A facile
strategy has been demonstrated for the selective synthesis
of highly stereoregular polyesters with cis-2,3-(exo, exo) or trans-2,3-(exo, endo) repeating units by the organocatalysts
mediated alternating copolymerization of cyclohexene oxide and norbornene
anhydride (NA) stereoisomers. The geometrical structure of polyester
can be tuned simply by modulating the type of NA isomers (endo- or exo-NA), monomer feed ratio, and
reaction temperature. The cis- (>99%) and trans-polyesters (>99%) exhibit high glass transition
temperature
up to 129.8 and 115.9 °C, respectively. The resulting polyesters
provide a versatile platform to incorporate various functional groups
through the robust thiol–ene reaction of the pendant norbornenyl
groups.
A (ONSO)CrCl complex-based binary
catalyst for efficient ring-opening
copolymerization (ROCOP) of epoxide and norbornene anhydride (NA)
in a stereoselective manner to afford polymers with variable stereoisomerism
is reported. The role of (ONSO)CrCl complex on the cis/trans selectivity of resulting polyester as well
as enhancement of the reaction rate has been revealed. The formation
of chelates between the endo-diester unit of the
polyester chain and the metal center plays a determinate role in the
stereoselectivity of the cis-(endo, endo)-polyester in solution copolymerization of endo-NA with epoxides in the presence of metal complex.
Additionally, the stereostructure of resulting polyester is also dependent
on the polymerization method, NA type, and the bulkiness of the substituent
of the formed ester units in the polyester chain. Accordingly, a proposed
mechanistic pathway for the stereostructure formation of polyesters
is provided.
Three isomeric 5-norbornene-2,3-dicarboxylic acid diethyl ester (NDDE) with endo-, exo-, and trans-configuration have been synthesized and employed as internal electron donors (IED) in 1-butene polymerization over magnesium chloride supported Ziegler-Natta catalysts. It was found that the configuration of NDDE plays a key role in tuning the catalyst activity, stereospecificity, molecular weight (MW), and polydispersity index (PDI) of resulting poly(1-butene). The type of catalyst with cis-5-norborneneendo-2,3-dicarboxylic acid diethyl ester as IED shows the highest catalyst activity, while catalyst with trans-NDDE as IED yields the poly(1-butene) with the highest MW and the most broad PDI. IR results showed that the NDDE with endo-, exo-, and trans-configuration have different coordination way to MgCl 2 , subsequently affecting the catalysts performance. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40758.
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