Synthesis and properties of new optically active and organosoluble poly(ester-imide)s containing L-valine moieties in the main chain by direct polycondensation reaction

Abstract

New optically active poly(ester-imide)s (PEIs) containing bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic diimide in the main chain were prepared by the reaction of N,N'-(bicyclo[2,2,2]oct-7- ene-2,3,5,6-tetra carboxylic)-bis-L-valine 4 as a diacid monomer with various aromatic diols 5a-g in a system of tosyl chloride (TsCl), pyridine (Py), and N,N-dimethylformamide (DMF). The reactions with TsCl were significantly promoted by controlling alcoholysis with diols, in the presence of catalytic amounts of DMF, to give a series of optically active poly(ester-imide)s. The resulting new polymers were obtained in good yields and inherent viscosities, ranging between 0.36 and 0.62 dL g^{-1}, and were characterized with FT-IR and ^1H-NMR spectroscopy, including specific rotation. All of these polymers were highly organosoluble at room temperature in solvents like N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), and sulfuric acid. The thermal stability of the resulting PEIs was evaluated with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques under a nitrogen atmosphere, which indicated that the residual weight percent of the polymers at 600 °C was 43.69%-60.5% and showed that they are moderately thermally stable.