Segmented block copolyesters using click chemistry

Copper(I) catalyzed azide-alkyne 1,3-Huisgen cycloaddition reaction afforded the synthesis of triazole-containing polyesters and segmented block copolyesters at moderate temperatures. Triazole-containing homopolyesters exhibited significantly increased (∼40 °C) glass transition temperatures (T _g) relative to high temperature, melt synthesis of polyesters with analogous structures. Quantitative synthesis of azido-terminated poly(propylene glycol) (PPG) allowed for the preparation of segmented polyesters, which exhibited increased solubility and mechanical ductility relative to triazole-containing homopolyesters. Differential scanning calorimetry demonstrated a soft segment (SS) T _g near -60 °C for the segmented polyesters, consistent with microphase separation. Tensile testing revealed Young's moduli ranging from 7 to 133 MPa as a function of hard segment (HS) content, and stress at break values approached 10 MPa for 50 wt % HS segmented click polyesters. Dynamic mechanical analysis demonstrated an increased rubbery plateau modulus with increased HS content, and the T _g's of both the SS and HS did not vary with composition, confirming microphase separation. Atomic force microscopy also indicated microphase separated and semicrystalline morphologies for the segmented click polyesters. This is the first report detailing the preparation of segmented copolyesters using click chemistry for the formation of ductile membranes with excellent thermomechanical response.