5-Ethylidene-2-norbornene (ENB) and 5-vinyl-2-norbornene (VNB) based alicyclic polyols for the synthesis of polyesters

Abstract

Amorphous polyesters derived from rigid alicyclic monomers with high glass transition temperatures are of great interest as potential substitutes for poly(carbonate)s. Therefore, 5-ethylidene-2-norbornene (ENB) and 5-vinyl-2-norbornene (VNB) were identified as interesting diol monomer precursors to enhance the thermal properties of polyesters. The regioselective synthesis of the corresponding diols from ENB and VNB was optimized and the first scale-up experiments gave promising results for a potential large-scale production of these polyester monomers. Moreover, for proof of concept, an alternative procedure was established to synthesize exclusively branched diols. Polymerization experiments were conducted with dimethyl terephthalate (DMT) as a model compound to compare the polyesters with commonly used poly(ethylene terephthalate)s. Therefore, a series of polyesters containing branched or linear regioisomers or a mixture of both regioisomers were produced, and structure–property relationships were investigated using GPC, TGA and DSC analyses. The T_g values ranged from 75 to 103 °C, depending on the branched and linear moieties in the polyester microstructure and their molecular weights. Moreover, isosorbide (IS) was introduced as a biobased comonomer, resulting in amorphous copolyesters with promising T_gs ranging from 81 to 97 °C.