Synthesis and characterization of thermoplastic copolyester elastomers modified with fumaric moieties

Abstract

A series of poly(ether-ester)s derived from dimethyl terephthalate (DMT), dimethyl fumarate (DMF), 1,4-butandiol (BD) and poly(tetramethylene oxide) (PTMO, M̄n = 1000 g/mol) was synthesized in a two stage process involving transesterification and polycondensation in the melt. The mole ratio of the starting components was selected to result in copolymers with a constant hard:soft segment wieght ratio (56:44). The amount of DMF was 10 mol %, referred to the total amount of the esters used. The synthesis was optimized in terms of both the concentration of catalyst, tetra-n-butyl-titanate, Ti(OBu)4 and thermal stabilizer N,N'-diphenyl-p-phenylenediamine, DPPD, as well as the temperature. The composition and structure of the synthesized poly(ether-ester)s were characterized by 1H-NMR. The number average molecular weights of the polymers calculated from the 1H-NMR spectra were compared with the corresponding values of the inherent viscosity (ηinh) in m-cresol and the complex dynamic viscosity (η*). The effect of the content of fumaric residues on the thermal properties of the synthesized copolyesters was also investigated using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA).