## 2 Results and Discussion
### Polymerization of Acrylonitrile and Styrene Initiated with PLA-PU Containing TPE Groups  
The anticipated formation of multiblock polylactide/poly(vinyl monomer) copolymers by the adaptation of the inifer concept [7] is presented schematically in Figure 3. In brief, assuming that, after the initiation of the radical polymerization of VM and several propagation steps, growing radicals will recombine, the introduction of VM blocks into PLA-based PU should proceed by the insertion of VM in the middle of the TPE groups present in PLA-PU. The idea presented in Figure 3 can be realized under one condition, i.e., when growing radicals are able to recombine. As is known from the literature, the termination of the polymerization of (meth)acrylates proceeds mainly by disproportionation [23; 24], so in this case, there is a limited possibility to recombine the growing... PLA-... -C(Ph)2-VM << fragments that are formed after the dissociation of the TPE groups and the attachment of several VM units once again into one chain. The opposite is the case in the polymerization of styrene, where the recombination of styryl radicals dominates over their disproportionation [23]. Another vinyl monomer-acrylonitrile has been found to be capable of polymerizing with  
Figure 3: Schematic representation of the formation of a PLA/PVM copolymer using a PLA-PU macroinifer. termination, mainly by recombination under appropriate conditions [25]. Considering this, in the present study, two vinyl monomers were chosen for the polymerization initiated by the PLA-PU macroinifer, i.e., acrylonitrile and styrene. Polymerizations were performed in two solvents with different polarities, DMF and anisole (the normalized solvent polarity parameter E\({}_{T}\)\({}^{N}\) = 0.386 for DMF and 0.198 for anisole [26]), by heating PLA-TPE macroinifer in the presence of a vinyl monomer to 85\({}^{\circ}\)C. The dependence of the amount of VM incorporated in the copolymer on the initial VM/PLA ratio was shown in our previous work [6], and thus in this study, polymerizations were performed using the same mass of AN or ST with respect to the PLA-based macroinifer. The products isolated by the double precipitation of the reaction mixture were analyzed by the \({}^{1}\)H NMR, FTIR, and SEC methods (Figures 4, S3 and S4). In the \({}^{1}\)H NMR spectra of the copolymers prepared in DMA or anisole, the signals corresponding to AN or ST units were clearly visible. (Figure 4 presents exemplary spectra of the products of VM polymerization). By comparison with the intensities of the appropriate signals, the VM/LA ratio could be calculated. Figure 4: \({}^{1}\)H NMR spectra of the PLA-PU (**a**), PLA/PST (**b**), and PLA/PAN (**c**) copolymers prepared in DMF or anisole as a solvent; (**b**_’,_c_**)—corresponding SEC curves. The applied substrates for the vinyl monomer polymerization and characterization of the obtained products are presented in Table 1.  
Relatively high conversion of acrylonitrile was achieved in both solvents, DMF and anisole, during the applied polymerization time. It appeared, however, that the polymerization of styrene was not efficient at 85 \({}^{\circ}\)C (relatively low conversion), and thus it was also performed at 95 \({}^{\circ}\)C. As expected, a higher temperature promoted the decomposition of the TPE groups and, consequently, the conversion of styrene. The SEC analysis of the radical polymerization products provides two types of information. The first important observation is that all curves show a rather broad but definitely monomodal distribution, indicating the formation of copolymers (both monomeric units corresponding to lactide and vinyl monomer were detected by \({}^{1}\)H NMR spectroscopy). However, unexpectedly, when polystyrene calibration was applied (no reliable calibration for PLA/PVM copolymers is available), the obtained PLA/PVM copolymers had lower molecular weights than the initial PLA-PU (Table 1). Although the desired result is an increase in the molecular weight, a Mn value decrease is also explainable.