The experimental results were compared to mechanistic DFT calculations. Preliminary calculations, presented in the Supporting Information (Figure ), indicate that the overall reaction proceeds according to a non-concerted mechanism, self-catalysed by the amine, in accordance with previous reports of the literature. Figure represents the mechanistic pathways for the first aminolysis of EDC, using ethylamine as a model of hexylamine for sake of simplicity. The initial step corresponds to the nucleophilic attack of the amine onto the carbonate group of CC accompanied by a proton transfer towards the catalytic amine to provide a cyclic amino alkoxide anion interacting with NH3 + by H-bonding, IS1A. It subsequently undergoes ring opening by C-O bond cleavage and a simultaneous proton transfer between NH3 + and the O atom of the carbonate to produce the targeted monohydroxyurethanes interacting by H-bonding with the catalytic amino function, 1a-EA and 1a'-EA, where EA stands for the catalytic ethylamine interacting with the two regioisomers at the end of the reaction. Clearly, 1a-EA, the (OH)II containing regioisomer, is much more stable than 1a'-EA, ΔE(1a'-EA-1a-EA) = 26 kJ mol , indicating that the formation of this regioisomer is thermodynamically favorable. Moreover, the energy difference between the intermediate species, IS1A, and the transition state, TS2, is much smaller in the case of the mechanistic pathway resulting in the formation of 1a-EA (ΔE = 18 kJ mol -1 ). Thus, the formation of 1a-EA is also kinetically favorable. Overall, the calculations are in accordance with the regiospecificity of the reaction observed experimentally, both under thermodynamic and kinetic control. The dihydroxyurethanes 2a and 2a' are obtained according to the same mechanistic pathway (Figure ). However, the energy difference between the two regioisomers is much smaller this time, ΔE(2a'-EA-2a-EA) = 5 kJ mol -1 , suggesting a moderated regioselectivity in favor of 2a formation under thermodynamic control. When considering the energy difference between the intermediate species, IS2A, and the transition state, TS4, the formation of 2a' is much more favorable (ΔE = 20 kJ mol -1 ). Experimentally, 2a:2a' = 68:32, indicating that the regioorientation of the reaction is in accordance with a thermodynamic control. The aminolysis of TDC was studied according to the same protocol than EDC. It was first reacted with 1 eq. of HA in DMSO at 25 °C ([TDC] = 1 mol L -1 and [NH2] = 1/2[CC]). The NMR analysis of the crude indicate that the reaction is chemoselective with only monohydroxyurethanes being formed (Figure and Figure to S14). Moreover, there is a strong regio-orientation in favor of 1b formation, the (OH)II containing regioisomer. However, contrarily to EDC, the reaction is not regiospecific, the regiosiomer 1b' is also formed to a small extent, with 1b : 1b' = 95 : 5. This result indicates a very mild impact of the stereoisomery of the vicinal dicarbonate onto the regioselectivity of the first aminolysis. The second-order rate constant k1,TDC of the ring-opening reaction of TDC is equal to 0.31 L mol -1 s -1 (Figure ). This value is high as compared to the values reported in the literature for the aminolysis of activated CC (cf. kester = 0.42×10 -4 L mol -1 s -1 at 25 °C). However, it is significantly smaller than k1,EDC (~ k1,TDC ×2) indicating an influence of the stereoisomery of the vicinal dicarbonate onto the first-aminolysis kinetics. Goldstein et al. already noticed the influence of stereoisomery onto the kinetics of the aminolysis of carbonated hexitol, i.e. vicinal tricarbonates (50 °C, DMF). The second-order rate constant of the first aminolysis varied according to the following order: isotactic > heterotactic > syndiotactic. They suggested that the evolution might be due to variation of steric factors resulting from different conformational isomerism of the vicinal tricarbonates. Based on this hypothesis, we tentatively used DFT calculation to predict the conformational analysis of EDC and TDC, i.e. the study of the relative energy between their different conformations. Figure represents the relative conformation energy diagram of both EDC and TDC in DMSO at 25°C, as a function of the torsion angle, 𝜃𝜃, between the half-planes 𝜋𝜋A and 𝜋𝜋B, where 𝜋𝜋A is defined by O1, C3 and C2 and 𝜋𝜋B is defined by O4, C2 and C3 (Figure ). The energy diagram of EDC exhibits a conventional profile with two local minima for 𝜃𝜃 = 65°and 295°, corresponding to gauche-conformers, and one absolute minimum, for 𝜃𝜃 = 180°, corresponding to the trans-conformer. The calculation of the population distribution according to a Boltzmann distribution, indicates that 92% of the molecules are in the trans conformation. In this conformation, the two carbonyl groups point in opposite direction and they are easily accessible for aminolysis. TDC exhibits three local energy minima as well, for 𝜃𝜃′ = 60°, 170° and 295°. However, the relative free energy of the gauche conformer associated to 𝜃𝜃′ = 295° is very close to those of the trans conformer (𝜃𝜃′ = 170°). The calculation of the population distribution indicates that 73% of the molecules are in the trans conformation and 27% in the stable gauche conformation for TDC (DMSO at 25°C). For both conformations, the positioning of the substituents results in higher steric interactions as compared to the trans conformer of EDC. The resulting steric bulk inhibits the nucleophilic attack of the carbonyl groups, which explains the difference between the kinetics rate constants of the aminolyses, k1,TDC and k1,EDC, as measured experimentally. Thus, the conformational analysis of vicinal di(carbonate)s illustrates well the impact of stereochemistry onto the reactivity of the CC functions. The subsequent ring-opening aminolysis of the in-situ generated mixture of 1b and 1b' (95:5), was studied by adding an additional equivalent of HA. Again, the 1 H NMR monitoring of the reaction provides the second-order rate constant, k2,TDC, of the second aminolysis reaction: k2,TDC = 0.064 L mol -1 s -1 (Figure ). Interestingly, k2,TDC = k2,EDC, indicating that contrarily to the first aminolysis reaction, the kinetics rate of the second aminolysis is not impacted by the stereochemistry of the vicinal di(carbonate). After completion of the second aminolysis reaction (4h, 60°C), the NMR analysis of the crude indicates that 64% of the overall hydroxyl groups are (OH)II, and 36% are (OH)I (see Figure to S19). In that case, the ratio of the regiosiomers can be estimated to be 2b:2b':2b'' = 30:65:5. Surprisingly, the regioselectivity of the second ring opening addition of TDC is inverted as compared to EDC. Indeed, calculations indicate that 80% of the hydroxyl groups formed during the second ring opening reaction of TDC are (OH)I, against 32% in the case of EDC. These results suggest that the regioselectivity is significantly impacted by the stereochemistry. Magliozzi et al. already noticed a similar effect for the aminolysis of the different enantiomeric forms of DGDC, but to a less extent. Indeed, PHUs derived from the racemic mixture of (R,R) and (S,S)-DGDC contain approximately 25% of (OH)I against 35% for PHUs derived from meso-DGDC. These results suggest that the conformational changes of the carbonates, from one stereoisomer to the other, impact not only the kinetics of their aminolysis, but also the orientation of the nucleophilic attack of the amine, and thus the regioisomery of the resulting hydroxyurethane. The mechanistic DFT calculation for the double ring opening aminolysis of TDC is presented in the Supplementary Information (Figure ). Similarly to EDC, the mechanistic pathway for the formation of the mono(hydroxyurethane)s in interaction with the catalytic ethylamine (EA), 1b-EA and 1b'-EA, indicates that the formation of 1b-EA, the (OH)II containing regioisomer, is much more favorable under thermodynamic control (ΔE(1b'-EA-1b-EA) = 32 kJ mol -1 ). The energy difference between the intermediary species, IS1b, and the transition state, TS2b, is essentially the same for the two regioisomers. Thus, the ratio 1b:1b' = 95:5 is in accordance with the thermodynamic control of the reaction suggested by DFT calculation. When considering the energetic pathway for the formation of the di(hydroxyurethane)s 2b and 2b' (the formation of 2b'' is not considered here), the energy difference between the two regioisomers is small, ΔE(2b-EA-2b'-EA) = 2 kJ mol -1 , suggesting only a slight regioselectivity in favor of 2b' formation, the regioisomer containing one (OH)II group and one (OH)I group. On the other hand, the energy difference between the intermediary species, IS2b, and the transition state, TS4b, indicate a slight regioselectivity in favor of 2b formation. Thus, the experimental ratio, 2b:2b':2b'' = 30:65:5, is in accordance with a thermodynamic control of the second aminolysis of TDC, despite the very small difference between the energy of the two regioisomers. By taking advantage of the remarkable difference of reactivity between the vicinal dicarbonates and their corresponding mono(hydroxyurethane)s in DMSO, PHUs synthesis was envisioned according to a one pot, two steps protocol. The principle, inspired from the results of the model reactions, is illustrated in Figure . It consists in, step 1, reacting 1 eq. of vicinal dicarbonate with 0.5 eq. of a diamine, Ai, at 25 °C, to obtain a bis(cyclic carbonate), BisCC-XAi, where X = E or T, with E standing for EDC and T for TDC, depending on the nature of the vicinal dicarbonate. Subsequently, in step 2, BisCC-XAi is reacted with an additional 0.5 eq. of diamine, at 60 °C, to initiate a polyaddition reaction resulting in the formation of the corresponding PHUs. In step 2, the diamine can be the same as step 1, Ai, or a new diamine, Aj. In the latter case, the corresponding PHU is expected to have an alternated structure, ⋯Ai-diHU-Aj-diHU⋯, where diHU stands for di(hydroxyurethane)s. It is worth noting that a similar strategy was used by Ousaka et al. for the synthesis of sequence-controlled PHUs derived from a petroleum-based spiro bis(six-membered cyclic carbonate). In their study, the diHU linkers were made of primary hydroxyl groups, (OH)I, solely. In our case, the vicinal dicarbonates (EDC vs TDC) offer the additional possibility to tune the structure of the alcohols ((OH)I vs (OH)II). In this study, four BisCC precursors were synthesized by reacting EDC and TDC with two diamines: an aliphatic diamine A1 = 1,6-Hexanediamine, and a short diether diamine A2 = 1,8diamino-3,6-dioxaoctane (Figure ). A typical synthesis proceeds by reacting 0.5 eq. of EDC solubilized in DMSO (1 mol L -1 ) with 0.5 eq. of A1 at 25 °C for 4h, to afford BisCC-EA1. BisCC-EA2, BisCC-TA1 and BisCC-TA2 were successfully synthesized according to the same protocol. In all cases, the 1 H NMR characterization of the crudes indicate that the reaction is brought to completion. The conversions of CC are reported in Table . Moreover, NMR analysis was used to measure the (OH)I : (OH)II ratios of the BisCC. For both BisCC-EA1 and BisCC-EA2, (OH)I : (OH)II = 0 : 100, in accordance with the model reaction of EDC with 0.5 eq. of HA. For BisCC-TA1, and BisCC-TA2, (OH)I : (OH)II ~ 10 : 90, again, in accordance with the model reaction of TDC with 0.5 eq. of HA. In order to validate the molecular structure of the BisCCs and to make sure that there is no oligomerization at this stage, the crudes were all analyzed by size exclusion chromatography (SEC). Figure represents the chromatograms of all the BisCCs. In all cases, a sharp and intense peak is observed for an elution time, te ~ 32 min. The analysis of the peaks (Polystyrene calibration) provides number average molar masses, Mn, that are in close agreement with the theoretical molar masses of the BisCC. They are all reported in Table . The corresponding dispersity, Ð, are very close from 1, confirming the formation of well-defined BisCC. It is worth noting that, on all chromatograms, a second peak is observed for an earlier elution time (te ~ 30.5 min). The corresponding Mn indicates the formation of BisCC dimers resulting from the reaction of two diamines with three vicinal dicarbonates. They represent only 5% of the total mass of the samples. This small fraction is tolerated in the next part of the work. It implies that a known amount of diHU-Ai-diHU-Ai-diHU sequence will be inserted in the polymer synthesized from these crude BisCCs.