Synthesis and characterization of siloxane-containing poly(urea oxamide) segmented copolymers

An unprecedented family of segmented polydimethylsiloxane poly(urea oxamide) (PDMS-UOx) copolymers displayed thermoplastic elastomeric behavior with improved thermomechanical properties compared to PDMS polyurea (PDMS-U) analogs. A two-step, PDMS end-capping sequence using diethyl oxalate and hydrazine generated difunctional oxamic hydrazide capped oligomers. Polymerization with HMDI provided high molecular weight copolymers, which yielded elastomeric films with monodisperse hard segments. Dynamic mechanical analysis (DMA) of PDMS-UOx copolymers revealed a broad, rubbery plateau that extended for >180 °C. The PDMS-UOx service window extended ∼120 °C further than a PDMS-U analog, presumably due to enhanced hydrogen bonding and concomitant microphase separation. DSC and WAXD elucidated the amorphous morphology of PDMS-UOx, and DMA, SAXS, and AFM confirmed a well-defined microphase-separated morphology. Incorporation of urea oxamide groups significantly affected microphase separation and thermomechanical properties, and these copolymers offer impact in adhesive and biomedical technologies due to low temperature reaction conditions for unique hydrogen bond containing segmented copolymers.