Enantioselective Crystallization of Diglycerol Dicarbonate: Impact of the Microstructure on Polyhydroxyurethane Properties

Abstract

Bicylic carbonates are precursors employed in non‐isocyanate polyurethane syntheses, namely polyhydroxyurethanes (PHUs) and, among them, ether‐activated biobased diglycerol dicarbonate (DGDC) is widely investigated. Herein, the original separation of DGDC stereoisomers, thanks to a recrystallization procedure, leading to enantiomers having different crystal lattices, that is, square transparent crystals and needle‐like structures, respectively, is reported. In this study, the separation and the characterization of the two crystal structures is first discussed and, second, the impact of the stereochemistry of DGDC on the corresponding PHUs properties is investigated.

Sequence-controlled polyhydroxyurethanes with tunable regioregularity obtained from biobased vicinal bis-cyclic carbonates

“…In our previous investigations of the impact of DGDC stereoisomery onto the microstructure of PHUs, only moderated variation of the Tg were observed between the PHUs obtained from the enantiopure meso-DGDC, (R,S), vs the racemic mixture of (R,R) and (S,S) DGDC. 10 In this case, the variation of the hydroxyl ratio were of about 10%. For EDC vs TDC, we observe a two-fold increase of the magnitude of the variation (~20%), which might explain the larger variation of the thermal properties of the PHUs.…”

“…The success of PHUs is largely related to the rapid development of sustainable procedures for the synthesis of 5CC precursors such as the CO2/epoxide coupling chemistry [3][4][5][6][7] or the carbonatation of biosourced 1,2-diols. [8][9][10][11][12] However, 5CC aminolysis comes with several drawbacks including (i) slow kinetics and extensive side reactions that hinder high polymerization degree [13][14][15] and (ii) a lack of regio-and stereo-control resulting in poorly defined polymers. 11,16 Many catalysts have already been proposed to accelerate the polymerization kinetics, including N-bases, metal salts and thiourea compounds.…”

“…It was recently reported by Maggliozi et al, who used a procedure of enantioselective crystallization to isolate two crystal structures of diglycerol dicarbonate (DGDC, Scheme 1): the enantiopure meso-DGDC, (R,S), and the racemic mixture of (R,R) and (S,S) DGDC. 10 These two crystals were polymerized in bulk with various diamines (110 °C). Interestingly, the characterizations of the resulting PHUs suggest a slight impact of the stereochemistry of DGDC onto the chain insertion efficiency and on the regioregularity of the chains.…”

“…These results confirm that the stereoisomery of bis(carbonate) impacts their thermal properties, as already noticed by Magliozzi et al for the stereoisomers of DGDC. 10…”

Sequence-Controlled Polyhydroxyurethanes with Tunable Regioregularity Obtained from Sugar-Based Vicinal Bis-cyclic Carbonates

“…Polyhydroxyurethanes (PHUs) are phosgene- and isocyanate-free polyurethanes (PUs) that are foreseen as a promising alternative to conventional PUs, when European and North American directives will restrict the use of allergenic and carcinogenic isocyanates. , They are usually obtained through the polyaddition reaction of diamines onto bis-five-membered cyclic carbonates (bis-5CCs), resulting in the formation of urethane linkages and hydroxyl groups (OH) (Scheme ). The success of PHUs is largely related to the rapid development of sustainable procedures for the synthesis of 5CC precursors such as the CO 2 /epoxide coupling chemistry − or the carbonation of biosourced 1,2-diols. − However, 5CC aminolysis comes with several drawbacks including the (i) slow kinetics and extensive side reactions that hinder high polymerization degrees − and (ii) lack of regio- and stereocontrol, resulting in poorly defined polymers. , Many catalysts have already been proposed to accelerate the polymerization kinetics, including N-bases, metal salts, and thiourea compounds. , While they accelerate the reaction, they currently do not solve the regio- and stereoregularity issues. Yet, regularity in the arrangement of polymer backbones’ neighboring units is of paramount importance, as it is critical to their bulk performances.…”