title: Crystalline stereocomplexed polycarbonates: hydrogen-bond-driven interlocked orderly assembly of the opposite enantiomers.
abstract: 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-trioxabicyclo[5.1.0]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.
authors.affiliation: State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China).
authors.forename: Ye
authors.initials: Y
authors.lastname: Liu
authors.forename: Wei-Min
authors.initials: WM
authors.lastname: Ren
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.forename: Chuang
authors.initials: C
authors.lastname: Liu
authors.forename: Xiao-Bing
authors.initials: XB
authors.lastname: Lu
keywords: carbon dioxide; crystalline; enantiopure polycarbonates; epoxides; polymer stereocomplexes