Access to Biorenewable and CO₂-Based Polycarbonates from Exovinylene Cyclic Carbonates

Abstract

We investigate the scope of the organocatalyzed step-growth copolymerization of CO 2 -sourced exovinylene bicyclic carbonates with bio-based diols into polycarbonates. A series of regioregular poly(oxo-carbonate)s were prepared from sugar-(1,4butanediol and isosorbide) or lignin-derived (1,4-benzenedimethanol and 1,4-cyclohexanediol) diols at 25 °C with 1,8diazabicyclo[5.4.0]undec-7-ene (DBU) as a catalyst, and their defect-free structure was confirmed by nuclear magnetic resonance spectroscopy studies. Their characterization by differential scanning calorimetry and wide-angle X-ray scattering showed that most of them were able to crystallize. When the polymerizations were carried out at 80 °C, some structural defects were introduced within the polycarbonate chains, which limited the polymer molar mass. Model reactions were carried out to understand the influence of the structure of alcohols, the temperature (25 or 80 °C), and the use of DBU on the rate of alcoholysis of the carbonate and on the product/linkage selectivity. A full mechanistic understanding was given by means of static-and dynamic-based density functional theory (DFT) calculations showing the determining role of DBU in the stability of intermediates, and its important role in the rate-determining steps is revealed. Furthermore, the origin of side reactions observed at 80 °C was discussed and rationalized by DFT modeling. As impressive diversified bio-based diols are accessible on a large scale and at low cost, this process of valorization of carbon dioxide gives new perspectives on the sustainable production of bioplastics under mild conditions.

Perspectives for the Upgrading of Bio‐Based Vicinal Diols within the Developing European Bioeconomy

“…[155] While PUHs are extensively used in elastomers, rigid and soft foams, coatings or additives, [156] PCs are exploited in automotive engineering, medical packaging and glass fibers. [157] As polymerizable building blocks, they have the potential to offer a more sustainable manufacturing of macromolecules as well as valorizing bio-based feedstock and carbon dioxide. Especially, the use of five membered cyclic carbonates offers an alternative route to PUH and PC conventional productions based on hazardous toxic phosgene and isocyanates (for PUHs).…”

“…Over the past decades, bio‐based five membered carbonates gained a significant interest in the polymer sector, especially as promising renewable sources of monomers aimed at the production of poly(β‐hydroxyurethane)s (PUHs) and poly(carbonate)s (PCs) [155] . While PUHs are extensively used in elastomers, rigid and soft foams, coatings or additives, [156] PCs are exploited in automotive engineering, medical packaging and glass fibers [157] . As polymerizable building blocks, they have the potential to offer a more sustainable manufacturing of macromolecules as well as valorizing bio‐based feedstock and carbon dioxide.…”

En Route to CO2-Based (a)Cyclic Carbonates and Polycarbonates from Alcohols Substrates by Direct and Indirect Approaches

“…Bis(α-alkylidene cyclic carbonates) were either prepared by direct coupling of bis-propagylic alcohols with CO 2 (aliphatic spacer R 2 , see Scheme 33) or by heck coupling of two CO 2 -based exovinylene cyclic carbonates with 1,4-diiodobenzene (aromatic spacer R 2 , see Scheme 33). These new monomers were further copolymerized via step growth with diols to obtain regioregular PCs with microstructures free of any defects [108,[219][220][221]. Indeed, unlike conventional 5-membered cyclic carbonates, the formation of ether linkages (via decarboxylation) was not observed.…”

Exovinylene Cyclic Carbonates: Multifaceted CO2‐Based Building Blocks for Modern Chemistry and Polymer Science

“…The same research group further synthesized oxo‐alkyl carbonates in good yields (60–70 %) from challenging bulky tertiary and/or sterically congested alcohols, respectively, by switching from NEt 3 to KCN, 2‐hydroxypyridine (10 mol%) or DBN (40 mol%) catalyst at 20–60 °C (products 33 g – j ) [108] . Recently, the alcoholysis of αCC was revisited by Detrembleur who utilized an organic (super)base (DBU) [109] or nBu 4 NOPh [54] (5 mol% vs αCC). Various oxo‐alkyl carbonates were easily fabricated from αCCs and 1‐butanol at 25 °C (within hours) or with less reactive benzyl alcohol or cyclohexanol at 80 °C (within 15 min) ( 33 k – n ).…”

“…Capitalizing on the catalyst findings for the CO 2 transformation (Section 3) and the transformation of αCCs (Section 4), bis‐α‐alkylidene cyclic carbonates (bisαCCs) have been synthesized either by carboxylative cyclization of CO 2 with bispropargylic alcohols or via Heck reaction of αCCs with 1,4‐diiodobenzene (Scheme 21). For the first methodology, bispropargylic alcohols with terminal or internal alkyne functionality have been synthesized by the Grignard reaction of diketones with ethynylmagnesium bromide (path a) [91, 92, 109] or via the ring‐opening of bisepoxides by butynediol (an industrial waste) (path b) [142] . These templates have been further transformed into the corresponding bisαCCs M1–M4 with yields of 72–95 % by catalytic CO 2 fixation ( p =20–100 bar, T =25–40 °C) using binary catalysts (CuI/nBu 4 NPhO or AgOAc/Dave Phos).…”