordered spectroscopy (DOSY) \begin{table}
\begin{tabular}{l l l l l l l} \hline \multicolumn{2}{c}{**Substrates**} & \multicolumn{2}{c}{**Conversion of**} & \multicolumn{2}{c}{**PLA/PVM Copolymers (a)**} \\ \hline \multicolumn{2}{c}{**Vinyl**} & \multirow{2}{*}{**Polymeriz. No**} & **Mol Ratio of** & \multirow{2}{*}{**Solvent**} & **VM [\%]** & **Mol Ratio of** & \multirow{2}{*}{**M\({}_{\text{n}}\), SEC (b)**} \\ \multicolumn{2}{c}{**Monomer, VM**} & & & & & **VM/LA, \({}^{1}\)H NMR** & \\ \hline \multirow{2}{*}{AN} & 1 & 4.8 & DMF & 85 & 7.0 & n.d. \\ \cline{2-6}  & 2 & 4.8 & Anisole & 70 & 3.8 & 16,600 \\ \hline \multirow{2}{*}{ST} & 3 & 2.5 & DMF & 37 & 0.4 & n.d. \\ \cline{2-6}  & 4 & 2.5 & DMF & 45 (95 \({}^{\circ}\)C) & 1.2 & 13,000 \\ \cline{2-6}  & 6 & 2.5 & Anisole & 33 & 0.5 & 11,600 \\ \hline \end{tabular}
\end{table} 
Table 1: Polymerization of VM with PLA-PU macroinifer (Mn = 37000, SEC), 85 \({}^{\circ}\)C, 24 h; the mass ratio of VM/PLA in the feed = 1. NMR [31]. By this NMR method, each component in a mixture can be virtually separated based on its own diffusion coefficient. DOSY NMR appeared to be very useful to study the polymerization kinetics and determine the structure and molecular weight of the formed product [32; 33; 34]. Figure 5 presents DOSY maps (with \({}^{1}\)H NMR spectra on the top) obtained for the PLA-PU/PAN copolymer, the PLA-PU starting polymer, and the separately prepared PAN homopolymer. Similarly, in Figure 6, DOSY maps for the PLA-PU/PST copolymer, the PLA-PU, and the PST homopolymer are shown. Figure 5: 2D DOSY NMR spectra of PLA-PU (**a**), PAN (**b**), and PLA/PAN copolymer (**c**) recorded in DMSO-d\({}_{6}\) (the area of the appearance of signals corresponding to the remaining solvents “s” is not shown). Figure 6: 2D DOSY NMR spectra of PLA-FU (**a**), PST (**b**), and PLA/PST copolymer (**c**) recorded in DMSO-d\({}_{6}\) (the area of the appearance of signals corresponding to the remaining solvents “s” is not shown). As can be seen in Figures 5 and 6 (and the data shown in Table S1), the diffusion coefficients for building blocks in pairs--PLA-PU, PAN (D\({}_{\text{av.