Unexpected Synthesis of Segmented Poly(hydroxyurea−urethane)s from Dicyclic Carbonates and Diamines by Organocatalysis
Ikusi/ Ireki
Data
2018-07-17Egilea
Bossion, Amaury
Hernández Aguirresarobe, Roberto
Irusta Maritxalar, María Lourdes
Taton, Daniel
Cramail, Henri
Grau, Etienne
Mecerreyes Molero, David
Su, Cui
Liu, Guoming
Sardon Muguruza, Haritz
Macromolecules 51(15) : 5556−5566 (2018)
Laburpena
A complete study of the effect of different organocatalysts on the step-growth polyaddition of a five-membered
dicyclic carbonate, namely diglycerol dicarbonate, with a poly(ethylene glycol)-based diamine in bulk at 120 °C was first carried
out. The reaction was found to be dramatically catalyst-dependent, higher rates being observed in the presence of strong bases,
such as phosphazenes (t-Bu-P4 or P4) and 5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). Unexpectedly, the as-formed urethane
linkages entirely vanished with time, as evidenced by FTIR and 13C NMR spectroscopies, while signals due to urea bond
formation progressively appeared. An advantage of the chemical transformation occurring from urethane to urea linkages was
further taken by optimizing the polymerization conditions to access a range of poly(hydroxyurea−urethane)s (PHUUs) with
precise urethane to urea ratio in a one-pot process. Characterization of the corresponding polymers by rheological
measurements showed that the storage modulus reached a plateau at high temperatures and at high urea contents. The
application temperature range of poly(hydroxyurea−urethane)s could thus be increased from 30 to 140 °C, as for regular
polyurethanes. Furthermore, SAXS and phase-contrast microscopy images demonstrated that increasing the urea content
improved the phase separation between soft and hard segments of these PHUUs. Altogether, this novel, straightforward,
efficient, and environmentally friendly strategy enables the access to non-isocyanate poly(urea−urethane)s with tunable
urethane-to-urea ratio from five-membered dicyclic carbonates following an organocatalytic pathway