As the environmental persistence and dependence on fossil-based resources of most polymers are increasingly viewed as unsustainable, degradable polymers based on renewable resources are desirable alternatives. However, to replace oil-based traditional polymers, these new polymers need to be cost and performance competitive. In particular, one challenge to address is that typically, the glass transition of renewable polymers (e.g. Poly(Lactic Acid), PLA) is low and that low heat resistance limits the range of applications of these materials. In this talk we will present different strategies that we have been using to develop monomers and polymers with enhanced thermal properties from chiral renewable feedstocks such as α-hydroxy acids (mandelic acid, lactic acid) or carbohydrates (e.g. mannose, thymidine, deoxyribose…) We have thus prepared stereoregular Poly(Mandelic Acid) (PMA) using a pyridine/mandelic acid adduct as an organocatalyst for the ring-opening polymerization of the cyclic O-carboxyanhydride of mandelic acid (manOCA). These highly isotactic chiral polymers exhibit an enhancement of the glass transition temperature (Tg) of 15 °C compared to the racemic polymer. We have also been investigating metal catalysts based on abundant metals for the isoselective polymerisation of racemic lactide (the lactone dimer of lactic acid) to obtain stereoblock PLAs which can form stereocomplexes of enhanced crystallinity. Finally, using CO2 as a carbonation agent, we have developed several novel cyclic carbonate monomers from various chiral sugar derivatives (e.g. from D-mannose and thymidine). The stereochemical differences between these sugars greatly influence the ability of the resulting monomers to be polymerised, the regioregularity of the polymer sequence, as well as their thermal properties. In particular, polycarbonates derived from D-mannose display a Tg higher than 150 °C.

Ring-opening polymerization of renewable chiral monomers: Catalytic strategies and monomer design towards biopolymers with high glass-transition temperatures

256th National Meeting (2018)

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