Crystalline Stereocomplexed Polycarbonates: Hydrogen‐Bond‐Driven Interlocked Orderly Assembly of the Opposite Enantiomers

Four novel crystalline stereocomplexed polymers are formed by mixing isotactic (R)‐ and (S)‐polycarbonates in 1:1 mass ratio. They show the enhanced thermal stability and new crystalline behavior, significantly distinct from the component enantiomer. Two stereocomplexed CO₂‐based polycarbonates from meso‐3,4‐epoxytetrahydrofuran and 4,4‐dimethyl‐3,5,8‐trioxabicyclo5.1.0]octane have high melting temperatures of up to 300 °C, about 30 °C higher than the individual enantiomers. Isotactic (R)‐ or (S)‐poly(cyclopentene carbonate) and poly(cis‐2,3‐butene carbonate) are typical amorphous polymeric materials, however, upon mixing both enantiomers together, a strong interlocked interaction between polymer chains of opposite configuration occurs, affording the crystalline stereocomplexes with melting temperatures of about 200 °C and 180 °C, respectively. A DFT study suggests that the driving force forming the stereocomplex is the hydrogen‐bonding between carbonate units of the opposite enantiomers.