Incorporation of different crystallizable amide blocks in segmented poly(ester amide)s

High molecular weight segmented poly(ester amide)s were prepared by melt polycondensation of dimethyl adipate, 1,4-butanediol and a symmetrical bisamide-diol based on ε-caprolactone and 1,2-diaminoethane or 1,4-diaminobutane. FT-IR and WAXD analysis revealed that segmented poly(ester amide)s based on the 1,4-diaminobutane (PEA(4)) give an α-type crystalline phase whereas polymers based on the 1,2-diaminoethane (PEA(2)) give a mixture of α- and γ-type crystalline phases with the latter being similar to γ-crystals present in odd–even nylons. PEA(2) and PEA(4) polymers with a hard segment content of 25 or 50 mol% have a micro-phase separated structure with an amide-rich hard phase and an ester-rich flexible soft phase. All polymers have a glass transition temperature below room temperature and melt transitions are present at 62–70 °C (Tm,1) and at 75–130 °C (Tm,2) with the latter being highest at higher hard segment content. The two melt transitions are ascribed to melting of crystals comprising single ester amide sequences and two or more ester amide sequences, respectively. These polymers have an elastic modulus in the range of 159–359 MPa, a stress at break in the range of 15–25 MPa combined with a high strain at break (590–810%). The thermal and mechanical properties are not influenced by the different crystalline structures of the polymers, only by the amount of crystallizable hard segment present.