## 2 Results and Discussion
### Chemical Composition of the Copolymers  
The chemical composition of copolymers was also calculated from the \({}^{1}\)H-NMR spectra by taking the ratio of the peak areas corresponding to the _rac_-LA methine protons at \(\delta\) = 5.1-5.3 ppm and the CL \(\varepsilon\)-methylene protons at \(\delta\) = 4.0-4.1 ppm [23]. _rac_-LA conversion was determined by \({}^{1}\)H-NMR in the comparison with integrated signal areas of the methylene groups next to the carbonyl group in the monomer at 5.08 ppm and the polymer at 5.15 ppm before the purification procedure. It should be noted that CL-LA heterodiads are overlapped in the LA methine signal and they have the same relative molar fraction as LA-CL dyad [23,24]. The results are summarized in Table 1 and presented in Figure 2.  
As it can be seen in Table 1, in a case of [bmim][BF\({}_{4}\)] as a solvent, the incorporation of LA units into polymer chains was incomplete at each case even at higher temperature (110 \({}^{\circ}\)C) and generally remained at a similar, low level (0.25-0.42). During reactions in [bmim][BF\({}_{4}\)], color changes in the reaction medium were observed from yellow at 80 \({}^{\circ}\)C to dark brown at 110 \({}^{\circ}\)C. This demonstrates that tetrafluoroborate anion in ILs can degrade during long-term reactions in the presence of water (co-initiator), resulting in the formation of hydrogen fluoride which probably can cause an enzyme deactivation. Moreover, it should be emphasized here that [bmim][BF\({}_{4}\)] tend to absorb more water than [bmim][NTf\({}_{2}\)]. Figure 1: \({}^{1}\)H-NMR spectrum of copolymers of _rac_-LA and CL (entry A2). In a case of [bmim][NTf\({}_{2}\)] as a solvent, the copolymer composition was generally close to the feed molar ratio of monomers. For example, in the case of B8 the molar LA composition was 0.62 when 0.67 was expected from feed molar ratio. One exception is sample B7--the molar LA composition was only 0.36 in this case (0.67 was expected from the feed molar ratio), because of incomplete monomer consumption after 7 days of polymerization. This can be observed due to non-dissolved _rac_-LA in the reaction tube as a result of low co-monomer (CL) content and short reaction time. Moreover, we observed a color change in a solvent at 110 \({}^{\circ}\)C after 14 days. However, the change was less than that seen with copolymerization in [bmim][BF\({}_{4}\)]. These results are convergent with the results of the homopolymerization of _rac_-LA and CL (results not shown) and demonstrate that CL is the most active co-monomer in our experiments, which enhances the polymerizability of _rac_-LA. Moreover, CL allows higher conversion of _rac_-LA and allows a higher \(M_{n}\) to be obtained for the copolymers [16]. For example, conversion of _rac_-LA synthesized in [bmim][NTf\({}_{2}\)] at 80 \({}^{\circ}\)C for 14 days increased from 0.59 (sample B8, CL molar ratio 0.38) to 0.86 (sample B2, CL molar ratio 0.54) and 0.94 (sample B5, CL feed molar ratio 0.67). For copolymers synthesized at  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Entry**} & **Solvent** & **Temp. ** & **Time** & \multirow{2}{*}{\({}^{\circ}\)C} & \multirow{2}{*}{**(days)**} & \multirow{2}{*}{\({}^{\circ}\)**L\({}_{\text{LA}}\)**b**} & \multirow{2}{*}{\({}^{\circ}\)**TelA**conv. & \({}^{\circ}\)**c**} & **Yield** & \multirow{2}{*}{\({}^{\circ}\)**M\({}_{\text{m}}\)**d**} & \multirow{2}{*}{\({}^{\circ}\)**M\({}_{\text{m}}\)**a**} & \multirow{2}{*}{\({}^{\circ}\)**M\({}_{\text{m}}\)**a**} \\  & **(1 mL)** & & & & & & & & & &  
110 \({}^{\circ}\)C in [bmim][NTf\({}_{2}\)], _rac_-LA conversion remained at the same, high level, approximately 0.90 in each case. The \(M_{n}\) of copolymers of _rac_-LA and CL also depends on the _rac_-LA/CL molar ratio, the kind of solvent and their purity. The \(M_{n}\) values of the copolymers determined by the GPC were in the range of 700-3100 g/mol and increased with increasing CL content in the feed.